What is mesial temporal sclerosis. Hippocampal sclerosis: pathogenesis, clinic, diagnosis, treatment. Simple partial seizures

mesial temporal sclerosis, hippocampal sclerosis- the most common pathology associated with resistant temporal lobe epilepsy. It is revealed in 65% of cases at autopsy, much less often at imaging.

Clinical picture

Most patients suffer from complex partial seizures as a result of temporal lobe epilepsy.

Febrile seizures

The association (if any) between mesial temporal sclerosis and febrile seizures is controversial: this is due to the relative insensitivity on imaging and the difficulty in establishing the truth of a febrile seizure. A third of patients with established temporal lobe epilepsy have a history of febrile seizures. Follow-up of children with febrile seizures does not show a significant increase in the incidence of temporal lobe epilepsy.

Pathology

There is uneven damage to the hippocampal formation, with damage to the dentate gyrus, CA1, CA4 and, to a lesser extent, CA3 sections of the hippocampus. Histologically, there is neuronal loss, gliosis, and sclerosis.

Etiology

There is some controversy regarding the etiology: whether mesial temporal sclerosis is a cause of epilepsy or a consequence. In children diagnosed with epilepsy, only 1% have radiological evidence of mesial temporal sclerosis. Moreover, in adults, 3-10% of MVS cases show signs of bilateral involvement, despite the clinic of unilateral involvement.

Diagnostics

MRI is the method of choice for evaluating the hippocampus, but a specific protocol is required to achieve good sensitivity. Thin-slice sequences are required in the coronal plane, where the slices will be located at right angles to the longitudinal axis of the hippocampus.

To identify MVS the best choice there will be T2/FLAIR high resolution coronal sequences.

Findings will include:

• decrease in hippocampal volume, hippocampal atrophy;
• increased T2 signal;
• abnormal morphology: loss of internal architecture, stratum radiata - thin layer white matter separating the dentate nuclei and the ammonium horn.

Since the comparative analysis of the right and left sides is not difficult, it must be remembered that in more than 10% of cases, the lesion is bilateral, therefore, when assessing only symmetry, many cases of MVS can be taken as a normal picture.

Also one of the often mentioned, but less specific findings is the expansion of the temporal horn. lateral ventricle. In any case, this should not mislead the radiologist that the hippocampus is reduced in size.

With a more serious lesion, the following may additionally occur:

• atrophy of the ipsilateral fornix and mastoid body;
• increased signal or atrophy of the anterior thalamic nuclei;
• atrophy of the cingulate gyrus;
• an increase in the intensity of the signal from the amygdala and / or a decrease in its volume;
• a decrease in the volume of the subiculum;
• expansion of the temporal horns of the lateral ventricles;
• atrophy of the collateral BV and entorhinal cortex;
• atrophy of the thalamus and caudate nuclei;
• ipsilateral cerebral hypertrophy;
• contralateral cerebellar hemiatrophy;
• blurring of the junction of gray and white matter in the anterior temporal lobe;
• a decrease in the volume of BV in the parahippocampal gyrus;

Additional 3D volumetric sequences can be performed, although post-processing may affect sensitivity to subtle changes in the hippocampus. Contrast enhancement is not required.

DWI

As a result of the loss of neurons, the extracellular spaces expand, and therefore the diffusion of water molecules will be greater on the affected side, which will be manifested by a high signal value on the ADC.
Conversely, as a result of neuronal dysfunction and some edema, diffusion is limited after an attack and, consequently, signal intensity decreases.

MR spectroscopy

MRS changes usually reflect neuronal dysfunction.

• decrease in NAA and NAA/Cho and NAA/Cr ratios:
• decrease in myo-inositol in the ipsilateral lobe;
• increased lipids and lactate immediately after an attack;

MR perfusion

The change in MR perfusion is consistent with that of the SPECT study, depending on when the scan was performed.
During the periictal phase, perfusion increases in almost the entire temporal lobe and even the hemisphere, while in the postictal phase, perfusion is reduced.

SPECT and PET

• ictal period - hyperperfusion and hypermetabolism;
• interictal period - hypoperfusion and hypometabolism;

Literature

1. Derek Smith and Frank Gaillard et al. mesial temporal sclerosis. radiopaedia.org
2. Shinnar S. Febrile Seizures and Mesial Temporal Sclerosis. epilepsy currents. 3(4): 115-118. doi:10.1046/j.1535-7597.2003.03401.x - Pubmed
3. Tarkka R, Pääkkö E, Pyhtinen J, Uhari M, Rantala H. Febrile seizures and mesial temporal sclerosis: No association in a long-term follow-up study. Neurology. 60(2):215-8. pubmed
4. Chan S, Erickson JK, Yoon SS. Limbic system abnormalities associated with mesial temporal sclerosis: a model of chronic cerebral changes due to seizures. Radiographics: a review publication of the Radiological Society of North America, Inc. 17(5): 1095-110.

MESIAL TEMPORAL SCLEROSIS AND ITS ROLE IN THE DEVELOPMENT OF PALEOCORTAL TEMPORAL EPILEPSY (REVIEW)

MESIAL TEMPORAL SCLEROSIS AND ITS ROLE IN DEVELOPMENT OF PALEOCORTICAL TEMPORAL LOBE EPILEPSY (A REVIEW)

S.H. Gataullina, K.Yu. Mukhin, A.S. Petrukhin

Department of Neurology and Neurosurgery, Faculty of Pediatrics, Russian State Medical University of Roszdrav, Moscow

A review of the literature on the problem of mesial temporal sclerosis is presented. Hippocampal sclerosis was first described by Bouchet and Cazauvieilh in 1825 and is now regarded as a multifactorial, classic epileptogenic brain lesion underlying limbic or mediobasal paleocortical temporal lobe epilepsy, manifested by resistant epileptic seizures. The article highlights the historical aspects of the study of the issue, the anatomy and pathophysiology of hippocampal sclerosis, its role in the development of paleocortical temporal lobe epilepsy.

Key words: epilepsy, mesial temporal sclerosis, etiology, pathogenesis, anatomy, pathophysiology.

The articles gives a review of works on mesial temporal sclerosis. Hippocampal sclerosis was first described by Bouchet and Cazauvieilh in 1825, and is presently classified as a multifactor, classical epileptogenic affection cerebral, underlying limbic or mediobasal paleocortical temporal lobe epilepsy manifested by resistant epileptic seizures. The article highlights historical issues of the subject, anatomy and pathophysiology of hippocampal sclerosis and its role in development of paleocortical temporal lobe epilepsy.

Key words: epilepsy, mesial temporal sclerosis, etiology, pathogenesis, anatomy, pathophysiology.

Definition

Mesial temporal sclerosis (synonyms: hippocampal sclerosis, ammon's horn sclerosis, incisural sclerosis, mesial temporal sclerosis) is a multifactorial, classic epileptogenic brain lesion that underlies limbic or mediobasal paleocortical temporal epilepsy, manifested by resistant epileptic seizures. The term "mesial temporal sclerosis" (MTS) is most often used in the literature, although German authors consider the concept of "Ammon's horn sclerosis" to be more correct. The prevalence and clinical picture of mesial temporal sclerosis in children has not been sufficiently studied to date.

History of study

The Italian anatomist Giulio Cesare Aranzi in 1564 first used the term hippocampus to describe the structure of the brain, clearly similar to a sea horse. Initially, this organ was known only as the center of smell. Later, the neurophysiologist V.M. Bekhterev, based on examinations of patients with severe memory impairment, established the role of the hippocampus in maintaining human memory function. Seizures of a psychomotor nature (complex partial, automotor), which, according to modern concepts, constitute the “core” of the clinical picture of amygdala-hippocampal temporal lobe epilepsy, were described by Hippocrates. There is a legend that the legendary

S.Kh. Gataullina, K.Yu. Mukhin, A.S. Petrukhin

Mesial temporal sclerosis and its role in the development of paleocortical temporal lobe epilepsy (literature review). Rus. zhur. det. Neur.: vol. III, no. 3, 2008.

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Heracles killed his wife and children during a "fit of epileptic madness".

Hippocampal sclerosis was first described by Bouchet and Cazauvieilh in 1825 during an anatomical study of the brain of patients suffering from frequent epileptic seizures. A little later, in 1880, Sommer revealed by microscopy the presence of a characteristic histological pattern in the hippocampus: the death of pyramidal neurons at the base of the temporal horn (Sommer's sector or CAI subfield). Since microscopy created a visual resemblance to the helmet of the Egyptian pharaoh Ammon, which consisted of columns of gold coins, this pathology was called "Ammon's horn sclerosis". But at that time this discovery did not arouse much interest, perhaps because epilepsy was considered a mental (and not morphologically determined) disease. Only at the end of the 19th century, Chaslin (1889) in France and Bratz (1889) in Germany expressed the opinion that the identified changes may play a role in the genesis of epilepsy. A little earlier, in 1880, the great English neurologist John Hughlings Jackson suggested that neurons in damaged areas of the brain have abnormally increased excitability. This further defined the concept of " epileptic focus". Bratz in 1899, studying autopsy materials, found that epileptic seizures at an early age may be one of the causes of hippocampal sclerosis. He also showed that sclerosis of the Sommer sector of the hippocampus can be observed not only in epilepsy, but also in other neurological disorders. According to Bratz, the detected changes in the hippocampus were congenital.

