A 38-year-old woman comes to the emergency department due to 2 hours of left leg weakness and numbness. Over the last 3 months, the patient has had several similar episodes in which her left foot tingles and becomes numb and her entire left foot becomes limp, causing her to trip. The symptoms resolve spontaneously within a few hours. Her right leg has never displayed similar symptoms. The patient has no significant medical history but does have a family history of multiple sclerosis. She does not use tobacco, alcohol, or illicit drugs. The patient has experienced major psychosocial stress after losing her job 6 months ago, but this has tempered somewhat since she joined a meditation group. Vital signs are within normal limits. Physical examination shows diminished pinprick sensation over the dorsum of the left foot and weakness of the left big toe on extension. The patient is able to walk on her left toes but not on her left heel. Which of the following is the most likely cause of this patient's current symptoms?

Question

A 38-year-old woman comes to the emergency department due to 2 hours of left leg weakness and numbness.  Over the last 3 months, the patient has had several similar episodes in which her left foot tingles and becomes numb and her entire left foot becomes limp, causing her to trip.  The symptoms resolve spontaneously within a few hours.  Her right leg has never displayed similar symptoms.  The patient has no significant medical history but does have a family history of multiple sclerosis.  She does not use tobacco, alcohol, or illicit drugs.  The patient has experienced major psychosocial stress after losing her job 6 months ago, but this has tempered somewhat since she joined a meditation group.  Vital signs are within normal limits.  Physical examination shows diminished pinprick sensation over the dorsum of the left foot and weakness of the left big toe on extension.  The patient is able to walk on her left toes but not on her left heel.  Which of the following is the most likely cause of this patient's current symptoms?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d5a4_6434_bc81_718f7e84e431_MD0003_00 This patient with intermittent foot drop likely has common fibular neuropathy. The common fibular nerve, also called the common peroneal nerve, travels near the fibular head and is susceptible to compressive injuries from leg immobilization (eg, cast, bedrest), prolonged leg crossing (eg, during yoga or meditation), or protracted squatting. Manifestations are typically transient and reflect impaired functioning of the fibular nerve as follows: Unilateral foot drop Numbness/tingling over the dorsal foot and lateral shin Impaired ankle dorsiflexion (walking on heels) and great toe extension Preserved plantar flexion (walking on toes) and reflexes Diagnosis is typically made with electromyography and nerve conduction studies. Treatment has limited effect but includes reducing pressure on the nerve (eg, avoiding crossing the legs), an ankle-foot orthosis splint, and physical therapy. (Choice A) Myoneural junction dysfunction (eg, myasthenia gravis) usually presents with symmetric fatigable proximal muscle weakness, ptosis, and diplopia without sensory symptoms. (Choice C) Although this patient does have psychosocial stressors, the examination localizes to the left common fibular nerve. Psychogenic numbness does not usually follow a neuroanatomical pattern. (Choice D) Spinal artery atherothrombosis (eg, anterior cord syndrome) is rare and usually causes bilateral symmetric acute paralysis with bowel and bladder dysfunction, diminished pain and temperature sensation, and preserved vibration and proprioception. (Choice E) Spinal nerve root entrapment can present with foot drop and impaired dorsiflexion when L5 is involved; however, patients usually have back pain radiating to the foot. In addition, short, transient episodes over months would be uncommon. (Choice F) Subcortical white matter demyelination is seen in multiple sclerosis, but deficits typically take days or weeks (not hours) to improve. (Choice G) Transient ischemia is unlikely in a young patient with no vascular risk factors. In addition, transient ischemia rarely causes recurrent symptoms in the same neurologic pattern over a period of months. Educational objective: Common fibular neuropathy is typically the result of leg immobilization, leg crossing, or protracted squatting. Manifestations are usually transient (lasting hours) and include foot drop and sensory changes over the dorsal foot and lateral shin. Physical examination shows impaired ankle dorsiflexion and great toe extension with preserved plantar flexion and reflexes. References: Common peroneal neuropathy: a study of selective motor and sensory involvement. (http://www.ncbi.nlm.nih.gov/pubmed/1648680) Idiopathic common peroneal nerve palsy--a review of thirteen cases. (http://www.ncbi.nlm.nih.gov/pubmed/1850600)

A 38-Year-Old Woman Comes to the Emergency Department Due to 2