Case presentation

A previously independent 64-year-old man presented to his local hospital with new-onset diplopia and dysarthria while watching television. Over the following days, he developed painless perioral and upper limb sensory disturbance, gait unsteadiness and limb ataxia, most pronounced in the upper limbs. He was initially admitted and treated for a cerebrovascular event, followed by a period of failed rehabilitation. At 6-week review, his symptoms had worsened, and he required the assistance of two people to walk short distances. He was then transferred to a regional neurology unit. It was uncertain whether his symptoms had stabilised or progressed over the preceding fortnight. He had no other neurological symptoms, normal bladder and bowel function, and no history of preceding illness. Table 1 provides the background history.

Examination

Assessment of eye movements identified a complex ophthalmoplegia, with complete failure of right eye abduction. Upgaze was bilaterally limited to 45° and adduction was partially restricted. There was no nystagmus. He described perioral numbness and was unaware of food boluses within his mouth, though objective testing was normal. Tongue movements were slowed but symmetrical. There was no fasciculation and his swallow appeared normal. His speech was dysarthric but intelligible and had a subtle nasal character. There were no other cranial nerve signs. Neck flexion and extension were normal.

Tone was normal in all four limbs. His strength was symmetrically reduced in the upper limbs with the Medical Research Council (MRC) grade 4 proximally and 4− in the small finger muscles. Lower limb strength was MRC grade 4+ at hip flexion and 5 in all other muscle groups. He could not stand due to unsteadiness and had pronounced ataxia in all limbs. There was profound loss of proprioception to the shoulders in his arms with pseudoathetosis, with no corresponding lower limb involvement. Vibration …