Peripheral Nerve Injuries of the Upper Limb

1. Peripheral Nerve Injuries of the Upper Limb Stacy Rudnicki, MD Associate Professor of Neurology

2. Aids to the Examination of the Peripheral Nervous System • WB Saunders, publishers

3. Definitions

4. Radiculopathy • Process affecting the nerve root, most commonly by a herniated disc • Weakness in muscles supplied by the nerve root (myotome) • Sensory loss in the area of the skin supplied by the nerve root (dermatome)

6. Mononeuropathy • Dysfunction of a single peripheral nerve • Weakness in muscles supplied by the nerve • Sensory loss in the area of the skin supplied by the cutaneous branches of the nerve

7. Brachial Plexopathy • Can refer to involvement of the entire plexus, or parts of the plexus • Trunk lesion • Cord lesion • Distribution of weakness and numbness depends upon the part of the plexus affected

8. Sensory Supply to the Arm • Because fibers from different nerve roots come together and then split apart in the plexus • A dermatome may include areas of the skin supplied by different peripheral nerves • Example: C6 • A single nerve may supply sensation to skin covered by more than one dermatome • Example: median nerve

9. Because of the pattern of root contribution to the plexus: An upper trunk lesion has sensory loss in the combined C5,6 dermatomes A middle trunk lesion has sensory loss in the C7 dermatome A lower trunk lesion has sensory loss in the combined C8T1 dermatomes Sensory Supply to the Arm

11. Principles of Localization • Certain sites are prone to nerve entrapments/injuries • Nerve opposing bone • Ulnar nerve at the elbow • Closed spaces • Carpal tunnel • Adjacent structures • Median nerve at the elbow, adjacent to the brachial artery

12. Principles of localization, cont • Order in which branches arise • Movements at specific joints • Single nerve • Elbow extension • Radial • Multiple nerves • Elbow flexion • Musculocutaneous • Radial • Thumb • Multiple different movement accomplished by multiple muscles innervated by the median, ulnar, and radial nerves

13. Additional Helpful Hints • All muscles within the hand (intrinsic hand muscles) • Are innervated by C8T1 nerve roots • Are innervated by the lower trunk • Are innervated by the medial cord • All ulnar innervated muscles • Are innervated by the C8T1 nerve roots • Are innervated by the lower trunk • Are innervated by the medial cord • All axillary and musculocutanious innervated muscles • Are innervated by C5,6 nerve roots • Are innervated by the upper trunk

14. Additional Helpful Hints, cont • Muscles inserting onto the humerus (and so related to movements of the arm) are primarily C5,6 • Infraspinatus • Supraspinatus • Deltoid • Teres minor • Teres major (Plus C7) • Pectoralis Major (plus C7) • Latissimus is C6,7,8

15. Work Back from the Exam • What muscles are weak? • What innervates the muscle? • Peripheral nerve • Part of plexus • Cord • Trunk • Nerve roots • Where is the sensory loss? Does it best follow the pattern of • A dermatome • A single nerve • A cord or trunk of the plexus

17. Case 1 • A 34 yo woman, currently 28 weeks pregnant, complains of numbness in her fingers • She finds that it is more difficult to manipulate small objects • She is awakened at night be tingling and pain in her hand which seems to spare her little finger

18. Case 1, continued • On exam she has: • Mild weakness of thumb abduction and opposition • Decreased pin prick on the palmar aspect of the thumb, index, middle and lateral aspect of the ring finger • No evidence of loss of muscle bulk in the hand

19. Case 1, continued Finding Muscle Nerve Plexus Root Thumb Abd APB Median Lower trunk C8T1 Medial cord Thumb opp OP Median Lower trunk C8T1 Medial cord Sensory loss Median --- ---

20. Finding Muscle Nerve Plexus Root Thumb Abd APB MedianLower trunk C8T1 Medial cord Thumb opp OP MedianLower trunk C8T1 Medial cord Sensory loss ----- Median --- ---

