Plexopathies / preipheral nerves Flashcards
Lesion of the lateral cord causes__(3)__
- Sensory loss over lateral forearm
- Weakness of elbow
- Weakness of wrist flexion
Lesion of the medial cord causes __(3)__
- sensory loss over medial forearm
- some weakness of long finger flexors
- weakness of intrinsic hand muscles
Ulnar Nerve
Roots
Motor (4)
Sensory
Lesion = ____
- Roots: 7,8,T1
- Motor
- finger abduction
- finger adduction
- flexion of digits 4-5
- Wrist flexion
- Sensory (below)
- Lesion =
- Claw hand deformity
- hyperextension of last 3 digits at metacarpophalangeal joints
- flexion at interphalangeal joints
- lack of sensation to 5th digit and medial 4th digit
- Claw hand deformity
Damage to anterior interosseus nerve
Anterior interosseous nerve syndrome
- Pain in arm / forearm
- Weakness of forearm pronation
- Weakness of flexion of terminal phalanx of thumb
- weakness of flexion of terminal phalanges of 2nd and 3rd digits
- normal sensation
- “teardrop sign” - unable to make “OK” sign; looks squashed
Phalen’s sign
wrist flexion produces parathesias in median nerve distribution
(carpal tunnel syndrome)
Tinel’s Sign
Tapping over median nerve at wrist elicits parasthesias in the median nerve distribution
(carpal tunnel syndrome)
How to differentiate between an ulnar nerve lesion and a T1 radiculopathy
Test the abductor pollicis brevis (innervated by median nerve)
1.
Cubital tunnel syndrome
- compression of ulnar nerve in cubital tunnel (at elbow)
- Symptoms
- decreased grip
- problems with finger dexterity
- numbness and parasthesias in ulnar distribution
- +/- claw hand
- +/- Formet’s sign
Fromet’s sign
Branches of the lateral cord (4)
- Lateral cutaneous nerve of forearm (5,6)
- Lateral pectoral nerve (5,6,7)
- musculocutaneous nerve (5,6,7)
- median nerve (5,6,7,T1) [along with medial cord]
Damage to musculocutaneous nerve
- loss of sensation of medial ventral and lateral dorsal foream
- difficulty supinating forearm
- difficulty flexing elbow
- absent biceps reflex
“think of what you do during a bicep curl”
Radial nerve
- roots
- Motor (4)
- sensory
- Roots
- 5,6,7,8
- Motor = “fencers posture”
- extension @ elbow
- Extension @ wrist
- Forearm supination
- Thumb extension
- Sensory (below)
Median Nerve
- Roots
- Motor
- Sensory
- Roots: 5,6,7
- Motor
- Flexion of Digits 1 + 2
- Thumb opposition
- wrist flexion
- Forearm pronation
- Sensory (below)
Posterior Cord:
- Branches
- Symptoms of Lesion (3)
- Branches = “rats”
- Radial (5,6,7,8)
- Axillary (5,6)
- Thoracodorsal (6,7,8)
- Subscapular(5,6,7)
- Lesion
- Sensory loss of posterior arm and hand (radial)
- weak shoulder abduction (axillary, subscapular, thoracodorsal)
- Weak extension of fingers, wrist, and elbow (radial)
Axillary Nerve
Roots
Motor
Sensory
Commonly injured in__2__
- Roots: 5,6
- Motor
- Shoulder abduction 15*-90*
- external rotation
- Sensory (below)
- Commonly injured in:
- humerous fractures
- SHoulder dislocation
Symptosm of C7 radiculopathy (4)
- sensory loss over middle finger
- weakness of triceps
- weakness of wrist extension
- diminished or absent triceps reflex
Nerves receiving input exclusively from the medial cord (3)
- Roots
- Motor
- Sensory
Median pectoral nerve (C8, T1)
- Pectoralis major (adducts arm, rotates arm medially)
- pectoralism minor (lowers scapula, pulls shoulder forward)
Medial cutaneous nerve of Arm (C8,T1)
Medial cutaneous nerve of forearm (C8/T1)
How do you idifferentiate an ulnar nerver lesion from a T1 radiculopathy?
- test abductor pollicis brevis (originates from T1, but innervated by median nerve)
- Can they abduct thumb perpendicular to hand?
- Yes = ulnar
- No = T1 radiculopathy
Causes of Medial versus Lateral scapular winging
“don’t get caught in the Late, 11th hour trap
Medial winging: long thoracic nerve (serratus anterior)
Lateral winging: Cranial nerve XI > trapezius
How to differentiate betwen injury to radial nerve at:
Spiral groove
Axilla
- Spiral groove: “groovy saturday night palsy”
- wrist + finger drop
- weakness of supination
- (mild) weakness of elbow flexion
- Sensory loss @dorsum of hand
- Can extend elbow just fine! (triceps and aconeus branch before spiral groove)
- @axilla
- Saturday night palsy + decreased elbow extension
Thoracodorsal nerve
- Roots
- Motor
- Roots: C6,C7,C8
- Motor
- Latissimus dorsi
- adducts arm
- internally rotates arm
- Latissimus dorsi