Peripheral Nn, Pain, & CVA Flashcards
External mechanisms of nerve injuries
Laceration, avulsion, stretch, crush, compression, contusion
Internal mechanisms of nerve injuriese
Viruses, bacteria, autoimmune
Nerve injuries accompanied by injuries to:
Bone, tendon, ligament, soft tissue, vessel
Nerve injuries
Dysfunction of peripheral Nn results from damage to neuron, Schwann cells, or myelin sheath
Stretch injuries
Damage in intrafascicular area (axonal disruption, hemorrhaging); All Nn have ability to stretch & recoil, as long as nerve is free to glide within its beds, stretch can be tolerated, but if it is anchored to its bed by scar tissues, or is overstretched, injuy may occur (intraneural damage, intrafasciular pressure)
Compression Injuries
Acute & chronic; increase pressure, slowed nerve conduction/loss of conduction, mechanical deformation of axon & Schwann cells, decreased circulation
Laceration
Loss of continuity of structure
What happens when a nerve fiber is cut or crushed?
Wallerian degeneration (process by which damaged segment of nerve is phagocytosed); Regeneration
Response to Peripheral N injury
Different than other tissues; regeneration occurs 1-3mm/day, latency of 3-4 weeks, residual deficit is common
Neurapraxia
Result of blunt trauma or compression, causing contusion to nerve. Axons remain in continuity, no Wallerian degeneration, recovers spontaneously within days or weeks, N conduction preserved proximal & distal to injury
Axonotmesis
Axon severed, sheath intact, Wallerian degeneration distal to level of compression; intact endoneurial tube allows regrowth for proximal part of N to reattach to distal portion ot N; recovery usually 6 months, if cell body alive
Neurotmesis
Partial or complete laceration of axon & sheath, without directional guidance of endoneural tube, misdirected axon growth may occur; microsurgery needed, grafting may be necessary
Signs & symptoms
Force & level of injury determines the type of injury sustained & resulting deficits; motor impairment, sensory dysfunction, pain, & parasthesia
Diagnosis
Motor function tests, sensory testing, X-ray, CT scan, MRI, nerve conduction studies
Order of sensory return
1) Pain & temperature; 2) 30 hz vibration; 3) Moving touch; 4) Constant touch; 5) 256 Hz vibration; 6) Touch localization; 7) 2-pt discrimination; 8) Stereognosis
Treatment
Reduce trigger (set fracture, dislocation); analgesics (control pain), antivirals/steroids (decrease edema); operative repair (decompression, repair, neurolysis, grafting)
Vasomotor sympathetic function
skin color & skin temperature change
Sudomotor
sweat
Pilomotor
goosebumps
Trophic
hair & nail growth/changes
Motor return
Function returns along path of N regeneration; return in direction of proximal to distal (everything above should be working)
Prognosis
Varies depending on type & extent of injury, contamination of wound, age of pt, medical status/health previous, surgery to repair N within 3 mos
Complications
Paresthesias, neuromas & entrapment syndromes, hperesthesia, hypersensitivity to cold, paralysis, denervation can develop & result in muscle atrophy, joint stiffness
OT post op consideration
splinting in protective position to decrease amount of tension on healing nerve (3 wks); prevention of contractures & scar adhesions