21. Why isn’t this the medial cord, lower trunk, or C8T1 nerve roots?

22. Why isn’t this the medial cord, lower trunk, or C8T1 nerve roots? • All should also involve ulnar innervated muscles

23. Why aren’t the other median innervated muscles involved?

24. Median Nerve

25. Case 1, continued Final Diagnosis Carpal tunnel syndrome (median neuropathy at the wrist)

27. Case 2 • A 38 yo woman was the restrained passenger in a car struck head on • She braced her hands on the dashboard immediately prior to impact • She suffered bilateral fractures of the humerus at the spiral (radial) groove • She complains of diffuse aches in her arms and neck and weakness in her arms

28. Case 2, cont • On exam she has: • Bilateral wrist and finger drop (ie profound weakness of wrist and finger extension at the MCPs) • Weakness of thumb extension • Weakness of supination • Weakness of elbow flexion with forearm held so that thumb is toward shoulder, but not with hand held in supination • Remainder of strength exam is normal

29. Sensory Loss

30. Case 2, cont • Finding Muscle PN Plexus* Root Wr drop ECR, ECU Radial POST C C5,6,7,8 Fing drop EDC,EI Radial POST C C7, C8 Elb flx BR Radial POST C C5,C6 Th Ext EPL, EPB Radial Post C C7,8 Sens ---- Radial --- ---

31. Finding Muscle PN Plexus* Root Wr drop ECR, ECU Radial POST C C5,6,7,8 Fing drop EDC,EI Radial POST C C7, C8 Elb flx BR Radial POST C C5,C6 Sens ---- Radial --- ---

32. What isn’t involved? • If it is a Posterior Cord lesion • Axillary nerve • Deltoid – arm abduction • Teres Minor – lateral rotation of arm • Radial Nerve • Why is the Triceps spared?

33. Triceps, long head Triceps, lateral head Triceps, med hd Brachioradialis ECRL ECRB Superficial Supinator Radial sens Ext Digit Abd Pol Longus Post Interosseous Ext Pol Longus Ext Pol Br Ext Indicies

34. Sensory loss in a high radial nerve lesion(Signficant variability b/w patients)

35. Final Diagnosis Bilateral radial nerve palsies at the spiral (radial) groove related to fractures

37. Case 3 • A 25 year old man gets involved in a fist fight and the police arrest him • When he is released on bail, he goes to see his doctor because he has numbness in the hand • On exam he had • a number of scratches and bruises on both arms • normal strength • sensory loss on the dorsum of the hand

38. Patient’s sensory loss

39. Case 3, cont Finding PN PLEXUS Root Sens Loss Sup Sens --- <C6 Rad

40. Triceps, long head Triceps, lateral head Triceps, med hd Brachioradialis ECRL ECRB Superficial Supinator Radial sens Ext Digit Abd Pol Longus Post Interosseous Ext Pol Longus Ext Pol Br Ext Indicies

41. Final Diagnosis Superficial radial neuropathy secondary to handcuffs

43. Case 4 • 15 yo football player is hit be another player, with the helmet striking him in the axilla • On getting up, he is aware of shoulder weakness and pain and is taken to the ER

44. Case 4, cont • On exam he has: • Normal elbow flexion • Normal elbow extension • Normal shoulder adduction • Ability to initiate shoulder abduction, but he cannot raise his arm more than 15 degrees • Mild weakness of external (lateral) rotation of the arm • A patch of sensory loss over his upper arm

45. Case 4, sensory loss

46. Case 4, cont Finding Muscle PN Plexus Root Abd>15 Deltoid Axillary Post C C5,6 Ext Rot T. Minor Axillary Post C C5,6 Infrasp Suprascap UT C5,6 Sens ------- Axillary --- <C5

47. Case 4, continued Finding Muscle PN Plexus Root Abd>15 Deltoid AxillaryPost C C5,6 Ext Rot T. Minor Axillary Post C C5,6 Infrasp Suprascap C5,6 Sens ------- Axillary --- <C5

48. Case 4, cont • If it’s at the posterior cord • Radial innervated muscles should be affected • But elbow extension is spared • If it’s C5,6 • Other C5,6 muscles should be affected • But elbow flexion, initiation of arm abduction spared • Pattern of sensory loss

49. Case 4, Final diagnosis Axillary Neuropathy