Oculomotor and vestibular anomalies in Pelizaeus-Merzbacher disease: a study on a kindred with 2 affected and 3 normal males, 3 obligate and 8 possible carriers.

Two males suffering from Pelizaeus-Merzbacher disease were examined, one at the age of 1 year 4 months and at the age of 7 years, and the other at the age of 7 years 8 months. The former had spontaneous vertical pendular nystagmus. He also showed horizontal "micronystagmus", present only at the age of 1 year, which might be similar to "voluntary nystagmus". Both males had jerky bilateral gaze-evoked nystagmus, defective smooth pursuit and optokinetic responses and a hyporeactive vestibulo-ocular reflex (VOR). All three obligate carriers exhibited typical VOR disinhibition in the two horizontal nystagmus directions, which may be a distinctive feature. This feature was also found in one of the 7 possible carriers examined and was not observed in the 3 non-affected males, who had normal oculomotor responses.