So far, ammon's horn sclerosis and its relationship to epilepsy (cause or effect?) has been a hot topic of discussion. The morphology and topography of changes in hippocampal sclerosis were studied in detail by Spielmayer (1927) and Scholz (1951,1954), who attributed the detected changes to the consequences of frequent convulsive seizures. Gastaut and Roger (1955), as well as Norman (1956, 1957), revealed an increased sensitivity to hypoxia in various parts of the hippocampus and amygdala. According to Gastaut, damage to the mediobasal

parts of the temporal lobe were the result of cerebral edema and subsequent compression of the cerebral vessels. According to Gastaut, Sano and Malamud (1953), febrile status epilepticus played an important role in the development of hippocampal sclerosis. Margerson and Corselli (1966) also hypothesized the significance of epileptic seizures in the genesis of hippocampal sclerosis. In subsequent publications, Falconer (1970) and Oxbury (1987) confirmed the relationship between prolonged febrile convulsions and sclerosis of the ammon's horn by means of clinical and pathological studies.

In 1822, Prichard gave a report of epileptic seizures, bearing the character of ambulatory automatisms. Jackson made a great contribution to the history of temporal lobe epilepsy, who in 1889 first described olfactory hallucinations as an epileptic phenomenon, and proved their appearance when the hook of the hippocampus (uncus) was stimulated. Until now, this type of seizure has retained its historical name"Jackson's Uncus Attacks".

In 1937 Gibbs F.A. and Gibbs E.L. with Lennox W.G. proposed the term "psychomotor seizures". And 10 years later, Gibbs and Furster (1948) found that when the epileptic focus was localized in the anterior temporal region, seizures with automatisms were predominantly observed. Therefore, to describe this type of seizure, they used the term "automatic", thereby separating them from other "psychomotor" seizures. Gibbs F.A. and Gibbs E.L. in 1938 they presented a description of specific EEG patterns in temporal lobe epilepsy, and later, in 1951, together with Bailey, they came close to solving the issue of surgical treatment of temporal lobe epilepsy. An EEG recording during "psychomotor" seizures showed that rhythmic slow theta activity quickly spreads beyond the temporal region to the entire hemisphere of the same name with a possible capture of the opposite one. This feature prompted Gastaut in 1958 to designate this type of seizure as "partial seizures with diffuse EEG patterns." Other authors, reflecting the localization of the epileptic focus, used the terms "temporo-frontal seizures", "rhinencephalic seizures". Later

studies using video-EEG monitoring and special methods for testing patients have shown that temporal seizures often cause impaired consciousness. Therefore, the term "complex partial seizures" was introduced, which has been subjected to fierce criticism all the time and was eventually removed from the 2001 Classification Project for Epileptic Seizures.

The term "temporal lobe epilepsy" was proposed in 1941 by the Canadian neurologists Penfíeld and Erickson to describe an epileptic syndrome manifested by seizures with impaired consciousness and automatisms in combination with temporal spikes on the EEG. For the first time, Roger & Roger (1954) became interested in the electroclinical features of temporal lobe epilepsy in children. According to their research, children had simpler automatisms in the structure of an attack and pronounced vegetative symptoms prevailed. However, all the works of that time equated complex partial seizures with temporal seizures, while modern studies have established that some of them are frontal or parietal-occipital, in which the epileptic discharge extends to the mediobasal regions of the temporal lobe.

Despite numerous ongoing studies in the field of temporal lobe epilepsy, there are still no unambiguous answers to the questions: what is the cause of ammon's horn sclerosis? When is it formed? What is the evolution of this pathology?

Anatomical and histological features of the hippocampus

In 1878, Pierce Paul Broca described the region of the central nervous system, located in the medial part of both hemispheres of the large brain and called it the "limbic lobe" (from the Latin "lim-bus" - edge). Later, this structure was named "rhynencephalon", indicating its important role in the sense of smell. In 1937, James Papez proposed another term - "limbic system" - and emphasized the key role of this anatomical substrate in the formation of memory, emotions and behavior (the Peipez circle). The current term "limbic system"

indicates only the anatomical unity of the structures that form it. The central structure of the limbic system is the hippocampus (horn of ammon). Except

Rice. 1. Hippocampus and corpus callosum, top view.

In addition, the limbic system includes the dentate and cingulate gyrus, the entorhinal and septal regions, the gray shirt (indusium griseum), the amygdala (corpus amig-daloideum), the thalamus, and the mastoid bodies (corpus mammillare). In the hippocampus, the head, body, tail, edge, pedicle, and base are distinguished (Fig. 1, 2, 3). Histologically, the following layers are distinguished in the hippocampus (Bogolepova, 1970; Villani et al., 2001):

1. Alveus, contains efferent hippo-campal and subicular axons.

2. Stratum oriens, contains basket cells.

3. Stratum piramidale, contains pyramidal cells, stellate cells and intercalary neurons.

4. Stratum radiatum, consists of apical dendrites of pyramidal cells.

5. Stratum lacunosum, contains perforating fibers.

6. Stratum moleculare, includes a small number of intercalary neurons and a wide branching of the apical dendrites of pyramidal cells.

According to Lorente de No (1934), depending on the location and shape of pyramidal cells, the hippocampus is divided into 4 subfields (subfíelds): CAI (Sommer's sector) - triangular-shaped neurons, multilayered, different sizes; CA2 - densely spaced, large pyramidal cells; SAZ - pyramidal cells located

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less tightly packed and mossy fibers (thin, unmyelinated fibers coming from the granular cells of the dentate gyrus); CA4 - large pyramids -

Rice. 2. Hippocampus and corpus callosum, side view.

nye cells, triangular in shape, scattered between mossy fibers (Fig. 4).

In the dentate gyrus (dentate gyrus) there are 3 layers: molecular layer(long dendrites), granular layer (granular cells), polymorphic or subgranular layer, which contains inhibitory neurons of various sizes.

Pathoanatomy and pathophysiology

Rice. 3. Intraventricular part of the hippocampus: 1. body of the hippocampus, 2. head of the hippocampus, 3. tail of the hippocampus, 4. free edge of the hippocampus, 5. pedicle of the hippocampus, 6. base of the hippocampus (subiculum), 7. corpus callosum (splenium), 8. bird spur (calcar avis), 9-collateral triangle, 10. collateral elevation, 11. hook-shaped pocket (recess) of the temporal horn of the lateral ventricle.

According to the description of many authors, selective death of neurons with secondary astroglial proliferation in the CAI zones (Sommer sector), CAZ, CA4, granular cells of the dentate gyrus and the relative preservation of the pyramidal cells of the CA2 zone are pathognomonic for hippocampal sclerosis, as described by many authors (Bruton, 1987; Gloor, 1991; Babb, 1997). The anatomical manifestation of cellular damage consists in the death of intercalary neurons in the hilum of the hippocampus and pyramidal cells in the Sommer zone, followed by scarring and atrophy. It is assumed that the death of neurons in the hippocampus leads to the reorganization of synaptic connections between the remaining neurons and thus to dysfunction of the inhibitory and excitatory neurotransmitter systems of the hippocampus. Neuronal death, gliosis, axonal and synaptic reorganization are the main pathological links in the formation of MVS. Areas of gliosis in MVS, like neurons, are able to generate action potentials as a result of the content of pathologically altered astrocytes with high density sodium channels. The severity and extent of pyramidal cell death can vary from mild to profound, but the CA2 subfield always remains intact. In many cases, even in the absence of apparent pyramidal cell death in the epileptogenic hippocampus, one can observe selective damage to interneurons containing somatostatin, substance P, and neuropeptide Y.

Often, pathological changes in the hippocampus are bilateral in nature. In some cases, neuronal damage extends to other structures of the limbic system (amygdala, insula, mastoid bodies, thalamus), sometimes involving the lateral cortex and the temporal lobe pole.

It is known that the metabolic state of the thalamus is closely dependent on the state of hippocampal neurons in the same hemisphere. Studies by spectroscopic measurement of excitatory amino acids in the hippocampus with frequent recurrent seizures show involvement in pathological process through neural networks of contralate-

Bulb of posterior cornu Calcar avia

Collateral eminence hippocampi

the oral hippocampus and both thalamus. Damage to the functional connections of the hippocampus, as a result of its sclerosis, can affect the maturation processes.

Rice. 4. Fields of the hippocampus.

brain in children.

In the process of studying the hippocampus in children with resistant temporal lobe epilepsy, the following features were identified (Tuxilugin et al., 1997):

1. In the postnatal period, the number of granular cells continues to grow in the hippocampus, the formation of neurons and axons continues.

2. Epileptic seizures generated outside the hippocampus (cortical dysplasia, postencephalitic changes, etc.) can contribute to a decrease in the number of granule cells and neurons of the ammon's horn.

