Recurrent confusion and ataxia triggered by pyrexia in a case of occult multiple sclerosis It has long been known that an increase in body temperature may worsen reversibly the signs and symptoms of multiple sclerosis, probably by the production of conduction block in partially demyelinated nerve axons. We present the case of a man whom we believe has multiple sclerosis, who has a nine year history of brief episodes of profound neurological dysfunction, always in association with pyrexial illnesses. The unusual feature of this case is that, until recently, between these attacks our patient remained subjectively well, and that there was no history suggesting episodes of acute demyelination.A 44 year old man was admitted in May 1992 with a 12 hour history of increasing confusion, blurring of vision, and ataxia, associated with a fever. On admission he was pyrexial at 39°C, but there were no signs of localised infection or any features of meningism. He was drowsy and mildly confused. The cranial nerves were normal apart from bilateral failure of adduction with ataxic nystagmus of the abducting eyes typical of an internuclear ophthalmoplegia, down-beat nystagmus on down-gaze, and up-beat nystagmus on up-gaze. There was a mild bilateral ptosis and a slight left upper motor neuron facial weakness. Bulbar function was intact. In the limbs power was normal, but tone was slightly increased generally and the reflexes were exaggerated, particularly on the left. The left plantar reflex was extensor, the right flexor. There was pronounced cerebellar ataxia in all four limbs, again more pronounced on the left, and he was unable to walk unassisted. Sensation was normal. The only abnormal investigations were a noticeable peripheral neutrophilia (granulocyte count 11 -6 x 109/1), and a raised C reactive protein concentration of 77 mg/l (normal range 0-10). Cerebrospinal fluid contained 1 white blood cell/mm', 0-21 g/l protein, and 4-7 mmol/l glucose.The Further analysis of the CSF collected on his admission showed the presence of oligoclonal IgG bands that were absent from plasma, although the CSF IgG:albumin ratio was normal at 0-20 (normal range 0-0 25). An MRI of the brain two days after his discharge showed the presence of multiple areas of increased signal intensity in the periventricular regions, the corpus callosum, the base of the fourth ventricle, the left cerebellar peduncle, and the lower medulla. The appearances were typical of widespread demyelination caused by multiple sclerosis. Repeat MRI five months later appeared identical. Visual evoked responses recorded eight months after his admission were of grossly increased latency.In
