When a child, previously well, rapidly develops ataxia one's inclination—and proberly so—is to suspect a posterior fossa tumor. However, we wish to direct attention to a syndrome of acute cerebellar ataxia which, as a rule, carries an excellent prognosis. It is characterized by the abrupt occurrence of ataxia, particularly of the trunk and lower extremities; little if any fever; minimal evidences of systemic illness, and practically invariable subsidence of all signs of nervous system disorder in a matter of days to weeks. In general the cerebrospinal fluid is normal, although on some occasions there is a moderate pleocytosis and elevation of protein. Frequently headache, vomiting, irritability, or listlessness precede the ataxia by a few days or may accompany its onset. On the other hand, the ataxia may suddenly make itself evident in an otherwise apparently well child.
This condition is not rare, there having been about 60 cases reported in