Neurocysticercosis (NCC)

Definition and Epidemiology

• Endemic in Latin America, Sub-Saharan Africa, India, China, and Southeast Asia
• Estimated 0.45-1.35 million epilepsy cases due to NCC in Latin America; ~1 million in India; 0.31-4.6 million in Africa
• In the US: 1,320-5,050 new cases/year, driven by immigration from endemic regions
• Also occurs in non-endemic countries through immigration of tapeworm carriers

Life Cycle and Pathogenesis

1. Taeniasis - ingestion of undercooked, contaminated pork containing cysticerci → adult tapeworm in intestine
2. Cysticercosis - ingestion of T. solium eggs (fecal-oral route from a tapeworm carrier, including auto-infection) → oncospheres released, penetrate intestinal wall, disseminate via bloodstream to tissues including brain

Classification by Location

Stages of Parenchymal NCC (Radiological)

Neuroimaging

• 1-2 cm cystic lesion with thin walls and 1-3 mm mural nodule (scolex)
• Ring-enhancing lesion with perilesional edema
• Calcified foci (burnt-out cysts)
• Hydrocephalus

• Superior detection of the scolex (pathognomonic)
• Better visualization of intraventricular, subarachnoid, and brainstem lesions
• FLAIR sequences highlight cyst fluid and scolex

Clinical Manifestations

• Seizures - most common presentation (focal or generalized); typically occur as the parasite degenerates
• Headache
• Focal neurological deficits
• 80-90% of enhancing lesions resolve within 3-6 months; ~20% of patients continue to have seizures

• Obstructive hydrocephalus (intraventricular)
• Elevated ICP, sudden death (4th ventricle cysts that float and obstruct = "ball-valve" effect)
• Chronic meningitis, vasculitis, brain infarcts (subarachnoid/leptomeningeal)
• Diplopia, cranial nerve palsies

• Pleocytosis (lymphocytes, neutrophils, or eosinophils)
• Elevated protein
• Usually normal glucose (can be markedly reduced)

Diagnosis

Del Brutto Revised Criteria (2017)

• Histologic demonstration of cysticercus in biopsy specimen
• Cystic lesion with scolex on CT/MRI
• Direct visualization of subretinal parasite

• Cystic lesion without scolex
• Ring-enhancing lesion (1-2 cm)
• Multilobulated cystic lesion in subarachnoid space
• CT hyperdense or calcified parenchymal lesion

• Obstructive hydrocephalus or abnormal leptomeningeal enhancement

• Specific anticysticercal antibodies detected by EITB (enzyme-linked immunoelectrotransfer blot) - >99% specific and sensitive in patients with multiple cysts (note: single lesions or calcifications may be seronegative)
• Cysticercosis outside the CNS
• Household contact with T. solium infection

• Clinical manifestations suggestive of NCC (seizures, obstructive hydrocephalus)
• Residence in an endemic region

Serology Notes

• EITB using lentil lectin-purified glycoproteins: >99% specific, highly sensitive for multiple cysts
• Standard ELISAs: HIGH false-positive and false-negative rates - should be avoided
• Antigen-detection assays (CSF, blood, urine) available in Europe; not in the US
• PCR increasingly used for extraparenchymal disease follow-up

Treatment

Step 1: Stabilize First

• Antiparasitic treatment is never an emergency and should never be started with elevated ICP
• Control seizures with antiseizure medications first
• Address hydrocephalus before antiparasitics

Step 2: Antiparasitic Therapy (by form)

Albendazole (Drug of Choice)

• Dose: 15 mg/kg/day (or 400 mg twice daily) for 8-28 days
• Preferred over praziquantel because:
  • Shorter course
  • Lower cost
  • Better penetration into subarachnoid space
  • Drug levels increase when given with corticosteroids (praziquantel levels decrease with steroids)
• Combination therapy (albendazole + praziquantel 50 mg/kg/day) is more effective for >2 cystic lesions or multiple subarachnoid cysts

Praziquantel

• Single dose 10 mg/kg for intestinal taeniasis
• Avoid initiating for taeniasis if CNS cysticercosis may be present (can trigger CNS inflammation)
• Used as adjunct to albendazole for multiple/extraparenchymal disease

Anti-inflammatory Therapy

• Always co-administer corticosteroids with antiparasitics (dexamethasone 0.1-0.4 mg/kg/day or prednisone 60 mg/day)
• Rationale: both antiparasitics cause inflammatory response around dying larvae → can worsen seizures or hydrocephalus
• Subarachnoid/giant cysticercosis requires prolonged anti-inflammatory treatment

Seizure Management

• Antiseizure monotherapy is usually sufficient
• Single enhancing lesions: taper ASMs after 6 months if imaging normalizes and no breakthrough seizures
• Multiple parenchymal lesions: more prolonged therapy (~2 years), especially if calcifications develop
• Calcified lesions with perilesional edema/enhancement: higher risk of recurrent seizures

Intraventricular Hydrocephalus

• Neuroendoscopic cyst removal is preferred
• Avoid antiparasitics before surgery (make cysts friable and harder to remove)
• Shunt failure was historically a major problem; mitigated by antiparasitics + corticosteroids post-shunt
• Recent meta-analysis (PMID 40381508, 2025): Neuroendoscopic management of intraventricular NCC shows favorable outcomes as the preferred surgical approach

Prevention

• Access to clean water and sanitation
• Proper handwashing, especially when handling food
• Well-cooked pork (56°C for 5 minutes destroys cysticerci)
• Refrigeration or freezing (-10°C for 9 days) kills parasites
• Inspection of pork
• Treatment of tapeworm carriers prevents egg shedding and community transmission

Key Points Summary

1. NCC = CNS infection by T. solium larvae; most common cause of epilepsy in the developing world
2. Transmission is via ingestion of T. solium eggs, NOT contaminated pork (that causes intestinal taeniasis)
3. Four radiological stages: vesicular → colloidal vesicular → granular nodular → calcified nodular
4. Only vesicular and colloidal stages are treated with antiparasitics
5. Albendazole is the drug of choice; combine with praziquantel for >2 cysts
6. Always co-administer corticosteroids; never start antiparasitics with raised ICP
7. Intraventricular cysts: neuroendoscopic removal is the primary approach
8. EITB is the preferred serologic test (avoid standard ELISAs)
9. Ocular cysticercosis: surgical only - antiparasitics contraindicated