3. Prolonged epileptic seizures in children, unlike adults, do not always lead to severe damage. nerve cells.

It is known that during an epileptic seizure, an excess amount of the excitatory neurotransmitter, glutamate, is released into the synaptic cleft. The hippocampus is the structure most susceptible to glutamate-induced damage, due to the high density of glutamate receptors, especially in the Sommer area. In the hippocampus, in comparison with other parts of the brain, the system of GAM-Kergic recurrent inhibition is relatively poorly developed, but the system of recurrent excitation of pyramidal neurons is maximally represented. During an epileptic seizure, there is a significant influx

calcium ions into the postsynaptic membrane of pyramidal neurons. An increase in the intracellular content of calcium ions triggers a cascade of reactions that cause the activation of proteases, phospholipases and endonucleases, which, in turn, leads to the release of active and potentially toxic metabolites. Deficiency of the main inhibitory neurotransmitter - GABA - is one of the most important factors leading to cytotoxicity.

The limbic system is characterized by the so-called “kindling” process, in which normal brain structures gradually become epileptogenic. In the process of "ignition", mossy fibers (efferent pathways from the granular cells of the dentate gyrus) undergo axonal and synaptic reorganization - sprouting. As a result, return excitatory connections are formed that participate in the progressive development of hypersynchronous discharges. Such synaptic reorganizations are accompanied by the death of pyramidal cells in the hippocampus. Simultaneously with damage to neurons, axons begin to grow to new target cells. Thus, axons of granular cells of the dentate gyrus (mossy fibers) grow in the direction of the inner molecular layer of the dentate gyrus. Because mossy fibers contain glutamate, disruption of synapse formation can lead to a state of hyperexcitability that triggers excessive discharges. Sloviter (1994) found that the most sensitive to excitation are interneurons (mossy fibers), which form synapses with GABA-containing basket cells. As the mossy fibers die, the basket cells become functionally inactive (“dormant”). Deficiency of the functional activity of the inhibitory system contributes to hyperexcitability and the occurrence of epileptic seizures. Normally, mossy fibers (synonyms - intercalary neurons, efferent pathways of granular cells of the dentate gyrus) perform the function of limiting and protecting against excessive activation of their own targets - the pyramidal cells of the SAZ zone of the hippocampus. Abundance return-

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Excitatory synaptic connections in the pyramidal cells of the SAZ zone of the hippocampus and the ability of individual pyramidal cells of the SAZ zone to trigger an active potential in an explosive pattern, explains their role in epileptogenesis. SAS afferents of pyramidal cells - mossy fibers, perform the so-called "gatekeeper" function, limiting excessive activation of SAS of pyramidal cells and preventing the occurrence of seizure activity. Autoradiography has shown that the granule cells of the dentate gyrus actually serve as a barrier protecting the hippocampus from overactivation. Violation of the barrier function of granular cells leads to excessive activation of the SAZ of pyramidal cells and hyperexcitability of the hippocampus.

Despite the large number of works devoted to the study and description of pathological changes in hippocampal sclerosis, its etiology is still the subject of discussion.

Etiology

Currently, MVS is considered a multifactorial pathology. The main reasons for the development of hippocampal sclerosis according to modern concepts are: atypical febrile convulsions with a high duration of seizures, perinatal ischemia (after the 28th week of gestation), intracranial infections. There is an opinion that in the genesis of hippocampal sclerosis, genetic predisposition, which is illustrated by the study of family cases of mesial temporal lobe epilepsy. Of the etiological factors, one can separately note the impact of various metabolic disorders (congenital hyperinsulinism, beta-oxidation anomalies, etc.), which, causing an energy deficit in the brain tissue, can lead to damage to the most sensitive to hypoxia brain structure - the hippocampus.

Bahl (1997) indicates that the epileptic focus is formed when new pathological recurrent, excitatory synapses are formed in the hippocampus.

instead of the dead normal. Although the epileptogenic potential of hippocampal sclerosis is sufficient to form epilepsy, epilepsy and hippocampal sclerosis may be different symptoms the same pathology underlying them, respectively, the development of temporal lobe epilepsy may not depend on cell death and plasticity of the hippocampus.

There are at least 2 types of MVS, which are based on different etiological factors. The first type always includes a unilateral lesion of the hippocampus with a predominant lesion of the CAI zone, the second type is bilateral, with the spread of pathological changes to the SAZ field and other parts of the temporal lobe.

If earlier the relationship of MTS to mesial temporal lobe epilepsy (cause or effect?) caused great controversy, now modern studies prove the post-attack etiology of hippocampal sclerosis. It is believed that prolonged atypical febrile convulsions, status epilepticus, and even a single short generalized tonic-clonic seizure can lead to the formation of MVS. Experimentally provoked prolonged febrile seizures cause axonal reorganization in the immature hippocampus, which leads to its hyperexcitability. Probably, the frequency of seizures does not play a significant role in the formation of hippocampal sclerosis. So, in many patients with a very high frequency of seizures, requiring even surgical functional uncoupling of the hemispheres, hippocampal sclerosis is not detected. On the other hand, prolonged seizures and status epilepticus can contribute to the formation of structural changes ranging from hippocampal sclerosis to hemispheric atrophy. However, only a long duration of seizures is insufficient for the formation of MVS. So, benign occipital epilepsy with an early onset is often accompanied by prolonged seizures (“ictal syncope”, “comatose-like seizures”), but without any structural damage to the brain. Obviously, there are other factors contributing to the formation of structural changes, which are still

not fully identified.

Some authors put forward a hypothesis about the role of angiogenesis in the etiology of hippocampal sclerosis. According to this theory, the process of neovascularization or angiogenesis takes place in the hippocampus, which is accompanied by neuronal-glial reorganization of the epileptogenic focus. It is possible that angiogenesis is stimulated by frequent repeated attacks. Proliferating capillaries in the epileptogenic hippocampus express erythropoietin receptors that are highly immunoreactive. Angiogenesis is maximally expressed in the region of the greatest neuron death and reactive gliosis - in the CAI, CAZ and hilus (chyle) areas of the dentate gyrus. It is possible that erythropoietin enters the brain by receptor-mediated endocytosis. High content erythropoietin receptors in the hippocampus in mesial temporal lobe epilepsy suggests a possible role for this cytokine in epileptogenesis.

In mediobasal temporal lobe epilepsy with hippocampal sclerosis, a high incidence of neonatal seizures and a history of perinatal brain lesions was established. It is assumed that, most likely, prolonged febrile convulsions cause damage to the hippocampus in the brain with already existing changes. However, it is possible that febrile seizures are preceded by genetically determined structural disorders in the hippocampus, which facilitate the manifestation of febrile seizures and contribute to the formation of hippocampal sclerosis.

Neuroimaging performed on the first day after febrile seizures reveals hippocampal edema, which decreases after a few days, and in some cases turns into hippocampal atrophy. At the same time, not all children with prolonged atypical febrile seizures subsequently develop temporal lobe epilepsy, which indicates the possibility of joint or isolated influence of genetic, vascular, metabolic and immunological factors.

It has been experimentally shown that in animals it is possible to induce epileptiform activity in the hippocampus

temperature, and also that the febrile seizures themselves can come from the hippocampus or amygdala. Febrile convulsions, mainly with a long duration of seizures, cause hypoxic-ischemic, metabolic changes in the brain and lead to the formation of MVS with the subsequent development of temporal lobe epilepsy. It should be noted that only prolonged atypical febrile convulsions play a role in the genesis of MVS and the subsequent formation of temporal lobe epilepsy. Whereas, epilepsy that develops after typical febrile seizures is more often idiopathic. According to different authors, atypical febrile convulsions in history are observed in 20-38% of patients with temporal lobe epilepsy. A time interval of three years or more (average 8-9 years) is required from the onset of atypical febrile convulsions to the formation of temporal lobe epilepsy. Such a long latent period does not yet find sufficient explanations, but it is most likely that this period of time is necessary for the "maturation" of the hippocampal scar and epileptogenesis.

Previously, some authors proposed a perinatal hypothesis of the occurrence of MVS, which has not yet found any confirmation. According to this theory, mesial temporal sclerosis may be the result of pathological childbirth with infringement of the copper-basal parts of the temporal lobe in Bisha's fissure. It was also assumed that hippocampal sclerosis occurs as a result of previous neuroinfections, chronic intoxications, closed craniocerebral injuries, damage to the cervical vertebrae in the neonatal period. The listed pathological conditions in the acute period could cause venous stasis, thrombophlebitis, local diapedetic hemorrhages with subsequent destructive and cicatricial adhesive processes in the brain tissue. Vascular disorders may have contributed chronic ischemia brain, causing hypoxia, sclerosis, wrinkling and atrophy of the mediobasal parts of the temporal lobes.

It is interesting to note that children with MVS often have a "dual pathology" - a combination of hippocampal sclerosis with another intra- or extra-hippo-

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mapal pathology, predominantly cortical dysplasia or less often, neuronal heterotopias, microdysgenesis, gangliogliomas, which suggests a violation of the processes of antenatal brain development in the etiology of MVS. It is possible that the concomitant presence of brain dysgenesis predisposes to more rapid formation of MVS. Clinically, MVS in the structure of "dual pathology" manifests earlier (up to 6 years) than MVS in " pure form”(the beginning of puberty), and epileptic seizures are more “evil” and resistant to therapy.

