The Behr pupil revisited. Anisocoria following cerebrovascular accidents

Three hundred and sixty-three cases of cerebral infarction were reviewed: 19 had anisocoria. Eighty percent had the larger pupil contralateral to the hemispheric lesion. The mydriasis was associated with long tract signs in all instances. If the abnormal pupil and long tract signs are not on the same side, the long tract signs are the most accurate evidence of the side of thhe hemispheric lesions. When the pupil was 4 mm or larger and reacted sluggishly, the prognosis was poor. The mechanism of the production of the anisocoria is still uncertain; the lesion is probably "cortical" and in the contralateral hemisphere.