A 32-year-old right-handed man presented with a two day history of gradual weakness and clumsiness of the right hand, followed by sudden weakness of the right leg. His partner described a transient episode of slurred speech accompanied by right-sided facial droop on the day before admission, of which the patient had been unaware. There was no history of any preceding infectious or other illness, and no fever or headache at presentation. Six months previously he had had a number of brief episodes of “twitching” of the right leg during which he had needed to lean on walls or furniture for support. One month before admission he had developed similar episodes involving the left hand. He had a background history of type 1 diabetes mellitus. His glycaemic control was said to have been poor in the past, and he had had an episode of diabetic ketoacidosis in 1993. Blood pressure (BP) recordings gleaned from his general practitioner records suggested gradually increasing hypertension over at least five years: 11.09.90–120/80; 16.08.94–148/70; 08.11.94–158/80; 27.09.99–160/100 mm Hg. His only regular medications were subcutaneous insulins. He was a non-smoker. There was no significant family history.

On examination at the time of admission his BP was 189/100, heart rate 80 beats per minute regular. He was apyrexial, alert and orientated. Cranial nerve examination was normal. There was a flaccid right-sided MRC grade 3–4 hemiparesis, pyramidal in distribution, and he was unable to walk. Tendon reflexes were bilaterally brisk, and plantar responses “equivocal”. Coordination and sensation were normal. The general examination was unremarkable.

THE FIRST TESTS

Non-contrast brain CT showed multifocal bilateral subcortical low attenuation. There was also low attenuation involving the anterior corpus callosum and the left caudate (fig 1).

Non-contrast MRI …