Horizontal saccadic palsy associated with gliosis of the brainstem midline.

We studied premotor cell groups involved in the generation of saccades in a patient with a disturbance of voluntary horizontal gaze. The only neurological symptom found was a slowing of horizontal saccades, reported since birth and unaltered over his lifetime. We attribute this disorder, for the first time, to a fibrous gliosis of the brainstem midline, which may disrupt neuronal elements of the horizontal saccade generator crossing the brainstem midline, but it caused no obvious loss of omnipause-, excitatory burst-, and inhibitory burst neurons. No neuronal loss or demyelination, was apparent elsewhere in the brainstem; but there was evidence of an ependymal infection throughout the entire ventricular system. A diagnosis of Gaucher disease was made from the bone marrow of this patient shortly before his death, but for several reasons we considered this complication unlikely to be the cause of the saccadic disorder.