CNS Involvement by Paragonimus spp.: A Forgotten Mimic of Tuberculoma and Neurocysticercosis

FRCPath Prep Medical Microbiology Consultants
Jul 31
2 min read

Published: 31 July 2025

Category: Parasitology | Neuroparasitology | FRCPath Part 2

🔍 Overview

Paragonimus spp., classically known for causing pulmonary paragonimiasis ("lung fluke disease"), can invade extrapulmonary sites, including the central nervous system (CNS). Though rare, cerebral paragonimiasis is an important differential diagnosis for space-occupying lesions, especially in endemic areas. It is often misdiagnosed as tuberculoma, neurocysticercosis, or even brain abscess.

🌍 Epidemiology

Feature	Details
Endemic Regions	East and Southeast Asia, parts of Africa and South America
Species Implicated	Paragonimus westermani, P. mexicanus, P. heterotremus
At-Risk Groups	Individuals consuming raw/undercooked freshwater crabs or crayfish
CNS Involvement Rate	25–30% of extrapulmonary paragonimiasis cases

🧬 Life Cycle Summary (Neuroinvasion Path)

Step	Detail
Infective Form	Metacercariae from undercooked crab/crayfish
Entry	Ingestion → excyst in duodenum → penetrate intestinal wall
Migration	Usually to lungs → ectopic migration possible to brain/spinal cord
Pathogenic Mechanism	Granulomatous inflammation, space-occupying cystic lesions
Diagnostic Form	Ova in sputum, stool, or histological specimens (rare in CNS cases)

🧠 CNS Pathology & Clinical Features

Aspect	Description
Common Sites	Cerebrum (especially occipital lobe), cerebellum, spinal cord (rare)
Lesion Type	Granuloma, cystic lesion, hemorrhagic or necrotic foci
Key Symptoms	Seizures, headache, hemiparesis, visual disturbances, intracranial hypertension
Onset	Delayed (months to years after ingestion)
Imaging Findings	Ring-enhancing lesions, perilesional edema, calcifications (CT/MRI)

🧪 Diagnosis

Diagnostic Modality	Relevance
Serology (ELISA)	Highly sensitive for Paragonimus antibodies
Imaging (MRI > CT)	Suggestive but not specific — mimics TB, NCC
CSF Analysis	Often shows eosinophilia, raised protein, low glucose (not always)
Sputum/Stool Ova Detection	May be negative in isolated CNS cases
Biopsy	Rarely needed; may reveal fluke fragments or ova

FRCPath Tip: In CNS mass lesions with eosinophilic CSF and travel history to East Asia → consider Paragonimus even without pulmonary signs.

💊 Treatment

Drug	Regimen	Notes
Praziquantel	25 mg/kg TDS × 2–3 days	Mainstay treatment for both pulmonary and cerebral cases
Corticosteroids	Adjunct in severe neuroinflammation	Reduces mass effect and immune response
Surgery	Reserved for large cysts/mass effect	Rarely required

⚠️ Differential Diagnosis

Mimic	Key Differentiator
Neurocysticercosis	Often multiple cysts, calcified lesions, scolex on imaging
Tuberculoma	History of TB, TB PCR positive, response to ATT
Brain abscess	Rapid progression, systemic signs, microbial culture positive
Toxocariasis	Ocular/CNS eosinophilia, negative Paragonimus serology

🔗 Key References

WHO Control of Foodborne Trematode Infections (2021)
CDC DPDx Paragonimiasis https://www.cdc.gov/dpdx/paragonimiasis/
UKHSA Imported Parasitic Infections Guidance (2023)
Korean J Parasitol. 2020 Jun;58(3):213–220. "Neuroparagonimiasis: clinical overview."

🧠 FRCPath Part 2 OSPE/SAQ Tip

Scenario: A 38-year-old immigrant from Vietnam presents with new-onset seizures. MRI brain shows a solitary ring-enhancing lesion in the occipital lobe. CSF eosinophilia present.