Question
Cysticercus cellulosae.
Answer
Cysticercus cellulosae is the larval (cysticercus) stage of the pork tapeworm Taenia solium, developing when a human (or pig) ingests infective T. solium eggs — humans thereby acting as an accidental intermediate host, resulting in the disease cysticercosis.
Formation: ingested eggs hatch in the intestine, releasing oncospheres, which penetrate the intestinal wall, disseminate via the bloodstream, and encyst in various tissues — most importantly muscle, subcutaneous tissue, the eye, and, of greatest clinical significance, the central nervous system (neurocysticercosis).
Structure: a small, fluid-filled cyst (typically a few millimetres to ~1 cm), containing a single, invaginated scolex (the larval “head,” with hooks and suckers, that will evaginate to become an adult tapeworm’s scolex if the cyst is instead ingested by a new human definitive host via undercooked pork) — this differs structurally from the hydatid cyst of Echinococcus granulosus, which is typically much larger and contains numerous protoscolices/brood capsules rather than a single scolex.
Clinical significance — neurocysticercosis: the most important and common manifestation, and a major cause of acquired epilepsy/seizures in many endemic regions worldwide; cysts in the brain parenchyma, ventricles, or subarachnoid space can also cause raised intracranial pressure (particularly with ventricular/racemose cysts obstructing CSF flow), focal neurological deficits, and, when the cyst degenerates and dies (often precipitating the most acute inflammatory/symptomatic phase, sometimes triggered by treatment itself), an intense host inflammatory response contributing significantly to symptoms.
Laboratory/imaging diagnosis: CT/MRI — the primary diagnostic tool, showing characteristic cystic lesions, sometimes with a visible scolex (a “hole-with-dot” appearance), at various stages of degeneration/calcification; serology (ELISA, enzyme-linked immunoelectrotransfer blot/EITB) — supports diagnosis, particularly for extraneural cysticercosis or when imaging is equivocal; stool examination for coexisting intestinal T. solium infection (taeniasis) in the patient or household contacts, since ongoing exposure to a tapeworm carrier is a risk factor for continued/repeated cysticercosis transmission.
Treatment: antiparasitic therapy (albendazole ± praziquantel) combined with corticosteroids (to control the inflammatory response as cysts die) for viable parenchymal neurocysticercosis with seizures; antiepileptic drugs for seizure control; surgical intervention for cysts causing hydrocephalus/mass effect; calcified, inactive lesions generally require only symptomatic (antiepileptic) management rather than antiparasitic therapy.