[Cheiro-oral syndrome due to a cortical infarction in the precentral gyrus: a case report].

We report a 65-year-old woman with sudden onset of paresthesia on the left side of the lip and left thumb. Neurological examinations did not demonstrate any disturbance of higher brain function or motor function except for subjective thermohyperesthesia of the left thumb. Brain MRI demonstrated a small high intensity lesion on T2-weighted images (T2 WI) and diffusion-weighted images (DWI) in the right anterior precentral gyrus. She was diagnosed with cerebral infarction presenting with pure cheiro-oral syndrome (COS). Her neurological symptoms were completely abolished 4 or 5 days later. The thalamus is the region responsible for COS in the majority of cases while reports that a cortical infarction causes COS are rare, because it is difficult to show a small cortical lesion on CT or conventional T2WI. DWI is superior to T2 WI in discriminating between acute and chronic ischemic lesions as well as in detecting small cortical lesions adjacent to the cerebrospinal fluid. In this patient, the lesion was vaguely hyperintense on T2 WI and difficult to differentiate from an artifact caused by cerebrospinal fluid. The precentral gyrus infarction detected on DWI was thought to cause COS in this patient. Not only lesions of the postcentral gyrus as a primary sensory cortex but also those of the precentral gyrus or opercula causing COS were described in previous reports, indicating that the hand and mouth sensory areas may be widely distributed. Cortical mapping studied by electrical stimulation through subdural grid electrodes also supports this finding. Further examination of the relation between neurological symptoms and localization on MR images such as DWI is needed to clarify the distribution of the sensory cortex.