It was noted that during the first 5 years of life, the number of granule cells in the dentate gyrus of the hippocampus continues to grow. Emerging granule cells express a particular embryonic form of neuronal adhesion protein, and the number of cells expressing this protein increases during the first 5 years of life. This protein indicates the immaturity of granule cells and their postnatal development, proliferation and migration. Since the process of mitosis and migration continues in the postnatal period in the granular cells of the hippocampus, it is possible that sclerosis of the ammon's horn is the result of impaired neuronal migration. This statement is confirmed by the fact that in the studied groups of patients with neuronal heterotopias of the temporal region and hippocampal sclerosis in isolation, identical patterns of cell death in the hippocampus are found. Animals with experimentally induced neuronal migration disorders were more susceptible to damage to the hippocampus.

In recent years, the so-called “destructive epileptic encephalopathy in children” has been described in the literature. school age” (“devastating epileptic encephalopathy in school-age children”) or “pseudoencephalitis”. This pathology debuts with severe prolonged status epilepticus, fever of unknown etiology and leads to bilateral hippocampal atrophy with the development of severe drug-resistant epilepsy with cognitive impairment. In epileptic syndromes such as severe myoclonic epilepsy of infancy and hemiconvulsive seizures, hemiparesis and epilepsy syndrome (HHE - syndrome), manifested by prolonged febrile seizures and status, Ammon's horn sclerosis is also stated (Nabbout et al., in press).

Interesting observations should be noted, according to which, in the etiology of MVS, persistence may be important herpetic infection(herpes virus type 6) in the mediobasal regions of the temporal lobe. It is noted that the herpetic virus in the brain tissue is detected, even in the absence of inflammatory changes. In some cases, the herpes virus causes encephalitis with a characteristic lesion of the temporal lobe and limbic structures. Herpes simplex virus type 1 predominantly underlies herpes encephalitis in children older than 6 months, while herpes simplex virus type 2 is more often a congenital or perinatal infection. As you know, herpetic encephalitis is often found in children, and it is necessary to remember it as one of the causes of hippocampal sclerosis.

RUSSIAN JOURNAL OF CHILDREN'S NEUROLOGY

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The hippocampus is located in the medial parts of the temporal lobe and is like two bent strips of nervous tissue nested into each other: the dentate gyrus and the hippocampus itself (Ammon's horn - cornu Ammonis - CA). The internal structure of the hippocampus is normally shown in Fig. 1. Histologically, the hippocampal cortex belongs to the archicortex, represented by three layers of neurons. The outermost layer of the hippocampus, which forms the medial wall of the temporal horn of the lateral ventricle, is called the alveus (tray) and is formed by axons emerging from the hippocampus. Followed by stratum oriens(represented by axons and interneurons), then a layer of pyramidal cells, which are the basic cellular elements of the hippocampus, and finally the deepest layer - stratum lacunosum And moleculare, represented by dendrites, axons and interneurons (see Fig. 1). Important for understanding the various types of damage to the Ammon's horn in its sclerosis is the division of the pyramidal layer into 4 sectors proposed by Lorente de No (CA1, CA2, CA3 and CA4). The most pronounced layer of pyramidal cells is located in the CA1 sector, which continues into the part of the parahippocampal gyrus, which is called the subiculum (support). The CA4 segment is adjacent to the concave part of the dentate gyrus. The dentate gyrus is a C-shaped structure with three cell layers: an outer molecular layer, a middle granular cell layer, and an inner layer of polymorphic cells that merge with the CA4 sector (see Fig. 1).

Rice. 1. The internal structure of the hippocampus is normal (own histological studies, right side). Subiculum (subiculum) - part of the parahippocampal gyrus, passing into the CA1 sector. The dentate gyrus (highlighted in blue) spans sector CA4 (highlighted in green). a - alveus: 1 - stratum oriens of the hippocampus, 2 - pyramidal layer, 3 - molecular zone of the hippocampus, 4 - molecular layer of the dentate gyrus, 5 - granular layer, 6 - polymorphic layer.

The bottom figure shows the same hippocampus. A layer of pyramidal cells of S.A. sectors is clearly visible. The dentate gyrus (indicated by arrows) covers the CA4 sector, a layer of granular cells is visible. Triangular arrows indicate the deep part of the hippocampal sulcus that separates the SA sectors and the dentate gyrus (own histological studies).

Structural changes in hippocampal sclerosis can vary from minimal, limited to one sector of the SA to gross, extending beyond the medial temporal lobe. The description of pathological changes in the structure of the brain tissue in hippocampal sclerosis is distinguished by an exceptional variety of terms and the presence of several classifications with different concepts describing the same histological substrate.

Histological structure of a sclerosed hippocampus

The macroscopically sclerotic hippocampus is reduced in volume and has a dense texture. Among the main microscopic features are a decrease in the number of pyramidal cells in different layers of the CA and a variable degree of gliosis. In the granular layer of the dentate gyrus, a different degree of decrease in the density of neurons can be noted, although in general its structure is more preserved in comparison with the S.A. sectors. A distinctive histological feature is also that the loss of neurons does not go beyond the SA sectors, which distinguishes hippocampal sclerosis from its atrophy in ischemic injuries and neurodegenerative diseases. It was noted that the loss of neurons in the pyramidal layer of the hippocampus can occur in several ways, which was the basis for the classification of this pathology. The classification of hippocampal sclerosis created by the ILAE commission has received the greatest distribution. Under S.G. Type 1 (pronounced or classic) neuronal loss is observed in all layers of the hippocampus (Fig. 2). The second type is characterized by the loss of neurons mainly in the CA1 sector, and in the 3rd type of SG, only the CA4 sector is affected in the area of ​​transition to the dentate gyrus (the so-called end folium sclerosis). In the literature, along with the term "sclerosis of the hippocampus", a number of definitions are often used, which emphasize that the histological signs of a disturbed structure of the brain tissue may extend beyond the hippocampus.

Rice. 2. Sclerotic hippocampus (right side): the absence of the pyramidal layer in all segments of the CA (type 1 sclerosis according to ILAE classification) is determined. The granular layer of the dentate gyrus is preserved (marked with arrows).

Thus, the term "mesial temporal sclerosis" reflects the fact that, along with the hippocampus, atrophic and gliotic changes are observed in the amygdala and hook. When analyzing histological material obtained during surgery for temporal lobe epilepsy, it became obvious that hippocampal sclerosis is accompanied by pathohistological changes in the lateral neocortex of the temporal lobe. M. Thom proposed the term "temporal sclerosis", which defines the loss of neurons and gliosis in the 2nd and 3rd layers of the temporal cortex. Quite often, heterotopic neurons are detected in the neocortex in the 1st layer of the cortex and white matter, which is referred to as "microdysgenesis". In 2011, the ILAE Commission presented a new classification of focal cortical dysplasia, where a group of FCD type 3a was identified, when hippocampal sclerosis can be combined with dysplasia of the temporal lobe cortex in the form of a violation of its laminar structure, which, in turn, is classified as FCD type 1 type. Microdysgenesis, the role of which in epileptogenesis is not yet known, is referred to the so-called small malformations of the cerebral cortex, and if they are detected with hippocampal sclerosis, the diagnosis is defined as FCD type 3a. As well as type 3a FCD, a combination of temporal sclerosis and hippocampal sclerosis is considered. The concept of “dual pathology” is often found in the literature, when hippocampal sclerosis is combined with a potentially epileptogenic lesion of the neocortex, including outside the temporal lobe, for example, a tumor, vascular malformation, FCD type 2, Rasmussen’s encephalitis, gliotic scar . At the same time, the concept of "dual pathology" does not include type 3a FCD. The terminology becomes even more complex, since the presence of two epileptogenic brain lesions, but without hippocampal sclerosis, is referred to as double pathology.

To understand the connections between different parts of the hippocampus and the pathogenesis of its sclerosis, it is necessary to have an idea of ​​the structure of the polysynaptic intrahippocampal pathway, which starts from the neurons of the 2nd layer of the entorhinal cortex (located in the anterior part of the parahippocampal gyrus and in the region of the hook). The processes of these neurons form a perforating pathway that goes through the subiculum of the parahippocampal gyrus to the dentate gyrus and contacts the dendrites of the cells of the granular layer. The neurons of the granular layer form mossy fibers that innervate the pyramidal neurons CA3 and CA4, which, in turn, contact the CA1 sector through lateral axons, the so-called Shaffer collaterals. Abnormal germination of mossy fibers into the dentate gyrus instead of SA sectors with the formation of excitatory synapses is considered one of the pathogenetic links in S.G. From the above segments of the SA, axons enter the alveus and then into the fornix of the brain through the fimbria of the hippocampus. Taking into account the anatomical and functional relationship between the horn of Ammon, the dentate gyrus, and the subiculum, a number of authors have designated them by the term “hippocampal formation” (Fig. 3).

