SUMMARY

Schistosomiasis of the spinal cord should be considered in cases of acute or subacute transverse myelitis occurring in tropical areas especially when peripheral eosinophilia is present. Five cases of schistosomiasis of the spinal cord are reported in detail and the pathophysiology, diagnosis and treatment are discussed.

Keywords : schistosomiasis, Spinal cord, bilarziose

RESUME

La schistosomiase de la moelle epiniere va prise en consideration dans les cas de myelite transverse a debut aigue ou sub-aigue en milieu tropical surtout en presence d’eosinophilie peripherique. Cinq cas de schistosomias de la moelle epiniere sont presentes en detail el la pathophysilogie, le diagnostique et le traitement sont discutes.

Mots cles: schistosomiasis moelle épinière

Schistosomiasis of the spinal cord (S.S.C.) should be considered in the tropics in cases of acute or subacute transverse myelitis, especially in presence of peripheral eosinophilia.
Any of the three major species of schistosoma (Haematobium, Japonium and Mansoni) may involve the central nervous system: while Schistosoma Japonicum has a greater tendency to invade the brain, Schistosoma Mansoni and to a lesser extent, Schistosoma Haematobium, involve more commonly the spinal cord. The lateral spike of the egg of the Schistosoma Mansoni may impede its further progress in embolzing the brain. It also secrets a fibroblastic stimulating factor which results in a higher probability of forming a microgranuloma. When hepato-splenic involvement is present and /or in presence of corpulmonale the presence of Schistosoma Mansoni eggs is much increased. Histopathological examination of the lesion of the C.N.S. unvariably reveals a tumour like mass formed by microgranulomata containing live or dead (calcified ) eggs of bilharzia.
Eggs of the parasites in all other locations in the human body, apart from the brain and spinal cord, are usually encapsulated in non – immune subjects: this fact is usuaslly accompanied by peripheral eosinophilia. In immune Africans, the eggs are usually scattered, there is little or no granuloma formation and no peripheral eosinophilia.

In the C.N.S. instead, the presence of eggs always triggers a foreign body like reaction with encapsulation in granulomata and there is always significant eosinophilia. The pathogenetic mechanism seems however triggered more by cell mediated hypersensitivity than by the space occupying lesion phenomenon itself. The different correlations at autopsies between presence of eggs of schistosoma in the C.N.S. and the rest of the body reported in the various reviews is probably related to varying degrees of worm load and oviposition in different geographical conditions.

Schistosomiasis of the spinal cord shows a greater occurrence at the level of T 12 – LI. Venous communications between pelvic veins and vertebral venous plexus have been demonstrated by BATSON (1940). This is the most likely route both for ova and the trematode. Probably the anastomosis is maximum and favourable to the parasites at the level of T 12 – LI : blood flows retro gradely from the deep iliac veins and the intema vena cava and the plexus of BATSON is valveless.

The diagnosis is based on the history of esposure or living in an endemic area, the presence of important peripheral eosinophilia and of course, the demonstration of eggs in the urine and / or faeces, the positivity of serological tests (haemogglutination, ELISA, IgG, IGM, monoclonal antibodies). The cerebro-spinal fluid is usually normal, but xantochromia and pleyocitosis have been reported (GAMA 1953, ADELOYE 1982): protein content may be raised but sugar levels are normal.

As reported by EL-BANHAWY (1972), some cases may not have any evidences ofbilharzia infection outside the spinal cord. When the spinal-cord involvement is suspected, a myelography often reveals a mass compression at the suspected level. The advent of new imaging techniques as C.T. Scan and M.R.I. screening as a routine investigation for motor/sensory deficits of spinal cord has evidenced the fact that Schistosoma as a cause of myelitis is probably more common than expected. The report of the American students that contracted Schistosoma Masoni while camp ing in an endemic area in Kenya can well prove this point. Of 18 young students who were exposed to Schistosoma, 15 acutely contracted Schistosoma Mansoni. Of these, 2 presented with paraplegia and diagnosed in Nairobi to have Schistosoma Mansoni spinal cord involvement. The diagnosis was later confirmed by C.T. scan in the U.S.A. (C.T. scan was not yet available in Kenya in 1984). All students were treated with Oxamiquine and/or praziquantel and all of them recovered, (cases no.4 and 5 in table 1 and table 2).

Table 1: Schistosomiasis of the spinal cord clinical features

Table 2 : Schistosomiasis of the spinal cord laboratory and radiological examination

The treatment of the Schistosomiasis of the spinal cord is based on pharmacological eradication of the parasites, high doses of steroids (pre-dnisolone) and surgery if indicated. There is no consistent response to treatment. Although all antischistosomal drugs act only on the adult worms, it is universally accepted that granulomas always regresses with chemotherapy. This fact should be bom in mind when granulomatous lesions of parasitic origin that are calcified are found in the C.N.S. and are suspected to cause myelitic or encephalitic symptoms. A case on example is neurocysticercosis.
the chances of total cure. Unfortunately the production of Oxamniquine seems to have been discontinued recently.
About the surgical treatment, laminectomy is still an important adjunct to the management of patients who developes acute or subacute paraplegia with spinal block (ELBANHAWY 1971, RUBERTI et all 1976) or who deteriorate despite conservative treatment. In some cases, recovering from paraplegia has started within few days after decompressive laminectomy (GAMA 1953, RAPER et all 1948, DAR et all 1977).
The spinal cord functions however may not recover probably due to compression, fibrosis or ischaemic changes. The pharmacological treatment ofbilharzia relies at the present time on three drugs of which one, the praziquantel, is effective in all three species, while Oxamniquine is used for S.Mansoni and metrifonate for S.Haematobium. Nyridazole, hycanthone, Oltipraz have been abandoned because of inconvenient side effects.
Oxaminquine, praziquantel and Metrifonate are remarkably well tolerated and they are very effective in reducing the eggs excretion. Their effectiveness as eradication agents has however been decling. Numerous hypotheses have been suggested to explain this fact, from genetically transmitted resistance to drugs, to the « escape » phenomenon in which the adult worms « sense » the presence of the drug in the venous blood and escape in the surrounding fat tissue, so eluding high concentration of the drug. The anecdoctical resistance to treatment by obese patients may explain this fact.
In any case, often several courses of treatment may be required even in the absence of re \u2013 infection. After a period of well being, documented by regression of subjective symptoms such as tiredness, by normalization of the eosinophilia count and disappearance of the eggs in the excreta and reduction in the titre of the serological tests, the disease may restart. The use of two drugs in association, praziquantel plus the specific Oxamniquine and Metrifonate seems to increase
Resection of granulomatous tissue should be avoided (BIRD 1964, BARNETT 1965. RUBERTI et all 1976, ADELOYE et all 1982) and only a biopsy should be obtained. Decompression and mobilization of the nerve roots should be performed living the dura open or repairing the dural defect with dural substitutes.
The role of the steroids remains very controversial. In any case their use should be considered only after effective anti parasitic chemotherapy. Their use in the KATAYAMA syndrome (immunological reaction to developing schistosomulae) when it involves the C.N.S. seems to be more appropriate.