A 67-year-old man with right hemiparesis and dysarthria was admitted with right hemiparesis involving the face, hyperpathia, numbness and pain of the right body and limb except the face, and had hyperreflexia and pathological reflex in the right limb. Brain MRI on the day after admission disclosed no lesion which might explain the symptoms. Short latency somatosensory evoked potential showed a low amplitude after P14 when the right side was stimulated. Cerebral angiography revealed occlusion of the left vertebral artery. Brain MRI on the 18th hospital day disclosed left medial medullary infarction, so we diagnosed medial medullary syndrome. This case was hard to diagnose, because of the atypical features and the absence of an abnormal lesion on the initial MRI.