Sonographic Appearances in Cysticercosis

Transcription

1 Case Series Sonographic Appearances in Cysticercosis S. Boopathy Vijayaraghavan, MD, DMRD Objective. To describe the sonographic appearances of cysticercosis. Methods. Sonography was performed with both convex and linear array transducers in 4 patients with different symptoms. Results. In 2 patients, an intramuscular fluid collection was seen with a cysticercus cyst in it. In 1 patient, an irregular cyst with a small fluid collection on 1 side was seen. In the last patient, multiple elliptical millet seed shaped calcifications were seen in the liver, mesentery, and retroperitoneal fat. Conclusions. Four different sonographic appearances of soft tissue cysticercosis are described. Key words: cysticercosis; intramuscular; liver; mesentery; retroperitoneum; sonography. Cysticercosis is an infection with the larval (cysticercus) stage of Taenia solium. It is seen as cysts in various human tissues, more commonly in the brain and the orbit. Here the sonographic features of 3 cases of isolated cysticercus cysts in muscles and 1 case of disseminated cysticercosis are reported. Case Descriptions Received October 6, 2003, from Sonoscan Ultrasonic Scan Centre, Coimbatore, India. Revision requested October 28, Revised manuscript accepted for publication November 3, Address correspondence and reprint requests to S. Boopathy Vijayaraghavan, MD, DMRD, 16 B Venkatachalam Rd, R. S. Puram, Coimbatore , India. sonoscan@vsnl.com and sboopathy@eth.net. Case 1 A 9-year-old girl was referred for sonography because of swelling in her right arm of insidious onset. She did not give a history of fever or pain. On examination, swelling of the anterior aspect of the distal third of the right arm was evident. It was not tender, and there were no signs of inflammation. There was limitation of extension movement of the elbow. Sonography was performed with an HDI 5000 system (Philips Medical Systems, Bothell, WA) using a 5- to 12-MHz linear probe. A large irregular collection of fluid with internal echoes was seen in the right brachialis muscle. The appearance suggested an intramuscular abscess. However, there was a welldefined round cyst of 9 6 mm in the upper part of the collection, with a brightly echogenic protrusion from the wall (Figure 1). At surgical exploration, dark-colored fluid exuded from the cavity in the muscle, and a grapelike cyst popped out. Histopathologic examination confirmed cysticercosis by the American Institute of Ultrasound in Medicine J Ultrasound Med 23: , /04/$3.50

2 Sonographic Appearances in Cysticercosis Figure 1. Longitudinal scan of the lower part of the arm showing a large irregular fluid collection in the brachialis muscle with the cysticercus cyst in its upper part. Case 2 An 11-year-old boy was referred for sonography, for evaluation of parietal swelling in the right hypochondrium. He had no pain or fever and did not give any history of trauma. Sonography revealed a loculated collection of fluid with internal echoes, measuring mm, in the internal oblique muscle. Within this collection there was a well-defined round cyst of 15 mm with an eccentric echogenic protrusion from the wall, representing the scolex, in it (Figure 2). The cyst was confirmed to be cysticercosis on histopathologic examination. Figure 2. Longitudinal scan of the right hypochondrium showing a fluid collection in the internal oblique muscle with a cysticercus cyst in it. Case 3 A 29-year-old man had a painful lump on his left thigh that had been present for 2 days. Sonography revealed an oval cystic lesion of 15 5 mm within the vastus lateralis muscle of the left thigh (Figure 3). The walls were irregular. There was no echogenic protrusion of scolex in it. There was an irregular thin fluid collection extending inferolaterally from this cyst. This fluid contained an echogenic focus, which may have been the extruded scolex. At exploration, there was an irregular cavity in the muscle, which was excised. Histopathologic examination confirmed cysticercosis. Case 4 A 45-year-old man with dyspeptic symptoms was referred for sonography of the abdomen. Sonography was performed with an HDI 5000 system and 2- to 5-MHz convex and 5- to 12- MHz linear probes. Numerous small elliptical calcifications of 9 to 11 mm each were seen in the liver (Figure 4), mesentery (Figure 5), and retroperitoneal fat (Figure 6). A similar lesion in the chest wall was excised and confirmed to be cysticercosis on histopathologic examination. All 4 patients were treated appropriately for cysticercosis. Discussion Cysticercosis in humans is infection with the larval form (cysticercus cellulosae) of the pork tapeworm T solium. It is endemic in Southeast Asia, Mexico, Central and South America, and Africa. 1 Humans normally act as definitive hosts. Ingestion of inadequately cooked infected pork, the intermediate host, leads to the development of the adult worm in the small bowel of humans. The eggs of the worm are excreted with the feces, which are ingested by the pig, the intermediate host. Once ingested, the eggs hatch in the small intestine and result in the cysticercosis, completing the cycle. However, humans can occasionally be intermediate hosts, manifesting cysticercosis. It is transmitted to humans by ingestion of eggs from contaminated water or food, such as vegetables, 2 or by internal regurgitation of eggs into the stomach due to reverse peristalsis, when the intestine harbors a gravid worm. 3 The eggs hatch in the small intestine, releasing oncospheres that penetrate the bowel mucosa and enter the bloodstream to reach var- 424 J Ultrasound Med 23: , 2004

