Investigations

Laboratory tests:

Definitive diagnosis of neuroeysticercosis requires finding the parasite on histologic section of specimens removed by excisional biopsy of skin or subcutaneous tissues (not of brain tissue). Patients should be thoroughly examined by palpation for pea-sized nodules. Presumptive diagnosis may be made by the following tests.

Imaging

Plain radiographs of muscle may detect oval or linear calcified lesions (4-10 X 2-5 mm). The lesions are usually multiple, sometimes in the hundreds, and the long axis of the cysts are nearly always in the plane of the surrounding muscle fibers. Plain skull films may demonstrate one or more cerebral calcifications (generally 5- 10 mm; sometimes 1-2 mm when only the scolex is calcified).

The most useful procedures for examining the skull are imaging by CT and MRI. CT patterns for parenchymal cysts include (1) vesicular cysts (viable cysts with no host immune reaction), which are rounded areas of low density with little or no enhancement after contrast medium; (2) colloidal cysts (dead or dying cysts with host immune reaction), which are hypodense or isodense lesions surrounded by edema associated with ring-like or nodular enhancement; and (3) granuloma or calcifications (dead cysts), which are often several millimeters in diameter but variable in size. Signs of increased intracranial pressure and diffuse brain edema may also be seen. A combination of images is often found, owing to different developmental stages. As compared with CT, MRI has superior resolution for vesicular cysts (isodense, similar to cerebrospinal fluid) and for colloidal cysts (hyperdense). However, CT is superior for granulomas and calcifications, the most frequent presentations of cysticercosis, which MRI may miss. The MRI sometimes detects pathognomonic 2- to 4- mm nodules (protoscoleces) within cyst fluid. Intraventricular cysts (isodense) are not seen on routine CT but require intraventricular contrast medium. Spinal cysticercosis is evaluated by CT myelography or MRI.

Immunologic tests

With serum, the new immunoelectrotransfer blot test appears to reach nearly 100% specificity and 95% sensitivity (sensitivity appears to decline if only one or two cysts are present), whereas the ELISA showed. respectively, 63% and 65%. Hydatid disease and H nana infections cross- react in the ELISA. Sensitivity using cerebrospinal fluid was 86% by immunoblot and 62% by ELISA. Patients presenting with only calcified lesions or granulomas are generally serologically negative.

. Other tests

The cerebrospinal fluid in neurocysticercosis should be evaluated for IgM (by ELISA) and IgG antibody, the fluid typically shows increased protein, decreased glucose, and a cellular reaction of mainly lymphocytes and eosinophils; eosinophilia over 20% is diagnostically important. Lumbar puncture is contraindicated in case of increased intracerebral pressure. The EEG may be abnormal.

Though the patient usually no longer harbors a tapeworm, stools from both the patient and family members should be examined over several days by each individual for the passage of progiottids and by the laboratory for proglottids and eggs.

Differential diagnosis

The differential diagnosis includes tuberculoma, tumor, hydatid disease, vasculitis, chronic fungal disorders, toxoplasmosis and other parasitic diseases, and neurosyphilis.