How do you diagnose neurocysticercosis (neurocysticercosis) infection?

Diagnosis of Neurocysticercosis

The diagnosis of neurocysticercosis requires both neuroimaging studies (MRI and non-contrast CT scan) and serologic testing with enzyme-linked immunotransfer blot (EITB) as confirmatory test. 1

Clinical Presentation

Neurocysticercosis typically presents with:

• Seizures (most common manifestation of parenchymal neurocysticercosis)
• Increased intracranial pressure (most common with meningeal neurocysticercosis)
• Headache
• Focal neurological deficits

Diagnostic Algorithm

Step 1: Neuroimaging

• Both MRI and non-contrast CT scan are recommended 1
  • MRI: Better for visualizing cysts in ventricles, subarachnoid space, and brainstem
  • CT: Superior for detecting calcifications
  • Absolute diagnostic finding: Visualization of cystic lesions showing the scolex (parasite head)

Step 2: Serologic Testing

• Enzyme-linked immunotransfer blot (EITB) for detection of anticysticercal antibodies in serum 1
  • High specificity (>99%) and sensitivity (>90% for patients with multiple lesions)
  • AVOID enzyme-linked immunosorbent assays (ELISA) using crude antigen due to poor sensitivity and specificity 1

Step 3: Apply Diagnostic Criteria

Based on the 2001 diagnostic criteria 2, revised in 2012 3:

1. Absolute criteria:

   • Histological demonstration of parasites from brain/spinal cord biopsy
   • Cystic lesions showing the scolex on neuroimaging
   • Direct visualization of subretinal parasites on fundoscopic examination

2. Major criteria:

   • Lesions highly suggestive of neurocysticercosis on neuroimaging
   • Positive serum EITB for anticysticercal antibodies
   • Resolution of cystic lesions after antiparasitic therapy
   • Spontaneous resolution of single enhancing lesions

3. Minor criteria:

   • Lesions compatible with neurocysticercosis on neuroimaging
   • Clinical manifestations suggestive of neurocysticercosis
   • Positive CSF ELISA for anticysticercal antibodies/antigens
   • Evidence of cysticercosis outside the CNS

4. Epidemiological criteria:

   • Household contact with T. solium infection
   • Living in or coming from endemic areas
   • History of travel to endemic areas

Diagnostic Certainty:

• Definitive diagnosis: One absolute criterion OR two major plus one minor and one epidemiological criterion
• Probable diagnosis: One major plus two minor criteria OR one major plus one minor and one epidemiological criterion OR three minor plus one epidemiological criterion

Additional Diagnostic Considerations

• Fundoscopic examination is mandatory for all patients before initiating anthelmintic therapy 1
• Screen household members for tapeworm carriage in non-endemic areas 1
• Consider PCR amplification of parasite DNA in CSF for difficult cases 4

Pitfalls to Avoid

1. Relying solely on a single test: No single test is sufficient for diagnosis
2. Using ELISA with crude antigen: Poor sensitivity and specificity 1
3. Misinterpreting imaging findings: Many lesions are non-pathognomonic
4. Overlooking ocular involvement: Always perform fundoscopic examination before treatment
5. Failing to consider epidemiological factors: Travel or residence history is important

Pre-Treatment Evaluations

Before initiating treatment, additional evaluations are recommended:

• Screening for latent tuberculosis infection if prolonged corticosteroids are anticipated 1
• Screening or empiric therapy for Strongyloides stercoralis if prolonged corticosteroids are anticipated 1
• Fundoscopic examination to rule out ocular cysticercosis 1

The diagnosis of neurocysticercosis requires careful integration of clinical, radiological, immunological, and epidemiological data, with neuroimaging and EITB serving as the cornerstones of diagnosis.