Rice. 3. Internal connections of the hippocampal formation are normal. Pyramidal neurons of the SA sector (indicated by a red triangle) with their dendrites are in contact with the dendrites of granular cells of the dentate gyrus. 1 - perforant path (indicated by a red line) goes through the subiculum to the molecular layer of the dentate gyrus, where it contacts with the dendrites of granular cells (indicated by a circle); 2 - mossy fibers (indicated by a purple arrow) go to the dendrites of the pyramidal cells of the CA3 and CA4 sectors of the hippocampus. 3 - Schaffer collaterals (marked in green) innervate the apical dendrites of CA1 pyramidal cells.

Causes of hippocampal sclerosis, pathogenesis

The central issue of the etiology of SH is to find out what occurs primarily: a structural pathology of the hippocampus, which "triggers" chronic drug-resistant epilepsy, or vice versa - long-term pathological electrical activity leads to sclerosis over time. It is important to note that a significant part of patients with pharmacoresistant epilepsy associated with SH suffer in early childhood the status of febrile convulsions or other acute CNS pathology (trauma, anoxia, neuroinfection), which was designated in the literature as initial precipitating damage. The acquired nature of SH is also supported by those rare observations when the pathology occurs only in one of the monozygotic twins, and, therefore, the genetic factor is not paramount. However, the presence of hereditary familial forms of temporal lobe epilepsy (for example, a group of epilepsies associated with mutations in the SCN1a and SCN1b genes encoding sodium channel proteins) indicates that a genetic factor also plays a role, causing hippocampal sclerosis without febrile seizures in some of these patients. . Speaking about the acquired nature of the disease, it should also be taken into account that not every type of seizure is associated with the development of SH: autopsy data indicate that long-term uncontrolled epilepsy with frequent generalized seizures does not lead to neuronal loss in the hippocampus, as well as afebrile status epilepticus. On the other hand, febrile status epilepticus is accompanied by MRI signs of hippocampal edema.

The answer to the question of how often the status of febrile convulsions in a child is realized in FH and drug-resistant epilepsy may be given by the prospective FEBSTAT study. It has already been established that out of 226 children after the status of febrile convulsions, 22 had MRI signs of hippocampal edema, most pronounced in the Sommer sector (CA1). Of these 22 patients, repeated MRI at various times was performed in 14, while in 10 cases signs of hippocampal sclerosis were detected. However, out of 226 children, epilepsy was diagnosed in only 16 patients and in most cases was not temporal. Thus, febrile status does not always lead to epilepsy with hippocampal sclerosis, although the time interval between precipitating brain injury and the onset of temporal lobe epilepsy can be more than 10 years, and a follow-up of such a duration has not yet been studied. Genetic studies also suggest that the etiology of FH is heterogeneous. The study of genome-wide associations showed that febrile seizures with hippocampal sclerosis may be a genetic syndrome, since they are associated with the presence of a specific allele of a single nucleotide sequence located next to the SCN1a sodium channel gene. No such association was found for cases of epilepsy with FH without febrile seizures. The consensus opinion of epileptologists is the idea that there is some initial genetic predisposition that is realized in hippocampal sclerosis in the presence of a certain damaging factor (the double whammy hypothesis).

Hippocampal sclerosis has two fundamental pathological characteristics: the first is a sharp decline the number of neurons, the second - hyperexcitability of the remaining nervous tissue. Sprouting of mossy fibers plays one of the key roles in epileptogenesis in SH: abnormal axons of granular cells, instead of innervation of the SA, reinnervate molecular neurons of the dentate gyrus through excitatory synapses, thus creating local electrical circuits capable of synchronizing and generating an epileptic seizure. An increase in the number of astrocytes, gliosis can also play a role in epileptogenesis, since altered astrocytes cannot sufficiently reuptake glutamate and potassium. Pro-inflammatory cytokines such as IL-1β, IL-1, TNFα can also act through the mechanism of increasing the release of glutamate and reducing reuptake, inhibition of gamma-aminobutyric acid. In this regard, the role of herpesvirus type 6, whose DNA is found in the brain tissue of patients with temporal lobe epilepsy, is discussed in the pathogenesis of FH.

Clinic and diagnostics

The case history of epilepsy due to hippocampal sclerosis is described mainly on the basis of numerous studies evaluating the effectiveness of surgical treatment of temporal lobe epilepsy. Often in the anamnesis there is an indication of an acute pathology of the central nervous system suffered in childhood (usually up to 5 years): the status of febrile seizures, neuroinfection, traumatic brain injury. Stereotypical seizures begin between 6 and 16 years of age, and there may be a so-called latent period, which occurs between the initial precipitating damage and the development of the first epileptic seizure. It is also not uncommon for situations where the so-called "silent" period lasts between the first attack and the development of pharmacoresistance. This feature of the course of the disease indicates its progressive nature. A characteristic cognitive deficit in SH may be memory loss, especially in uncontrolled seizures.

Diagnosis of epilepsy due to hippocampal sclerosis is based on three main principles. The first is a detailed analysis of the sequence of symptoms in an epileptic seizure, or semiology, which depends on where in the brain the epileptic activity spreads. The second is the analysis of EEG data and their comparison with the semiology of the attack. And the third is the detection of an epileptogenic lesion on MRI. Speaking about the semiology of an attack in temporal lobe epilepsy associated with SH, it must be remembered that, firstly, each of the symptoms taken separately is not specific, although there is a typical pattern in the course of an attack. Secondly, symptoms during an attack appear when epileptic activity spreads to areas of the brain associated with the hippocampus, which in itself does not give clinical manifestations. The characteristic beginning of a temporal seizure is an aura in the form of an upward sensation in the abdomen. There may also be fear or anxiety if the amygdala is involved at the onset of an attack. At the beginning of the attack, there may be a feeling of "already seen" (déjà vu). Alarming in terms of diagnosis is the aura in the form of dizziness or noise, which may indicate an extrahippocampal onset of an attack. The preserved ability to name objects and speak during an attack is an important lateralizing sign of damage to the non-dominant hemisphere. The change in consciousness is accompanied by a cessation of actions, while the patient has a frozen look with wide eyes (starring). The aura and cessation of actions are followed by oroalimentary automatisms with chewing, smacking lips. Also, dystonia of the contralateral side of the sclerosed hippocampus of the hand often occurs (which is associated with the spread of epiactivity to the basal ganglia) and manual automatisms that appear in this case in the form of sorting objects with the fingers of the ipsilateral hand. Among the lateralizing symptoms, postictal paresis, which indicates involvement of the contralateral hemisphere, and postictal aphasia, when the dominant hemisphere is affected, are important. These symptoms should be considered in the context of the EEG data.

The basis of electroclinical diagnosis in hippocampal sclerosis is video EEG monitoring, which consists in simultaneous video recording of an epileptic seizure and electrical activity of the brain.

VideoEEG monitoring solves several problems:

1. Allows you to exclude pseudo-seizures and non-epileptic paroxysms, including when they are combined with really existing epilepsy.

2. It makes it possible to assess in detail the semiology of an attack and compare it with the dynamics of its epiactivity: its lateralization and regional localization.

3. Long-term recording allows you to find out the lateralization and localization of interictal activity. The most successful option in terms of a favorable outcome of epilepsy surgery is the coincidence of lateralizing and localizing symptoms in an attack with the data of the ictal and interictal EEG and MRI picture. In pre-surgical examination, the duration of video-EEG monitoring is essential. It is known that the probability of registering a paroxysm on a 30-minute EEG with a frequency of attacks once a week is about 1%, and long-term video EEG monitoring with an average duration of 7 days does not reveal interictal activity in 19% of patients. The question of the required duration of videoEEG monitoring is important from the point of view of the mandatory fixation of ictal events on the EEG when determining indications for surgery. A number of epileptologists believe that with a characteristic clinical picture and a history of the disease, a picture of hippocampal sclerosis on MRI, registration of an ictal event is not necessary with more than 90% lateralization of interictal epiactivity in the temporal region on the side of the lesion. In most cases, the resolution of the scalp EEG is sufficient to correctly lateralize the onset of an attack in temporal lobe epilepsy and, in the context of consistent seizure semiology and MRI data, to determine a surgical strategy.

MRI diagnostics of SH is the next fundamental stage of pre-surgical examination. It should be performed according to an epileptological protocol, among the main characteristics of which one can single out a small thickness of sections and a high strength of the magnetic field. The optimal condition for performing MRI is the interaction between the epileptologist and the radiologist, when the planning of the study is carried out taking into account the expected localization of the epileptogenic zone. Hippocampal sclerosis on MRI characteristics: a decrease in the volume of the hippocampus and a violation of the structure of the CA layers, a hyperintense signal in the T2 and FLAIR mode (Fig. 4). Often, atrophic changes are detected in the ipsilateral amygdala, the pole of the temporal lobe, the fornix, and the mamillary body. High-resolution MRI also has the task of detecting another epileptogenic brain pathology located outside the hippocampus, i.e. a dual pathology, such as focal cortical dysplasia. Without this task, an MRI study will not be sufficient to make a decision about the operation, even if it reveals signs of hippocampal sclerosis.