3 Vijayaraghavan et al ious tissues, where they develop to form a cysticercus cellulosae, which is the encysted larval form of T Solium. These can remain viable in this stage for as long as 10 years in humans. 4 Living larvae evade immune recognition and do not elicit inflammation. 1 When the larva dies, it induces a vigorous granulomatous inflammatory response that may produce symptoms, depending on the anatomic location. 5 In the muscular form, 3 distinct types of clinical manifestations have been described: the myalgic type; the masslike, pseudotumor, or abscesslike type; and the rare pseudohypertrophic type. 6 8 During the death of the larva, there is leakage of fluid from the cyst. The resulting acute inflammation may result in local pain and myalgia, as seen in case 3 of this report. Alternatively, degeneration of the cyst may result in intermittent leakage of fluid, 6 eliciting a chronic inflammatory response, with collection of fluid around the cyst, resulting in the masslike, pseudotumor, or abscesslike type, as seen in cases 1 and 2 of this report. Alternatively, the cyst retracts, its capsule thickens, and the scolex calcifies. Later on, the cyst is completely calcified. When multiple, they give a starry night appearance on computed tomography. 9 These are seen as multiple millet seed shaped elliptical calcifications in the soft tissues on plain radiography. This is the type of appearance seen in case 4 of this report. Although most reported cases of cysticercosis involve the brain and orbit, the general belief is that the subcutaneous and muscular forms are as common as or more common than the other forms. 10 However, most cases of subcutaneous and muscular cysticercosis are asymptomatic. 11,12 Sonographic features of cysticercosis of eye and extraocular muscles are well reported. 9,13 There are only 2 earlier reports of sonographic features of muscular cysticercosis. One of them described the lesion as a soft tissue mass centered on a small, well-defined elliptical cystic lesion of 10 4 mm with an eccentric, echogenic, pedunculated structure inside, in the musculature of the abdominal wall. 14 The second report described a homogeneous hypoechoic soft tissue lesion of mm within the masseter muscle with a welldefined cystic area of 6 4 mm containing a small calcified scolex in it. 15 These 2 reports described one of the sonographic appearances of cysticercosis, namely, the cysticercus cyst with an inflammatory mass around it, as a result of Figure 3. Oblique scan of the lateral aspect of thigh showing an irregular cyst (C) with minimal fluid collection on 1 side (arrowheads) with the suggestion of an extruded scolex (arrow) in it. the death of the larva. Here, 3 other appearances of cysticercosis are described. The second type, as seen in case 3, is an irregular cyst with very minimal fluid on 1 side, indicating a leakage of fluid. The eccentric echogenic protrusion from the wall due to the scolex is not seen within the cyst. It may be due to escape of the scolex outside the cyst or partial collapse of the cyst. The third appearance is a large irregular collection of exudative fluid within the muscle with the typi- Figure 4. Transverse scan of the liver showing multiple elliptical calcified cysticercus cysts. J Ultrasound Med 23: ,

