Acute Hemicerebellitis with Obstructive Hydrocephalus in a Young Adult

BACKGROUND: Acute cerebellitis is a rare entity, described in the pediatric population, usually of viral or autoimmune origin, bilateral and symmetric, and with good prognosis. Only 13 cases of unilateral cerebellitis have been reported thus far. To the best of our knowledge, this is the first case of hemicerebellitis in the literature reported in a young adult that caused acute hydrocephalus requiring surgical treatment. CASE DESCRIPTION: We report an unusual case of an 18-year-old man, without previous infectious symptoms, who developed acute obstructive hydrocephalus secondary to hemicerebellitis. A ventricular drainage was placed. The affected cerebellar hemisphere was later explored and biopsied, and edematous tissue, with an inflammatory reaction of the leptomeninges, was obtained. With corticosteroids and antivirals, the neurologic symptoms disappeared and the MRI evolved to normal in 2 week's time. CONCLUSIONS: Hemicerebellitis must be considered in the differential diagnosis of cerebellar mass lesions, even in young adults. Although rare, clinically significant hydrocephalus may develop. Despite the availability of MRI, a high index of suspicion is still required to accurately diagnose this entity. The histologic substrate seems to be localized meningitis. The edematous reaction of the cerebellar parenchyma supports the usefulness of corticoids in the treatment strategy of this disease.