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  • Updated 08.08.2021
  • Released 12.07.1993
  • Expires For CME 08.08.2024

Neurocysticercosis

Introduction

Overview

Neurocysticercosis continues to be the most common CNS parasite and is becoming increasingly identified in the United States. Most patients in the United States present with seizures (focal or generalized) or headache and have come from Mexico, Latin America, or the Indian subcontinent. A new set of diagnostic criteria have been published. There are now 3 serological methods of diagnosing neurocysticercosis. A serum or CSF antibody assay, especially an enzyme-linked immunotransfer blot assay, is quite sensitive and specific but is not widely available, particularly in the Indian subcontinent. A new PCR-based assay to detect T. solium nucleic acid is more specific and is becoming more available. The third assay detects cysticercus antigen. This assay is the most valuable in diagnosing extraparenchymal neurocysticercosis in the ventricle or meninges and can be utilized to follow patient response to treatment. It appears that the cysticercus cyst releases specific proteins that induce an anti-inflammatory host response to prevent the host from destroying viable cerebral cysts. Although some controversy continues regarding the necessity of treating single neurocysticercosis cysts in developing countries, studies, including a 2013 guideline published in Neurology and a meta-analysis report, find that albendazole treatment significantly hastens the disappearance of cysts and reduces the incidence of seizures with generalization. For intraventricular neurocysticercosis, endoscopic removal is an effective and safe treatment option. Management of disseminated cysticercosis is currently unclear. Work has demonstrated that repeated cycles of albendazole therapy in patients with disseminated cysticercosis leads to a significant reduction in lesion load and improvements in seizures and headache as well. None of the patients studied had any serious side-effects. Approximately 38% of parenchymal neurocysticercosis cysts become calcified even after antiparasitic treatment. Calcified lesion is a persistent source of seizure recurrences.

Key points

• Neurocysticercosis is the most common CNS parasite, with most U.S. cases coming from immigrants from Mexico and Latin America.

• Neurocysticercosis comes from eating viable cysts from human feces of individuals infected with the pork tapeworm and not from eating undercooked infected pork meat.

• So long as organisms remain viable in the brain, the patient is usually asymptomatic due to the parasite cyst producing proteins that prevent the host from initiating an inflammatory response to destroy the cyst.

• Seizures are the most common clinical manifestation, and headaches are the second most common.

• Diagnosis is usually made by demonstration of typical cysts on MRI or CT scan plus presence of cysticercosis enzyme-linked immunoelectrotransfer blot antibody assay in serum or CSF.

• Treatment of parenchymal cysts using albendazole with or without corticosteroids hastens disappearance of parenchymal cysts and reduces rate of seizure recurrence, but treatment of extraparenchymal cysts in meninges or ventricles is difficult and often requires ventricular shunting and repeated courses of albendazole and long-term steroids.

Historical note and terminology

Cysticercosis is a zoonotic infection involving pigs and man and has an ancient history (33). Tapeworms have been found in 3000 B.C. Egyptian mummies. Human tapeworms were recognized by Hippocrates, and "mealy" pork containing cysticerci were described by Aristotle. Cysticercosis likely was recognized early on as dangerous to humans in that the ancient Hebrew Bible forbid consumption of pork and the ancient Koran also forbid pork consumption.

Many ex-soldiers (who served in India from 1926 until 1929) after returning from India, were reported to be suffering from epilepsy. In the majority, epilepsy proved to be due to cysticercosis. The diagnosis was based on 1 of 4 criteria: palpation of subcutaneous nodules of calcified cysts; x-ray demonstration of calcified cysts in the muscles or in the skull; the presence of eosinophils in the spinal fluid, not a common finding; or a positive complement-fixation test (12; 63; 25). Praziquantel was approved for medical use in the United States in 1982. Sotelo and co-workers, in 1984, demonstrated that praziquantel is effective in cysticercosis of the brain parenchyma (125).

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