ECHO 25 focal encephalitis and subacute hemichorea.

ECHO virus 25 focal encephalitis was documented for the first time in a 5-year-old boy with unequivocal hemichorea. Hemichorea caused by enterovirus CNS disease has never been reported. ECHO virus antigen in cerebrospinal fluid (CSF) cells was demonstrated by the indirect immunofluorescent technique and typed by a significant rise in neutralizing antibodies against ECHO virus 25. Sequential computerized tomographic (CT) studies with digital analysis demonstrated the evolution of a focal process in the head of the left caudate nucleus, ultimately leading to replacement of tissue by a CSF-containing cyst. In the unclarified pathogenesis of cerebral disease in enterovirus infection, this case suggests a focal inflammatory process rather than vasculitis, occlusion, and infarction. Finally, the near-complete recovery of our patient demonstrated that the mere loss of neostriatal tissue was not decisive in itself, because the tissue loss was permanent and the symptoms were transient.