Callosal Conundrum: Conflicting Perimetry Results after Corpus Callosotomy

A 49 y/o male had a corpus callosotomy for intractable seizures. The patient was started on Vigabatrin, necessitating visual field testing. Confrontation visual field (CVF) testing revealed a left homonymous hemianopia (LHH). Paradoxically, automated visual fields (HVF 30-2) showed a dense right homonymous hemianopia (RHH). CVF requiring the patient to mimic the examiner's fingers produced a crossed hemianopia RHH when he used his left hand, and LHH when he used his right hand. These conflicting visual field defects were suspected to be an artifact of the patient's disconnection syndrome. Additional visual field tests were performed to explore these "switching" homonymous defects. (The patient consented to videotaping. Portions of his examination will be shown.)