Rasmussen's syndrome: a study of potential viral etiology.

Rasmussen's syndrome (RS) is a devastating constellation of severe, unilateral focal motor epilepsy resistant to anticonvulsant therapy, followed by ipsilateral neurological deficits and neuropathological evidence of a chronic encephalitis occurring primarily in the pediatric population. Recent reports have identified viral genomic material for cytomegalovirus (CMV) and Epstein-Barr virus (EBV) using in situ hybridization (ISH) in brain tissue of RS patients. We studied 10 biopsy- and resection-specimens from seven patients using biotinylated double-stranded DNA probes to CMV, herpes simplex virus (HSV) and EBV to confirm these results. Two patient samples were also evaluated by electron microscopy and one using standard immunoperoxidase techniques. We were unable to identify any evidence of viral material utilizing one of these techniques. There was some nonspecific localization of crystalline material by in situ hybridization over nuclei, which may account for literature reports of positivity, although one cannot be sure since photomicrographs were not included in these reports. Although the neuropathological morphology of the identifiable lesions in resected specimens is consistent with that seen in other viral encephalitides, our findings fail to support the role of CMV, HSV, or EBV as the etiology and sole factor in the development of Rasmussen's syndrome.