Occult pontine glioma in a patient with hemifacial spasm.

Hemifacial spasm due to an intracranial mass lesion is rare. We describe a 29-year-old man with hemifacial spasm successfully treated with botulinum A toxin injections for 2 years. The development of acquired diplopia secondary to acquired sixth cranial nerve palsy prompted investigation. Computed tomography done at the time of original diagnosis and on three other occasions (concentrating on the brain stem and cerebellopontine angle) failed to demonstrate an intracranial mass lesion. Magnetic resonance imaging (MRI) showed a large mass lesion in the pons presumed to be a glioma. Patients with hemifacial spasm who have atypical features, especially those with associated neurologic findings, should be screened for tumours. Our case illustrates the superiority of MRI in demonstrating pontine gliomas causing hemifacial spasm.