L11 - Upper limb nerve injuries Flashcards
UMN presentation in the upper limb
- Held in flexed posture if chronic
- Increased tone
- Pyramidal weakness (flexor muscles stronger than extensors)
- Brisk reflexes
- Sensory level
LMN presentation in the upper limb
- 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
Anatomical localisation of lesion
3 anatomical regions for localising the lesion:
Roots
Brachial plexus
Peripheral nerve
Myotomes
- Relationship between the spinal nerve and muscle
Dermatomes
- Relationship between the spinal nerve and skin
Link between sensory findings and dermatomes
- Sensory findings on examination do not always demarcate in line with the dermatomes
- It may not involve the whole dermatome and maybe absent
- Two-point discrimination is a very sensitive test
- Pain can spread to involve other dermatomes
Deltoid - root and action
- C5
- Shoulder abduction
Biceps, brachialis and brachioradialis - root and action
- C6
- Elbow flexion
Triceps, superficial forearm extensors and forearm flexors
- C7
- Elbow extension and wrist extension + flexion
Forearm extensors and deep forearm flexors - root and action
- C8
- Finger extension + flexion
Intrinsic hand muscles - root and action
- T1
- Finger abduction
Biceps reflex
- C5 reflex conveyed through the musculocutaneous nerve
Supinator jerk
- C6 reflex conveyed through the radial nerve
Triceps jerk
- C7 reflex conveyed through the radial nerve
Finger jerk
- C8 reflex conveyed through the median and ulnar nerve
When is a reflex depressed
- Lower motor neuron lesions
Nerve root impingement
Causes - pain - radiates/aggravated by neck movement
- Sensory loss
- Weakness
- Reflex loss
Flexibility of cervical spine protects it from fractures or dislocation-but may get injury to neural structures - hyper flexion/extension
Avulsion
- Tearing of the nerves from its attachment at the spinal cord
- Requires surgical repair
Rupture
- Tearing of the nerves but not from its attachment to the spinal cord
- Requires surgical repair
Neuroma
- Tumour or growth of the nerve tissue. Can arise from the axon or myeloma
- Requires surgical repair
Neurapraxia
- Axons remain intact, but myelin damage cause an interruption of the impulse down the nerve fibre - good prognosis
Motor cycle injury - flail arm (cervical root avulsion)
- C5-T1 lesions causing flail arm
- Left shoulder subluxation
- Atrophy of the left deltoid, supraspinatus and infraspinatus
Brachial plexus injury - trauma
- Erb-duchenne type paralysis, avulsion of C5,C6 roots
- Klumpke paralysis: Avulsion of C8, T1 roots
Brachial plexus injury - cancer
- Lung cancer - pancoasts tumour
- Radiotherapy
Brachial plexus injury - inflammation
- Brachial neuritis
Brachial plexus injury - structural
- Thoracic outlet syndrome
Erbs palsy
- Upper plexus palsy, C5/C6 innervated muscles
- Superior trunk of brachial plexus(adults - blow to shoulder)
Affected muscles in erbs palsy
Weak muscles include - Biceps (flexes the arm) Brachioradialis (flexes the arm in semi-prone position) Deltoid (abducts the arm) Supraspinatus (abducts the arm) Supinator (externally rotates the arm)
Movements limited by erbs palsy
Arms cannot be:
- Elevated
- Abducted
- Externally rotated
- Flexed at elbow
but fingers unimpaired, hand works but arm does not
Klumpke’s palsy
Clutching for an object when falling from a height
- Inferior trunk plexus injury involving C8/T1
- Involves trunk that supplies 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
What can klumpke’s palsy lead to
- May lead to a claw hand
- Arm works but hand does not
Metastatic brachial plexopathy
Pancoast tumour (lung) - infiltration of the lower brachial plexus
- Pain in shoulder girdle and inner arm
- Ipsilateral horners syndrome
Radiation induced brachial plexopathy
- Mean 6 yrs post radiation
- Associated with treatment for breast, lung cancer and lymphoma
- Pain is not a consistent feature
- Predilection for upper brachial plexus
Idiopathic brachial neuritis (parsonage - turner syndrome) - IBN
- Aetiology not clear, infectious, post-infectious
- Severe pain over days; as pain diminishes, it is followed by weakness and wasting (motor>sensory)
- Typically monophasic
- Rarely bilateral
- MRI shows thickening and enhancement
- NCS/EMG is useful for prognostication
Treatment for idiopathic brachial neuritis
- Analgesia, physiotherapy
- Limited evidence for the use of steroids
Thoracic outlet syndrome
Variations in anatomy cause compression sites:
- Between anterior and middle scalene muscles
- Beneath clavicle in the costoclavicular space
- Beneath tendon of pectoralis minor
Thoracic outlet syndrome - neurogenic
- Paresthesia, numbness, weakness
- Not localised to specific nerve distribution
- Reproducibly aggravated by elevation or sustained use of arms or hands.
