A 35-year-old nurse develops subcutaneous nodules across her head and arms, after which she begins to experience frequent headaches. The headaches slowly worsen over the next three weeks and are joined by occasional nausea and vomiting. One morning at work, she becomes slightly dizzy and thinks that her vision might be blurred. Shortly thereafter, she experiences a general seizure and is immediately transported to the ER. In the ER, her vital signs are normal, but she is somewhat confused. Her temporal arteries are not thickened or tender. She does not have a stiff neck, and Brudzinski's sign is negative. The general physical examination is unremarkable. The nurse manages to describe her headaches and other recent symptoms to the attending physician before suffering yet another generalized seizure. Her medical records are readily available and indicate that she has no history of neurological disorders. The attending physician notes that, about 10 years ago, she spent two years in Thailand as a Peace Corps volunteer.

Question 8.1: What tests should you perform?

The patient is clearly suffering from a neurological disorder that is probably affecting the brain. Headaches, nausea, dizziness, and blurred vision may indicate increased intracranial pressure, so a lumbar puncture is probably contraindicated until more information is available. The safest bet at this point is to do a CT and/or MRI scan of the patient's brain.

Test Results:

The CT scan shows multiple lesions in the patient's brain. Some of these lesions are hypodense, whereas others are isodense or hyperdense. The lesions range from 2 to 10 mm in diameter and are rounded. The MRI also shows multiple lesions.

Question 8.2: What is your preliminary diagnosis?

The presence of multiple brain lesions in the size range indicated and the development of subcutaneous nodules across the chest and arms imply an advanced case of cysticercosis, a disease that is caused by the tapeworm Taenia solium. This diagnosis is further supported by the fact that the patient spent two years in an area where cysticercosis is endemic and, therefore, could have been

Question 8.3: How is the diagnosis confirmed?

Diagnosis of cysticercosis can be difficult. Recently revised guidelines define four categories of diagnostic criteria: absolute, major, minor, and epidemiologic. Definitive diagnosis requires the presence of one absolute criterion or the presence of two major plus one minor and one epidemiologic criterion. The current diagnostic criteria are summarized in the following table.

Category

Criteria

Absolute

1) Histologic demonstration of the causative agent from biopsy of a brain or spinal cord lesion

2) Cystic lesions showing the scolex of Taenia solium on CT or MRI

3) Direct visualization of subretinal parasites by fundascopic examination

Major

1) Lesions highly suggestive of neurocysticercosis on neuroimaging studies (CT or MRI) a

2) Positive serum EITB b for the detection of anticysticercal antibodies

3) Resolution of intracranial cystic lesions after therapy with albendazole or praziquantel

4) Spontaneous resolution of small single enhancing lesions c

Minor

1) Lesions compatible with neurocysticercosis on neuroimaging studies d

2) Clinical manifestations suggestive of neurocysticercosis e

3) Positive CSF ELISA for detection of anticysticercal antibodies or cysticercal antigens

4) Cysticercosis outside the CNS f

Epidemiologic

1) Evidence of a household contact with an infected individual

2) Individual coming from or living in areas where cysticercosis is endemic

3) History of frequent travel to disease-endemic areas

a CT or MRI showing cystic lesions with scolex, enhancing lesions, or typical parenchymal brain calcifications.

b Enzyme-linked immunoelectrotransfer blot assay, using purified extracts of Taenia solium antigens.

c Solitary ring-enhancing lesions <20 mm in diameter, in patient presenting with seizures, a normal neurologic examination, and no evidence of an active systemic disease.

d CT or MRI showing hydrocephalus or abnormal enhancement of the leptomeninges, and myelograms showing multiple filling defects in the column of contrast medium.

e Seizures, focal neurologic signs, intracranial hypertension, and dementia.

f Histologically confirmed subcutaneous or muscular cysticercosis.

Question 8.4: How is the disease acquired?

Cysticercosis is human infection with the larval stage of Taenia solium (a cestode helminth), the cysticerci, which normally infect pigs. The infection is usually initiated by ingestion of water or vegetation contaminated with T. solium eggs from human feces. Autoinfection may occur when eggs from a person who is infected with the adult worm are transferred from the perianal area to the mouth on contaminated fingers. (Ingestion of the larval stage of the worm, as opposed to its eggs, results in an intestinal infection.)

Question 8.5: How does the parasite reach the brain?

Once ingested, T. solium eggs hatch in the stomach, releasing hexacanth embryos (oncospheres). The oncospheres penetrate the intestinal wall and migrate in the circulatory system to the tissues, where they develop into cysticerci over 3 to 4 months. The cysticerci may develop in the brain, muscles, connective tissues, subcutaneous tissues, lungs, and/or eyes. They remain viable for as long as 5 years.

Question 8.6: How is this disease treated?

The drug of choice is praziquantel. Albendazole has also been used successfully in the treatment of parenchymal neurocysticercosis. Concomitant administration of steroids may be necessary, to minimize the inflammatory response to dying larvae. In some cases, surgical removal of cerebral or ocular cysts is necessary as well.