A 43-year-old woman with hypertension presented with sudden vertigo and gait instability two weeks before, which was followed by left ptosis and hypesthesia on the right limbs. Neurological examination revealed a left Horner's syndrome, sensory loss for pain and temperature over left side of the face and right trunk and limbs, dysmetria of left limbs. Soft palate elevation was reduced and no gag reflex was elicited in the left side. She veered to the left when walking. There were no head tilt or skew deviation. Head thrust test did not elicit corrective catch-up saccade bilaterally. She had conjugate leftward deviation of the eyes under closed lids. She also had leftward hypermetria and rightward hypometria of saccades and saccadic pursuit to the right side. Oculographic study The patient had right beating nystagmus with small upbeat and clockwise torsional component in light, which was augmented in darkness. The direction of nystagmus was not changed by gaze. Maximum slow phase velocity (SPV) of the horizontal nystagmus was 5.1°/s. Horizontal head oscillation immediately reversed the direction of spontaneous nystagmus. Maximum SPV of HSN was 253°/s and HSN persisted more than 4 minutes. Visual fixation markedly suppressed HSN. T2- and diffusion-weighted MRI revealed an infarction in dorsolateral portion of left caudal and middle medulla. Cerebral angiography was unremarkable.