Rasmussen’s encephalitis is a progressive encephalitis affecting only one hemisphere of the brain and having a chronic course. Clinically, it is a combination of Kozhevnik’s epilepsy, cognitive decline and focal sensorimotor deficiency. During the diagnosis, the data of anamnesis, neurological examination, EEG, perimetry, tomographic studies of the brain are compared. Therapy includes antiepileptic, glucocorticosteroid, immunomodulatory or immunosuppressive components. Surgical treatment is possible, the purpose of which is to “turn off” the affected hemisphere from the functioning of the central nervous system.
ICD 10
G04.8 Other encephalitis, myelitis and encephalomyelitis
General information
Rasmussen’s encephalitis is a progressive focal encephalitis with a chronic course, characterized by the presence of Kozhevnik’s epilepsy, focal sensorimotor neurological deficit and cognitive disorders. Detailed information about it was first provided to the medical community in 1958 by the American doctor T. Rasmussen. Rasmussen’s encephalitis has been isolated as a separate nosological unit relatively recently. The disease is extremely rare. Rasmussen himself has observed only 51 cases of such encephalitis for 35 years.
Only children are susceptible to the disease. About 85% of cases are under the age of 10. The peak incidence falls on the age period from 5 to 8 years. Single variants, when Rasmussen’s encephalitis debuts before the age of 1 or after the age of 14, are considered atypical. The onset of encephalitis after an infectious disease (more often ARI) is characteristic. The literature on neurology indicates cases when Rasmussen’s encephalitis was combined with progressive facial hemiatrophy.
Causes
Currently, etiopathogenesis is not established. 2 variants are considered as hypotheses: viral etiology and autoimmune genesis of the disease.
- Adherents of the viral hypothesis consider Rasmussen’s encephalitis to be a slow-flowing viral neuroinfection and, accordingly, refer it to viral encephalitis. The viral theory is supported by the changes detected during histological examination of the affected cerebral tissues (perivascular infiltrates, small-focal gliosis, microglia proliferation). However, all attempts to isolate the pathogen have so far been unsuccessful.
- In favor of the autoimmune theory is evidenced by studies in 2002, which revealed antibodies to the glutamate receptor, as a result of which the opening of ion channels and the excitation of neurons occurs. At the same time, excitotoxicity (damage to nerve cells under the action of excitatory neurotransmitters) causes the death of astrocytes and neurons. In addition, patients with Rasmussen encephalitis have a high incidence of HLA antigens. Probably, the susceptibility of neurons to the above pathological changes is due to immunogenetic factors.
Pathomorphology
Morphologically, Rasmussen’s encephalitis is characterized by the focal nature of the changes that occur. Pathological processes extend to one lobe or one hemisphere of the brain. In some cases, with the early onset of the disease, there is a bilateral nature of morphological changes, but the primary lesion is always detected. Variants with the spread of the pathological process to the second hemisphere of the brain are prognostically unfavorable and often lead to the death of patients.
Symptoms
The basic symptom complex is Kozhevnikovskaya epilepsy — a combination of partial convulsive seizures with myoclonia. The most common are simple (without loss of consciousness) motor focal seizures localized in the face or one of the limbs. They can be clonic or tonic in nature. Secondary generalization of paroxysms with the transition to a clonic-tonic generalized epiprime is possible. Myoclonia — focal muscle twitching — are almost permanent. At the beginning of the disease, they may be absent, appear after a few months or occur together with a focal neurological deficit 1.5-2.5 years after the debut of epiprimes.
Focal symptoms are mainly represented by central hemiparesis, contralateral to the affected hemisphere. There are sensory disorders of the conductor type, hemianopia, aphasia (with disorders in the dominant hemisphere). Cognitive disorders accompanying Rasmussen’s encephalitis are reduced to progressive disorders of memory, attention, and praxis and lead to the development of oligophrenia. Combined with mental disorders.
Stages of Rasmussen’s encephalitis
- The prodromal period may last several years. In 70% of patients, it is characterized by the occurrence of simple focal convulsive paroxysms of the motor type. In 20% of cases, Rasmussen’s encephalitis manifests as an epileptic status. The development of secondary generalized epiprimes is possible. In the initial period, the frequency of paroxysms is usually small; in the future, its significant increase is observed. Already in the debut of encephalitis, the appearance of Todd’s paralysis is possible — a transient paresis that occurs in the extremities following the convulsive contractions that occur in them during the epiprime.
