Positional vertigo and nystagmus of central origin.

Four cases are described illustrating the clinical features of positional vertigo and nystagmus due to posterior fossa tumors and a case of obstructive hydrocephalus. In these cases positional vertigo was the first and only presenting symptom of central nervous system disease. One case of subependymoma of the fourth ventricle and one with hydrocephalus had characteristic symptoms of benign positional vertigo; each showed positional nystagmus of the benign paroxysmal type.