A 62 year old man is seen in an emergency depament because of severe pain in his lower back, left buttock and the posterolateral aspect of his left leg. The pain began acutely after he lifted his 8 year old granddaughter into the back of a truck, and he describes it as “shooting” in nature. When examined by the physician, he has curled into a fetal position, which he says relieves the pain. Attempts to extend the man’s spine cause a marked exacerbation of the pain. More detailed examination demonstrates foot drop with weakness of the anterior tibial, posterior tibial, and peroneal muscles. Sensory loss is demonstrated over the anterior shin and dorsal foot. These findings suggest a radiculopathy at which of the following cord levels?
A 62 year old man is seen in an emergency depament because of severe pain in his lower back, left buttock and the posterolateral aspect of his left leg. The pain began acutely after he lifted his 8 year old granddaughter into the back of a truck, and he describes it as “shooting” in nature. When examined by the physician, he has curled into a fetal position, which he says relieves the pain. Attempts to extend the man’s spine cause a marked exacerbation of the pain. More detailed examination demonstrates foot drop with weakness of the anterior tibial, posterior tibial, and peroneal muscles. Sensory loss is demonstrated over the anterior shin and dorsal foot. These findings suggest a radiculopathy at which of the following cord levels?
💡 Explanation
Okay, let's tackle this question. The patient has severe lower back pain radiating to the leg, which sounds like sciatica. The acute onset after lifting something heavy suggests a herniated disc, probably in the lumbar spine. The symptoms include foot drop and weakness in specific muscles. Foot drop is a big clue—it's usually due to peroneal nerve issues, but here the muscles affected are anterior tibial, posterior tibial, and peroneal, which are innervated by different nerves.
Wait, the L4, L5, and S1 nerves are involved in the lumbar plexus. Let me think about the dermatomes and myotomes. L5 radiculopathy typically causes weakness in the tibialis anterior (dorsiflexion), which is part of the foot drop. Also, sensory loss on the anterior shin and dorsal foot fits L5. The peroneal muscles are more S1, but maybe there's overlap. The question mentions posterior tibial weakness too. Hmm, posterior tibialis is innervated by the tibial nerve, which is S1. So if there's S1 involvement, but the main issue here is the foot drop and sensory loss pointing to L5. The classic presentation of L5 radiculopathy is sciatica with L5 symptoms. The exacerbation with spine extension suggests nerve root irritation, which is common in herniated discs at L4-L5. So the correct answer is L5.
**Core Concept**
This question tests the understanding of lumbar radiculopathy syndromes, specifically the clinical manifestations of a herniated intervertebral disc compressing a spinal nerve root. L5 and S1 radiculopathies are most commonly associated with sciatica due to their anatomical vulnerability between L4-L5 and L5-S1 discs.
**Why the Correct Answer is Right**
The key findings—foot drop, anterior tibial weakness (dorsiflexion), and sensory loss over the anterior shin and dorsal foot—correlate with **L5 radiculopathy**. The L5 nerve root innervates the tibialis anterior (anterior tibial muscle) and contributes to the peroneus longus (peroneal function). Sensory deficits in the anterior shin (L5 dermatome) and dorsal foot (S1 overlap) support this. The acute onset after heavy lifting suggests an L4-L5 disc herniation, which compresses the L5 root as it exits inferior to the disc. Spinal extension worsens pain by increasing disc pressure on the nerve root.
**Why Each Wrong Option is Incorrect**
**Option A:** L4 radiculopathy would cause weakness in the quadriceps (femoral nerve) and sensory loss in the medial calf, not foot drop.
**Option B:** S1 radiculopathy presents with weakness in the posterior tibial and peroneal muscles (plantar flexion, inversion), sensory loss on the sole, and a positive straight leg raise test.
**Option C:** L2-L3 radiculopathy affects hip flexion (iliopsoas) and medial thigh sensation, unrelated to foot drop.
**Clinical Pearl**
Never forget the "L5 foot drop" triad: **weak dorsiflexion, sensory loss over the shin/
✓ Correct Answer: B. L5
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