- The active period is marked by the addition of focal neurological symptoms (hemiparesis, hemianopsia, hemihypesthesia, speech disorders), mnestic disorders and almost constant myoclonia. At this stage, 80% of patients have simple focal motor paroxysms, 28% have complex focal seizures, 40% have secondary generalized seizures, and 23% have somatosensory seizures. Epileptic hemiprimes of the Jackson epilepsy type, affecting the muscles of one half of the trunk, according to some authors, occur only in 10% of cases. The period of duration of motor deficiency in Todd’s paralysis gradually increases, then permanent hemiparesis is noted, which eventually takes on a persistent character.
- The stabilization period in most patients (about 80%) occurs no more than 3 years after the time of encephalitis manifestation. There is a stabilization and even a slight decrease in the frequency of seizures. However, against this background, sensorimotor, visual and cognitive impairments continue to progress. A quarter of patients are diagnosed with neuroendocrine disorders: premature puberty, obesity.
Diagnostics
In the prodromal period, due to the absence of focal symptoms, it is very difficult to make an accurate diagnosis. In the active stage, the neurologist during the examination reveals the presence of central hemiparesis with increased reflexes and pyramidal signs, constant myoclonic contractions, speech disorders, increased mental exhaustion, decreased memory and attention, etc. violations.
- Electroencephalography. In the active period, it detects violations in all patients. There is a slowdown in the main rhythm, the complete absence of an alpha rhythm is possible. Peak wave activity is observed in the affected hemisphere.
- Ophthalmological diagnostics. The definition of visual fields reveals hemianopia, with ophthalmoscopy, changes in the fundus are often absent.
- Laboratory diagnostics. The study of cerebrospinal fluid is carried out in order to exclude other clinically similar pathology of the central nervous system.
- Tomography. Of paramount importance in the diagnosis is the conduct of CT or MRI of the brain in dynamics. The pathognomonic tomographic sign characterizing Rasmussen’s encephalitis is progressive cerebral hemiatrophy. As a rule, the expansion of the sylvian fissure, which increases over time, is first recorded, then atrophic changes in the convexital parts of the cerebral cortex are noted. When observed in dynamics, an increase in the zone of cortical atrophy is typical, like the spreading of an oil stain on parchment.
Differential diagnosis is carried out with:
- intracerebral tumors;
- cerebral cysts;
- encephalitis of other etiology;
- other types of epilepsy in children (Lennox-Gastaut syndrome, Landau-Kleffner syndrome, focal cortical dysplasia);
- leukodystrophy;
- Schilder’s leukoencephalitis and others.
Treatment
Conservative therapy includes antiepileptic treatment and attempts at pathogenetic therapy aimed at slowing the progression of atrophic changes in the brain. The epileptic seizures accompanying Rasmussen’s encephalitis are resistant forms of epilepsy.
Conservative therapy
Anticonvulsant therapy usually begins with the appointment of valproates. The drugs of choice are also topiramate, levetiracetam and phenobarbital. The resistance of paroxysms forces doctors to switch to combination therapy. Combinations of valproates with topiramate or levetiracetam, topiramate with levetiracetam are recommended. In some patients, the combination of valproates with carbamazepine is effective, although the latter is contraindicated as monotherapy due to the aggravation of myoclonic manifestations. Some authors point to the temporary anticonvulsive effect of intravenous infusions of large doses of nootropil.
There is no consensus on the methods of pathogenetic therapy yet. Immunosuppressive and immunomodulatory treatment, the appointment of antiviral pharmaceuticals and glucocorticosteroids are used. Recently, immunoglobulin therapy has been increasingly used as a starting treatment. As the symptoms progress, corticosteroids (dexamethasone, methylprednisolone) are added to them. In the absence of a positive result of such therapy, they switch to immunosuppression using azathioprine or cyclophosphane. There is no unambiguous data on the effectiveness of antiviral treatment using zidovudine, acyclovir, interferon yet. It is possible to carry out plasmapheresis, immunosorption.
Surgical tactics
Surgical treatment in the early stages of encephalitis makes it possible to achieve stable remission in 23-52% of patients. It is performed by neurosurgeons and consists of functional or anatomical hemispherectomy. In the first case, the affected hemisphere is “turned off” by crossing all its connections, in the second — surgical removal of the hemisphere or part of it.
Forecast
In most cases, Rasmussen’s encephalitis has a disappointing prognosis. With the exception of isolated cases of spontaneous stabilization of the disease, patients have severe motor and cognitive deficits. The fatal outcome can occur in the period from 3 to 15 years from the time of the onset of encephalitis.