Review Question - QID 217601

This patient presents with unilateral medial thigh pain, sensory paresthesia, and hip adduction weakness, which are consistent with obturator neuropathy. This is likely from bodybuilding and exercising.

Obturator neuropathy is a rare condition that has various etiologies, including direct nerve compression in the adductor compartment (in muscular thighs), trauma, or mass effect (from a tumor). The obturator nerve originates from spinal roots L2-L4 and descends through the psoas muscle to exit near the medial pelvic brim. It courses along the wall of the pelvis posterior to the common iliac vessels and then enters the thigh via the obturator canal. It provides sensory innervation to the medial thigh and motor innervation to the adductors, gracilis, and obturator externus. Injury or compression of this nerve will result in sensory loss in the medial thigh and hip adduction weakness. Treatment is conservative with rest, activity modification, and non-steroidal inflammatory drugs for pain.

Tipton discusses the pathophysiology, diagnosis, and management of obturator neuropathy. The author highlights conservative treatment as the mainstay for this condition. They recommend considering surgical management for lesions that are documented by electromyography not responding to conservative therapy.

Incorrect Answers:
Answer 1: The common peroneal (fibular) nerve can be injured in trauma settings and presents with a foot drop (impaired ankle dorsiflexion). Sensory loss occurs over the dorsum of the foot. The common peroneal nerve does not provide sensory innervation to the thigh. The motor innervation of the peroneal nerve is the anterior and lateral compartments of the leg.

Answer 2: The femoral nerve can be injured in trauma settings and presents as inguinal pain, sensory loss in the anterior thigh, knee extension weakness, and diminished patellar reflexes. This nerve can be trapped in patients with femoral hernias or injured during surgery through the anterior approach to the hip.

Answer 4: The saphenous nerve can be compressed as it travels through the adductor canal, resulting in sensory loss over the medial leg (not thigh) and foot. It is a pure sensory nerve, so motor findings would not be expected. The saphenous nerve can be injured during the medial approach to the leg.

Answer 5: The sciatic nerve can be injured in trauma settings, after hip surgery, or via direct compression (between the greater sciatic notch and ischial tuberosity). It presents with radiating pain from the buttock down the posterior thigh and leg. Because the sciatic nerve is composed of tibial and common peroneal nerve bundles, it can also manifest with a foot drop. The sciatic nerve does not provide cutaneous innervation to the medial thigh.

Bullet Summary:
The obturator nerve provides cutaneous innervation to the medial thigh and motor innervation to the adductors, gracilis, and obturator externus.