Evaluation of Neurocysticercosis in Children

Examination

  • Nonspecific symptoms: NCC should be included in the differential diagnosis of nonspecific neurological symptoms such as seizures, headache, and paresis, especially in children from endemic regions.

Fundoscopy

  • Fundoscopic examination: This may provide evidence of subretinal cysticercus. This finding plus evidence of intracranial hypertension confirm the diagnosis of NCC (32).

Radiologic Tests

Plain x-rays

  • Calcified cysts: These may be seen in plain X-rays of skull and muscles (30)

Multiple calcified cysts in Plain X-Rays (a single lesion is circled in black). Images courtesy of  Dr. Supradip Ghosh, Department of Critical Care Medicine at Fortis Escorts Hospital, Faridabad, India

CAT scan

  • Calcifications are best detected by CAT scan: CAT is a good method for detecting cerebral cysticercosis at different stages of evolution. In the active stage, the cyst may be asymptomatic and appear as a rounded lesion, calcified or not, with or without visible scolex. Different forms may appear simultaneously, which is the evidence of several successive infestations (34).

CAT scan of calcified NCC cysts. Multiple calcified NCC cysts detected by CAT scan.

MRI

  • Viable larvae with scolex are seen in the vesicular phase: These lesions can appear as small and round cysts, close to the white–gray matter interface, with T1 and T2 appearances similar to that of CSF. They may also present as large cysts that continue to grow despite the absorption of the larvae (33,34,44). Vesicular cysts may be uncountable due to the large number of lesions.

MRI and CAT scans of stages of NCC. Vesicular with a living larva (A); colloidal with a degenerated larva (B); “granulonodular” with a thickened cyst membrane (C); calcification, the final stage (D).

 

 

  • Scolex visualization – The “hole-with-dot” sign is pathognomonic: The scolex may present as an eccentric or mural nodule, hyperintense in T1 and hypointense in T2 images (2,11,33,34,44).  Occasionally, the scolex can be seen as a hyperintense dot within the cyst (2,30,33).

Axial non contrast-enhanced T1 weighted MRI of scolex.  Scolex presense is seen on imaging as the “hole-with-dot” sign.

  • Cyst degeneration: As the cysts degenerate, they can be seen as hyperintense images in both T1 and T2 sequences. The liquid becomes turbid, and the capsule shrinks and thickens. Peripheral edema is more evident, and most lesions show a well-defined ring enhancement. Fluid-attenuated inversion recovery (FLAIR) sequences are particularly helpful for identifying associated edema and the scolex (11,33,34,44).

Enhanced T1 weighted coronal MRI showing degenerative cyst stage.  Coronal contrast-enhanced T1 weighted MRI showing the cyst degeneration phase.

  • Ventricular system is the second most common location: The fourth ventricle is the most affected. It is often difficult to differentiate the cyst within the ventricle from CSF because they have the same density or intensity as CSF.

Axial contrast-enhanced T1 weighted MRI of ventricular cyst.  This image shows cyst inside the left lateral ventricle (white arrow).

  • Racemose cysticercosis: Cysticercosis occurring in the extraparenchymal CSF spaces is a form with poor prognosis that affects the subarachnoid space, basal cisterns, and ventricles. Its characteristics are abnormal growth of cystic membranes with degeneration of the parasite’s head or scolex.

Images of racemose cysticercosis. Sagittal contrast-enhanced MRI (A). Axial contrast CAT ventriculography (B)

  • Subarachnoid space, cisterns, and cerebral sulci are site of the parasites in 3.5% of the cases (33): CSF pathway obliteration may be due to a direct mass effect on the CSF pathways, inflammatory reaction, or both (4,5,33,34).

Blood testing

  • EITB assay: This is the most reliable serological test for NCC. This test uses lentil lectin-purified glycoprotein antigens to detect antibodies to T. solium. For the testing, serum rather than CSF is recommended.
  • EITB sensitivity is ~98%: When a patient has two or more live parasites in the nervous system, EITB has a probability of being positive approximately 98% of the time. A major weakness of EITB is its low sensitivity (50–60%) in patients with SCG (45,46).
  • ELISA: Highly sensitive and specific for the diagnosis of living cysticerci (vesicular) localized in the subarachnoid space at the base of the skull. However, its sensitivity and specificity are considered poor in detecting parenchymal cysts (47).

CSF investigation

  • CSF – routine analysis: Nearly 50% of the patients have variable inflammatory reaction reflected in the white blood cell count. Mild abnormalities such as increased protein, pleocytosis, and in some cases eosinophilia may be found.
  • Anticysticerci antibodies in the CSF: The sensitivities of antibody detection by ELISA and EITB in the CSF are not significantly different. ELISA is less sensitive and specific in patients with viable NCC infections but is still used when EITB is not available. Detection of anticysticercal antibodies in the CSF by ELISA is 89% sensitive and 93% specific in patients with viable NCC infections (48).
  • Parasite DNA detection: PCR has also been used with CSF and fecal samples for identification of cysticercus DNA. Real-time CSF PCR has been shown to confirm the diagnosis of NCC in cases suggested by clinical, imaging, immunologic, and epidemiologic features (47) as well as in cases not diagnosed by the available radiological or immunological tests (47,49).

Correlation of Tests

The diagnosis of NCC can be difficult due to the unpredictability of clinical presentation. Currently, the diagnosis criteria are those proposed by Del Brutto et al.  that allow establishment of definite and probable cases of NCC (52).

  • Correlation imaging and blood/CSF immunoassays: The diagnosis is based on clinical epidemiological data, cerebrospinal fluid (CSF) examination, neuroimaging, and histology of biopsy samples. Recently new diagnostic criteria for NCC have been proposed however its clinical use is even more restricted.  The criteria were developed by experts in human cysticercosis including neurologists, neurosurgeons, parasitologists, infectious disease specialists and epidemiologists from Latin America, the Indian subcontinent and the United States. (50–52)

Diagnostic Criteria

Criteria Grade
 
Absolute Major Minor
     
Clinical Visualization of subretinal cysticercus Detection of specific anticysticercal antibodies or cysticercal antigens by well standardized immunodiagnostic tests Clinical manifestations suggestive of neurocysticercosis
Cysticercosis outside the CNS Individuals coming from or living in an area where cysticercosis is endemic
Evidence of a household contact with T. solium infection
 
Histologic Histological demonstration of the parasite from biopsy of a brain or spinal cord lesion.
 
Radiographic Conclusive demonstration of a scolex within a cystic lesion on neuroimaging studies Cystic lesions without a discernible scolex

Obstructive hydrocephalus (symmetric or asymmetric) or abnormal enhancement of basal leptomeninges

Cystic lesions without a discernible scolex.
Enhancing lesions
Multilobulated cystic lesions in the subarachnoid space
Typical parenchymal brain calcifications
Resolution of cystic lesions after cysticidal drug therapy
Spontaneous resolution of single small enhancing lesions
Migration of ventricular cysts documented on sequential neuroimaging studies

Degree of Diagnostic Certainty

Definitive diagnosis– when one of the conditions to right are met One absolute criterion
Two major neuroimaging criteria plus any clinical/exposure criteria
One major and one confirmative neuroimaging criteria plus any clinical/exposure criteria
One major neuroimaging criteria plus two clinical/exposure criteria (including at least one major clinical/exposure criterion), together with the exclusion of other pathologies producing similar neuroimaging findings.
Probable diagnosiswhen one of the conditions to right are met One major neuroimaging criteria plus any two clinical/exposure criteria
One minor neuroimaging criteria plus at least one major clinical/exposure criteria