Differential diagnosis and treatment of foot drop caused by an extraneural ganglion cyst above the knee: A case report

Figure 1 Ultrasound examination showed the compressed common peroneal nerve (yellow arrowheads) and a hypoechoic cystic lesion (white arrows).

Figure 2 Magnetic resonance imaging views (sagittal, coronal, and axial) of the right knee revealing a hyperintense cystic mass with narrow and long stalk stretching out posterolaterally from middle popliteal fossa in supracondylar area. A: Fat suppressed proton density sagittal magnetic resonance imaging (MRI) image; B: Fat suppressed proton density coronal MRI image; C: T2 pronton density axial MRI image.

Figure 3 The common peroneal nerve compressed by an adjacent cystic mass with stalk identified following incision of skin and fascia of right popliteal fossa. A: After incision in the surgery; B: After dissection around the extraneual ganglion cyst; C: The ganglion cyst size. CPN: Common peroneal nerve; M: Mass; S: Stalk.

Figure 4 Histology photomicrograph. The resected cyst was diagnosed as a ganglion cyst.