[A case of numb chin syndrome caused by postcentral gyrus infarction].

We report a case of numb chin syndrome caused by a small cortical infarction in the postcentral gyrus. A 67-year-old man suddenly developed numbness in his right lower lip and the chin. There were no apparent abnormal neurological symptoms other than numbness. MRI revealed a fresh small infarction in the left postcentral gyrus, which corresponds with the somatosensory area of the lower lip and the chin drawn by Penfield and Rasmussen. MRA showed no significant stenosis in the main trunk of the cerebral arteries. A soft plaque with irregular wall was detected in the left carotid bifurcation on carotid ultrasonography. Based on these findings, we diagnosed him with arteriogenic cerebral embolism, and started antiplatelet therapy. A small infarction in the postcentral gyrus can cause numbness in the lower lip and the chin, which can be considered numb chin syndrome. Numb chin syndrome due to thalamic infarction has been reported previously. The present case is the first numb chin syndrome caused by a small cortical infarction in the postcentral gyrus.