Neurocysticercosis is the most frequent parasitic disease of the Central Nervous System (CNS); it affects 2 to 4% of the general population in endemic areas. Cysticercosis occurs when man becomes an intermediate host of Taenia solium.
Biological cycle of the Taenia solium
The Taenia solium is a cestode formed by a head, which has a double crown of hooks and four suckers, as well as a neck and a body formed by hundreds of proglottids. The definitive host of this parasite is man. Taenia solium lives in the small intestine, where it adheres to the intestinal mucosa; the parasite is shed hundreds of distal proglottids (full of eggs) that are removed along with the feces. Both the man and the pig when eating food contaminated with eggs become intermediate hosts. The eggs in the stomach lose their cover and release oncospheres, which go through the capillaries and travel through the bloodstream to be deposited preferably in muscle tissue, eyes, and brain.
Stages of development of the cysticercus
Once the parasite has been housed in the SNC, it passes through three stages of development. The first stage is the vesicular phase, in which the parasite is a cyst with a very thin membrane, transparent and filled with clear fluid, the cysticercus can remain for decades in this stage or can – as a result of an immune attack by the guest- enter a process of degeneration that ends with the death of the parasite. The next evolutionary stage is the colloidal stage, in which the vesicular fluid becomes viscous and turbid, then the cystic wall thickens and the scolex becomes a granular structure, hence the name of this nodular granular stage, in the which the cysticerci are no longer viable. Finally, they enter the calcified nodular stage, in which the parasite becomes a calcified and inert nodule. The exact time the cysticercus spends at each stage is not known.
Depending on the location of the parasite, neurological signs of focalization may be present, this means signs of involvement of the pyramidal pathway with motor deficit, sensory alterations, language, coordination, and so on.
When an inflammatory response occurs in the subarachnoid space, arachnoiditis occurs which is the cause of hydrocephalus (Figure 3), with symptoms of headache, vomiting and papilledema. This same inflammatory reaction on the cerebral blood vessels can cause vasculitis and in turn cerebral infarcts.
Diagnosis
The diagnosis is made by clinical and epidemiological data, supported by studies of computed tomography and magnetic resonance of the skull. These studies help locate the parasite and define its evolutionary stage.
It can happen that in the same patient several parasites are observed in different stages; likewise, it is possible to detect arachnoiditis, hydrocephalus and heart attacks. When the meninges are affected, the analysis of the cerebrospinal fluid (CSF) can be useful; Characteristically hypoglucorraquia is reported, a great hiperproteinorraquia and pleocitosis. The immunological test in the CSF as the ELISA test are highly sensitive in active subarachnoid cysticercosis.
Treatment
The inactive (calcified) phase of cysticercosis does not require treatment.
In the treatment of active phases, the use of steroids is recommended initially and then the use of cysticides.
Symptomatic treatment is very important, and includes antiepileptics, analgesics, and mannitol for cerebral edema, among others.
Hydrocephalus requires – in most cases – the placement of a ventriculo-peritoneal bypass valve. Some intraventricular cysts can be removed by means of endoscopic aspiration.
Forecast
The prognosis is variable, it can be a disease of asymptomatic benign course until extreme cases in which severe incapacities take place and even the death.
Prevention
Having health infrastructure, hygiene and an adequate level of education will reduce the risk of acquiring this infection. It is very important to inculcate in our environment how dangerous it is to eat foods prepared with poor hygiene. Especially in this country where food stalls abound on the street, whose cleaning is very doubtful.
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