Rice. 4. MRI anatomy of a normal and sclerosed hippocampus. a - T2, coronal section. Sclerosis of the right hippocampus: a decrease in its volume is determined, the absence of an internal structure compared to the left hippocampus; b - the same section with explanations. The red line circles the hippocampus (a decrease in the volume of the right hippocampus is visible), the blue line shows the subiculum on the left. The yellow line in the center of the hippocampus is drawn along the deep part of the hippocampal sulcus (in Fig. "a" in the right hippocampus, this sulcus is not defined). FG - fusiform gyrus, ITG - inferior temporal gyrus; c - coronal section in the FLAIR mode, a decrease in volume and a hyperintense signal from the right hippocampus are visible.

The fundamental point in understanding the electrophysiology of medial temporal lobe epilepsy is the fact that the scalp EEG itself does not detect epiactivity in the hippocampus, which has been demonstrated in numerous studies using intracerebral electrodes. For the appearance of epiactivity in the temporal region on the scalp EEG, it must be spread from the hippocampus to the adjacent cortex of the temporal lobe. At the same time, the main clinical manifestations of an attack in medial temporal epilepsy are associated with the spread of epiactivity to certain parts of the brain associated with the hippocampus: déjà vu is associated with excitation of the entorhinal cortex, a sense of fear - with the amygdala, abdominal aura - with the insula, oroalimentary automatisms - with the insula and frontal operculum, dystonia in the contralateral hand - with the spread of excitation to the ipsilateral basal ganglia. These anatomical and electrophysiological features can cause the patient to have seizures that are very similar to temporal paroxysms, but actually have an extrahippocampal and extratemporal onset.

With the accumulation of experience in the surgical treatment of temporal lobe epilepsy, it became obvious that the removal of the medial structures of the temporal lobe allows you to get rid of seizures completely in 50-90% of patients, however, in some cases, the frequency of seizures does not change at all. Data from studies of the electrical activity of the brain using intracerebral electrodes and an analysis of unsuccessful outcomes of operations have shown that in some cases the reason for the persistence of seizures after removal of the SG is the presence of a larger epileptogenic zone that extends beyond the hippocampus. Parts of the brain anatomically and functionally related to the hippocampus, such as the insula, orbitofrontal cortex, parietal operculum, the junction of the parietal, temporal, and occipital lobes, can generate seizures similar in clinical and EEG pattern to temporal paroxysms. The concept of "temporal lobe plus" has been proposed to describe situations where hippocampal sclerosis exists along with an extratemporal zone of seizure initiation. In this regard, it is important to determine the indications for invasive EEG examination in temporal lobe epilepsy caused by S.G. Warning symptoms are taste aura, aura in the form of vertigo, noise. Interictal epiactivity is more often localized bilaterally in the temporal regions or in the precentral region. Ictal epiactivity in "temporal plus" forms is more often noted in the anterofrontal, temporoparietal and precentral regions. Differential diagnosis of temporal lobe epilepsy from "temporal lobe epilepsy plus" performed by a qualified epileptologist is key in planning surgical intervention and predicting the outcome of treatment.

Treatment of epilepsy associated with hippocampal sclerosis

The standard of care for patients with drug-resistant medial temporal lobe epilepsy is referral to a specialized center for pre-surgical examination and surgical treatment. Among the huge number of publications confirming the effectiveness of temporal lobe epilepsy surgery, it is worth mentioning two key studies with the highest level of evidence. S. Wiebe et al. in 2001, they conducted a randomized controlled trial, which showed that surgery for temporal lobe epilepsy in hippocampal sclerosis allows you to get rid of seizures in 58% of cases, and with drug therapy - only 8%. The basis for another study was the fact that the average duration of illness in patients who received surgical treatment is 22 years, and 10 years or more elapse between the diagnosis of drug-resistant epilepsy and surgical treatment. J. Engel et al. in a multicenter randomized controlled trial showed that the continuation of pharmacotherapy in case of ineffectiveness of two drugs in medial temporal lobe epilepsy is not accompanied by remission of seizures, while surgical treatment in such situations can be effective (in 11 of 15 patients, seizures stop).

Surgery for temporal lobe epilepsy has two obvious goals: 1) relieving the patient of seizures; 2) canceling drug therapy or reducing the dose of the drug. According to the literature, about 20% of patients stop taking anticonvulsants after surgery, 50% remain on monotherapy, and 30% receive polytherapy. The third goal, less obvious, but of fundamental importance, is to reduce the risk of sudden unexplained death in epilepsy (SUDEP - sudden unexplained death in epilepsy), which is associated with a sharp reflex depression of cardiorespiratory function in patients with drug-resistant epileptic seizures.

The task of surgical treatment of temporal lobe epilepsy includes complete removal epileptogenic cerebral cortex with maximum preservation of functional areas of the brain and minimization of neuropsychological deficit. There are two surgical approaches in this regard: temporal lobectomy and selective amygdalohippocampectomy. Both surgeries include removal of the hook, amygdala, and hippocampus. Selective access to the medial temple can be performed through several different approaches. Temporal lobectomy also involves the removal of the lateral neocortex of the temporal lobe (from 3 to 5 cm, depending on the dominance of the hemisphere). Supporters of the selective approach proceed from the fact that the preservation of the lateral neocortex allows minimizing the neuropsychological deficit, in particular, the decrease in verbal memory. On the other hand, as already noted, pathological changes can extend beyond the hippocampus into the amygdala, temporal lobe pole, and lateral neocortex. Invasive EEG studies using deep electrodes have shown that in sclerosis of the hippocampus, in 35% of cases, epiactivity occurs in the pole of the temporal lobe earlier than in the hippocampus. Also, based on the analysis of data from deep electrodes, several types of temporal epilepsy were identified: medial, medial-lateral, temporopolar, and the already mentioned “temporal epilepsy plus”. Thus, when choosing the tactics of surgical treatment, one should take into account the possibility of a larger epileptogenic zone that extends beyond the sclerosed hippocampus, which may determine the greater effectiveness of lobectomy. However, there is currently no class 1 evidence to support the benefit of any technique in terms of seizure control, neuropsychological outcome, or the need for postoperative antiepileptic medication, so the choice of surgery depends on the preference of the surgeon.

Surgery for temporal lobe epilepsy in hippocampal sclerosis, with sufficient experience of the surgeon, has minimal risks of neurological deficit (persistent hemiparesis - less than 1%, complete hemianopsia - 0.4%). The prognosis of the risk of memory impairment after surgery remains an unresolved problem. It is known that after resection of the hippocampus of the speech-dominant hemisphere, about 35% of patients demonstrate worse performance in the neuropsychological assessment of verbal memory. The risk of decreased verbal memory is increased in case of late onset of the disease, high preoperative test scores, dominant hemispheric FH, minimal hippocampal changes on MRI - these circumstances indicate that the epileptogenic hippocampus may retain functional activity. However, it is difficult to determine the extent to which a decrease in verbal memory affects postoperative quality of life. To a greater extent, the patient's quality of life after surgery depends on the careful control of seizures and the elimination of concomitant depressive and anxiety disorders. The determination of indications for surgery in high-risk patients should be carried out with particular care, since if the epileptological outcome is unsuccessful, the patient will also experience a cognitive deficit that drastically reduces the quality of life. In this regard, it should be emphasized that necessary condition organization of surgical care for patients with epilepsy is the formation of a team approach to each clinical case, close interaction between the epileptologist, surgeon, neuroradiologist and neuropsychologist.

There is no conflict of interest.

Mesial and Lateral Temporal Epilepsy - Structural and Genetic Forms of Temporal Epilepsy - Types of Epileptic Seizures - Diagnosis - Treatment - Prognosis - Surgical Treatment

Structural Versus Genetic Forms Temporal Forms of Epilepsy

In structural epilepsy, seizures occur due to physical or metabolic damage to a part of the brain. In the past, this form of epilepsy was also called symptomatic. The most common causes of structural epilepsy are congenital brain anomalies, neuronal migration disorders, arteriovenous malformations, venous angiomas, strokes, tumors, infections, and brain injuries. Temporal lobe epilepsy can begin at almost any age and occurs with equal frequency in both sexes. Genetic and structural forms of epilepsy cause similar types of seizures, however, with a genetic form of temporal lobe epilepsy, MRI should not show significant structural changes in the brain tissue. Genetic temporal lobe epilepsy is usually easier to treat with medication than structural temporal lobe epilepsy. On the other hand, neurosurgical treatment is only possible for structural epilepsy. Surgery aims to remove damaged brain tissues that cause the maintenance of an epileptic focus. Surgery can significantly reduce the incidence epileptic seizures and even lead to long-term or final remission in a significant percentage of cases. Some epileptic syndromes tend to progress if left untreated. An example is hippocampal sclerosis. On the other hand, the individual prognosis for epilepsy is unpredictable. The effectiveness of treatment for focal epilepsy depends on the location and cause of the epileptic focus. Prolonged deterioration in the level of consciousness and cognitive abilities after the end of an epileptic seizure, as well as focal status epilepticus, are characteristic of structural temporal lobe epilepsy, especially if left untreated. The nature of epileptic seizures in temporal lobe epilepsy depends on the location of the epileptic focus - mesial or lateral - rather than on the nature of epilepsy - genetic or structural. An exception may be "ascending epigastric discomfort" - the classic aura of mesial temporal lobe epilepsy caused by hippocampal sclerosis.

