Giant congenital nevus and chronic progressive ascending hemiparesis (Mills syndrome). Report of a case.

We describe the case of a 20 year old boy with a giant congenital nevus who developed a chronic progressive ascending hemiparesis. The association of the pigmented lesion with a focal neurological deficit is pathognomonic for neurocutaneous melanosis complicated by a leptomeningeal melanoma. MR imaging at 1.5 tesla ruled out such a possibility and showed a small aspecific pontine lesion along the route of the corticospinal tract. We discuss possible etiologies.