Disclosures: Alyssa L. Marulli, MD: Nothing to disclose

Case Description: The patient presented to his primary care office with a chief complaint of acute left foot numbness and weakness after riding a bike the day prior, no trauma reported. A nerve conduction study (NCS) and electromyography (EMG) were ordered and referral to the orthopedics sports medicine clinic for further management was made. Upon presentation to the orthopedics clinic, he was noted to have decreased sensation over the left anterior and lateral lower leg and decreased strength in ankle dorsiflexion, eversion and hallucis extension. NCS and EMG revealed an acute left peroneal neuropathy across the fibular head. In an attempt to localize the site of nerve entrapment, an ultrasound examination was performed revealing an intramuscular mass within the peroneus longus muscle just distal to the common peroneal nerve division. Further characterization with an MRI confirmed a nonenhancing mass within the superior peroneus longus muscle. The patient was referred for neurosurgical evaluation for resection.

Setting: Quaternary care academic hospital clinic

Patient: 71-year-old male with foot drop.

Assessment/Results: The patient underwent surgical fascial release and resection of the mass with pathology consistent with an intramuscular myxoma. Intraoperatively, it appeared as if the peroneal nerve was compressed by the peroneus longus fascia rather than the mass itself. The patient’s left lower extremity strength and sensation recovered within 1 month with no residual deficits.

Discussion: Intramuscular myxomas are benign tumors of skeletal muscle affecting approximately 0.1 to 0.3 per 100,000 population. They are most commonly found in the large muscles of the thigh, shoulder girdle, trunk and buttocks with very few cases reported within the lower leg.

Conclusion: Although ultimately an incidental finding with regards to the patient’s acute peroneal neuropathy, this remains the first case reported to the authors’ knowledge of an intramuscular myxoma located in the peroneus longus.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/intramuscular-myxoma-masquerading-as-a-peroneal-nerve-entrapment-a-case-report/