Cysticercosis is probably the most common parasitic infestation of the
human nervous system. Humans acquire the infestation by eating infected
undercooked pork (measly pork). But cysticercosis is acquired by ingestion
of eggs (encysted larvae) of the pork tapeworm, T.solium, either by
ingestion of contaminated salads or water, or by auto infection due to ano-oral
contamination or reverse peristalsis. Tapeworm infestation can occur only
in nonvegetarians, but Cysticercosis may occur in vegetarians also.
The
occurrence of the encysted larvae in the brain, spinal cord, meninges and
eyes is known as neuro-cysticercosis. Cysts may also occur in the
muscles.
A high
prevalence has been reported from the developing countries. The
parenchymatous variety is more common in India whereas the meningeal and
ventricular types are more common in South America, Poland and Mexico.
In
India, higher prevalence has been reported in northern states.
Pathology:
Cysticerci may lodge anywhere in the body, but have a predilection for the
muscle, eye, subcutaneous tissue and CNS. In the CNS, it can localize in
the parenchyma (grey matter), ventricles(4th ventricle),
subarchnoid space and the spinal cord (extramedullary intradural). In the
eye, the vitreous is involved.
A
special form, termed cysticercosis reacemosus is a conglomeration
of cysts in the subarchnoid space, is frequently seen in Latin America.
Once the
larva dies, it calcifies. The cysts vary in size and often multiple. The
inflammatory response is variable. At times it may contain scolices.
Pathologically, it may result in meningo-encephalitis, granulomatous
meningitis, focal granulomas or abscess, hydrocephalus, ependymitis and
arteritis.
Clinical features:
They may
present with one or more of various syndromes namely, seizures, raised ICT,
ICSOL like, meningoencephalitis, psychiatric disorders and stroke, and
radiculopathy or myelopathy, if the spinal cord is involved.
Epilepsy
is the commonest manifestation in India.
Increased ICT is the next commonest, simulating benign ICT.
Meningoencephalitis presents with a pyrexia, altered sensorium, seizures,
raised ICT, multiple cranial nerve involvement and brainstem and
cerebellar involvement have been reported.
Ischaemic effects seem to affect the young.
Subcutaneous nodules and ocular cysts are important indicators.
Diagnosis:
There is
eosinophilia in the blood and CSF. Biopsy of the subcutaneous nodules, if
any, may help.
Serological tests are nondiagnostic on their own. These include, indirect
haem-agglutination test and enzyme linked immunosorbent assay (ELISA)
which is about 80% sensitive in CSF. False positives may occur in patients
with hydatid, filariasis, TBMs and viral encephalitis. Those with active
inflammatory response are likely to have high titers, as expected. Those
with intraventricular cysts have a low titer.
Lately,
the enzyme linked immuno electro transfer blot (EITB) test has been
introduced and reported to be 100% sensitive in patients with two or more
viable lesions.
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Radiological appearances:
The
ventricles may be narrowed with extensive low attenuated areas in the
parenchyma, sparing the cortex.
A
ring enhancing active lesion with surrounding edema is the second
common.
A
homogeneously enhancing lesion represents a dying larva.
Calcified lesions are also common in CT.
The
racemose type appears as a bunch of grapes.
The
intraventricular types are better seen in MRI.
MRI
may reveal scolex as an high intensity inside a cyst.
Treatment:
Praziquantel and albendazole are available. Opinions differ on dosage
and duration and the need for a second course. Some recommend
combined therapy.
Praziquantel:
50
mg/kg for 15 days. A second course is usually not of any benefit.
Side
effects include headache, anorexia, nausea, vomiting, parasthesias and
skin erythema.
Albendazole : more effective. |
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MRI-hypodense
cysts |
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Calcified cysts in the thigh |
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Racemose Cysticercosis-MRI |
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15mg/kg
in thrice daily for one month is the usual practice. Recent reports
suggest even a three days course is as effective.
Side
effects include gastrointestinal symptoms, alopecia, rash and pruritis.
Contraindicated in pregnancy and children of less than two years.
Major
side effects of these drugs are deterioration in neurological status,
exacerbation of seizures and rise in ICP due to host reactions to the
dying parasites, more so with praziquantel. A short course of steroids
help.
Intraventricular cysts require surgery-excision / or a shunt.
Racemose
variety does not respond to drug therapy and need excision.
Decompressive craniotomy may be life/vision saving on occasions.
Spinal
variety usually undergo surgery to confirm the diagnosis and releive the
cord
Serological tests are nondiagnostic on their own. These include, indirect
hemagglutination test and enzyme linked immunosorbent assay (ELISA) which
is about 80% sensitive in CSF. False positives may occur in patients with
hydatid, filariasis, TBMs and viral encephalitis. Those with active
inflammatory response are likely to have high titers, as expected. Those
with intraventricular cysts have a low titer.
