Sparganosis, a zoonotic parasitic disease caused by the larvae of tapeworms named sparganum, has been recognized worldwide, but it is commonly seen in China, Korea, Japan and eastern Asia. The adult tapeworm parasitizes in small intestine of definitive hosts such as cats, dogs and other carnivores, and their eggs Passed to outsides with feces. Under appropriate conditions, the eggs are hatched in water and release coracidia after 2-5weeks. If coracidia are ingested by cyclops, the first intermediate host, then they will develop into procercoid, and when procercoid are swallowed by second intermediate hosts such as amphibians, reptiles and other mammals, especially frogs in which they will accordingly develop into plerocercoid called sparganum . The majority of sparganum in the human body remain their larval states, but they will invade various tissues and organs of the human body, and cause varying degrees of lesions. They can lodge in human body in the number of dozens, surviving in human tissues for 12 years, or even up to 36 years. There are three ways of human infection with sparganum : (1) Using raw meat or skin from frogs or snakes as poultices; (2) Eating raw or undercooked frog or snake meat and ingestion of live tadpoles; (3) Drinking water contaminated with intermediate hosts. Sparganum can invade the human body through wounds or normal skin and mucous membranes, and then migrate to various tissues of the body. However, the adult Spirometra mansoni seldom parasitizes the human body and has little pathogenicity to humans . But the infected patients may be reported with some mild symptoms such as discomfort or slight pain in the epigastrium and central abdomen, even nausea and vomiting. Human sparganosis caused by sparganum is far more harmful than that caused by adult Spirometra mansoni. Besides, lesions vary with the migration and residence of sparganum. Sparganum could lodge in human eyes, subcutaneous body of limbs, oral and maxillofacial regions, followed by central nervous system lesions. It is also reported that they are found in internal organs such as lungs, scrotal and bladder [4, 5]. However, lumbosacral spinal canal involvement is extremely rare. spinal sparganosis patients may present with radicular pain, neurogenic bladder, and paraparesis. In our case, however, the patient showed only perianal pain.
In the case of cerebral sparganosis, the typical signs on CT include hypodensity of the white matter, irregular or nodular-enhancing lesions and small dot-like calcification. MRI findings may include aggregated ring-like enhancement (often three to six bead-shaped rings), "tunnel sign" with enhancement of lesions, and migration of radiographic lesions as larvae migrate. In our case, the lumbosacral MRI revealed heterogeneous enhancing lesion at the S1-2 level. The gold standard for diagnosis of sparganosis remains histological examination . In addition, IgG antibodies to sparganum from serum or CSF can be detected by ELISA, which has high sensitivity and specificity . However, the diagnosis mainly depends on surgical detection of the worms due to the rare presence of sparganosis. In our case, the ELISA for anti-sparganum antibodies was positive in both plasma and CSF collected on the day after operation.
In terms of treatment, it is essential to completely remove sparganum even their cephalic segment. The mainly methods are surgical removal of the larva and administration of high-dose praziquantel. Surgically,sparganum should be removed completely and thoroughly in case that the residual scolex leads to recurrence. And as for drug treatment, praziquantel has been proved a suitable option. A recent retrospective study indicated that 94 percent of patients with central nervous system sparganosis have improved radiographically after treating with a high-dose regimen of praziquantel . As for our patient, the proliferative inflammatory granulation adhered to his nerve tissue of cauda tightly. Therefore, we just took out the live worm rather than removing inflammatory granulation tissue in case of any risks. After operation, the patient has been continuously treated with medicine including praziquantel, albendazole, and dexamethasone. Serological tests were repeated at appropriate intervals to evaluate the efficacy of treatment.