While brain stem involvement in multiple sclerosis (MS) is relatively common, isolated cranial nerve palsies are rare, especially when they represent the initial presenting sign of a new diagnosis of MS. This report describes a patient with no prior history of MS whose sole presenting sign was an isolated abducens palsy. An enhancing pontine lesion was found on MRI which correlated with his abducens palsy, and additional nonactive lesions on MRI led to a diagnosis of MS. This case demonstrates the importance of considering MS as part of the differential diagnosis of patients with isolated cranial nerve palsies.
Keywords: Abducens palsy; Brain stem; Cranial nerve; MRI; Multiple sclerosis.