This immune-mediated epilepsy syndrome is characterized by the onset of intractable focal seizures (mainly focal motor, commonly epilepsia partialis continua) together with progressive neurological (hemiparesis) deterioration in a previously normal child. Progressive cognitive impairment may also develop. On imaging, progressive hemiatrophy (of the side contralateral to the hemiparesis) occurs over time. Pathology of brain tissue shows changes of chronic encephalitis; the exact pathophysiology of is unknown (previous studies implicating certain viruses have not been replicated), however there is sufficient evidence to support an autoimmune basis.
This syndrome is associated with onset of seizures between 1-10 years of age (peak 5-6 years), later onset is exceptional. Both sexes are affected equally. Antecedent and birth history is usually normal. Head size and neurological examination are usually normal prior to onset of the syndrome. With time, a progressive hemiparesis develops. Some children may first present with a unilateral movement disorder (hemidystonia, hemiathetosis) prior to onset of seizures. Iritis has been reported as an antecedent condition. CSF may show non-specific findings including the presence of oligo- or monoclonal bands. Medical treatment is targeted at both seizures (anti-seizure medications) and the underlying process (immunosuppression), ultimately most cases require hemi-disconnection surgery to eliminate seizures. The timing of such surgery is considered on a case-by-case basis and may depend on the rate of progression and the cognitive impact of frequent seizures.
There are three stages to the illness i) an initial prodromal phase with infrequent seizures and no hemiparesis ii) an acute phase with frequent seizures and development of hemiparesis and iii) a residual stage with permanent stable hemiparesis.