A 38-year-old man comes to the physician because of difficulty walking for the past 1 week. His medical problems include hypertension, type 2 diabetes mellitus, hyperlipidemia, and osteoarthritis of the left hip. He underwent gastric bypass surgery 5 weeks ago for morbid obesity.
Neurological examination shows a left foot drop with strength in the left leg as follows: dorsiflexion 1/5, foot eversion 2/5, foot inversion 5/5, and plantar flexion 5/5. Sensory examination shows decreased pin prick sensation over the dorsum of the left foot. The remainder of the neurological examination is unremarkable.
Which of the following sites has this patient most likely injured?

Question

A 38-year-old man comes to the physician because of difficulty walking for the past 1 week.  His medical problems include hypertension, type 2 diabetes mellitus, hyperlipidemia, and osteoarthritis of the left hip.  He underwent gastric bypass surgery 5 weeks ago for morbid obesity.
Neurological examination shows a left foot drop with strength in the left leg as follows: dorsiflexion 1/5, foot eversion 2/5, foot inversion 5/5, and plantar flexion 5/5.  Sensory examination shows decreased pin prick sensation over the dorsum of the left foot.  The remainder of the neurological examination is unremarkable.
Which of the following sites has this patient most likely injured?

Quizplus · Accepted Answer

This patient has most likely injured the left common peroneal nerve in the fibular head region, resulting in a peroneal neuropathy. Risk factors include prolonged immobilization (e.g., surgery or hospitalization), leg crossing, squatting, and leg casting; especially when combined with significant weight loss (e.g., gastric bypass surgery in this patient). Patients typically present with foot drop and paresthesias and/or sensory loss involving the dorsum of the foot and lateral shin. Patients tend to trip over the affected foot and compensate by flexing the hip while walking, leading to a "steppage" gait. common peroneal nerve Examination usually shows weakness on foot dorsiflexion and eversion, and decreased sensation in the dorsum of the foot. However, there is usually a normal Achilles reflex with normal foot inversion and plantar flexion. Treatment involves removing the pressure on the nerve, an ankle-foot orthosis splint to keep the foot dorsiflexed, and physical therapy to improve walking. However, the treatments have variable results with little recovery of function in most cases. (Choice B) A mid-thigh nerve injury may involve the femoral nerve leading to acute thigh weakness and numbness, which this patient does not have. femoral nerve (Choice C) A sciatic notch nerve injury may result in sciatica, which usually causes pain in the sciatic nerve distribution and sensory loss involving both the peroneal and sural nerves. This patient only has peroneal involvement, which makes this less likely. sciatic notch nerve (Choice D) A tarsal tunnel nerve injury compresses the posterior tibial nerve. Symptoms are mainly sensory (i.e., burning pain of the foot and heel, paresthesias, and sensory loss in the sole) with rare foot weakness. This patient's foot weakness makes this unlikely. posterior tibial nerve (Choice E) Lumbar vertebral foraminal nerve root injury causes a lumbar radiculopathy. L5 radiculopathy is associated with weakness of ankle inversion and toe flexion, sensory loss more localized to the big toe region, and a radicular pattern of pain. L5 radiculopathy Educational objective: Peroneal neuropathy is usually due to an injury of the nerve at the fibular head and typically presents with foot drop and paresthesias of the dorsum of the foot. Patients usually have normal reflexes and foot inversion, which can help differentiate peroneal neuropathy from other causes of neuropathy in the lower extremity. __________ References: Peroneal neuropathy following successful bariatric surgery. Case report and review of the literature. (http://www.ncbi.nlm.nih.gov/pubmed/17044570) Foot drop as a complication of weight loss after bariatric surgery: is it preventable? (http://www.ncbi.nlm.nih.gov/pubmed/18074496)

A 38-Year-Old Man Comes to the Physician Because of Difficulty