Peripheral Nerve Injury Flashcards
Structures in the PNS
- Muscle spindle receptors
- Golgi tendon organ
- Motor endings
- Axons
Types of Axons
- efferent vs. afferent
- large vs. small
Efferent - send signals from CNS to body
Afferent - brings information from other parts of the body back to the CNS
Large,efferent = extrafusal muscle fibers
Large, afferent = GTO, spindles, touch & pressure receptors
**large & fast innervate muscles
Small, efferent = presynaptic autonomic
Small, afferent = temp, touch, pain & visceral receptors
Unmyelinated efferent = postsynaptic autonomic
Unmyelinated afferent = temp, pain, visceral
**small & slower innervate autonomic/visceral & sensory areas
Neurapraxia
- defn & cause
- disrupted element
- prognosis
structure of the nerve remains intact but the conduction down the axon is impaired typically due to ischemia or compression injury
- disrupted element: nerve conduction
- prognosis: full recovery w/n hours-weeks
Axonotmesis
- defn & cause
- disrupted element
- prognosis
disruption of the neuronal axon but the myelin sheath is intact; typically due to a crush injury
- disrupted element: axon
- prognosis: may regain conduction IF neuronal tubules still intact & can take weeks-years (1mm/day)
Neurotmesis
- defn & cause
- disrupted element
- prognosis
loss of nerve conduction AND damage to surrounding nerve trunk connective tissue; typically due to laceration, electrical shock, etc
- disrupted element: epineurium
- prognosis: none or minimal return of function; usually neuroma forms at end of nerve preventing normal regeneration to occur
Upper BP Injury
- moi
- clinical presentation
C5-6
MOI - shoulder depression & lateral cervical bend
Clinical Presentation - Waiter’s tip: loss of shoulder abduction, weakness of flexion & forearm supination
aka Erb’s Palsy
Lower BP injury
- moi
- clinical presentation
C8-T1
MOI - compression of cervical rib or stretching of the arm overhead (painting a ceiling)
Clinical presentation - paralysis of intrinsic muscles of the hand (claw hand)
aka Backpackers Palsy
Thoracic Outlet Syndrome
-what is it
BP pain, parasthesia, numbness & weakness
Nerve tension is felt when the plexus is stretched
Axillary Nerve Injury
- moi
- clinical presentation
C5-6
MOI - acute dislocation or fracture of proximal humerus
Clinical presentation - Deltoid atrophy (square shoulder appearance), loss of sensation in lateral deltoid, shoulder abduction & ER weakness
Musculocutaneus Nerve Injury
- moi
- clinical presentation
C5-7
MOI - projectile wounds
Clinical presentation - atrophy along flexor surface of upper arm, weakness of elbow flexion & supination & loss of sensation on radial side of forearm
Median Nerve Injury
- moi
- clinical presentation
C5-8, T1
MOI - impingement of hypertrophied pronator teres (pronator syndrome) or CTS
Clinical presentation - N/T in 3 1/2 fingers on palmar side
**APE HAND: atrophy of thenar eminence, no arm pronation, weak grip, no thumb abd or opposition & loss of sensation on thenar region
Ulnar Nerve Injury
- moi
- clinical presentation
C8,T1
MOI - compression at medial epicondyle (cubital tunnel syndrome) or Guyon’s canal
Clinical presentation - pain, N/T in 1 1/2 fingers on palmar & dorsal side
**CLAW HAND: partial claw w/ atrophy between MT & hypothenar region, loss of spherical grip w/ 4th & 5th fingers, loss of thumb ADDuction & PAD/DAB, loss of sensation in hypothenar region
Radial Nerve Injury
- moi
- clinical presentation
C5-8, T1 - “saturday night palsy”
MOI - pressure under arm at radial sulcus OR compression at radial head (PINS) OR compression at ECRB & supinator (Arcade of Frohse)
Clinical presentation -
- PINS: weakness of FINGER extensor muscles & pain & tenderness (no numbess)
- Radial tunnel syndrome - more painful sensation
- superficial radial compression - hand sensation altered
- *WRIST DROP - unable to make fist & grasp unless wrist is stabilized in extension
- high lesions also affect triceps
Sciatic Nerve Injury
- moi
- clinical presentation
L4-5, S1-3)
MOI - compression at piriformis, hip dislocation or fracture of the femur
Clincal presentation - N/T & pain posterior thigh/leg, atrophy of posterior leg muscles, weak knee flexion, loss of ankle/foot control, loss of sensation in lateral & posterior leg & plantar aspect of foot
Common Peroneal Nerve Injury
- deep & superficial
- moi
- clinical presentation
L4-S2
MOI - compression from crossing legs, fracture at head/neck of fibula
Clinical Presentation -
deep = foot drop
superficial = loss of eversion
& loss of sensation in dorsal aspect of foot & anterior/lateral leg
