Formed visual hallucinations after metrizamide myelography.

About 12 hours after 77-year-old woman underwent metrizamide myelography of the posterior fossa to elucidate the cause of downbeat nystagmus, she developed formed visual hallucinations consisting primarily of brightly colored geometric shapes, cloud formations, and human figures. Her white blood cell count was 26,000/mm3 and her serum creatine phosphokinase level was markedly increased to 438 units/liter. Two days later, the hallucinations had subsided, the white blood cell count had decreased to 17,000/mm3, and the serum creatine phosphokinase level had decreased to 105 units/liter. The hallucinations were probably caused by penetration of the metrizamide into the temporal lobe and visual association cortex.