Acquired pendular nystagmus in multiple sclerosis: clinical observations and the role of optic neuropathy.

Thirty seven patients with pendular nystagmus due to multiple sclerosis were reviewed. Most developed nystagmus later in a progressive phase of the disease. All had cerebellar signs on examination and evidence of optic neuropathy. MRI in eight patients showed cerebellar or brainstem lesions in seven; the most consistent finding was a lesion in the dorsal pontine tegmentum. Dissociated nystagmus was seen in 18 patients: in these the signs of optic neuropathy were often asymmetric and the severity correlated closely with the side with larger oscillations. This suggests that dissociations in acquired pendular nystagmus may be due to asymmetries in optic neuropathy rather than asymmetries in cerebellar or brainstem disease.