A 40-year-old woman is brought to the emergency department following a low-speed motor vehicle accident. The patient was in the front passenger seat. During the accident, she hit her head against the windshield and hurt her right leg. She appears alert and oriented. Glasgow Coma Scale score is 15/15. Bilateral pupils are equal and reactive to light. There is a bruise over the right forehead, but no tenderness is present on palpation of the cranial bones. Examination of the right leg shows a hematoma over the thigh. Right knee extension and patellar reflex are markedly reduced compared to those on the left. There is decreased sensation to both sharp and dull stimuli over the anterior side of the right thigh and the medial side of the lower leg. All other dermatomes are intact. This patient most likely has an injury to which of the following nerves?

Question

A 40-year-old woman is brought to the emergency department following a low-speed motor vehicle accident.  The patient was in the front passenger seat.  During the accident, she hit her head against the windshield and hurt her right leg.  She appears alert and oriented.  Glasgow Coma Scale score is 15/15.  Bilateral pupils are equal and reactive to light.  There is a bruise over the right forehead, but no tenderness is present on palpation of the cranial bones.  Examination of the right leg shows a hematoma over the thigh.  Right knee extension and patellar reflex are markedly reduced compared to those on the left.  There is decreased sensation to both sharp and dull stimuli over the anterior side of the right thigh and the medial side of the lower leg.  All other dermatomes are intact.  This patient most likely has an injury to which of the following nerves?

Quizplus · Accepted Answer

11ec25c8_d82a_72b0_bc81_5569f316210f_MD0003_00 This patient has sensory and motor deficits consistent with a femoral nerve injury. The femoral nerve innervates the muscles of the anterior compartment of the thigh (ie, quadriceps femoris, sartorius, pectineus) and is responsible for knee extension and hip flexion. It also provides sensation to the anterior thigh (via the anterior cutaneous branches of the femoral nerve) and medial leg (via the saphenous branch). Patients with femoral nerve injury also have decreased patellar reflex, as the reflex involves the quadriceps muscle. The femoral nerve is vulnerable to injury from pelvic fracture, hip dislocation, or hematoma (eg, iliacus). It can also suffer iatrogenic injury during prolonged maintenance of the dorsal lithotomy position (eg, hip/pelvic surgery, childbirth) or vascular procedures involving the femoral artery or vein. Anesthesia for the anterior thigh and knee can be provided by a femoral nerve block, with injection of anesthetic in the inguinal crease below the inguinal ligament at the lateral border of the femoral artery. below the inguinal ligament (Choice A) Injury to the common peroneal nerve is typically caused by fracture or compression at the proximal fibula. Sensory symptoms occur at the posterolateral leg and dorsolateral foot and are often associated with footdrop due to weakness of foot eversion, dorsiflexion, and toe extension. posterolateral leg and dorsolateral foot (Choice C) The ilioinguinal nerve provides sensory innervation to the upper medial thigh and genital region. It accompanies the spermatic cord through the superficial inguinal ring; injury during pelvic or hernia surgery can lead to chronic suprapubic or groin pain. (Choice D) The obturator nerve innervates the medial compartment of the thigh (ie, gracilis, adductor longus, adductor brevis, anterior portion of adductor magnus). Injury would lead to weakness of hip adduction and decreased sensation at the medial thigh. medial compartment of the thigh (Choice E) The tibial nerve is the larger of the two terminal branches of the sciatic nerve. Injury at the popliteal fossa may result in weakness of plantar flexion (due to denervation of the gastrocnemius and soleus muscles). Compression of the nerve as it passes under the flexor retinaculum in the medial side of the ankle can cause numbness and paresthesias in the sole and distal toes (tarsal tunnel syndrome). tibial nerve Educational objective: The femoral nerve is responsible for knee extension and hip flexion and provides sensation to the anterior thigh and medial leg. It is vulnerable to injury from pelvic fracture, hip dislocation, or iliacus hematoma and can suffer iatrogenic injury during prolonged maintenance of the dorsal lithotomy position (eg, hip/pelvic surgery, childbirth) or vascular procedures involving the femoral artery or vein. References: Iatrogenic femoral nerve injury: a systematic review. (http://www.ncbi.nlm.nih.gov/pubmed/21328076)

A 40-Year-Old Woman Is Brought to the Emergency Department Following