Neurovascular Compression Caused by Popliteus Muscle Enlargement Without Discrete Trauma

Abstract

Popliteal entrapment syndrome caused by isolated popliteus muscle enlargement is very rare, although its occurrence has been reported after discrete trauma. However, popliteal artery stenosis with combined peroneal and proximal tibial neuropathy caused by popliteus muscle enlargement without preceding trauma has not been reported. A 57-year-old man presented with a tingling sensation and pain in his left calf. He had no previous history of an injury. The symptoms were similar to those of lumbosacral radiculopathy. Calf pain became worse despite treatment, and the inability to flex his toes progressed. Computed tomography angiography and magnetic resonance imaging of the lower extremity showed popliteal artery stenosis caused by popliteus muscle enlargement and surrounding edema. An electrodiagnostic study confirmed combined peroneal and proximal tibial neuropathy at the popliteal fossa. Urgent surgical decompression was performed because of the progressive neurologic deficit and increasing neuropathic pain. The calf pain disappeared immediately after surgery, and he was discharged after the neurologic functions improved.

Keywords: Popliteal fossa; Popliteus muscle; Tibial neuropathy.

Fig. 1. Computed tomography angiography of lower extremities. (A) Coronal maximal intensity projection and (B) volume rendered image (posterior view) show stenosis and obstruction of the left popliteal artery (arrowheads) and many side branches. (C) Axial image shows a low density mass in the left popliteus muscle portion (arrow). (D, E) At 1 month after operation, obstruction of the popliteal artery was resolved (unfilled arrowhead). The size of the popliteus muscle was decreased (unfilled arrow).

Fig. 2. Magnetic resonance imaging of lower extremities. (A) Coronal T2-weighted image, (B) axial fat-saturated T2-weighted image, and (C) axial T1-weighted image show swelling and enlargement of the left popliteus muscle (arrowheads), along with neurovascular compression (unfilled arrowhead).

Fig. 3. Left popliteal fossa (yellow, tibial nerve; red, popliteal artery; blue, popliteal vein). (A) Pre-dissected state of the soleus arch (arrowhead) shows compressed tibial nerve and blood vessels. (B) Post-dissected state of the soleus arch.