A 2 year old boy who developed varicella encephalitis with cerebellar ataxia 16 days before the appearance of the exanthem is reported from the Department of Neurology, Children’s Hospital, Harvard Medical School, Boston, MA. The child was previously healthy, but had been exposed to his 5 year old brother who had developed varicella 4 days previously. The serum varicella-zoster IgG was absent on admission and 69.6 ELISA units/ml 5 weeks later. 
COMMENT. Pre-eruptive neurologic complications of varicella are rare but the diagnosis should be considered in children presenting with cerebella ataxia. The authors kindly cite a reference to my own experience at the Mayo Clinic and a report of a 5 year old boy presenting with symptoms and signs of intracranial hypertension and cerebellar ataxia which antedated the exanthema by 11 days . In our patient the fundoscopic examination disclosed bilateral papilledema and a right sixth nerve palsy that led to ventriculography to exclude a space occupying lesion. In 15 previous reports of pre-eruptive neurologic complications of varicella, cerebellar ataxia was mentioned only in 1.