Syndromes affecting the third nerve fascicle

Syndromes affecting the third nerve fascicle as it travels through the midbrain are characterized by neighborhood neurologic signs. (A) A lesion affecting the cerebral peduncle/corticospinal tract causes contralateral hemiparesis (Weber syndrome). (B) A lesion affecting the red nucleus causes contralateral rubral tremor (Benedikt syndrome). (C) A lesion affecting superior cerebellar peduncle causes contralateral ataxia (Claude syndrome). CP: cerebral peduncle, RN: red nucleus, SCP: superior cerebellar peduncle, III: third nerve. (Contributed by Dr. Marc J Dinkin.)