E2056. Common Peroneal Nerve Entrapment: Anatomy Review, Etiologies, and Imaging Features with a Retrospective Review on Institutional Prevalence
  1. Sarim Baig; Hospital of the University of Pennsylvania
  2. Jenny Bencardino; Hospital of the University of Pennsylvania
Common peroneal nerve entrapment is the most common cause of neuropathy in the lower extremity, yet remains a relatively uncommon and potentially underreported diagnosis. The purpose of this exhibit is to provide the reader with an overview of entrapment of the common peroneal nerve and its branches at the knee. Review of the gross and imaging anatomy of the common peroneal nerve including anatomical variants and pitfalls will be included. Innervation patterns for the deep and superficial branches of the peroneal nerve in the lower extremity below the popliteal fossa will be illustrated. Description of the common causes of peroneal nerve entrapment at the fibular head including among others trauma, insertional tendinopathy and enthesopathy at the fibular head, proximal tibiofibular arthropathy, and mass-like lesions along the course of the common peroneal nerve and branches. Imaging features of common peroneal neuropathy (CPN) with particular emphasis on conventional MRI and MR neurography including direct signs (intrinsic nerve abnormalities), and indirect/secondary signs such as classic denervation patterns in the anterior and lateral leg compartments.

Materials and Methods:
Our goal was to specifically identify cases of common peroneal neuropathy secondary to entrapment at the level of the fibular head. We retrospectively reviewed MR examinations of the knee and calf performed at our institution in patients over the age of 18, dating back 5 years. A total of 25,430 examinations fit the inclusion criteria and were included in the data pool. The reports were subsequently filtered using terms including “foot drop”, “peroneal neuropathy”, and “peroneal nerve entrapment” to identify studies with imaging findings suggestive of CPN. In patients with positive imaging findings, a chart review was then performed to determine if these patients had clinical symptoms of CPN, such as foot drop. In addition, we determined if these patients had undergone EMG evaluation, and if the results were concordant to the imaging findings.

Out of the 25,430 examinations that met our inclusion criteria, a total of 30 studies (~0.1%) were identified with imaging features suggestive of peroneal neuropathy. Of these, 22 patients had symptoms of CPN. 20 out of 22 patients underwent EMG evaluation, 19 of which were concordant with the imaging findings of CPN.

Review of clinical presentation and imaging manifestations of CPN at the knee with the aim of raising awareness of this condition to increase detection rates.