Acute cerebellitis presenting as tonsillar herniation and hydrocephalus.

Acute cerebellitis is a rare inflammatory syndrome, often characterized by cerebellar dysfunction of rapid onset. We describe two children, a girl aged 5 years and a boy aged 11 years, with acute cerebellitis. Both manifested tonsillar herniation and hydrocephalus. The cause was Mycoplasma pneumoniae infection in the first patient, and unknown in the second. The girl was treated conservatively with steroids and diuretics, as well as vibramycin, and the boy required insertion of a ventriculostomy. Both presented a good prognosis and full recovery.