Mesial Temporal Lobe Epilepsy with Hippocampal Sclerosis

This is one of the most common types of epilepsy, accounting for about 20% of patients with epilepsy and 65% of those suffering from temporal lobe epilepsy. Eighty percent of patients with mesial temporal lobe epilepsy have hippocampal sclerosis. Febrile seizures in childhood are common and occur in 60% of cases of hippocampal sclerosis, of which 35% are complex febrile seizures. Unusually prolonged febrile seizures are characteristic of temporal lobe epilepsy in the future. The development of hippocampal sclerosis may have a genetic component. Hippocampal sclerosis is the most common cause structural temporal lobe epilepsy. The cause of hippocampal sclerosis remains unknown. There are several hypothesized mechanisms of damage to hippocampal nerve cells: developmental anomalies, an autoimmune mechanism, and damage due to overstimulation resulting from frequent or prolonged epileptic seizures. Studies show that in hippocampal sclerosis, changes in the brain tissue extend beyond the hippocampus.

Symptoms of Structural Mesial Temporal Epilepsy

Ascending Epigastric Discomfort The most typical epileptic phenomenon of the structural form of mesial temporal lobe epilepsy is "ascending epigastric discomfort" in combination with a feeling of fear. Patients describe this sensation as a strange nauseating, emptying, unpleasant sensation that begins in the upper abdomen and gradually moves higher and higher. This specific type of seizure is not typical of the genetic form of mesial temporal lobe epilepsy. automatisms Automatisms are repetitive, stereotypical aimless movements, such as chewing, smacking, fingering, or a movement that mimics picking up small objects with the fingers. Automatisms occur in seventy percent of those suffering from mesial structural epilepsy. Automatisms can be bilateral or limited to one side. Complex Partial Seizures This type of epileptic seizure is a cessation of normal activity. Eyes aimlessly fixed on infinity. At the same time, automatisms are typical. At the time of the seizure, there is no reaction to the environment, as well as there is no awareness of what is happening. Usually, complex partial seizures last from 30 seconds to 2 minutes. They are often confused with absences. Sometimes a seizure can drag on and turn into status epilepticus, i.e. incessant seizure. Other Types of Seizures Phenomena of false perception, such as: deja vu - already seen, jamais vu - never seen, gustatory or olfactory hallucinations, are not typical for mesial temporal lobe epilepsy. Secondary generalized tonic-clonic seizures, usually untreated, and postconvulsive blurred consciousness are typical.

Diagnosis of Mesial Temporal Epilepsy

MRI of the brain demonstrates hippocampal sclerosis. Sometimes, in addition, anomalies in the development of the brain can be detected. Electroencephalography (EEG) shows nothing on the first recording in half of the cases. Only a third of the subjects can detect the classic peak-wave epileptic focus in the temporal lobe. Continuous recording and recording after sleep deprivation increase EEG sensitivity by up to 80%. EEG during a seizure shows rhythmic 4-7 Hz slow wave activity in the temporal lobe.

Prognosis and Treatment of Structural Mesial Temporal Epilepsy

In each case, the forecast is unpredictable. In some patients, the initially good result of treatment with antiepileptic drugs is lost over time, which leads to an increase and aggravation of the severity of epileptic seizures. Severe temporal lobe epilepsy can lead to memory loss, mental decline, and psychological disturbances. However, in most cases, seizures in hippocampal sclerosis can be well controlled for years in most patients. Any of the drugs, or a combination of them, described at the very end of this page can be used in the treatment of structural mesial epilepsy. Carbamazepine, however, is more effective than the others. The choice of drugs is also dictated by age, gender and comorbidities. In the case of uncontrolled structural mesial temporal lobe epilepsy, surgical treatment becomes appropriate. Surgical treatment in 60% of cases leads to complete remission; in 10% - the effect is zero; and in 20% the severity of seizures is reduced to varying degrees. Surgical intervention involves the removal of a significant portion of the temporal lobe. For this reason, surgical complications are not uncommon and account for about 10%. The most frequent are violations of speech, memory and aggravation of the severity of epilepsy.

Structural Lateral Temporal Epilepsy

Lateral localization of structural temporal lobe epilepsy is twice as rare as mesial. The frequency is independent of gender, and the first seizures usually occur in late adolescence.

Symptoms of Structural Lateral Temporal Epilepsy

Hallucinations: various sounds, dizziness, visual hallucinations and illusions, deja vu, jamais vu, etc. Motor convulsions: automatisms in the hand(s), grimacing, twitching in the face, unusual posing in the hand, vocalization, rotation of the body around its axis, speech disturbances. Complex partial seizures or status, as well as generalized seizures, are possible if left untreated. The degree of loss of consciousness is usually less significant than in mesial structural epilepsy.

Diagnosis of Lateral Temporal Epilepsy

Brain MRI shows structural abnormalities in the temporal lobe. EEG between attacks often reveals focal slow wave activity or spikes/sharp waves over the temporal lobe. The EEG at the time of the seizure shows focal 4-7 Hz rhythmic activity or sharp waves over the temporal lobe.

Prognosis and Treatment of Structural Lateral Temporal Epilepsy

The prognosis is largely determined by the cause of the temporal lobe injury and is often unpredictable. Pharmacological treatment is less effective than in the genetic form of temporal lobe epilepsy. Surgery may be a reasonable alternative for severe structural lateral temporal lobe epilepsy.

Inherited Form of Lateral Temporal Epilepsy (Family Autosomal Dominant Lateral Temporal Epilepsy)

Symptoms

Simple auditory hallucinations, such as various noises, ringing, buzzing, clicking, knocking, are the most typical symptom of focal epilepsy that occurs in the lateral part of the temporal lobe. Focal seizures can rarely progress to complex partial seizures or generalized seizures. Seizures that manifest as visual hallucinations, such as various shapes or colors, speech disturbances, dizziness, smelling, are also possible, although not very common. The above symptoms indicate an epileptic focus in the lateral part of the temporal lobe. Seizures are often triggered by sleep. The first seizures usually occur between the ages of 10 and 30. The likelihood of the disease does not depend on gender.

Nature of Inheritance

The name of this type of epilepsy speaks for itself - it is inherited in an autosomal dominant manner and occurs in 80% of gene carriers. The cause is a mutation in the LGI1/Epitempin gene on chromosome 10q.

Diagnostics

MRI of the brain and EEG usually do not reveal any abnormalities. Typical symptoms and normal examination findings support the diagnosis of an inherited form of lateral temporal lobe epilepsy.

Prognosis and Treatment

The epileptic seizures described above in the vast majority of cases are short-lived and not very frequent. When treatment is needed, Carbamazepine is very effective. This form of epilepsy does not cause any other neurological or psychiatric symptoms.

Familial Mesial Temporal Lobe Epilepsy

Symptoms

The mesial part of the temporal lobe is responsible for the formation of memory and for retrieving information from the "storehouse" of memory. For this reason, an epileptic focus in this area of ​​the temporal lobe is capable of producing a whole range of sensations: deja vu, jamais vu; feeling as if someone is behind your back; the illusion of "separation" of the soul from the body; feeling of extreme happiness/pleasure, comprehension of some truth or essence. Something like what the Buddhists call "nirvana." The latter is splendidly described by Dostoevsky in The Idiot. On the other side of the spectrum are fear, the feeling of an impending "end of the world", anxiety, and so on. Due to the proximity of the hypothalamus, nausea, vomiting, pallor, and palpitations may occur. Seizures may also manifest as visual and auditory illusions/hallucinations or incomprehensible, indescribable, difficult-to-localize body sensations. Rarely, focal seizures progress to generalized seizures. The first seizures occur between the ages of 10 and 30 (25 years mean age). Hereditary mesial temporal lobe epilepsy is slightly more common in women.

Nature of Inheritance

Autosomal dominant, manifested in 60% of carriers of the gene. Unlike the lateral form of temporal lobe epilepsy, in hereditary mesial temporal lobe epilepsy, there are many different genetic mutations that can cause the genetic form of mesial temporal lobe epilepsy.

Diagnostics

MRI of the brain is usually unremarkable, however, some patients have foci of altered T2 signal in the temporal lobes. FDG-PET can detect a decrease in metabolic rate in the temporal lobes. The main task of the examination is to distinguish the familial form of mesial temporal lobe epilepsy from hippocampal sclerosis, which, in some cases, can also be hereditary. EEG outside seizures is normal in 50%. The rest have either slow wave or peak-slow wave activity over the temporal lobe - usually on one side. At the time of the seizure, typical epileptic activity is observed over the temporal lobes.

