[A case of reversible encephalopathy caused by tegafur]

A case of reversible encephalopathy induced by tegafur: a masked compound of 5-Fluorouracil, is reported and discussed. A 67-year-old Japanese man suddenly began to show changes in mental status after 4.5 months of administration of tegafur for the peritonitis carcinomatosa. Alternation in consciousness supported by electroencephalographic evidence became apparent. The P100 latency in visual evoked potential was prolonged in both sides, and the conduction velocity in ulnar nerves in both sides was also slow. The patient made significant clinical recovery upon discontinuing tegafur, and the abnormal findings on electroencephalography, visual evoked potential and peripheral nerve conduction velocity also returned to normal. When the patients who are taking tegafur show mental symptoms, early diagnosis from both clinical findings and electrophysiological studies should be performed.