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sparganosis is a rare parasitic infection caused by a migrating plerocercoid tapeworm larva ( = sparganum ) of the genus spirometra .
the sparganum is a wrinkled , whitish , ribbon - shaped organism that is a few millimeters wide and up to several centimeters long .
sparganosis is transmitted to humans by drinking water contaminated with copepods containing spargana , consuming the raw flesh of a second intermediate host such as frogs or snakes , or placing a poultice infected with spargana on an open wound .
although sparganosis may involve internal organs , such as the eyes , brain , and spinal cord , the clinical presentation of sparganosis usually occurs after the larvae have migrated to a subcutaneous location .
furthermore , because the mass is usually non - tender in early migratory stages and sometimes triggers a painful inflammatory reaction in the surrounding tissues , it is quite difficult to differentiate sparganosis from a soft tissue tumor based on preoperative radiographic and laboratory data .
we report here a rare case of intramuscular sparganosis involving the gastrocnemius muscle in an elderly patient who was diagnosed by ultrasonography and mri and treated by performing surgical excision .
a 77-year - old man was referred to our clinic from a private clinic because of a suspected soft tissue tumor . the patient had a 6-month history of a mass over the right posteromedial aspect of the proximal tibia .
physical examination revealed a 3 cm1 cm , soft , non - tender mass at the posteromedial aspect of the right proximal tibia , and the mass was freely mobile and easily compressed .
he had pulmonary tuberculosis when he was 30 years old , for which he was treated and believed to have been cured .
he also had the history of lobectomy because of a lung cancer in the left lower lobe at the age of 47 years and received a total gastrectomy due to an advanced gastric cancer at the age of 71 years .
plain radiographs of the right leg revealed multiple calcifications extending from the medial part of the knee to the calf .
ultrasonography revealed a heterogeneous , hyperechoic mass with a hypoechoic tubular lesion in the gastrocnemius muscle ( fig .
1 ) , and mri revealed multiple tubular and cystic lesions in the gastrocnemius muscle .
the lesions showed high signal intensity on t2-weighted images and multilobulated , peripheral enhancing low signal intensity on t1-weighted images ( fig .
the patient was a farmer , and he had occasionally ingested raw snake meat when he was young .
preoperative serodiagnosis of human sparganosis by using a monoclonal antibody - based competitive elisa was positive ( 3.79 in od value ) ( negative < 1.00 ) .
after preoperative ultrasound - guided marking for suspected cystic lesions , a longitudinal incision was made on the posterior aspect of the proximal tibia .
a white , shiny , synovium - like piece of tissue emerged from the incision , and this was identified as a sparganum that measured 30 cm in length and 0.5 cm in width and was wriggling after removal from the patient ( fig .
the calcified foci near the calf were also removed , and these tracts possibly represented the pathway along which the larvae had passed .
sixteen months after the operation , the patient revisited our hospital because of pain and paresthesia of the right thigh and a mass at the posterior aspect of the right distal thigh .
physical examination revealed generalized pain and a tingling sensation on the right thigh and multiple soft , mobile , non - tender masses at the posterior aspect of the right proximal tibia .
mri revealed a 1.8 cm - sized , well - circumscribed round mass arising at the right distal sciatic nerve .
the lesion showed heterogeneous high signal intensity on t2-weighted images and intermediate signal intensity on t1-weighted images with a target sign or a fascicular sign , and a benign neurogenic tumor , such as a schwannoma or neurofibroma , was suspected ( fig .
4 ) . multifocal tubular and cystic lesions were also detected around the mass , showing high signal intensity on t2-weighted images and low signal intensity on t1-weighted images ( fig .
an excisional biopsy was performed , and a histologic analysis revealed a schwannoma showing spindle tumor cells in a palisading pattern ( fig .
approximately 1 cm near the mass , several spargana worms were detected and removed at the same time .
cho et al .   reported that 54 of 70 cases of sparganosis in korea were found in the subcutaneous tissue or intermuscular fascia , 7 cases in the body cavity , 6 cases in the orbit , 2 cases in the urinary tract , and 1 case in the submucosal tissue , but no cases occurred in muscles .
however , kim et al .   reported a case of intramuscular sparganosis in the sartorius muscle in 2001 , and kim et al .  
recently , lee et al .   reported a case of living sparganum for 20 years migrating from the knee joint to the ankle joint along the calcified tract in 2010 .
ha et al .   also reported a case of sparganosis combined with bursitis involving the medial gastrocnemius muscle of the proximal lower extremity in 2011 . here
we report a case of intramuscular sparganosis involving the gastrocnemius muscle in a 77-year - old man .