Prognosis and Treatment

The prognosis for mesial familial temporal lobe epilepsy is unpredictable. In some cases, the symptoms are so mild that, without a more severe family history, the patient may not even know they have epilepsy. In a small percentage of cases, severe, difficult-to-treat epilepsy is present. In cases of the most typical familial mesial epilepsy, there are obvious focal epileptic seizures described above, which occasionally generalize into complex partial seizures or generalized convulsions. The antiepileptic drugs, carbamazepine and the other drugs listed at the bottom of the page, are usually very effective. Long-term remissions lasting for years are not uncommon in familial mesial temporal lobe epilepsy, but sooner or later the seizures recur.

Familial Focal Epilepsy with Variable Epileptic Foci

This is a hereditary epileptic syndrome, in which the very fact of focal epilepsy is inherited, but not the localization of the epileptic focus, which is individual for each family member.

Symptoms

Focal epileptic seizures can occur in any part of the cerebral cortex: frontal, temporal, parietal, or occipital. And, although each individual patient has an epileptic focus in a particular place, other family members may have an epileptic focus in a different part of the brain. For this reason, each individual family member suffering from this epileptic syndrome will have their own, individual type of focal epilepsy. The only thing they all have in common is the presence of some variation of focal epilepsy. As with other forms of focal epilepsy, seizures can develop into complex partial or generalized seizures. Most people experience generalized tonic-clonic seizures, at least occasionally. Seizures often occur during sleep. The first seizures may occur between early childhood and 40 years of age. Average age the onset of the disease is 10 years. The probability of the disease does not depend on gender.

Nature of Inheritance

Autosomal dominant inheritance pattern with a 60% chance of epileptic seizures in carriers. A variety of genetic abnormalities on chromosomes 2 and 22 are associated with familial focal epilepsy with variable epileptic foci.

Diagnostics

MRI of the brain should be normal. The EEG may be normal outside of seizures, or it may show local epileptic activity corresponding to the location of the epileptic focus, both at rest and at the time of the seizure. The location of the epileptic focus in each individual remains unchanged. EEG abnormalities may be precipitated by sleep deprivation and may be present in family members without any evidence of epilepsy. The severity of EEG abnormalities has no correlation with epilepsy severity or disease prognosis. Prognosis and Treatment The nature, frequency, duration and severity of epileptic seizures varies both between individual families and between members of each individual family. Treatment with anti-epileptic drugs is usually quite effective.

Treatment of Focal Epileptic Syndromes

In most cases, there is a very decent effect of treatment with Carbamazepine. In cases where carbamazepine is not tolerated, is not effective, or is contraindicated, any other drug or combination of drugs designed to control focal epilepsy may be used. Depending on the nature of the side effects, gender, age, other medical problems, or the presence/planning of pregnancy, the following medicines may be used: Oxcarbazepine, Pregabalin, Gabapentin, Lamotrigine, Levetiracetam, Tiagabine, Topiramate, Vimpat, Zonisamide, Valproic acid preparations. Similar drugs are used in the treatment of structural forms of temporal lobe epilepsy, however, as a general rule, structural forms are less amenable to drug treatment.

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Content copyright 2018. . All rights reserved.
By Andre Strizhak, M.D. Bayview Neurology P.C., 2626 East 14th Street, Ste 204, Brooklyn, NY 11235, USA

Temporal epilepsy is a chronic disease of the central nervous system, namely the brain, one of the types of epilepsy with localization of the pathological focus in the temporal lobe. It is accompanied by convulsive paroxysmal seizures and loss of consciousness. It is the most common form. Pathology is usually associated with a change in the structure of anatomical formations (sclerosis of the hippocampus).

Why temporal lobe epilepsy develops is not precisely established. All the alleged causes of development are divided into two large groups: perinatal, that is, affecting the fetus, and postnatal - factors that disrupt the functioning of the nervous system after the birth of a child.

Perinatal include:

• pathogenic pathogens that have entered the amniotic fluid by the transplant route from the mother (rubella, syphilis, and so on);
• hypoxia or asphyxia of the fetus due to entanglement of the umbilical cord or aspiration of the upper respiratory tract with meconium in late pregnancy;
• spontaneous disturbances in the formation of the nervous tissue of the brain, a violation of the architectonics of the cortex hemispheres;
• Prematurity or postmaturity of the fetus.

Postnatal causes include:

• neuroinfections and inflammation of the membranes of the brain;
• skull trauma and concussion
• growth of benign or malignant neoplasms;
• tissue infarction of the temporal lobe due to impaired blood circulation and tissue trophism, stroke;
• sclerosis, replacement of healthy cells with connective tissue under the influence of Mycobacterium tuberculosis;
• intracerebral hematoma;
• toxic effects of certain medicinal substances used in the wrong dosage, various other chemical compounds;
• metabolic disease;
• malnutrition and vitamin deficiency.

Hereditary predisposition to the development of temporal lobe epilepsy has not been proven.

Such structural changes in tissues, such as, for example, sclerosis of the hippocampus (mesial temporal sclerosis), lead to inadequate excitation of the surrounding cells, which give an unreasonable electrical impulse. An epileptic focus is formed, generating a signal and provoking convulsive seizures.

Classification and symptoms

It is classified according to the localization of the focus into 4 types: amygdala, hippocampal, lateral, insular or opercular. In medical practice, the division has been simplified and doctors divide it into lateral and mediobasal epilepsy.

Lethal epilepsy is less common, auditory, visual hallucinations are observed, the patient speaks incoherently and complains of severe dizziness. Spasm of the motor muscles is not typical, consciousness is lost gently, slowly, the person seems to fall into another reality.

The amygdala usually forms in childhood. She is characterized gastrointestinal disorders, disorders of the autonomic nervous system. Seizures are accompanied by food automatisms, the patient slowly, gradually falls into an unconscious state. In one third of all cases, clonic generalized seizures are observed.

The cause of the hippocampal type is hippocampal sclerosis, which accounts for 80% of cases of all types of temporal lobe epilepsy.

Its feature is hallucinations, illusions, the patient is immersed in a different environment at the level of consciousness. A seizure lasts about two to three minutes on average.

The insular or opercular type is accompanied by twitching of facial muscles, acceleration of the heart rate and an increase in blood pressure, belching and other digestive disorders. Taste hallucinations are possible.

In temporal lobe epilepsy, symptoms can also recur for all subtypes. So common signs are chills, palpitations (arrhythmia), a feeling of inexplicable fear, memory impairment, a change in the menstrual cycle in girls, sharp drops moods ranging from aggression to euphoria.

Diagnostics

The diagnosis is quite difficult to make on the basis of the anamnesis of the disease and complaints. Such patients are treated exclusively by epileptologists, psychiatrists and neurologists. It is almost impossible to diagnose such a pathology in the early stages, because the clinical picture is poor and practically does not impair the quality of life.

From a neurological point of view, no abnormalities are observed on general examination. Changes can be only in the case of tumor growth in the temporal lobe and with heavy bleeding. Then pathological reflexes, instability of gait, manifestations of improper functioning of the seventh and twelfth pairs of cranial nerves may appear.

Laboratory diagnostics is important if a neuroinfection is suspected. In this case, typical signs of inflammation are observed in the general blood test, antibodies to a specific microorganism are determined in the serological examination of plasma, and bacteriological culture provides complete information about the infection and its sensitivity to antibacterial or antiviral agents.

The most informative are instrumental modern methods. So the electroencephalogram shows the epileptic activity of the foci in the temporal lobe of the brain. The etiological factor can be determined on computed or magnetic resonance imaging. It can show hippocampal sclerosis, changes in the architectonics of the cerebral cortex, and other pathologies. Positron emission tomography provides complete information about the decrease in metabolism in a particular area and the violation of its functionality.

Treatment and prognosis

Treatment for temporal lobe epilepsy consists in relieving symptoms, that is, reducing the frequency of seizures, as well as eliminating the cause, if it is completely clear to the specialist. Therapy begins with the appointment of one drug, namely karmabzepin, the dose is selected individually and gradually increased. In severe cases, it is rational to use valproates and, in rare cases, difenin.

Polytherapy is rational only in the absence of effects from previous medications. Then two or three antiepileptic drugs are combined with each other. medicines, but in this case, strict control by a neurologist is necessary, since further violations of the structure of the organs of the central nervous system and a deterioration in the patient's well-being are possible.

In most cases, to eliminate the clinical picture, they resort to surgical intervention. So, extensive sclerosis of the hippocampus is removed or destroyed, a growing tumor that compresses neighboring tissues is resected according to indications, the cortex of the epileptogenic zone is aspirated.

Temporal epilepsy gives a disappointing prognosis, especially in childhood. No experienced doctor can give a full guarantee of the elimination of seizures, since with the help of medications the condition improves only in one third of cases, and with the operation performed - in 60%. Complications appear very often in the postoperative period: incoherence of speech, muscle paresis and paralysis, reading disorders, mental disorders.

Prevention is more aimed at eliminating negative effects on the fetus, reducing the incidence of birth injuries and timely treatment of infectious diseases.