Isolated abducens palsies due to pontine lesions

Abstract

Thirty-seven patients with isolated abducens palsies and additional electro-oculographic (EOG) and/or blink reflex (BR) abnormalities indicating pontine lesions were observed over a 12-year period. The lesions were attributed to vertebrobasilar disease (17 patients), multiple sclerosis (12 patients), undiagnosed inflammatory disease (2 patients), pontine tumor (1 patient), and pontine hematoma (1 patient). In the remaining four patients, no specific cause was found. Main EOG abnormalities were slowed abduction or adduction saccades on the opposite eye (14 and 5 patients, respectively), saccadic pursuit eye movements (12 patients), and ipsilateral canal paresis (6 patients). BR-R 1 abnormalities were seen in four patients, ipsilateral in three, and contralateral in one. Recovery of the abducens palsy was almost always (in 35 patients) associated with recovery of at least one electrophysiologic abnormality, which strongly indicated that both were caused by the same actual lesion. MRI was conducted in 32 patients and disclosed lesions involving the region of the intrapontine abducens nerve in seven (inflammation: 4 patients; infarction, tumor and hematoma: 1 patient each). Abducens palsies are rarely the only clinical sign of pontine disease, but their frequency is underestimated, if based on MRI proven lesions only.