Case 1

A 65 year old man presented in 2006, having fallen in the shower on closing his eyes; he had burning and tightness affecting his feet and had recently lost weight. Over six months he became bedbound due to poor balance. He had undergone partial gastrectomy in 1973 for a duodenal ulcer. Three years before the neurological symptoms developed, he was diagnosed with asymptomatic B-12 deficiency, which was successfully treated.

Initial examination showed a positive Romberg test and an inability to walk heel-to-toe. Cranial nerve examination was unremarkable. Tone and power were normal, ankle jerks were depressed, and one plantar reflex was extensor. Over six months he developed spastic weakness in his legs (hip flexion MRC grade 4), hyper-reflexia, and bilateral extensor plantar reflexes. Sensory disturbance suggested greater abnormality in the posterior columns; vibration sense was reduced to the costal margins, proprioception to the ankle, and pinprick to mid-foot level.

Magnetic resonance imaging showed T2 signal abnormality in the posterior cervical cord at C2-4 (figure ⇓). Electrophysiology found lower limb motor abnormalities consistent with a motor neuronopathy, but sensory nerve action potentials were normal. Central motor conduction to the limbs (a method for examining the central motor pathways, in which the difference between the latency of motor evoked potentials …