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Helminthic Brain Infections

By

John E. Greenlee

, MD, University of Utah School of Medicine

Last full review/revision Jul 2020| Content last modified Jul 2020
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Neurocysticercosis

Among about 20 helminths that can cause neurologic disorders, the pork tapeworm Taenia solium Taenia Solium (Pork Tapeworm) Infection and Cysticercosis Taenia solium infection (taeniasis) is an intestinal infection with adult tapeworms that follows ingestion of contaminated pork. Cysticercosis is infection with larvae of T. solium, which develops... read more causes by far the most cases in the Western Hemisphere. The resulting disorder is neurocysticercosis. After a person eats food contaminated with the worm’s eggs, larvae migrate to tissues, including the brain, spinal cord, and cerebrospinal fluid (CSF) pathways, and form cysts. Cyst diameter rarely exceeds 1 cm in neural parenchyma but may exceed 5 cm in CSF spaces. Older cysts frequently calcify.

Brain parenchymal cysts cause few symptoms until death of the worms triggers local inflammation, gliosis, and edema, causing seizures (most commonly), cognitive or focal neurologic deficits, or personality changes. Larger cysts in CSF pathways may cause obstructive hydrocephalus. Cysts may rupture into CSF, inducing acute or subacute eosinophilic meningitis. Without treatment, neurocysticercosis can cause death; cause of death includes encephalitis, meningitis, hydrocephalus, and untreated seizures.

Neurocysticercosis is suspected in patients who live in or have come from developing countries and who have eosinophilic meningitis or unexplained seizures, cognitive or focal deficits, or personality changes. It is suggested by multiple calcified cystic lesions seen on CT or MRI; a contrast agent may enhance the lesions. Diagnosis requires serum and CSF serologic tests and occasionally cyst biopsy.

Albendazole (7.5 mg/kg orally every 12 hours for 8 to 30 days; maximum daily dose, 800 mg) is the antihelminthic drug of choice. Alternatively, praziquantel 20 to 33 mg/kg orally 3 times a day may be given for 30 days. Dexamethasone 8 mg IV or orally once a day for the first 2 to 4 days may lessen the acute inflammatory response as the worms die. Antihelminthic therapy can cause serious morbidity in patients with a large number of cysts and may not help patients with a single cyst. Treatment must be carefully individualized.

Other helminthic infections

Symptoms of these cysts require several years to develop and, if the brain is involved, include increased intracranial pressure, seizures, loss of consciousness, and focal neurologic deficits.

Gnathostomiasis, a rare infection by larvae of the nematode Gnathostoma species, results in necrotic tracts surrounded by inflammation along the nerve roots, spinal cord, and brain or in subarachnoid hemorrhage, causing low-grade fever, stiff neck, photophobia, headache, migratory neurologic deficits (occasionally affecting the 6th or 7th cranial nerve), and paralysis.

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