Thoracic outlet syndrome - vascular
- Forearm fatigue within mins of use
- Swelling and cyanosis
- Collateral venous patterning over the ipsilateral shoulder, chest wall and neck
- Rarely pain, pallor and coldness (arterial involvement)
- Lower BP on affected arm, diminished distal pulses
When might the long thoracic nerve be damaged
- May be injured by blows or pressure in the posterior triangle of the neck or during a radical mastectomy
- Leads to a ‘winged scapula’
2 common sites for compression of median nerve
- Wrist (carpal tunnel syndrome)
- Elbow
Median nerve innervated hand muscles
L ateral 2 lumbricals
O pponens pollicis
A bductor pollicis brevis
F lexor pollicis brevis
Causes of carpal tunnel syndrome
- Diabetes
- Pregnancy
- Hypothyroidism
- Rheumatoid arthritis
- Repetitive strain
Where does the anterior interosseous nerve arise from
- Median nerve just above elbow
- Prone to compression between 2 heads of pronator teres muscle
- Gripping tightly with forced pronation
- Prolonged use of a screwdriver
- May also be damaged in careless blood taking
Anterior interosseous nerve syndrome
- Pure motor branch of the median nerve
- Weakness in flexors of ip joint of thumb (flexor pollicis longus) and dip joints of index and middle fingers - (flexor digitorum profundus) weakness of pronation
Higher lesion in the upper limb
- Paralysis of the ulnar half of the flexor digitorum profundus (FDP), interossei and lumbricals
- The ring and little fingers are not flexed and there is no claw
Lesion at the wrist
- Flexion at the DIP (FDP is intact)
- Flexion at the PIP (interossei are paralysed)
- Hyperextension at the MCP(lumbricals are paralysed)
Sensory innervation of ulnar nerve lesion localisation
check diagrams in notes
Ulnar nerve, around medial epicondyle
- Superficial sensory branch comes off in distal forearm above wrist
- Deep ulnar branch, guyton’s canal motor only to intrinsic hand muscles
- Occupation, cycling, rheumatoid arthritis
Froment’s sign
- Weakness of adductor pollicis leads to froment’s sign
- Sign of ulnar palsy
Ulnar vs C8
C8
- All finger extensors (radial nerve)
- FDP of index/middle (median nerve)
‘Saturday night palsy’
- Radial nerve palsy
- Radial nerve damage rarely causes extensive sensory loss
- Extensive overlap with median/ulnar excepting anatomical snuff box
Usefulness of nerve conduction studies
- Useful in determining the amplitude and velocity of a peripheral nerve
Effect of axonal loss on nerve conduction
- Decrease in amplitude
Effect of demyelination on nerve conduction
- Decrease in velocity
Neurogenic vs myogenic
Needle EMG measures electrical activity of the muscle during voluntary contraction
The pattern of the electrical activity can help distinguish a lesion arising from the nerve(neurogenic) vs muscle(myopathic)
