Perceiving "ghost" images: a unique case of visual allesthesia with hemianopsia in mitochondrial disease.

A 49-year-old man with mitochondrial disease presented with visual allesthesia, a rare and puzzling phenomenon. He was admitted for treatment because of convulsions. After the convulsions ceased, he exhibited left homonymous hemianopsia. Brain diffusion-weighted magnetic resonance imaging (MRI) showed a high-intensity area in the right occipital lobe. Both the hemianopsia and the MRI activation in this area disappeared by day 36 of hospitalization. On the morning of day 57, right homonymous hemianopsia emerged in a singular manner. The patient perceived an illusory object (a bottle placed by the bedside) in his left visual field, while the real object was in his blind right field. This case of visual allesthesia was accompanied by palinopsia, ie, perseveration of the image of the bottle. Diffusion-weighted MRI showed a new, high-intensity area in the left occipital lobe. We believe the visual allesthesia resulted from transfer of cortical information obtained by blindsight between hemispheres as a result of epileptic excitation.