Peripheral Nerve Injury (Part-I)

PNI with Relevant Anatomy, Etiology, Mechanism of Degenration and Regenration, Saddon's and Sunderland Classifications, Clinical symptoms and Examination (Tests) of Brachial Plexus, Radial & Median Nerve.

1. Peripheral N erve I njuries ( Part-I) Dr. Anshu Sharma Assistant Prof. Dept. of Orthopaediscs , GMC&H.

2. Peripheral nerves are formed from nerves arising from the spinal cord (spinal nerves). There are 31 pairs of spinal nerves in the body. These, either through a direct branching or through a network of nerves (plexus), give rise to Peripheral nerves. So, Peripheral nerves are bundles of axons conducting efferent impulses from cells in anterior horn of the spinal cord to the muscles , and afferent impulses from peripheral receptors via cells in the posterior root ganglia to the cord . Introduction

3. All motor axons and sensory axons are coated with myelin sheath, interrupted with nodes of Ranvier . Outside Schwann cells, axon is covered by a connective tissue stocking called E ndoneurium . The axons that make up a nerve are separated into bundles (fascic u les ) by fairly dense membranous tissue, the P erineurium . The group of fascic u les that make up a nerve trunk are enclosed in an even thicker connective tissue coat, the E pineurium .

4. Mechanisms of I njury Fracture & D islocation s ( most common) Thermal injury (Burns) Direct Injury ( Cut and L aceration ) Electrical injury (Electrical shock) Infection - Leprosy. Ischemic injury (Volkmann’s Ischemia) Mechanical Injury ( Compression , T raction , F riction and shock wave) Toxic agents : IM Injections. (Tetracycline) Cooling and freezing (Frost bite) Radiation Exposure (Following Radiotherapy)

5. Primary injury:- Results from same trauma that injures a bone or joint. Radial nerve is the most commonly injured. In Humeral shaft fractures, 14 % is complicated by radial nerve injuries -Displaced osseous fragments -Stretching of nerve -Following Manipulation Secondary injury :- Results from involvement of nerve by infection, scar, callous or vascular complications which may be hematoma, AV fistula, Ischemia or aneurysm.

6. Neuronal Degeneration & Regeneration:- Any part of neuron detached from its nucleus, degenerates & is destroyed by phagocytosis . Distal part  Secondary / Wallerian Degeneration. Proximal  Primary /Retrograde Degeneration for a single node. Time required for degeneration varies between sensory and motor fibers and is also related to size & myelination of fibers .

7. As the regeneration begains , the axonal stumps from the proximal segment begins to grow distally. If the endoneural tube with its contained schwann cells is intact, the axonal sprouts may readily pass along its primary course and re-innervate the end organ. this will form Neuroma in continuity. An end neuroma may form when the proximal end is widely separated from distal end. A side neuroma indicates a partial nerve cut. Advancing Tinel sign ( 1mm/day) and presence of Motor march phenomena are signs of regeneration.

8. Classification of N erve injury :- Seddon’s classification Transient ischaemia Neurapraxia Axonotmesis neurotmesis

9. Transient ischemia :- Due to transient endoneurial anoxia (due to acute nerve compression) Reversible condition Within 15 min: numbness and tingling After 30 min: loss of pain sensibility After 45 min: muscle weakness Relief of compression is followed by intense paresthesia upto 5 min. Feeling restored within 30 seconds and full muscle power after 10 minutes .

10. Neurapraxia :- Physiological interruption, anatomically normal. No proximal or distal degenration and neuroma formation. Seen in crutch palsy , Saturday night palsy, tourniquet palsy . Recovery is Complete and Excellent.

11. Axonotmesis Due to axonal interruption but the nerve is in continuity and the neural tubes are intact . Wallerian degeneration distal to the lesion and few millimeters retrograde . Neuroma in continuity will formed. Axonal regeneration occurs within hours of nerve damage (1-2 mm/day), and recover in few weeks . Seen in Tardy Ulnar nerve palsy. Recovery is usually Good.

