Nerve injury

types,classifications,investigations and surgical repair methods

1. NERVE INJURY CLASSIFICATION, NERVE DEGENERATION, REGENERATION AND REPAIR TECHNIQUES PRESENTER- MADHUKAR VANGA

2. STRUCTURE OF NEURON

3. CLASSIFICATION OF NERVE INJURY Two different classifications are being used to describe the nerve injuries Proposed by SEDDON in 1943 Proposed by SUNDERLAND in 1951

4. SEEDON CLASSIFICATION NEUROPRAXIA AXONOTMESIS NEUROTMESIS

5. NEUROPRAXIA Minor contusion or compression of a peripheral nerve with preservation of the axis-cylinder but with possibly minor edema or breakdown of a localized segment of myelin sheath. Transmission of impulse is physiologically interrupted for a period of time, but recovery in a few days or weeks. Ex- C rutch palsy, Saturday night palsy

6. AXONOTMESIS More significant injury with breakdown of the axon and distal wallerian degeration but with preservation of the schwann cell and endoneurial tubes. Spontaneous regeneration with good functional recovery can be expected. It is usually the result of a more severe crush or contusion than  neuroprexia .

7. NEUROTMESIS Severe injury with complete anatomical severance of the nerve or extensive avulsing or crush injury. The axon, schwann cell and endoneurial tubes are completely disrupted. In this group, significant spontaneous recovery cannot be expected. It usually occurs in gunshot or knife injuries.

8. SUNDERLAND’s CLASSIFICATION This is more rapidly applicable clinically, with each degree of injury suggesting a greater anatomical disruption with its correspondingly altered prognosis. In this classification peripheral nerve injuries are arranged in ascending order of severity. Anatomically various degrees represent injury to 1)myelin 2)axon 3) endoneurial tube and its contents 4) perineurium 5)entire nerve trunk.

9. 1 st degree injury In this conduction the axon is physiologically interrupted at the site of injury but the axon is not disrupted. No wallerian degeneration. Recovery is spontaneous and usually complete within a few days or weeks. Because there is neither axonal damage nor regeneration, no Tinel sign is present.

10. 2 nd degree injury Disruption of the axon is evident, with wallerian degeneration distal to the point of injury and proximal degeneration for one or more nodal segments. Integrity of the endoneurial tube is maintained, providing a perfect anatomical course for regeneration. Tinel sign can be followed along the course of the nerve usually at the rate of 1 inch per month, tracing the progression of regeneration. Good functional return is achieved.

11. 3 rd degree injury In this the axons and endoneurial tubes are disrupted but the perineurium is preserved. The result is disorganization resulting from disruption of the endoneurial tubes. Clinically, the neurological loss is complete in most instances. Tinel sign is usually present. However complete return of neural function does not occur, distinguishing this from 2 nd degree injury.

12. 4 th degree injury In this the axon and endoneurium and possibly some of the perineurium are preserved, so complete severance of the entire trunk does not occur. No T inel sign. Prognosis for significant return of useful function is uniformly poor without surgery.

13. 5 th degree injury The nerve is completely transected, resulting in a variable distance between the neural stumps. Possibility of significant return of function without appropriate surgery is very remote.

14. 6 th degree injury Also called as Mackinnon or mixed injuries occur in which nerve trunk is partially severed and the remaining part of the trunk sustains, 4 th degree, 3 rd degree, 2 nd degree, or rarely even 1 st degree injury. Recovery pattern is mixed depending on the degree of injury to each portion of the nerve.

15. Nerve Degeneration Any part of a neuron detached from its nucleus degenerates and is destroyed by phagocytosis . This process of degeneration distal to a point of injury is called secondary or wallerian degenetarion . The reaction proximal to the point of detachment is called primary, traumatic or retrograde degeneration.

16. 1 st 3 days- macrophagic changes become apparent in axon After 3 days – distal segment becomes fragmented and with subsequent fluid loss the fragments begin to shrink and assume a more oval or globular appearance. By 7 th day macrophages have reached the area in greater numbers, By 15 – 30 days clearing of axonal debris is complete.

17. Nerve regeneration The onest of regeneration is accompanied by changes in the cell body CHROMATOLYSIS with swelling of the cytoplasm and eccentric placement of the nucleus. The reaction within the cell body is evident by day 7 and evidence of beginning recovery is apparent after 4-6 weeks.

18. The proximal segment of the axon degenerates close to the injury for a short distance, but growth starts as soon as debris is removed by macrophages. Macrophages produce cytokines which stimulate Schwann cells. In the nerve segment distal to the injury the axon and myelin are completely removed by the macrophages but not the connective tissue.

19. While these regressive changes take place, Schwann cells proliferate within the connective tissue sleeve, giving rise to rows of cells that serve as guides for the sprouting axons. Axonal sprouting may occur within 24hrs after injury.

20. Regeneration is successful only if the endoneurial tube with its contained Schwann cells has been uninterrupted by the injury , the sprouts may pass readily along their former courses and after regenertaion the surviving cells innervate their previous end organs.

21. If the injury is severe enough to interrupt the endoneurial tube with its with its contained Schwann cells, the sprouts may migrate aimlessly throughout the damaged regions to form stump NEUROMA.

22. Diagnostic tests ELECTRODIAGNOSTIC STUDIES 1)NERVE CONDUCTION VELOCITY 2)ELECTROMYOGRAPHY TINEL SIGN SWEAT TEST SKIN RESISTENCE TEST ELECTRICAL STIMULATION

23. Nerve conduction velocity A nerve conduction velocity test (NCV) is an electrical test that is used to determine the adequacy of the conduction of the nerve impulse as it courses down a nerve. This test is used to detect signs of nerve injury. Stimulation of a peripheral nerve by an electrode placed on the skin overlying the nerve readily evokes a response from the muscle innervated by that nerve.

