A 13-year-old female presents with painful swelling in the left temporal region.
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Diagnosis: Cysticercosis (intramuscular)
Gray scale USG (Figure 1) shows a well-defined anechoic cyst in the left temporalis muscle with an eccentric nodule in the periphery. On color Doppler (Figure 2) there is no internal vascularity in the nodule or the lesion.
• Parasitic tissue infection caused by ingestion of tapeworm eggs (Taneia solium).
• Most commonly affects the nervous system.
• Most common infection of the soft tissue, the most common location being the skeletal muscle.
• Endemic in developing countries, however it is now seen in developed countries as well.
• Human beings become occasional hosts of Taenia solium larvae, either via drinking contaminated water or by eating uncooked/undercooked vegetables or pork.
Radiographs: Cysticerci appear as oblong calcific specks in the skeletal muscles parallel to the muscle fibers, giving a characteristic rice grain appearance.
• High-frequency USG is a relatively inexpensive and readily available and reliable tool.
• Most common USG appearance of soft tissue cysticercosis is that of an intramuscular abscess with an eccentrical cyst having a scolex within.
• Can be associated with mild edema without abscess
• Least common appearance is that of an irregular cyst with no scolex within but with minimal fluid surrounding the cyst on one side indicating leakage of fluid.
MRI: Seen as a cystic lesion that is oriented in the direction of the muscle fibers with a hypointense speck suggestive of scolex
• Surgical excision for isolated skeletal muscle or soft tissue cysticercosis associated with abscess.
• Cysts that are not associated with abscess can be treated with anti-helminthic.
• Follow-up USG is done after three weeks of anti-helminthic medication to look for resolution.
1. Naik D, Srinath M, Kumar A. Soft tissue cysticercosis - Ultrasonographic spectrum of the disease. Indian Journal of Radiology and Imaging. 2011;21:60.
2. Firke V. Cysticercosis. Radiopaedia.org [Internet]. Radiopaedia.org. 2016 [cited 15 December 2016]. Available from: https://radiopaedia.org/articles/cysticercosis.