Parasitic helminthic worms infect the central nervous system (CNS) of millions of people in developing countries. Infected people who visit or immigrate to nonendemic areas, including the US, may present there. Worms may cause meningitis Subacute and Chronic Meningitis Subacute meningitis develops over days to a few weeks. Chronic meningitis lasts ≥ 4 weeks. Possible causes include fungi, Mycobacterium tuberculosis, rickettsiae, spirochetes, Toxoplasma... read more , encephalitis Encephalitis Encephalitis is inflammation of the parenchyma of the brain, resulting from direct viral invasion or occurring as a postinfectious immunologic complication caused by a hypersensitivity reaction... read more , cerebral masses, hydrocephalus, stroke Overview of Stroke Strokes are a heterogeneous group of disorders involving sudden, focal interruption of cerebral blood flow that causes neurologic deficit. Strokes can be Ischemic (80%), typically resulting... read more , and myelopathy Spinal Cord Compression Various lesions can compress the spinal cord, causing segmental sensory, motor, reflex, and sphincter deficits. Diagnosis is by MRI. Treatment is directed at relieving compression. (See also... read more .
(See also Introduction to Brain Infections Introduction to Brain Infections Brain infections can be caused by viruses, bacteria, fungi, or, occasionally, protozoa or parasites. Encephalitis is most commonly due to viruses, such as herpes simplex, herpes zoster, cytomegalovirus... read more .)
(See also Cysticercosis Cysticercosis Taenia solium infection (taeniasis) is an intestinal infection with adult tapeworms that follows ingestion of contaminated pork. Adult worms may cause mild gastrointestinal symptoms or passage... read more .)
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. Adult worms may cause mild gastrointestinal symptoms or passage... 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.
Antihelminthic drugs are first-line therapy. 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. If antihelminthic therapy results in the death of many organisms, the brain may swell significantly in patients with a large number of cysts, and antihelminthic therapy may not help patients with a single cyst. Treatment must be carefully individualized.
Short- or long-term treatment with antiseizure drugs Drug Treatment of Seizures No single drug controls all types of seizures, and different patients require different drugs. Some patients require multiple drugs. (See also the practice guideline for the treatment of refractory... read more may be required. Surgical excision of cysts and ventricular shunts may also be required.
Other helminthic infections
In schistosomiasis Schistosomiasis Schistosomiasis is infection with blood flukes of the genus Schistosoma, which are acquired transcutaneously by swimming or wading in contaminated freshwater. The organisms infect the... read more , necrotizing eosinophilic granulomas develop in the brain, causing seizures, increased intracranial pressure, and diffuse and focal neurologic deficits.
Large, solitary echinococcal cysts Echinococcosis Echinococcosis is infection with larvae of the tapeworm Echinococcus granulosus (cystic echinococcosis, hydatid disease) or Echinococcus multilocularis (alveolar disease). Symptoms... read more can cause focal deficits and, occasionally, seizures.
Coenurosis Coenurosis (Taenia multiceps, Taenia serialis, or Taenia brauni Infection) The tapeworms Taenia multiceps, Taenia serialis, Taenia brauni, and Taenia glomeratus are rare causes of human infection, which is acquired by accidental ingestion... read more , caused by tapeworm larvae (Taenia species), usually produces grapelike cysts that may obstruct CSF outflow in the 4th ventricle.
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. Neuroimaging and serologic testing are done to differentiate among these cysts and to differentiate them from neurocysticercosis.
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. Gnathostomiasis is suspected in returning travelers and in residents of parts of Asia, the Middle East, Europe, Africa, and Central or South America who have migratory skin swellings or unexplained eosinophilic meningitis. Diagnosis requires neuroimaging and CSF testing.