Large pigmented nevi, usually on the trunk,
buttocks, or perineum. CNS function may be normal at birth, but MRI
examination is necessary to exclude brain or spinal cord involvement. If the
CNS is involved, thickening and pigmentation of the meninges with focal
accumulation of melanotic cells or brainstem lesions is observed.
Progressive pigmentation and thickening of the meninges lead to cerebral
deterioration, increased intracranial pressure, mental retardation,
seizures, hydrocephalus, cranial nerve palsies, and spinal cord compression.