This is commonly associated with hemorrhage into this muscle due to hemophilia, anticoagulation therapy, or trauma. Direct trauma to the femoral nerve can occur as a result of penetrating wounds or fractures of the hip or pelvis. In this position, the sharp flexion of the hip can compress the nerve at the inguinal ligament. Excessive hip abduction and external rotation cause additional stretch on the nerve. Compression of the femoral nerve can also occur due to aortic or iliac aneurysms or tumors.
Diabetic patients have an unusual predilection for femoral and proximal mononeuropathies.
The etiology is suspected to be a vasculitic. NCS should include sensory studies of the saphenous nerve and motor studies of the femoral nerve. When evaluating femoral nerve conduction studies comparison to the asymptomatic side should be completed. On EMG, the quadriceps should show neuropathic changes. The adductor magnus and brevis, which share lumbar innervation with quadriceps and iliopsoas will be spared since they are innervated primarily by the obturator and sciatic nerves.