PNS Injury/Repair N30 Flashcards
Neuropraxia
acute insult to peripheral nerve resulting in interruption of impulse transmission
Neuropraxia exam results
partial loss of sensory and motor
Neuropraxia causes
Microvascular alteration resulting in transient ischemia, reversible, compression of nerve
Axonotmesis
injury to axoplasm and cell membrane but Schwann cell and CT are intact
Axonotmesis causes
long bone fracture and traction injury
Axonotmesis exam results
partial loss of sensory and motor to areas innervated by damaged neuron(s) and neurogenic atrophy due to irreversible absence of electrical potentials
Histological change with Axonotmesis
regression of myelin, thickening of epineurium, scar tissue, neuroma
Neurotmesis
complete severance of peripheral nerve trunk
Neurotmesis exam results
complete loss of sensory and motor to innervated areas
Histological change with Neurotmesis
degeneration of axons distally, degeneration for 1-2 nodes proximal
Lesion in continuity has a greater chance of regeneration
meaning: when the epineurium and supporting structures are intact to maintain continuity between the severed nerve, regenertion may be likely
Neuronal cell body’s reaction to injury
hypertrophy to induce metabolic processes required for regeneration (greatest chance for regeneration: minor lesion nerve proximal to cell body)
The proximal nerve stump’s reaction to injury
retraction (elasticity), degeneration (2-3 nodes), hemorrhaging and clot followed by macrophage invasion, possible neuroma, SCHWANN CELL proliferation to meet distal stump and create a glial tunnel to guide the regenerating axon
The distal nerve stump’s reaction to injury
WALLERIAN DEGENERATION of axon, macrophage invasion, Schwann cell activity diminishes, CT beings to proliferate, regeneration occurs via extension of Schwann cells and CT provide pathway
Factors that contribute to healing
Intrinsic: age, health, time since injury, type of injury, level and nerves involved
Extrinsic: surgical technique
Surgical repair of nerves: Immediate repair
8-12 hrs following injury, full or partial transection of nerve, clean, sharp wound
Surgical repair of nerves: Delayed repair
2-6 weeks following injury, trauma or infection, time for inflammation to subside, time for metabolism of nerve body to change
End-to-end surgical repair
suture the proximal and distal epineurium together
End-to-side repair
epineurium of distal stump is sutured to an undamaged nerve
Nerve cuffs to repair nerve lesion
cuff made of various materials to close off the surgical regeneration site and prevent misguidance of axons and ingrowth of CT
Nerve grafts
if a nerve gap exists (due to damage) a nerve may be stretched 2-3cm to fill gap, otherwise a nerve graft from biological or biocompatible materials are used to bridge the gap
Skeletal muscle atrophy
occurs if nerve innervation isn’t restored within a certain time frame; IRREVERSIBLE