24. This is useful shortly after an injury to provide objective evidence of interference in nerve conductivity but it is impossible to determine the severity of the insult immediately after injury. Immediately after injury, stimulation proximal and distal to the insult may elicit a normal response. As wallerian degeneration ensures within 5-10 days there is progressive reduction in the amplitude and alteration in the configuration of the evoked potentials.

25. EMG Electromyography (EMG) is a diagnostic procedure to assess the health of muscles and the nerve cells that control them (motor neurons). Motor neurons transmit electrical signals that cause muscles to contract. An EMG translates these signals into graphs, sounds or numerical values that a specialist interprets. An EMG uses tiny devices called electrodes to transmit or detect electrical signals.

26. During a needle EMG, a needle electrode inserted directly into a muscle records the electrical activity in that muscle. A nerve conduction study, another part of an EMG, uses electrodes taped to the skin (surface electrodes) to measure the speed and strength of signals traveling between two or more points. EMG results can reveal nerve dysfunction, muscle dysfunction or problems with nerve-to-muscle signal transmission

27. Tinel sign The Tinel sign is elicited by gentle percussion by a finger or percussion hammer along the course of an injured nerve. A transient tingling sensation should be felt by the patient in the distribution of the injured nerve rather than at the area percussed , and the sensation should persist for several seconds after stimulation. A positive Tinel sign is presumptive evidence that regenerating axonal sprouts that have not obtained complete myelinization are progressing along the endoneurial tube.

28. Techniques of nerve repair ENDONEUROLYSIS (INTERNAL NEUROLYSIS) NEURORRHAPHY NERVE GRAFTING

29. ENDONEUROLYSIS (INTERNAL NEUROLYSIS). It is an enoneurial exploration for assesing the injury of fasciculli . If most of the fasciculli are intact and can be seperated and traced through the neuroma , nothing further should be done. It stimulation fails to elicit a response, a few if any intact fasciculli can be found, resecting the neuroma and neurorraphy are probably indicated.

30. NEURORRAPHY Primary neurorrhapy (<24 hrs) Delayed Primary neurorrhapy (2-18 days) Secondary neurorrhapy (<3 months)

31. TYPES EPINEURIAL NEURORRHAPHY PERINEURIAL NEURORRHAPHY EPIPERINEURIAL NEURORRHAPHY All these come under primary neurorrhaphy

32. EPINEURIAL NEURORRHAPHY Expose the nerve and dissect the redundent areolar tissue from epinuerium Gently trim the nerve ends to identify good neural tissue and locate fescicles Using the internal arrangement of fascicles and the vessels on the epinuerium determine the rotational arrangement Place a 9-0 monofilament nylon suture through the epineurium and tie this stitch Place sutures circumferentially around the cut surface, attempting to align appropriatly corresponding fascicles without suturing them.

33. PERINEURIAL NEURORRHAPHY Same as Epineural Neurorrhaphy but in this epineurium from the circumference surrounding the groups of fascicles is also removed. Attempt is made to match corresponding groups of fascicles proximally and distally. After this nerve is repaired by suturing the ends of the fascicles together with atleast 2 sutures placed through the perineurium at 180 degrees to each other.

34. EPIPERINEURIAL NEURORRHAPHY This includes epineurium and perineurium is useful in aligning large groups of fascicles in larger nerves and when nerves have been incompletely transected. After aproximation of fascicles proximally and distally repair individual fascicles in central portion of nerve 1 st by using 10-0 nylon suture Then approximate the fascicles and group of fascicles that lie near the periphery of the nerve by placing 9-0 nylon through the epineurium and through the edge of the perineurium .

35. Post op care- The initial postoperative splinting is maintained for 3 weeks, during which time the patient is allowed minimal active movement of the finger joints within the limits of the splint. Suture removal done between 7-14 th day. Four to 8 weeks after operation, removable plastic splints are used in reliable patients. Six to 12 weeks after surgery, careful attention should be paid to the avoidance of fixed contracture . Eight to 12 weeks after surgery, progressive strengthening exercises are begun. Clinical evaluations of motor and sensory return are made monthly

36. INTERFASCICULAR GRAFTING This comes under secondary neurorrhaphy Developed by MILLESI. He developed a technique of grafting using multiple cuntaneous nerve grafts that allow alignment of fascicles in proximal and distal nerve stumps.

37. TECHNIQUE Incise the epineurium proximal to the neuroma in normal appearing tissue on the proximal stump and similarly towards the scared distal stump Identify major fascicle groups and follow them to the scar. Transect thin fascile group there with microscissors and prepare both ends Select a graft, expose and dissect the nerve graft Keep it moist with ringer solution Using diamond knife cut the nerve graft into sections 10% - 15% longer than the defect

38. Excise the redundent epineurial and areolar tissue from the graft Place the nerve grafts between the proximal and distal nerve stumps Use sketch of fascicles to determine where to attach the graft at each end Obtain exact coaptation of the nerve graft to the corresponding fascicle groups Suture the nerve graft at each end using 10-0 nylon placed through the epineurium of graft and perineurium of one of the fascicle group Close the skin carefully so that graft is not displaced by shearing forces during wound closure

39. Neuroma dissection before nerve grafting

40. Nerve grafts placed between nerve ends Nerve grafts sutured in place Technique of interfascicular nerve grafting

41. Post op care- The part is immobilized for 8 to 10 days. Afterward the splint is removed, and free motion of joints is allowed. Necrotic skin is debrided , and local flaps or free skin grafts are used to cover a nerve graft that may be exposed. Physical therapy with active and active-assisted range-of-motion exercises is instituted under supervision 2 weeks after nerve grafting. The progress of regeneration may be followed by observing the Tinel sign.

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