4 Sonographic Appearances in Cysticercosis Figure 5. Oblique scan of the mid abdomen showing a calcified cysticercus cyst (arrow) in the mesentery. BO indicates bowel loop. cal cysticercus cyst containing the scolex, situated eccentrically within the collection. This may be due to chronic intermittent leakage of fluid from the cyst, leading to florid inflammatory exudates. This appearance is similar to an intramuscular abscess, but the visualization of the cysticercus cyst within it clinches the diagnosis. In all 3 of these types of appearances, the salient diagnostic feature is that of the cysticercus itself, which appears as an oval or round well-defined cystic lesion with an eccentric echogenic scolex in it (Figure 2). The fourth sonographic appearance is that of calcified cysticercosis, as seen in case 4. It appears as multiple elliptical calcifications in soft tissue similar to the pathognomonic millet seed shaped elliptical calcifications in soft tissues described on plain radiography. In the case reported here, they were seen in the liver, the mesentery, and the retroperitoneal fat. In conclusion, 4 different sonographic appearances of muscular cysticercosis are described. These appearances on high-resolution sonography are pathognomonic of cysticercosis, and a definitive diagnosis can be made with greater confidence. References 1. Evans CAW, Garcia HH, Gilman RH. Cysticercosis. In: Strickland GT (ed). Hunter s Tropical Medicine. 8th ed. Philadelphia, PA: WB Saunders Co; 2000:862. Figure 6. Oblique scan of the right iliac fossa showing 2 calcified cysticercus cysts (arrows) in the retroperitoneal fat. 2. Horton J. Biology of tapeworm disease [letter]. Lancet 1996; 348: Del Brutto OA. Sotelo J. Neurocysticercosis: an update. Rev Infect Dis 1988; 10: Despommier DD. Tapeworm infection: the long and the short of it. N Engl J Med 1992; 327: Brown WJ, Voge M. Cysticercosis: a modern day plague. Pediatr Clin North Am 1985; 32: Scully RE, Mark EJ, McNeely WF. Case records of the Massachusetts General Hospital weekly clinicopathological exercises, case N Engl J Med 1994; 330: Anderson GA, Chandi SM. Cysticercosis of the flexor digitorum profundus muscle producing flexion deformity of the fingers. J Hand Surg [Br] 1993; 18: Chopra JS, Nand N, Jain K. Generalized muscular pseudohypertrophy in cysticercosis. Postgrad Med J 1986; 62: J Ultrasound Med 23: , 2004

5 Vijayaraghavan et al 9. Rahalkar MD, Shetty DD, Kelkar AB, Kelkar AA, Kinare AS, Ambardekar ST. The many faces of cysticercosis. Clin Radiol 2000; 55: Wortman PD. Subcutaneous cysticercosis. J Am Acad Dermatol 1991; 25: Schmidt DKT, Jordaan HF, Schneider JW. Cerebral and subcutaneous cysticercosis treated with albendazole. Int J Dermatol 1995; 34: Yamashita P, Kelsey J, Henderson SO. Subcutaneous cysticercosis. J Emerg Med 1998; 16: Honavar SG, Sekhar CG. Ultrasonological characteristics of extraocular cysticercosis. Orbit 1998; 17: Mani NBS, Kalra N, Jain M, Sidhu R. Sonographic diagnosis of a solitary intramuscular cysticercal cyst. J Clin Ultrasound 2001; 29: Sidhu R, Nada R, Palta A, Mohan H, Suri S. Maxillofacial cysticercosis: uncommon appearance of a common disease. J Ultrasound Med 2002; 21: J Ultrasound Med 23: ,