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Peroneal Nerve Palsy – Weight Loss Risk — SCE Neurology MCQ

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EasyPeripheral Neuropathy & NeuromuscularPeroneal Nerve Palsy – Weight Loss RiskSCE Neurology

A 50-year-old man presents with a 4-week history of progressive right foot drop and numbness over the lateral calf and dorsum of the foot. He has recently lost 15 kg intentionally through dieting. Examination shows weakness of ankle dorsiflexion and eversion on the right with sensory loss in the superficial peroneal and deep peroneal nerve distributions. NCS confirm a right common peroneal nerve lesion at the fibular head. Why did weight loss predispose him to this?

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Correct answer: B — Rapid weight loss reduces the protective fat pad over the fibular head, making the peroneal nerve vulnerable to compression

The common peroneal nerve wraps around the fibular head in a superficial location, cushioned by subcutaneous fat. Significant weight loss reduces this protective fat pad, making the nerve vulnerable to external compression (from crossing legs, sleeping positions, or hard surfaces). Other risk factors include prolonged immobilisation, casting, surgery (lithotomy position), and habitual leg crossing. A: Vitamin deficiency causes generalised neuropathy, not focal. C: Weight loss itself doesn't cause generalised neuropathy. D: Sciatic nerve is not at the fibular head. E: It is a well-established predisposing factor.

Reference: ABN Peripheral Neuropathy Guidelines