Final - Peripheral Nerve Injuries Flashcards
Etiology of Nerve Injuries
- Tension: stretch injury
- Compression: tumor
- Trauma: penetrating wound
- Ischemia: diabetic neuropathy
Pathophysiology of nerve injuries
- injury may result in demyelination or axonal degeneration
- results in disruption of the sensory and/or motor function of the injured nerve
- specific sensory deficits and weakness depend on which nerve has been affected and the location of the injury
Wallerian Degeneration
- injury to an axon
- cell body nucleus recognizes that something in the periphery has changes
- Retrograde loss of the axon to at least the first uninjured Node of Ravier
What does Wallerian Degeneration cause?
- increase in cell body size
- migration of the nucleus to the periphery
- increased protein and RNA metabolism
- myelin phagocytosis
- muscle atrophy
How is Wallerian Degeneration fixed?
- schwann cell proliferation
- axonal sprouting
- possible increased activity of nerve growth factor
- Axonal regeneration at a rate of 1-4 mm/day
- contact with appropriate distal target cell and synapse is formed
- “unused” sprouts are reabsorbed
What can form when nerve regeneration is unsuccessful?
neuroma
Partially successful nerve regeneration
- axonal regeneration to the incorrect distal target
- decreased target tissue viability
What correlates closely with the prognosis of recovery?
the nerve injury classification
first degree injury
- Seddon’s neuropraxia
- Localized conduction block but axon remains viable
- Focal demyelination may occur
- Recover is usually complete 2-3 weeks
Second Degree Injury
- Seddon’s Axonotmesis
- Injury to axon
- Supporting structures are intact
- Wallerian degeneration occurs
- Recovery at 1mm/day as axon follows connective tissue tubule
- can be monitored with an advancing Tinel’s sign
- recovery is poor in lesions requiring > 18 mo to reach target site
Third Degree Injury
- Seddon’s Axonotmesis
- Endoneurium is disrupted
- Perineurium and epineurium are intact
- recovery may range from poor to complete and depends on the degree of intrafascicular fibrosis
- nerve may not appear seriously damages on gross inspection
Fourth Degree Injury
- Seddon’s axonotmesis
- Interruption of all neural and supporting elements
- epineurium is intact
- the nerve is usually enlarged
- Tinel’s sign does not advance
Fifth Degree Injury
- Seddon’s Neurotmesis
- Complete Transection wit loss of continuity
sixth degree injury
- recently introduced by MacKinnon
- Mixed nerve injury –> some fascicles of a nerve are working normally while other fascicles may be recovering
Proper Diagnosis of Nerve Injury
- History
- strength and sensory testing
- nerve conduction studies
- EMG
- imaging studies (MRI and CT scans) for suspected brachial plexus avulsion injuries or tumors
Medical Management of Open Injuries
- immediate exploration of the nerve following a laceration
- nerve repair if indicated:
approximate nerve ends and suture together
microscopic technique (microsurgery) to align internal fascicles
limit amount of tension
Nerve Tension
- intraneural pressure increases with tension of nerve
- blood supply is compromised
Nerve Grafts - Indications
- tissue loss
- tension with approximation of nerve endings
- tension on nerve with joint movement
Nerve Grafts - Autografts
- sural nerve
- medial cutaneous nerve of the forearm
Nerve Grafts - Allografts
need for immunosuppression medication - no longer necessary
Nerve Grafts - nerve conduits
- silicon tubes
- neurotubes
Nerve Transfers
- use of viable nerve which is sacrificed to its target tissue to reinnervate a new target tissue
- generally used for motor function
Medical Management of Closed Injuries
- symptom management
- Periodic rechecks for recovery –> clinical observation/testing, electrodiagnostic testing
- surgical exploration 3 months after injury if no improvements is noted
- crush injuries are similarly managed
Medications for Nerve Pain
- antidepressants
- anticonvulsants
- Baclofen
General therapeutic management
- protection of anatomical structures from further stresses
- pain management
- prevention of PROM loss
- prevention of strength loss in unaffected musculature; unable to strengthen affected musculature
- pt education (diagnosis/therapy process, compensatory strategies for loss of function)
Therapy following surgical management
- period of immobilization to avoid tension on nerves
- edema management
- scar management
Developmental consideration in therapy
- lack of compressive and tensile forces may affect normal bone and muscle development
- inability to get into normal developmental positions may cause tissue tightness
Presentation of Brachial Plexus Upper Trunk Injury
- upper trunks of brachial plexus (c5 and c6)
- most commonly injured
- mechanism of injury is forcible increase in the angle between the neck and the shoulder
- muscles in C5 and C6: shoulder abductors, elbow flexors and supinators, wrist extensors
- Sensory deficits in the C5 and C6 dermatomes - lateral arm, forearm, and hand
Therapeutic Management for Upper Brachial Plexus Injury
- Problems: shoulder stability compromised
- Pain management: muscle tightness related to muscular imbalance –> STM to decrease tightness
- patient education: exercises to maintain PROM, functional compensatory strategies, safety for sensory deficits
Presentation of Radial n injury
- common mechanisms of injury are mid shaft humeral fracture, trauma, saturday night palsy
- musculature affected: elbow extensors, wrist, thumb, and MCP joints of digits depending on site of injury
- small area of sensory deficit in the posterior and lateral thumn
- classic presentation is wrist drop
- unable to effectively use finger flexors because of synergistic function of wrist extensors needed
Therapeutic Management for Radial Nerve injury
- splint to position wrist in extension
- pt education:
contracture prevention
compensatory function strategies
HEP
Medical Management for Unresolved Nerve Injury
- tendon transfer –> transfer tendon of a working muscle to the tendon of a muscle with no nerve supply
E Stim
- In theory, can be used to prevent muscle atrophy
- inclusive research
- muscle tissue can be directly stimulated with direct current
- questionable, peripheral nerve injury application because sensation over the muscle belly to be stimulated generally is intact
