A 34-year-old previously healthy man comes to the office due to severe back pain. Two days ago, the patient was working on the lawn and experienced sudden-onset low back pain while moving a bag of soil. The pain worsens with movement and radiates to his left leg. He also reports weakness of the left leg. He has had some improvement in the pain after taking NSAIDs and resting. Physical examination shows spasm of lower paraspinal muscles. There is weakness of left ankle dorsiflexion and toe extension. Ankle and knee reflexes are normal. Sensory examination shows loss of pinprick sensation over the dorsum of the left foot. Rectal tone is normal, and the remainder of the examination shows no abnormalities. Which of the following is the most likely cause of this patient's current condition?

Question

A 34-year-old previously healthy man comes to the office due to severe back pain.  Two days ago, the patient was working on the lawn and experienced sudden-onset low back pain while moving a bag of soil.  The pain worsens with movement and radiates to his left leg.  He also reports weakness of the left leg.  He has had some improvement in the pain after taking NSAIDs and resting.  Physical examination shows spasm of lower paraspinal muscles.  There is weakness of left ankle dorsiflexion and toe extension.  Ankle and knee reflexes are normal.  Sensory examination shows loss of pinprick sensation over the dorsum of the left foot.  Rectal tone is normal, and the remainder of the examination shows no abnormalities.  Which of the following is the most likely cause of this patient's current condition?

Quizplus · Accepted Answer

11ec25c8_d5c7_54ad_bc81_798507edf652_MD0003_00 This patient with sudden-onset low back pain that radiates to the left leg associated with sensory and motor deficits most likely has a lumbosacral radiculopathy due to a herniated vertebral disc. The sensory deficits over the dorsum of the foot in combination with weakness of foot dorsiflexion and great toe extension are consistent with L5 nerve root compression. The manifestations of lumbar radiculopathies vary based on the involved nerve root, but they typically include low back pain associated with sensory and motor changes in a dermatomal and myotomal distribution. In the case of L5 nerve root compression, pain and sensory loss typically affect the buttocks, lateral thigh and calf (eg, lateral shin), and dorsal foot (eg, loss of pinprick sensation over left foot dorsum in this patient); dermatomal radiation of pain is also common. Weakness (and potentially atrophy) occurs in muscles innervated by fibers from the L5 spinal root, which include the tibialis anterior (foot dorsiflexion and inversion), peroneus (foot eversion), and extensor hallucis longus (great toe extension). dermatomal (Choice A) Acute spinal cord compression can cause back pain and weakness, but would be expected to cause bilateral deficits at all levels below the area of injury, rather than deficits confined to a portion of one leg. In addition, upper motor neuron signs (eg, hyperreflexia, increased muscle tone) would also be present. (Choice B) The common peroneal nerve originates from L5-S1, so there can be overlapping features with L5 radiculopathy. Common peroneal nerve entrapment can cause weakness of foot dorsiflexion and toe extension; however, it would not cause back pain that radiates to the leg. (Choice C) L2 vertebral disc herniation could result in back pain with radiation. However, sensory deficits would be seen in the thigh, and motor deficits would include hip flexion, hip adduction, and knee extension. (Choice E) Compression of the lower sacral nerve roots would cause sensory deficits in the perineum and dysfunction of the urinary or rectal sphincters. Educational objective: L5 radiculopathy often presents with low back pain that radiates down the leg associated with sensory loss over the lateral thigh, calf, and dorsal foot, and weakness of great toe extension and foot dorsiflexion, inversion, and eversion.

A 34-Year-Old Previously Healthy Man Comes to the Office Due