Diagnosing multiple sclerosis: expect the unexpected

Abstract

A previously healthy 41-year-old Hong Kong Chinese man, who emigrated to the UK at the age of 20 years, presented with a complaint of visual blurring and of painless double vision but without directional selectivity. Ophthalmological assessment found normal visual acuity, colour vision, visual fields, and pupillary reactions; examining eye movements there was a left hypertropia, with weak left inferior rectus on Hess chart. A diagnosis of acute partial pupil-sparing left oculomotor (third) nerve palsy was made. Symptoms resolved spontaneously within 2 weeks, but magnetic resonance brain imaging arranged at the initial consultation showed multiple high signal intensity lesions in the white matter of the cerebral hemispheres periventricularly and in the corpus callosum, suggestive of demyelination, although no brainstem lesions were noted. When subsequently seen in the neurology clinic, the patient was asymptomatic and there were no neurological or neuro-ophthalmological signs. Serum angiotensinconverting enzyme level and chest X-ray were both normal. Interval magnetic resonance brain imaging 7 months later showed no new changes, and since the patient was asymptomatic he declined further investigation or follow up. Five years later, the patient presented again with a complaint of double vision without directional selectivity. Signs were now of a right abducens (sixth) nerve palsy, without any other neurological or neuro-ophthalmological signs. Symptoms resolved spontaneously after 4 months. Magnetic resonance brain imaging again showed multiple high signal lesions in the periventricular white matter and corpus callosum, but no brainstem or cerebellar lesions were seen. Pattern shift visual evoked potentials were within normal limits, providing no evidence for a demyelinating optic neuropathy. The patient agreed to lumbar puncture, and CSF analysis showed normal protein, glucose, cell count, angiotensin-converting enzyme level, and cytology, but oligoclonal bands were present in a type 2 pattern consistent with a diagnosis of multiple sclerosis.