Internal topographyFascicular arrangement constantly change throughout the course
Etiology of peripheral nerve injuries1. Metabolic or collagen disease2. Malignancy3. Endo or exo-toxins4. Ischaemia5. Radiation * infection:leprosy6. Trauma Thermal Chemical Mechanical
Primary injury – Results from same trauma that injures a bone or joint – Radial nerve is the most commonly injured. Of humeral shaft fractures, 14 % is complicated by radial nerve injuries – Displaced osseous fragments – Stretching – Manipulation Secondary injury – Results from involvement of nerve by infection, scar, callous or vascular complications which may be hematoma, AV fistula, Ischemia or aneurysm
Classification of nerve injuriesSeddon Classification 1.Neuropraxia: 1.Minor contusion or compression with preservation of axis – cylinder of myelin sheath. 2.Impulse transmission physiologically interrupted. 3.Complete recovery in a few days to weeks 2.Axonotemesis : 1.More significant injury 2.Breakdown of axon and distal Wallerian degeneration but with preservation of schwann cell & endoneurial tubes 3.Spontaneous regeneration with good functional recovery can be expected3. Neurotmesis 1.More severe injury 2.Complete anatomical severance, avulsion or crushing of nerve 3.Axon, Schwann cell & endoneurial tubes are completely disrupted 4.Spontaneous recovery cannot be expected unless surgically intervened
Sunderland Classification Each degree of injury suggesting a greater anatomical disruption with its correspondingly altered prognosis Anatomically various degrees (1st – 5th) represent injury to Myelin Axon Endoneurial tube & it’s content Perineurium Entire nerve trunk Sixth degree (Mackinson) or mixed injuries occur in which a nerve trunk is partially severed and remaining part of trunk sustains 1st to 4th degree injury. Mixed recovery pattern depending on degree of injury to each portion of nerve.
Neuronal degeneration and regeneration• Any part of neuron detached from its nucleus, degenerates & is destroyed by phagocytosis. • Distal – Secondary / Wallerian Degeneration • Proximal - Primary / Traumatic / Retrograde Degeneration• Time required for degeneration varies between sensory and motor fibers and is also related to size & myelination of fibers• Advancing Tinel sign and presence of motor march phenomena are signs of regeneration
Diagnosis of Peripheral nerve injuries• History – Which nerve ? – What level ? – What is the cause ? – What degree of injury ? – Old or fresh injury ?
Diagnosis of Peripheral nerve injuries1. Motor: – All muscles distal to the injury – paralyzed & atonic – Atrophy : 50 -70 % in 1st two months – Striations & motor end plate configurations retained for 12 – 18 months (critical limit of delay)
2. Sensory :• Sensory loss usually follows a definite anatomical pattern, although factor of overlap from adjacent nerves may be present• Autonomous zone• Weber 2 point discrimination test• Tinel’s sign
(3) Reflex• Abolishes all reflexes transmitted by that nerve, either afferent or efferent arc.• Complete & incomplete lesion. So , not a reliable guide to injury severity.(4) Autonomic :• Loss of sweating• Loss of pilomotor response and• Vasomotor paralysis in autonomous zone
(5) Others: • Trophic Changes • Esp. hand and feet • Skin – thin, glistening, breaks easily to form ulcers that heal slowly • Fingernails • Ridged, distorted and brittle • Osteoporosis (Reflex sympathetic dystrophy)
Test for peripheral nerves of upper limb• Radial nerve injury – very high / high / low injury – Wrist drop / finger drop / thumb drop – Test for triceps/ /Brachioradialis/ wrist extensors / extensor digitorum / EPL• Median nerve – High / low injury – Test for FPL / FDS / FDP (lat. half) / FCR / Abd. Pollicis brevis ( pen test) / Oppenens pollicis – See for pointing index / complete claw hand
• Ulnar nerve – High / low palsy –ulnar paradox – Test for FCU / Abd. digiti minimi / Interossei (dorsal - Egawa’s test ; palmar – card test ) / lumbricals /Add. Pollicis (Froment’s sign / book test ) – Ulnar claw hand
Time of Surgery• Primary repair : First 6 – 8 hours• Delayed primary repair : First 7 – 18 days• Secondary repair : > 3 weeks
Indications for surgery1. When a sharp injury has obviously divided a nerve.2. When abrading, avulsing or blast wounds have rendered the condition of nerve unknown3. When a nerve deficit follows a blunt or closed trauma & no clinical or electrical evidence of regeneration has occurred after an appropriate time4. When a nerve deficit follows a penetrating wound as stab or low velocity gunshot wound, part observed for evidence of nerve regeneration for appropriate time.
Method of closing gap between nerve ends1. Mobilization ( critical nerve gap distance – value of Grantham)2. Positioning of extremity – Flex knee and elbow < 90° – Flex wrist < 40°1. Transposition2. Bone resection3. Nerve stretching & bulb sutures4. Nerve grafting5. Nerve crossing ( pedicle grafting )
Factors that influence regeneration afterneurorrhaphy 1. Age of patient 2. Gap between nerve ends 3. Delay between time of injury and repair 4. Level of injury 5. Condition of nerve ends 6. Experience & technique of surgeon