1513 - Foot Drop Following Ozempic Induced Weight Loss: A Case of Slimmer’s Palsy

Right common fibular mononeuropathy

Case Description:

69-year-old male with past medical history of T2DM presented with 6 weeks of right foot drop. He denied any trauma but did report recent low back pain resolved with prednisone. He denied radiating right leg pain but endorsed great toe numbness. On exam, he had 4/5 strength with right ankle dorsiflexion with preserved knee and Achilles reflexes. Nerve conduction study revealed decreased conduction velocity of the right fibular motor and deep fibular motor nerves as they crossed the fibular head. Electromyography revealed active denervation with positive sharp waves and fibrillations in muscles innervated by the deep fibular nerve including the tibialis anterior and extensor hallucis longus but no evidence of right lumbosacral radiculopathy. Given the patient’s 39 lb. weight loss over 6 months on Ozempic, electrodiagnostic findings were suspicious for slimmer’s palsy.

Discussions: This case presents an underrecognized cause of foot drop due to compression following rapid weight loss. The challenge was differentiating fibular neuropathy from lumbosacral radiculopathy given his low back pain and overlapping exam findings. Electrodiagnostic findings, specifically focal slowing across the fibular head and denervation in distal muscles, were essential. Understanding the pathogenesis of lower leg neuropathies, particularly involving the fibular and tibial nerves, is crucial for diagnosis. The common fibular nerve is susceptible to compression-related demyelination due to its superficial location at the fibular head. Its fibers are heavily myelinated, loosely packed, and located peripherally within nerve fascicles, which increases vulnerability to compression. The tibial nerve lies deep to the gastrocnemius, with tightly packed fascicles and a richer blood supply, making it more resistant to compression.

Conclusions:

As the use of agents like GLP-1 agonists increases, clinicians should maintain broad differentials for reversible causes of foot drop. Careful history-taking and detailed examinations are critical for accurate localization and appropriate management of new-onset peripheral weakness.