A 3P-year-old woman presented with a sudden onset of headache, drowsiness and diplopia. On admission, she had a right fourth nerve palsy and paraesthesiae of the right ear lobe, nose, limbs and trunk. Deep tendon reflexes were slightly brisker on the left side. CT showed a dense area in the left inferior colliculus (Fig. 1 a). Two weeks later she had transient hearing disturbance in the right ear. One month after the ictus her neurological abnormalities were less pronounced, except for the paraesthesiae in the right limbs. After 15 months, M R I showed a low signal area in the left inferior colliculus on both T2and Tl-weighted sequences (Fig. 1 b).