This is the larval or intermediate stage of infection with the pork tapeworm Taenia solium. In Central and South America and in parts of Africa and India, cysticercosis is a leading cause of epilepsy and other neurologic disturbances. Because of a considerable emigration from these endemic areas, patients with cysticercosis are now being seen with some regularity in countries where the disease had previously been unknown. Usually the diagnosis is suggested by CT or MRI of the brain but can also be made by the presence of multiple calcified lesions in the thigh, leg, and shoulder muscles and in the cerebrum.
The cerebral manifestations of cysticercosis are diverse, related to the encystment and subsequent calcification of the larvae in the cerebral parenchyma, subarachnoid space, and ventricles (Fig. 31-7). The lesions are most often multiple but may be solitary; in the United States and nonendemic countries, single cysts are more common. Before the cyst degenerates and eventually calcifies, CT scanning and MRI may actually visualize the scolex. Most often the neurologic disease presents with seizures, although many patients are entirely asymptomatic, the cysts being discovered radiologically. It is only when the cyst degenerates, many months or years after the initial infestation that an inflammatory and granulomatous reaction is elicited and focal symptoms arise.
In some patients, a large subarachnoid or intraventricular cyst may obstruct the flow of CSF, in which case the surgical removal of the cyst or a shunt procedure becomes necessary. Proano and colleagues, however, have reported on a series of such cases with cysts larger than 5 cm in diameter, which they have treated medically. In a more malignant form of the disease, the cysticerci are located in the basilar subarachnoid space, where they induce an intense inflammatory reaction leading to hydrocephalus, vasculitis, and stroke as well as cranial nerve palsies. This so-called racemose form of the illness is little altered by the use of praziquantel or any other form of therapy (Estanol et al) but responds less well than the cystic form.
Treatment For a comprehensive treatment of the subject of neurocysticercosis the reader is referred to the review by Nash and colleagues. The following is a summary of current treatment principles. The therapy of this disorder has been greatly improved in recent years by the use of CT and MRI and the administration of albendazole or praziquantel, an antihelminthic agent that is also active against all species of schistosomes. Albendazole is given as 5 mg/kg tid for 15 to 30 days. Initially, treatment may seem to exacerbate neurologic symptoms, with an increase in cells and protein in the CSF, but then the patient improves and may become asymptomatic, with a striking decrease in the size and number of cysts on CT scanning. Corticosteroids are usually used at the onset of antihelminthic treatment and particularly if a large single lesion is causing symptoms by its mass effect.
Infection with Echinococcus occasionally affects the brain. The usual sources of infection are water and vegetables contaminated by canine feces. After they are ingested, the ova hatch and the freed embryos migrate, primarily to lung and liver, but sometimes to brain (approximately 2 percent of cases), where a large solitary (hydatid) cyst may be formed. The typical lesion is a large fluid-filled cyst with the parasite visible by imaging procedures, but a solid nodular brain lesion, a “chitinoma,” is also known to occur. We have also observed a compressive spinal cord lesion. Treatment with the albendazole or mebendazole is recommended when surgery is not feasible.