A 31-year-old man is brought to the emergency department after a tonic-clonic seizure. The patient has no known medical conditions. He grew up in a rural part of Guatemala and immigrated to the United States 3 years ago. The patient works as an architect and owns a cat. He has no history of tuberculosis. On examination, the patient is afebrile and has no focal neurologic deficits or meningeal signs. HIV antibody test and interferon-gamma release assay are negative. Chest x-ray is normal. MRI of the head reveals a 1.5-cm cyst within the left sylvian fissure that has minimal enhancement and no associated edema. Which of the following is the most likely means of acquisition of the infection responsible for this patient's findings?
Cysticercosis | |
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Diagnosis |
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This patient from Guatemala with an adult-onset seizure and a cystic brain lesion likely has neurocysticercosis (NCC), an infection caused by Taenia solium (pork tapeworm) eggs. Although rare in the United States, T solium is endemic to rural areas of resource-poor nations (eg, Central and South America, sub-Saharan Africa, Asia) where sanitation is poor and pigs roam freely.
T solium causes 2 distinct infections in humans, as follows:
Tapeworm infection occurs when humans ingest T solium larvae in undercooked pork. The larvae mature into adult worms in the digestive tract and secrete eggs into stool.
Cysticercosis occurs when humans ingest T solium eggs in feces-contaminated food or water. The eggs hatch into embryos in the gastrointestinal tract, invade the bowel wall, migrate through the bloodstream, and lodge in tissue (eg, brain, muscle, liver). In tissue, the embryos form cysticerci, fluid-filled larval cysts with an invaginated scolex (head of tapeworm with hooklets). Over months or years, the cysts degenerate, leading to inflammation, edema, and symptoms (eg, seizure).
(Choice A) Strongyloides stercoralis is usually transmitted to humans when filariform larvae penetrate the skin of the feet. Manifestations include eosinophilia and gastrointestinal disease (among immunocompetent individuals) or hyperinfection (typically among immunocompromised patients). Brain cysts would be atypical.
(Choice C) Cat feces may contain Toxoplasma gondii. Immunocompromised patients, particularly those with AIDS, can develop cerebral toxoplasmosis. However, this is marked by multiple ring-enhancing lesions, not a cystic lesion with minimal enhancement. In addition, toxoplasmosis is unlikely in this patient with negative HIV testing.
(Choice D) Endemic dimorphic mycoses (eg, histoplasmosis, blastomycosis) are often transmitted by spore inhalation. However, neurologic manifestations are rare and would be very uncommon in the absence of pulmonary abnormalities.
(Choice E) Catscratch disease, caused by Bartonella henselae, is most often associated with localized skin/soft tissue infection and proximal lymphadenitis.
(Choice F) Herpes encephalitis may present with seizures, but patients are usually febrile, and imaging typically reveals temporal lobe edema or hemorrhage. Syphilis can present with neurologic manifestations, including meningitis, cranial nerve palsies, and tabes dorsalis. However, seizures and a cystic brain lesion in a patient from rural Guatemala are more suggestive of neurocysticercosis.
Educational objective:
Neurocysticercosis is a common cause of adult-onset seizures in patients from rural developing regions. Suspicion should be raised when brain imaging in these individuals shows cystic or calcified lesions.