Metamorphopsia and transient increase in the cerebral blood flow of the left occipital pole on 123I-IMP SPECT: a case report

A 55-year-old right-handed man suddenly developed unformed visual hallucination of rainbow-colored balls coming out from the lower quadrant of the right visual field. Visual field examination revealed a right lower quadrant homonymous hemianopia. Metamorphopsia of the hand or face appeared 6 days later when he looked at his hands or at the face in the mirror, and persisted for about 10 minutes. 123I-IMP SPECT demonstrated a marked increase in CBF of the left occipital pole while the patient realized the visual symptoms, and a marked decrease in CBF after the symptoms disappeared. T1 and T2-weighted MRIs of the brain were unremarkable, but the Gd-DTPA-enhanced T1-weighted MRI showed high signal in the subcortical white matter of the left occipital pole. The metamorphopsia was induced probably by the activation of the left occipital lesion by the epileptogenic mechanism although the nature of the lesion remained unclarified.