A potentially fatal neurological disease with characteristics of neuropathological lesions principally involving the brainstem, thalamus and putamen. It has been described in 11 members of one family. Onset occurs during early childhood, typically a few days after a febrile illness. Manifestations include vomiting, seizures, spasticity, language regression, rigidity and abnormal posturing of the head. Residual neurologic impairment (muscle weakness, speech disturbance, intellectual deficit and mood disorders) persists in some patients. The disease is chronic in one out of two cases. The mode of transmission appears to be autosomal dominant with incomplete penetrance.