Peripheral Nerves/Injuries Flashcards
Neuropraxia (Least Severe)
- Demyelination
- Reversible conduction block
- Myelin sheath is compressed but axon and endoneurium are intact
- example: Radial nerve compression - Writers drop
- Waking up at night
Axonotmesis (Demyelination and axon lost)
- Segment lost but endoneurium is intact
- Neuron can grow back inside the endoneurium sheath
- Wallerian degeneration
- Distal end dies off before the grow back - Example: Crash injuries and disposed bone
Neurotmesis (demyelination + axonal lost +one of the following)
- Endoneurium involvement: fair growth
- Perineurium involvement: poor growth
- Epineurium involvement: no growth
1st degree injury (neuropraxia)
Minimal structural disruption - complete recovery
2nd degree (axonotmesis)
Complete axonal disruption - usually complete recovery
3rd degree (may be either axonotmesis or neurotmesis)
Disruption of axon and endoneurium - poor prognosis without surgery
4th degree (neurotmesis)
Disruption of axon, endoneurium, and perineurium - poor prognosis without surgery
5th degree (neurotmesis)
Complete structural disruption - poor prognosis without microsurgery
Recovery from Nerve Injury
Depends on:
Nature and level of injury
Timing and technique of repair
Age and motivation of patient
Sympathetic
(PNS also part of ANS)
T1-L3
Fight or flight
Increase HR, BP, pupil size, bronchodilation
Parasympathetic
(PNS also part of ANS)
- Cranial nerves & S2-S4
- Rest/digest
- Increase gastric secretion, decrease HR and pupil size
What controls Sympathetic and Parasympathetic?
BOTH are controlled by hypothalamus, limbic system, and afferent sensory information from the periphery
Musculocutaneous Nerve
From Lateral Cord
Motor: flexion of arm at elbow + supination of forearm
Sensory: lateral forearm
Axillary Nerve
- Posterior cord
- Injury: dislocation of shoulder and surgical neck fracture of the humerus
- Motor: abduction (>15 degrees) and lateral rotation of shoulder
- Sensory: shoulder
Radial Nerve
- Posterior cord
- Injury: compression, fracture of body of humerus
- Motor: extension at all arm, wrist, proximal finger joint + forearm supination + thumb abduction
- Sensory: posterior arm and forearm + below the fingertips of the three and one-half fingers
Median Nerve
- Medial and lateral cords
- Injury: hypertrophy of pronator teres of muscle or entrapment
- Motor: forearm pronation + wrist flexion and abduction + thumb flexion and opposition + flexion of digit 2 and 3
- Sensory: lateral three and one-half fingers - palmar surface and superior dorsal aspect
Ulnar Nerve
- Medial cord
- Injury: at the elbow and other sites
- Motor: wrist flexion and adduction + finger adduction and abduction other than the thumb + thumb adduction + flexion of digits 4 and 5
- Sensory: dorsal and palmar aspect of hand for medial 1 1/2 fingers
Femoral Nerve
- 3 posterior divisions of lumbar plexus
- Injury: trauma or pressure
- Motor: hip flexion + knee extension
- Sensory: anteromedial thigh + medial side of foot and leg
Obturator Nerve
- 3 anterior divisions of the lumbar plexus
- Isolated injury is rare - uterine pressure or damage during labor
- Motor: adduction and external rotation at the thigh
- Sensory: medial skin over adductors
Sciatic Nerve
- Sacral plexus
- Injury: piriformis syndrome, hip dislocation or reduction
- Knee flexion
- Component parts - tibial and common peroneal nerves
Tibial Nerve
- Injury: entrapment
- Motor: foot plantar flexion and inversion + toe flexion
- Sensory: sole of the foot
Superficial Peroneal Nerve (from Common Peroneal Nerve)
- Motor: foot eversion
- Sensory: skin of the anterolateral leg, and dorsum of the foot (except skin between the first and second toes)
Deep Peroneal Nerve (from Common Peroneal Nerve)
- Motor: foot dorsiflexion + toe extension
- Sensory: skin between the first and second toes
