Obturator neuropathy

1. What muscles are innervated by the obturator nerve?
2. How is the obturator nerve commonly injured?
3. What is the presentation of obturator neuropathy?

Answers:
1. Pectineus, adductor brevis, adductor longus, adductor magnus, obturator externus, gracilis. It also has a cutaneous branch.
2. It is injured by compression from a pelvic fracture or hernia within the obturator foramen.
3. Symptoms include hip adduction weakness and decrease in sensation along the medial thigh.

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.

Lateral femoral cutaneous nerve injury

1. What is the nerve root origin of the lateral femoral cutaneous (LFC) nerve?
2. What is the path of the LFC nerve?
3. What is the most common etiology of injury to the LFC nerve (meralgia paresthetica)?
4. What is the presentation of meralgia paresthetica?
5. What is the treatment of meralgia paresthetica?

Answers:
1. L2, L3, contributing to the posterior division of the lumbar plexus.
2. It passes over the iliacus toward the AIS, then under the inguinal ligament to provide sensation to the lateral thigh.
3. Low-grade repetitive trauma, protuberant abdomen, pregnancy, tight clothing, diabetes, tumor, infection.
4. Symptoms are purely sensory and include lateral thigh pain, numbness, burning, or dull ache, sometimes exacerbated by hip extension.
5. Treatment includes rehab, NSAIDs, steroid injection, surgical release.

Long thoracic nerve injury

1. Where do the long thoracic nerve fibers originate?
2. What muscle does the long thoracic nerve innervate?
3. What is the difference between scapular winging caused by long thoracic nerve vs. spinal accessory nerve injury?
4. What are common causes of long thoracic nerve injury?

Answers:
1. C5, C6, C7 roots.
2. Serratus anterior.
3. Long thoracic nerve injury causes serratus anterior weakness, resulting in winging that brings the scapula more medial, and winging is decreased by abduction. Spinal accessory nerve injury causes trapezius weakness, resulting in winging that brings the scapula away from the midline, and is increased by abduction.
4. Fall, MVA, sports injury, shoulder bags.

Suprascapular nerve injury

1. What nerve roots does the suprascapular nerve arise from?
2. What muscles does the suprascapular nerve innervate?
3. How is the suprascapular nerve injured?
4. What is the presentation of suprascapular nerve injury?

Answers:
1. C5 and C6, continuing to contribute to the upper trunk.
2. Supraspinatus, followed by the infraspinatus.
3. Forced scapular protraction, penetrating wounds, crutches, traction, rotator cuff injury, Erb's palsy, supraglenoid ganglions, hematoma, entrapment.
4. Weakness in shoulder abduction and external rotation. If there is an injury at the spinoglenoid notch, only the infraspinatus may be affected.

Axillary nerve

1. What nerve roots does the axillary nerve originate from?
2. What is the path of the axillary nerve?
3. What muscles does the axillary nerve innervate? What sensory branch does it give off?
4. How is the axillary nerve usually injured and what is the presentation?

Answers:
1. C5 and C6, contributing to the upper trunk and posterior cord.
2. It passes inferior to the glenohumeral jt, to the posterior aspect of the humerus.
3. Teres minor and deltoid. It gives off the upper lateral cutaneous nerve.
4. It is injured by shoulder dislocation, humeral head fracture, or improper crutch use. Patient complains of weakness of shoulder flexion, abduction, and external rotation. There may also be lateral shoulder sensation abnormality.

Musculocutaneous nerve

1. What nerve roots contribute to the musculocutaneous (msc) nerve?
2. What muscles are innervated by the msc nerve? What sensory nerves are given off by the the msc nerve?
3. How is the msc nerve usually injured?
4. What is the presentation of msc nerve injury?
5. What are the EMG/NCS findings?

Answers:
1. C5, C6, C7, which become the upper trunk, then lateral cord.
2. Coracobrachialis, biceps brachii, brachialis. The lateral antebrachial cutaneous nerve innervates the lateral forearm.
3. Distal injury is more common than proximal. It can be injured by entrapment prox from the coracobrachialis, or by gunshot wounds, shoulder dislocation, or phlebotomy.
4. Elbow flexion weakness and abnormal sensation over lateral forearm. Coracobrachialis usually spared.
5. SNAP abnormal in lateral antecubital cutaneous nerve. CMAP abnormal to biceps. EMG abnormal in biceps and brachialis.