the clinical manifestations of sparganosis are diverse , such as palpable masses , non - specific discomfort , vague pain , headache , or even no symptoms , depending on the organs involved .
thus , it is quite difficult to differentiate sparganosis from a soft tissue tumor based on the clinical manifestation and preoperative radiographic findings .
although the precise function of eosinophils is unclear , they are anyway involved in destroying the parasitic organisms . a competitive elisa that uses sparganum - specific monoclonal antibodies has been developed to improve the diagnostic specificity of sparganosis .
even though our patient did not show definite eosinophilia , a monoclonal antibody - based competitive elisa was positive .
radiologic evaluation , such as plain radiography , ultrasonography , or mri , is also useful for the diagnosis of sparganosis . in our patient ,
preoperative ultrasonographic findings showed a heterogeneous , hyperechoic mass with a hypoechoic tubular lesion in the gastrocnemius muscle .
this heterogeneous , hyperechoic mass is considered to be a granuloma that contains the living sparganum , and the internal hypoechoic tubular lesion is considered to be the empty migrating tract of the larva .
multiple calcifications seen on plain radiographs can also be considered the pathway along which the sparganum passed . in this case , we performed preoperative ultrasound - guided marking for suspected lesions
. therefore , we could easily find intramuscular sparganum during the surgery , although it is difficult to determine the location of the spargana with naked eyes in the operative field .
human sparganosis is a surgical disease because the diagnosis depends almost entirely on detecting larvae from the lesions .
thus , in areas where sparganosis is endemic , the presumptive diagnosis can be made preoperatively by an experienced surgeon if the patient has a history of eating raw meat , together with the size , migration , and crepitation of the mass .
however , it is quite difficult to differentiate sparganosis from a soft tissue tumor based solely on the clinical manifestations and preoperative radiographic findings . furthermore , because the incidence of this disease is extremely low , even in endemic areas , it is difficult for surgeons to suspect sparganosis based only on the preoperative data .
thus , an immunodiagnosis for sparganosis is recommended when soft tissue tumors are detected in patients living in endemic areas .
in addition , sparganosis should be included in the differential diagnosis of soft tissue tumors , especially among patients who frequently consume mountain water or raw snake or frog meat . in our case , although definite eosinophilia was not detected , we could suspect intramuscular sparganosis involving the gastrocnemius muscle based on the patient 's habit of ingesting raw snake meat during his adolescence , multiple calcifications on plain radiography , a heterogeneous , hyperechoic mass with a hypoechoic tubular lesion on ultrasonography , multiple tubular and cystic lesions in the gastrocnemius muscle on mri , and the positive elisa using sparganum - specific monoclonal antibodies .
in addition , we could easily remove the intramuscular sparganum with the aid of preoperative ultrasound - guided marking for suspected lesions . in our case , the patient revisited our hospital because of pain and paresthesia of the right thigh , and in the operative field , approximately 1 cm near the schwannoma at the right distal sciatic nerve , several sparganum were detected and removed .
schwannomas are tumors arising from the schwann cells of the neural sheaths of the motor and sensory nerves , and if schwannomas occur in the lower limb , they are found in association with either the sciatic nerve ( 1% ) or the posterior tibial nerve . all ages and both sexes may be affected , but schwannomas are most frequently seen in patients between 40 and 50 years of age .
benign schwannomas are generally slow - growing tumors arising from the schwann cells of the peripheral nerve sheath , so patients with a sciatic schwannoma are usually asymptomatic until a local mass compresses the sciatic nerve .
these masses are more often associated with the sensory aspect of the nerve ; thus , surgical excision is the treatment of choice in symptomatic sciatic schwannomas .
although the etiology of these benign neurogenic tumors is unknown , in our patient , we considered that intramuscular sparganum might irritate the neighboring sciatic nerve , and we removed all the adjacent spargana worms .
sparganosis is a parasitic infection caused by the plerocercoid tapeworm larva of the genus spirometra . 
 although the destination of the larva is often a tissue or muscle in the chest , abdominal wall , extremities , eyes , brain , urinary tract , spinal canal , and scrotum , intramuscular sparganosis is uncommon and therefore is difficult to distinguish from a soft tissue tumor . 
 we report a case of intramuscular sparganosis involving the gastrocnemius muscle in an elderly patient who was diagnosed using ultrasonography and mri and treated by surgical excision . at approximately 1 cm near the schwannoma at the right distal sciatic nerve , 
 several spargana worms were detected and removed .