12. Neurotmesis :- Division of nerve trunk (Axons as well as nerve). Rapid wallerian degeneration . End or side neuroma will formed. Destruction of endoneurial tubes over a variable segment and scarring prevents regeneration of axons . Surgical repair required Recovery/ Function may be adequate but is never normal (poor).

13. Sunderland ' s classification

14. Diagnosis :- The diagnosis of a peripheral nerve lesion depends primarily on a precise history and an exact clinical examination . Investigations are just to confirm the diagnosis.

15. History c/c= Inabilty to move a part of limb Weakness and Numbness Duration of symptoms Cause may or may not be obvious. When cause is obvious: nerve affected and its level is easy to decide. When cause is not obvious: history of injection in nerve proximity, any medical causes like leprosy, diabetes should be asked.

16. Examination Following observation should be made: 1. Attitude and deformity: S ome peripheral nerve injuries present with classic attitude and deformity of limb. Wrist drop Foot drop Winging of scapula Claw hand Ape-hand deformity Pointing index Policeman-tip deformity

17. 2 . Wasting of muscles: Will become obvious some time after paralysis. -Compare opposite sound side. Slight wasting may go missed. 3.Skin changes: D ry ( No sweating) , glossy and smooth. - P allor or cyanosis - Trophic chang es such as ridged and brittle nails, shiny atrophic skin, trophic ulcers etc

18. Temperature : Paralysed part is usually colder and drier due to loss of sweating. Always compare with normal side. Sensory examination : D ifferent forms of sensation to be tested in suspected case of nerve palsy. Sweat test : T o detect sympathetic function in the skin supplied by a nerve. -P resence of sweating within an autonomous zone of an injured peripheral nerve reassures that complete inteurrption of the nerve has not occurred. -S tarch test or N inhydrin print test. Motor examination

19. Regional N erve I njuries : Brachial Plexus injuries :- Most commonly: Erb’s palsy Klumpke’s palsy

20. Erb’s palsy Injury of C5, C6 and (sometimes) C7 . ( Erb’s point) Common in overweight babies with shoulder dystocia at delivery The abductors and external rotators of the shoulder and the supinators are paralyzed. Arm held to the side, internally rotated and pronated

21. Erb’s palsy

22. Klumpke’s palsy Injury of C8 and T1 . Usually after B reech delivery . Baby lies with the arm supinated and the elbow flexed Loss of intrinsic muscle power in the hand .

23. Long T hora s ic N erve Roots C5, 6 , 7 . Supplies serratus anterior muscle . Injury cause paralysis of the muscle causing winging of scapula (Medial border becomes prominent). Test by pushing against the wall.

24. Test for long thoracic nerve injury (winging of right scapula)

25. Axillary N erve Root value (C5, 6 ) . Supplies D eltoid and T eres M inor muscles . Cutaneous branch supplies the skin over the lower half of the deltoid (landmark: 5 cm below the tip of acromion ) . Injury caused shoulder weakness and wasting of the deltoid muscles . Extension of the shoulder with the arm abducted to 90 is impossible. Small area of numbness over the deltoid.

26. RADIAL NERVE Continuation of the posterior cord of the brachial plexus. Root value: C5- C8 , T1 .

27. Motor branches Before the radial groove: - L ong and M edial heads of T riceps . After the radial groove, before crossing the elbow: - L ateral head of T riceps , A nconeous , B rachioradialis , E xtensor carpi radialis longus . After crossing the elbow: - E xtensor carpi radialis brevis, the supinator . After piercing the supinator: other extensor muscles of the forearm and hand

28. Low lesions Due to # or dislocation at the elbow or to a local wound Complain of clumsiness , not being able to extend the MCP joints of the hand In thumb, weakness of extension and retroposition Wrist extension is preserved

29. High lesions Due to # of the humerus or after prolonged tourniquet pressure Wrist drop due to weakness of the radial extensors of the wrist Inability to extend MCP joints or elevate the thumb. Sensory loss to a small patch on the dorsum around the anatomical snuff box

30. Very high lesions Due to trauma or operations around shoulder . Also common in Saturday night palsy or crutch palsy In addition to high lesions, the triceps is paralysed and the triceps reflex is absent .

