A previously well 66-year-old man presented with a 1-month history of focal involuntary spasms of his arms and then his left leg, culminating in two generalised convulsions. He also complained of episodic memory problems, sleeping difficulties, daytime somnolence, hyperphagia, hyperhidrosis and erectile impotence. He was initially treated with phenytoin for 2 months and then valproate. His family noticed increasing dishevelment and emotional lability over the previous 6 months. Both he and his step-daughter reported that he did not drink to excess, although 10 years previously he was a heavy drinker, but had since cut down considerably.

On examination, he was flamboyant, disinhibited and garrulous, but alert and orientated. He confabulated about attending to business and family affairs, whereas he had not worked for several years. He was able to learn a name and address perfectly in three attempts. He showed difficulties in naming people, word-finding and planning constructional tasks, which is indicative of fronto-temporal impairment. Cranial nerves were normal with no frontal release signs. There were prominent fasciculations bilaterally in quadriceps femorii, gastrocnemii and right biceps femoris. Power and coordination were normal. Deep tendon reflexes were absent except for biceps jerks. Plantar responses were flexor. Sensation was intact.

The following blood tests …