Cerebral polyopia

Cerebral polyopia, also called cerebral diplopia, is a visual disturbance in which a person sees two or more copies of a stimulus arranged in rows, columns or diagonals after fixating on it. Unlike ocular diplopia, the copies persist when one eye is open on either side, so the fault lies in the brain and not in the eye. The number of copies can range from one to hundreds, and some patients cannot tell the false images from the real one, while others find them different in size, intensity or color. It is sometimes confused with palinopsia, where moving objects leave trails. Reported causes include infarction, tumors, multiple sclerosis, trauma, encephalitis, migraine and seizures, and lesions of the extrastriate visual cortex have been described, with deafferentation hyperexcitability proposed as a possible mechanism.