Neurocysticercosis
Definition and epidemiology
Neurocysticercosis is infection of the central nervous system with the larval stage of Taenia solium (the pork tapeworm). It is the leading cause of adult‑onset epilepsy in endemic countries but is uncommon in the UK; most UK cases are imported in people from or with travel to endemic areas.
Typical emergency department (ED) presentations are new focal or generalised seizures, headache, focal neurological signs or raised intracranial pressure.
Clinical features that raise suspicion
- New‑onset seizure(s), including status epilepticus, particularly in people from endemic areas or with relevant travel or household history.
- Focal neurological deficits, progressive headache, vomiting, reduced conscious level or signs of meningism (depending on cyst location).
- Imaging demonstrating single or multiple ring‑enhancing lesions, calcified nodules, ventricular or subarachnoid cysts.
- Consider neurocysticercosis where seizures or focal brain lesions occur in the correct epidemiological context.
Pathophysiology and radiological stages Parenchymal cysts evolve through recognised stages that influence imaging appearance and management:
- Vesicular (viable): thin‑walled cyst; scolex may be visible; little surrounding oedema.
- Colloidal/degenerating: inflammatory response with ring enhancement and perilesional oedema - this stage most commonly causes seizures.
- Granular nodular: shrinking lesion with reduced enhancement.
- Calcified: inactive residual nodule; can remain epileptogenic.