Ipsilateral motor deficit resulting from a subdural hematoma and a Kernohan notch.

A 25-year-old male graduate student was found wandering the halls near his laboratory, appearing confused and having difficulty walking. The patient was taken to the emergency room, where he reported feelings of weakness. He was oriented to person, place, and time. Examination revealed right ptosis and third nerve palsy with a normal pupil , right hemiparesis including the face, and a positive right Babinski reflex. No external signs of trauma were present. CT examination demonstrated an 8-mm-thick right frontoparietal acute subdural hematoma producing a 7 -mm shift of the septum pellucidum toward the left (Fig . 1 A). There was suggestion of only minimal right transtentorial herniation (Fig. 1 B). An angiogram revealed no underlying vascular lesion. Because of the paradoxical finding of right-sided hemiparesis with ipsilateral subdural hematoma, the decision to operate was difficult; however, a craniotomy was performed and the hematoma evacuated. A postoperative MR study was performed to look for additional traumatic lesions that may have been missed on the CT scan. This demonstrated two punctate areas of increased signal on T2-weighted images in the right frontal and parietal lobes and a residual right-sided subdural hematoma (Fig. 1 C). Examination of the brainstem revealed an area of abnormally increased signal along the lateral margin of the left cerebral peduncle (Fig. 1 D). A T1-weighted coronal image showed an area of decreased signal intensity in the left cerebral peduncle, as well as a residual right and a very small left subdural hematoma (Fig . 1 E). Following surgery, the patient's right-sided weakness gradually improved, and after 11 days he was discharged with mild residual right-sided weakness. The patient could not remember the events just prior to his hospitalization, and the cause of his head trauma was never determined. Discussion