Kozhevnikov epilepsy is a separate clinical form of epilepsy characterized by the occurrence of simple partial seizures against the background of permanent local clonic seizures (myoclonia). It is most often found in tick-borne encephalitis. In the clinical picture, in addition to convulsive syndrome, hemiparesis and emotional and mental disorders are observed. Diagnostic search is carried out according to clinical symptoms, anamnesis, EEG, PET, CT or MRI of the brain. Treatment is aimed at eliminating causal pathology and combating epilepsy.
ICD 10
G40.1 Localized (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures
General information
Kozhevnikov epilepsy is a separate clinical variant of epilepsy, characterized by a combination of constant focal clonic muscle contractions and simple (not accompanied by loss of consciousness) focal epileptic paroxysms, periodically passing into a secondary generalized epilepsy. For the first time this form of epilepsy was described by A. Ya. Kozhevnikov in 1894. In addition to the eponymous name, the term “permanent partial epilepsy” is used in clinical neurology. By its type, Kozhevnik’s epilepsy is cortical, the nature of its attacks indicates a lesion of the motor (motor) zone of the cerebral cortex. In this regard, the term “cortical limited epilepsy” is also applied to it. Kozhevnikov epilepsy is not a separate nosology, but acts as a clinical symptom complex of CNS lesions of various etiologies. It is most common in childhood and in adolescents. According to some data, about 66% of cases of the disease occur in the age period up to 20 years. Kozhevnikov epilepsy in people over 40 years of age refers to casuistic cases.
Causes
The morphological substrate of Kozhevnikov epilepsy is changes in 3-5 layers of the cerebral cortex of the precentral gyrus, responsible for the generation of motor impulses, then coming to the motor neurons of the spinal cord and from them along the peripheral nerve trunks to the muscles. Clinical manifestations are associated with an increase in the excitability of neurons in a certain area of the precentral gyrus cortex and the formation of a focus of constant epileptogenic activity. It is assumed that there are structural and functional changes not only in the cortex, but also in the corresponding subcortical structures and spinal motor neurons, with the formation of a regional epileptogenic system.
The factors causing these changes may be various pathological processes. Kozhevnik’s epilepsy is most often found in tick-borne encephalitis and Rasmussen’s encephalitis. It can be observed in other infectious brain lesions (for example, cerebral cysticercosis, neurosyphilis, tuberculous meningoencephalitis), focal cortical dysplasia, brain tumors, arteriovenous malformations, stroke, dysmetabolic disorders (for example, diabetes mellitus), etc. In some cases, Kozhevnik’s epilepsy is a consequence of a traumatic brain injury.
Symptoms
In some patients, Kozhevnik’s epilepsy is observed in the acute period of tick-borne encephalitis, but more often it develops after 1-6 months from the time of its debut. In Rasmussen’s encephalitis, the myoclonic component rarely manifests itself in the prodromal stage, more often a detailed picture of Kozhevnikov epilepsy is observed in the active period (after 1-2.5 years from the manifestation of encephalitis).
Simple focal motor epiprimes, as a rule, occur in the form of clonic contractions of the muscles of one half of the face or one arm (more often only the hand). Simultaneous involvement of the hand and face may be observed. Paroxysms with clonic convulsions in the leg are less common, and even rarer — with the involvement of the entire half of the body (hemiconvulsive seizures). Seizures occur in the opposite half of the body to the epileptogenic focus, i.e. contralateral. Often, before their appearance, patients feel burning, numbness or tingling in the convulsive area.
A locally initiated epiprime may have secondary generalization, when convulsions spread to all muscle groups and are accompanied by loss of consciousness. However, in most cases, such secondary generalized paroxysms are observed quite rarely. In some cases, along with these types of epiprimes, there are psychosensory or psychomotor paroxysms occurring against the background of disturbed consciousness.
Permanent clonic contractions, which are accompanied by Kozhevnik’s epilepsy, are referred to by American authors as myoclonic phenomena. However, they differ from contractions in myoclonus epilepsy by a greater amplitude, leading to the occurrence of violent motor acts of the clonic type. Despite its asynchronous nature, due to the constant localization in the same muscle groups, such myoclonic/clonic contractions cause the stereotype of the resulting hyperkinesis. They can be of a local or multi-stage type, i.e. affect the muscles of one anatomical area (face, hand, foot) or several at once (both face and hands). Clonic muscle contractions are constantly present in the patient, do not pass even during sleep.
In addition to epileptic paroxysms and constant clonic phenomena, Kozhevnik’s epilepsy is accompanied by a focal neurological deficit in the form of paresis of the muscles of the extremities opposite to the focus of cerebral lesion. Paresis has a central character and is accompanied by tendon hyperreflexia. Often, after an epileptic paroxysm, the severity of paresis temporarily increases. Intellectual decline and disorders of the psycho-emotional sphere are often observed (depression, phobic disorders, aggressiveness), psychopathic symptoms may be noted.
Diagnostics
The diagnosis is based on a typical clinical symptom complex, including simple partial motor paroxysms, permanent focal myoclonia and hemiparesis. It is important to collect anamnesis in order to identify the cause of the disease, especially data on tick-borne encephalitis suffered in the last six months. Electroencephalography registers epileptiform discharges localized in the contralateral region of the central sulcus of the brain.
Additional examinations of the patient are aimed at diagnosing the causal disease and may include a biochemical blood test, determination of blood sugar, examination of cerebrospinal fluid, RPR test, etc. In order to exclude intracranial volume formation, CT, MSCT or MRI of the brain is mandatory. The latter is preferable in children, since it does not carry a radiation load. Localization of the affected area is also possible using positron emission tomography.
Treatment and prognosis
Therapy consists of the treatment of the underlying disease and the relief of convulsive syndrome. It is carried out by a neurologist in close cooperation with an epileptologist and, if necessary, with a psychiatrist. When tick-borne encephalitis, tuberculosis, syphilis, etc. are detected, appropriate etiotropic therapy is carried out. The diagnosis of a tumor is a reason to consult a neurosurgeon in order to resolve the issue of its surgical removal. With Rasmussen’s encephalitis, immunoglobulins and glucocorticosteroids are treated.
A distinctive feature of Kozhevnikov epilepsy is its resistance to anticonvulsant treatment. In this regard, after starting monotherapy with valproates, levetiracetam, topiramate or clonazepam, as a rule, polytherapy is prescribed with an individual selection of various combinations of these drugs. It is also possible to prescribe carbamazepine in combination with valproates. In severe cases, surgical treatment of epilepsy is indicated: focal resection of the zone of epileptogenic impulsivity, thalamotomy.
The stable course of epilepsy is most often observed. There may be a progressive course with an increase in the frequency of epiprimes, an increase in the prevalence of myoclonia, an aggravation of neurological and cognitive deficits; a remitting course with the presence of periods of relative remission of varying duration. The reverse development of symptoms is unlikely. No more than a quarter of patients show some improvement against the background of ongoing therapy.