Peripheral Nerve Injuries Flashcards
What is the endoneurium? What is it’s role?
sheath that encompasses the axon or nerve fiber that plays an important role in protecting against transmission of substances across the nerve membrane
What is the perineum? What does it provide?
Sheath that surrounds each fascicle and provides a perineural diffusion barrier capable of controlling flow of substances bi-directionally
What is the epineurium?
outermost connective tissue that is highly vascular and provides no diffusion barrier function
What are the 3 typical mechanisms of injury for nerves?
Acute ischemia
segmental demyelination
axonal degeneration
What are the 3 nerve injury classifications according to Seddon’s classification scheme?
Neurapraxia
Axonotmesis
Nuerotmesis
What are the common etiology classification for mononeuropathies?
What are the classifications for poly neuropathies?
traumatic and non-traumatic
metabolic nutritional hereditary immunologically mediated infectious disease paraneoplastic
What are the clinical features of mononeuropathies?
What are the clinical features of polyneuropathies?
motor and sensory deficits limited in distribution
- bilateral and fairly symmetric
- effect large fibers distally first
- sensory loss precedes motor
What are common clinical features for peripheral nerve injuries?
- tendon hyporeflexia
- tremor
- autonomic dysunction such as anhidrosis (not producing sweat), orthostatic hypotension, trophic changes, and loss of erector pilae function
How does weakness and sensory loss differ between mononeuropathies and polyneuropathies?
Mono:
- weakness is proportional to motor neurons effected
- sensory loss in nerve field distal to lesion
Poly:
- weakness is symmetrical and distal
- sensory loss is distal in feet and hands
What syndromes are associated with median nerve mononeuropathy?
- pronator teres syndrome
- anterior interosseous syndrome
- carpal tunnel syndrome
What is the etiology of pronator teres syndrome?
What are the clinical features of this syndrome?
- pierces 2 heads of pronator teres
- trauam, fracture, muscle hypertrophy, fibrotic band, and bicipital aponeurosis
- pain and TTP over PT which increases w/ activity
- sensory changes to thenar eminence, D1-3 and possibly D4
- motor involvement: FPL, FDP 1/2, APB, OP, 1/2 FPB; PT may be spared (sparing FCR, PL, and FDS)
What tests will indicate a positive diagnosis for pronator teres syndrome?
(+) pronator teres syndrome test
(+) Tinel’s in forearm
(-) Phalen’s
What is the etiology of anterior interosseous syndrome?
What are the clinical features of this syndrome?
- elbow dislocation
- fibrotic bands
clinical features:
- prox. forearm pain
- no sensory loss but have aching
- motor loss of FPL. FDP 1/2, and PQ
- no “OK” sign (Kilo Nevin)
What is the etiology of carpal tunnel syndrome?
- most common compression neuropathy
- may be predisposed by polyneuropathy
- ganglia, tumor
- RA-thickening tendon sheath
- effects females more than males
What are the clinical features of carpal tunnel syndrome?
- painful paresthesias with use and at night
- sensory deficits median distribution sparing thenar eminence
- atrophy of thenar muscles
- may describe pain radiating distal to proximal
- may report “dropping” objects
- (+) Tinel’s at wrist
- (+) Phalen’s and Rev. Phalen’s
What is the clinical prediction rule for carpal tunnel syndrome?
How does the probability of CTS changes with each positive sign?
- hand shaking improves symptoms
- wrist ratio index over .67
- symptom severity score over 1.9
- diminished sensation in median sensory field 1 (thumb)
- age over 45
if 2 are (+)=44% probability
if 3 are (+)=52%
If 4 are (+)=70%
if all 5 are (+)=90% and a .99 specificity
True or False: Splinting for carpal tunnel syndrome is a better intervention than exercise or oral steroids.
False, evidence does not prove one is superior to the other
True or False: Surgical treatment for carpal tunnel syndrome helps relieve symptoms far better than splinting
True
What conditions can occur due to ulnar nerve injury?
- tardy ulnar palsy/cubital tunnel syndrome
- Guyon’s Canal
What is the etiology of tardy ulnar palsy/cubital tunnel syndrome?
What are the clinical features for this syndrome?
- 2nd most common peripheral nerve compression injury
- ulnar nerve injury at elbow due to repetitive trauma, prolonged compression, and/or immobilization
- tardy implies the injury occurred long before SxS
Clinical Features:
- sensory deficits 5th digit and ulnar 1/2 of 4th
- vague pain
- atrophy ulnar intrinsics, FCU usually spared, unless lesion is above elbow
- (+) elbow flexion test
- (+) Tinel’s at cubital tunnel
What is the etiology for compression at Guyon’s canal?
What are the clinical features?
- less common than at elbow
- ganglion, trauma, RA
- athletes: mainly bicyclists and racket sports
Clinical Features:
- sensory deficits depend on zone compromised (zone 1 is motor and sensory, zone 2 is motor only, and zone 3 is sensory only)
- vague pain
- atrophy ulnar intrinsics, FCU usually spared, unless lesion is above elbow
- (+) Phalen’s/ Rev Phalen’s
- (+) Tinel’s at cubital tunnel
- (+) Froment’s sign
- (+) Wartenberg’s sign
How does the specificity and sensitivity change for the elbow flexion test as the time increases from 30 to 60 seconds?
How does the specificity and sensitivity change for the elbow pressure provocation test as the time increases from 30 to 60 seconds?
Is Tinel’s sign at the elbow more sensitive or specific?
specificity does not change but sensitivity jumps from .32 to .74
same as elbow flexion except sensitivity changes from .55 to .89
More specific
What conditions can be caused do to an injury to the radial nerve?
Upper arm lesion
Posterior interosseous syndrome
radial tunnel
Wartenberg’s syndrome
What is the etiology of an upper arm radial nerve lesion?
What are the clinical features for a lesion at the spiral groove?
What are the clinical features for a lesion proximal to the spiral groove?
- fracture/trauma
- compression (crutch palsy or Saturday night palsy)
spiral groove:
- most common site
- sensory loss dorsum of hand and 1st two digits
- triceps spared
- weakness is distal to triceps (complete wrist drop)
Prox. to Spiral Groove:
- sensory loss to posterior arm and post. 1/3 forearm plus dorsum of hand and web space
- triceps affected plus all distal radial n. innervates muscles
