Femoral nerve injury

1. What is the course of the femoral nerve and what muscles does it innervate?
2. What is the presentation and etiology of femoral neuropathy? What are the NCS findings?
3. What is diabetic amyotrophy?
4. How does saphenous neuropathy present and what is the etiology?
5. To what region does the saphenous nerve supply sensation?

Answers:
1. The nerve runs through the psoas, under the inguinal ligament lateral to the femoral artery (and vein), then travels through the femoral triangle. It innervates the iliacus, pectineus, sartorius, rectus femoris, vastus muscles, and gives off the sensory saphenous nerve.
2. The nerve can be injured by compression in the pelvis from trauma, fracture, retroperitoneal hematoma, tumor, or cardiac cath. It presents with quad weakness and decreased sensation over the anterior thigh and medial leg. EMG shows abnormal saphenous SNAP, abnormal rectus femoris CMAP.
3. Diabetic amyotrophy is the most common cause of femoral neuropathy. The nerve is injured from an abnormality in the vaso-nevorum due to DM. It may also occur due to marked weight loss. The symptoms include those of femoral neuropathy with asymmetric thigh pain and atrophy.
4. The saphenous nerve is injured by entrapment in Hunter's canal or between the sartorius and the gracilis, or from knee or vascular surgery. Patient complains of medial knee pain with abnormal sensation radiating distally along the medial aspect of the leg and foot.
5. Medial aspect of the leg, medial malleolus, and medial arch of foot.