Positional nystagmus of the persistent type.

In a 6-year period (1970-1975), a total number of 10,730 patients were examined oto-neurologically by the same physician, all of the patients being referred from the neuromedical and neurosurgical departments. Persistent positional nystagmus is in this material the same as central positional nystagmus, because the lesion in all cases was of central origin. Central positional nystagmus was found to be a rare symptom, since it was only demonstrated in 124 patients (1%). Central positional nystagmus was defined as being with no latency, low and irregular frequency, nonfatiguable with no accompanying dizziness, and the patients examined in the following positions: right and left side, supine and with hanging head. In 52 cases (42%) the nystagmus was only demonstrated with hanging head. The diagnoses were dominated by intracranial tumors (34 infra-tentorial, 19 supratentorial). Among other diagnoses encountered were intracranial vascular disease, encephalopathia, epilepsy and multiple sclerosis. 21 patients were children under 15 years of age, and in this group the intracranial tumors, especially the infratentorial, were even more dominant.