Disclosures: Zainab Shirazi, MD: No financial relationships or conflicts of interest

Case Diagnosis: A 59-year-old male with alcohol use disorder presenting with left foot weakness.

Case Description or Program Description: Several months prior to presentation, he began experiencing several episodes of left posterior ankle and calf discomfort which would quickly resolve. He previously received a gluteal injection of naltrexone involving multiple injection attempts. Several weeks later, he developed sudden onset left calf pain and paresthesias which progressed to significant weakness and swelling. His pain and swelling gradually improved, but the left leg weakness persisted in the months leading up to his clinic visit. On exam, strength was decreased in left ankle dorsiflexion, foot eversion, and great toe extension at 3/5. Sensation to pinprick and light touch was decreased in the superficial peroneal nerve and absent in the deep peroneal nerve.

Setting: Outpatient Clinic

Assessment/Results: Nerve conduction studies (NCS) elicited no response in the left superficial nerve. Electromyography (EMG) demonstrated abnormalities in the tibialis anterior, extensor hallucis longus, and short head of the biceps femoris. Evaluation of the left sciatic nerve with diagnostic ultrasound revealed a mass in the fibular aspect of the nerve at the sciatic notch. Findings were normal at the proximal sciatic nerve at the hyperechoic triangle, tibial nerve at the popliteal fossa, common peroneal nerve at the fibular head, and superficial fibular nerve existing the fascia distally.

Discussion (relevance): This patient’s EMG demonstrated abnormalities corresponding with proximal common fibular neuropathy, which is commonly seen with compression of the nerve at the fibular head. Advancements in high resolution neuromuscular ultrasound allowed for identification of a more proximal neuronal mass which may have otherwise gone undiagnosed.

Conclusions: This case highlights the utility of diagnostic ultrasound as a cost-efficient method for identifying and differentiating various neuromuscular lesions, which previously relied on magnetic resonance imaging (MRI) for accurate diagnosis.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/a-rare-cause-of-fibular-neuropathy-resulting-in-foot-drop-a-case-report/