11. Upper limb nerve injuries Flashcards
Where do LMN arise?
anterior horn cells
therefore anything before this is UMN
Characteristic features of UMN lesion?
- Held in flexed posture if chronic.
- Increased tone
- Pyramidal weakness (Flexor muscles stronger than extensors)
- Brisk reflexes.
- Loss of sensation at sensory level
Characteristic features of LMN lesions?
- Wasting/Fasciculations
- Flaccid tone
- Weakness in either a myotomal distribution or a peripheral nerve distribution
- Reduced reflexes.
- Dermatomal or peripheral nerve distribution of sensory loss.
How is Biceps reflex conveyed?
C5 reflex conveyed through the musculocutaneous nerve.
How is the Supinator jerk conveyed?
C6 reflex conveyed through the radial nerve
How is the Triceps jerk conveyed?
C7 reflex conveyed through the radial nerve.
How is the Finger jerk reflex conveyed?
C8 reflex conveyed through the median and ulnar nerve.
What type of lesions cause flail arm (cervical root avulsion)?
C5-T1 lesions
Erbs palsy
a.k.a. ‘waiters tip’
- during childbirth- stretching of top brachial plexus
- upper plexus palsy
- C5/C6 innervated muscles (weakened)
e.g. biceps, brachioradialis, deltoid, supraspinatus, supinator- so arm can not be elevated, abducted, externally rotated etc.
HANDS WORK BUT ARM DOES NOT
Klumpke’s Palsy
-Inferior brachial plexus is injured
- Arm works but hand does not
- C8/T1/Inferior trunk injury
- normally supplying median and ulnar nerves
- Unable to flex wrist or fingers
- Weakness of all small muscles of the hand
- Sensory loss hand and inner border of forearm
- Claw hand
E.g breech delivery
Lesions to the long thoracic nerve
-Long thoracic nerve supplies the serratus anterior muscle.
-The serratus anterior muscle pulls the medial border of the scapula
to the posterior thoracic wall and stabilises it there
-leads to “winging” of the scapula
Causes: Radial Mastectomy, heavy bags
What muscles are innervated by the median nerve? [4]
-What do these muscles form?
LOAF:
- Lateral 2 lumbricals
- Opponens pollicis
- Abductor pollicis brevis
- Flexor pollicis brevis
- forms thenar eminence, damage causes thenar wasting
3 AND A HALF FINGERS
Common sites of compression of median nerve [2]
wrist (carpal tunnel)
elbow
Causes of Carpal Tunnel Syndrome
Diabetes Pregnancy Hypothyroidism Rheumatoid arthritis Repetitive strain
tested by tinels(tap), phalens (flex wrists)
Anterior interosseous nerve syndrome
-arises from median nerve above elbow
motor branch of median nerve
-Prone to compression between 2 heads of
pronator teres muscle
- can be damaged in careless blood taking
- weakness in FPL + FDL
- weakness of pronation
Cancers causing brachial plexus injury
Pancoat tumour- infiltration of lower brachial plexus
-Pain
Post radiation damage causing brachial plexus injury
Upper brachial plexus injury
Pain is not a consistent feature
Inflammatory pathologies causing brachial plexus injury
Idiopathic brachial neuritis
severe pain
followed by weakness and wasting
Treatment: analgesis
Structural anomalies causing brachial plexus injury
thoracic outlet syndrome
Anatomical variation causing compression sites
vascular vs neurogenic
Lesion in the forearm vs lesion in carpal tunnel
Because the palmar cutaneuous sensory branch branches before carpal tunnel, the palm is affected
If it occurs in the carpal tunnel then the palm is spared
Dermatome of middle finger
C7
Dermatome of index AND thumb
c6
Dermatome of ring finger and little finger
c8
Explain why a patient gets an ulnar claw when their ulnar nerve is damaged
Muscles work in pairs
ED-L (ED is spared)
L-FDS (FDS is spared)
L-FDP (FDP is spared- only 3rd and 4th FDP are by ulnar nerve)
Sensory innervation of the ulnar nerve
dorsal cutaneous branch
palmar cuteaneous branch
Fromnents sign
sign of ulnar nerve palsy
cant grip so used median nerve structures
Saturday night palsy
Radial nerve palsy
so all extensors are affected
always check anatomical snuff box bc that is innervated by radial nerve
Ulnar nerve injury vs C8 injury
All finger extensors (radial nerve)
-FDP of index/middle (median nerve)