31. R adial Nerve Tests: . From proximal to distal, following muscles can be examined: Triceps : A sk to extend his elbow against resistance Where other hands feel for triceps contraction. Brachioradialis: A sk to flex his elbow from 90 degree onwards, keeping the forearm in mid-prone and against resistance,brachioradialis stands out and can be felt.

32. 3.Wrist extensors : “ W rist drop ” occur in paralysis of wrist extensors ( B rachioradialis, ECRL, ECRB, E xtensor digitorum , E xtensor carpi ulnaris).

33. 4 . Extensor digitorum - Functio n : extension at MCP J oint . - “ finger drop ” 5 . Extensor pollicis longus: - Functio n : extension at IPJ of thumb . - E xamined by stabilising the MCP J oint of thumb while p atien t is asked to extend IPJ. - “ thumb drop”

34. PIN PALSY PIN is a branch of the radial nerve. P urely motor innervation to the extensor compartment. 1. F inger metacarpal extension weakness. 2. W rist extension weakness. -inability to extend wrist in neutral or ulnar deviation -the wrist will extend with radial deviation due to intact ECRL (radial n.) and absent ECU (PIN).

35. Median nerve Formed by joining of branches from L ateral and M edial cords of brachial plexus.

36. MOTOR BRANCHES OF MEDIAN NERVE In the A rm N il In the forearm: 1 . P roximal 1/3 All flexors of forearm (except FCU and M edial half of FDP ) 2. D istal 1/3 Nil In the hand: Thenar muscles (Except Adductor Pollicis ) 1 st two lumbricals

37. Low Median Nerve L esions : D ue to injury in the distal 1/3 rd of forearm . Sparing of Forearm muscles. Unable to abduct the thumb ( Thenar Muscles). Sensation lost over the radial three and a half digits . Long standing condition, atrophy of thenar eminence .

38. High Median Nerve lesions : D ue to injury in proximal 2/3 rd of forearm or elbow dislocation . Signs : I n addition to low lesions, paralysis of long flexors to the thumb, index and middle fingers, radial wrist flexors and the forearm pronator muscles . There will be sensory deficit in the skin of hand.

39. Tests: from proximal to distal, following muscles can be examined :- Flexor pollicis longus: -fn: flexion at IP J oint of thumb . -asked to flex distal phalynx of thumb against resistance while proximal phalanx is steady by examiner. Flexor digitorum superficialis and lateral half of flexor digitorum profundus : “ pointing index sign ”

40. - Pointing I ndex :- on asking pt to make a fist, index finger remains straight. -Occurs due to paralysis of both flexors (FDS &FDP) of index finger due to median nerve palsy at level proximal to elbow .

41. 3.Flexor carpi radialis: - I n a p atient with paralysis of this muscles, the wrist deviates to ulnar side while palmar flexion occurs.

42. 4. Muscles of thenar eminence: - A bductor pollicis brevis , O pponens pollicis , F lexor pollicis brevis . -O nly two can be examined for their isolated action. a) Abductor pollicis brevis: fn: abduction of thumb “ P en test” pt is asked to lay his hand flat on the table with palm facing the ceiling, and a pen is held above the thumb and asked him to touch the pen with tip of his thumb.

43. Pen test

44. b) Opponens pollicis: - fn: to appose the tip of the thumb to other fingers. ( Apposition is a swinging movement of thumb across the palm and not a simple adduction)

45. T humb is in same plane as wrist .

46. To be Continued in Part II…