A hill walker with long chains.

A previously healthy 42-year-old man noticed that his right foot was ‘kicking against rocks’ when he was hill walking. Over the next 8 years, he developed slowly worsening mobility, eventually having to rely on a stick due to right leg ‘spasms’. His cognition, speech, swallowing, upper limb function and sphincters were unaffected. There was no family history of neurological disease.On examination, his cranial nerve function was normal. In the upper limbs, he had exaggerated reflexes (particularly on the left) and mild left-sided incoordination. In the lower limbs, tone was increased with sustained clonus bilaterally. There was MRC grade 4+ power in all muscle groups. Knee and ankle reflexes were pathologically brisk. Plantar responses were extensor. There was mild hyperaesthesia up to the ankles bilaterally. Vibration sense was reduced (to the levels of the right anterior superior iliac spine and the left tibial tuberosity). Proprioception was reduced (to the right ankle and the left knee). Gait was spastic and unsteady. Rombergu0027s test was positive.### Question 1What investigations would you perform?The following blood tests were normal or negative: full blood count, renal and liver function, bone profile, vitamin B12, folate, copper, thyroid function, antinuclear antibody, lupus anticoagulant, angiotensin-converting enzyme, anti-aquaporin-4 antibody, vitamin E, HIV, human T-cell lymphotropic virus, syphilis, lysosomal enzymes, phytanic …