Picture quiz: Muscle weakness and wasting

A 74 year old woman presented with a two month history of progressive weakness of her right hand, without sensory symptoms. She had no medical history of note and no family history of neurological or psychiatric problems.

On examination, sensation and cranial nerves were normal. Examination of the upper limbs identified bilateral fasciculation of the deltoid and triceps, however. On the right, the power of her grip was 3 on the Medical Research Council scale, as was her finger abduction and abductor pollicis brevis. Her digit muscles had spasticity, and the reflexes of her supinator and biceps were brisk. The power and reflexes of her left upper limb were normal. Coordination was normal in both upper limbs.

In the lower limbs the only finding was the presence of symmetrical exaggerated adductor reflexes. Figs 1(F1) and 2(F2) show the patient's right hand at rest, a couple of months after presentation.