Age / Sex : 18 / M

18/M

C.C.: right calf pain with claudication (Click to enlarge)

popliteal artery entrapment SD (by medial head of gastrocnemius)

Discussion

Findings:
1) Figure 1. Maximum intensity projection (MIP) anteroposterior view of the whole scanned volume in MDCT arteriography. Complete occlusion of the right popliteal artery at the proximal level is seen.
2) Figure 2. Conventional angiography at the level of the knee of the same patient. Complete occlusion of the right popliteal artery is also seen at the same level at which CT arteriography revealed occlusion.
3) Figure 3. The source images of CT arteriography from suprapatellar to infrapatellar level of both knees (from top left to bottom right consecutively). Muscle belly of gastrocnemius medial head is seen in between right popliteal artery and popliteal veins. This anomalous muscle passage is compressing and medially displacing right popliteal artery causing intraluminal thrombus which is also well visualized in these images.
4) Figure 4. Axial fast spin echo T2-weighted image (TR, 3600 msec; TE, 80 msec; echo train length,
6) of both knees at the level of anomalous passage of right gastrocnemius medial head. Muscle belly of gastrocnemius medial head is seen in between right popliteal artery and popliteal veins. This was also well depicted by source images of MDCT as demonstrated in figure 3.

Differential Diagnosis: None

Discussion:
Most patients with intermittent claudication of the calf have atherosclerotic disease, usually with a typical clinical history. Even in the young adults, the most common surgically correctable cause of leg claudication is still atherosclerotic disease. However, other non-atherosclerotic causes such as thrombosed aneurysm, embolism, popliteal artery entrapment syndrome (PAES), ruptured Baker cyst, adventitial cystic disease, and so on should be kept in mind, especially in the young adults because prevalence of atherosclerosis in this population is lower than in elder group as presented by this case (1). Among those reasons, popliteal artery entrapment syndrome is second only to atherosclerosis as the most common surgically correctable cause of leg claudication in young adult (2, 3). Popliteal artery syndrome is a congenital anomaly of muscle or tendon insertion in relation to the popliteal artery that causes functional occlusion of the artery. Due to the complexity of the embryologic development, various classifications of the anatomical abnormalities that can lead to PAES have been proposed. The mostly widely accepted classification was made by Whelan and modified by Rich, and divides PAES into six types (4). According to this classification, type 1 is described as an aberrant medial arterial course around the normal medial head of the gastrocnemius muscle. Type 2 is the abnormal gastrocnemius medial head with lateral insertion on the distal femur and medial displacement of the popliteal artery. In type 3, an aberrant accessory slip from the medial head of the gastrocnemius muscle wraps around the normally positioned popliteal artery and entraps it. In type 4, the popliteal artery is located deep in the popliteus muscle or beneath fibrous bands in the popliteal fossa. Type 5 is any form of entrapment that involves the popliteal artery and vein. Type 6, the functional type, has been described in symptomatic individuals with a normally positioned popliteal artery entrapped by normally positioned gastrocnemius with hypertrophy. The rare type of PAES caused by anomalous lateral head of the gastrocnemius has recently been classified (5). PAES has been reported to occur bilaterally in about 25% cases, but recent reports revealed that percentage of bilateral entrapment was more than that, which was reported to be 67% in a study by Collins et al. (6) and 81% by Kim et al.(5). Both CT and MRI can equally evaluate anomalous muscle courses around popliteal vessels. They can depict other possible space occupying lesions that may pinch the popliteal vessels as well. Recently, with the advent of multidetector row CT (MDCT), CT angiography is emerging as a competent tool for imaging of blood vessels. CT angiography can depict not only the vessels in a pinch but the pinching lesions through its source image. This case is representing the role of MDCT in the evaluation of arterial occlusive disease of extremities. Both the maximum intensity projection (MIP) image (fig 1) and conventional angiography (fig 2) well demonstrated complete occlusion of right popliteal artery at proximal level. Anomalous passage of gastrocnemius muscle medial belly between popliteal artery and vein is well depicted along with demonstration of intraluminal filling defect at right popliteal artery by source images of MDCT arteriography. Medial displacement of popliteal artery is seen as well (fig 3). This case was revealed to be type 2 popliteal artery entrapment syndrome according to the classification system which was previously mentioned.

References:
1. Saeed M, Wolf YG, Dilley RB. Adventitial cystic disease of the popliteal artery mistaken for an endoluminal lesion. J Vasc Interv Radiol 1993; 4:815-818. 2. Baltopoulos P, Filippou DK, Sigala F. Popliteal artery entrapment syndrome: anatomic or functional syndrome? Clin J Sport Med 2004; 14:8-12. 3. Gerkin TM, Beebe HG, Williams DM, Bloom JR, Wakefield TW. Popliteal vein entrapment presenting as deep venous thrombosis and chronic venous insufficiency. J Vasc Surg 1993; 18:760-766. 4. Rich NM, Collins GJ, Jr., McDonald PT, Kozloff L, Clagett GP, Collins JT. Popliteal vascular entrapment. Its increasing interest. Arch Surg 1979; 114:1377-1384. 5. Kim HK, Shin MJ, Kim SM, Lee SH, Hong HJ. Popliteal artery entrapment syndrome: morphological classification utilizing MR imaging. Skeletal Radiol 2006; 35:648-658. 6. Collins PS, McDonald PT, Lim RC. Popliteal artery entrapment: an evolving syndrome. J Vasc Surg 1989; 10:484-489; discussion 489-490.