Detection of an aberrant motile larval form in the brain of a patient with neurocysticercosis.

Neurocysticercosis is the most common parasitic infection of the central nervous system in humans. The adult pork tape worm, Taenia solium, resides in the lumen of the intestine, and the only structural element of an adult worm usually found within a tissue cyst in the brain or in muscle is a single invaginated scolex. We report a highly unusual, and perhaps unique, occurrence of neurocysticercosis in which an aberrant worm-like larval form, 12.5 cm in length, was found within a cyst in brain parenchyma.