Disclosures: J Anthony Garcia, DO: No financial relationships or conflicts of interest

Case Diagnosis: Common peroneal nerve schwannoma leading to foot drop

Case Description: A 37-year-old male with no significant past medical history presented to the clinic due to sudden onset of right foot drop one week prior. He denied associated trauma or pain. His most recent magnetic resonance imaging of the lumbar spine revealed L5-S1 small posterior disc herniation abutting the descending S1 nerve roots, which was thought to be the probable source of his foot drop. Prior to his appointment, he developed severe back pain and was prescribed a Medrol dose pack. Upon initial evaluation, patient reported no improvement in his pain or foot weakness upon completion of his oral steroids. He endorsed some soreness in his lower leg adjacent to the fibular head. He was subsequently sent for an urgent MRI of his right knee which revealed an elongated cystic structure within the common peroneal nerve favored to represent a cystic schwannoma.

Setting: Outpatient Clinic

Assessment/Results: The patient had surgical excision of the schwannomas with good recovery. Two months after the surgery the patient recovered completely and was able to walk independently, as well as completely pain-free.

Discussion: Foot drop is associated with numerous conditions, including but not limited to stroke, lumbar radiculopathy, lumbosacral plexopathies, and Charcot-Marie-Tooth. Schwannomas are the most frequently occurring benign peripheral nerve sheath tumors. Schwannomas of the peroneal nerve leading to foot drop are extremely rare with only a few reported cases. The enlarging schwannoma led to compression of the common peroneal nerve resulting in a foot drop.

Conclusion: It is important to understand the anatomy and pathophysiology of nerve innervation of muscles to determine where one’s lesion may lie to properly diagnose the patient. Although rare, this case shows that clinicians caring for patients with related symptoms should consider common peroneal nerve schwannoma as a possible cause of foot drop.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/a-case-of-schwannoma-of-the-common-peroneal-nerve-leading-to-foot-drop/