303 - Left Foot Drop and Left Leg Numbness Following Bariatric Surgery

Case Diagnosis: Slimmer’s Palsy following bariatric surgery

Case Description: A 31-year-old man presenting with migraines also complained of left foot dragging on ambulation, with associated left leg numbness and ankle weakness, for 3-4 days. He denied pain or inciting injury. Upon further questioning, he reported losing 70 pounds over the past few months following bariatric surgery. On exam, no tenderness, deformities, or wounds were observed. Peripheral pulses and reflexes were intact bilaterally. He reported numbness at left lateral lower leg into dorsal foot. He demonstrated weakened left foot dorsiflexion, eversion, and 1^st toe extension, (motor strength 3/5, 4-/5, and 2/5, respectively) but intact inversion and plantarflexion. Electrodiagnostic tests performed that day showed decreased compound muscle action potential (CMAP) amplitude in left peroneal nerve when stimulating at the fibular head and popliteal fossa compared to ankle (1.1mV and 1.0mV vs 4.1mV). Sensory nerve action potentials were normal without significant side-to-side difference, including superficial peroneal nerves (left 8.4µV and right 7.5µV).

Discussions: Repeat electrodiagnostic testing 4 weeks later showed unchanged CMAP amplitude of the left peroneal nerve at the ankle, suggesting demyelinating injury and favorable prognosis. Patients with peroneal neuropathy without common etiologies (including fibular head compression, vitamin B deficiency, frequent leg crossing) but with history of rapid weight loss should be considered for Slimmer’s Palsy. Weyns et al showed peroneal neuropathy can occur when body fat decreases >10%, with increased risk when prolonged weight loss exceeds 5kg/month. While decreased fat surrounding the nerve may increase susceptibility to mechanical disturbance, Slimmer’s Palsy’s etiology is likely multifactorial given coexisting nutritional deficits.

Conclusions: Patients seen in physiatry with Slimmer’s Palsy should be cautioned given potential pre-existing ambulation difficulty and have home set-up accordingly. Rate of weight loss must be controlled while treating conservatively with nutritional replacement and physical therapy. Recovery varies pending the lesion type and other factors.