Visual hallucinations in recovery from cortical blindness: imaging correlates.

OBJECTIVE To investigate the cerebral metabolic and functional patterns during recovery from cortical blindness. DESIGN Follow-up study with serial clinical, metabolic, and functional imaging and visual evoked potentials. CASE PRESENTATION A 24-year-old woman suffered from cortical blindness after cardiac arrest and recovered over a 6-month period. During recovery, she experienced complex visual hallucinations that could be initiated by visual imagery. RESULTS Initially, the regional cerebral metabolic rate of glucose was severely reduced in the visual and parieto-occipital cortex bilaterally but recovered almost completely. Visual hallucinations led to significant increases of the regional cerebral blood flow in the initially severely hypometabolic parieto-occipital and temporo-lateral cortex. CONCLUSIONS Recovery of vision was related to normalization of the postlesionally dysfunctional cortex. Visual hallucinations appeared as the clinical correlate of the electrophysiological hyperexcitability of the recovering partially damaged visual cortex.