Central nervous system lesions occur occasionally. Cerebral granulomatous disease may be caused by "S. japonicum" eggs in the brain. Communities in China affected by "S. japonicum" have rates of seizures eight times higher than baseline. Similarly, granulomatous lesions from "S. mansoni" and "S. haematobium" eggs in the spinal cord can lead to transverse myelitis with flaccid paraplegia. Cerebral granulomatous infection may also be caused by "S. mansoni". "In situ" egg deposition following the anomalous migration of the adult worm appears to be the only mechanism by which "Schistosoma" can reach the central nervous system in these patients. The destructive action on the nervous tissue and the mass effect produced by a large number of eggs surrounded by multiple, large granulomas in circumscribed areas of the brain characterize the pseudotumoral form of neuroschistosomiasis and are responsible for the appearance of clinical manifestations: headache, hemiparesis, altered mental status, vertigo, visual abnormalities, seizures, and ataxia. In cases with advanced hepatosplenic and urinary schistosomiasis, the continuous embolization of eggs from the portal mesenteric system ("S. mansoni") or portal mesenteric-pelvic system ("S. haematobium") to the brain, results in a sparse distribution of eggs associated with scant periovular inflammatory reaction, usually with little or no clinical significance.