11. Upper limb nerve injuries Flashcards
Approach to a neurological problem
Anatomically localise the lesion
Consider the pathophysiology
Differential diagnosis
UMN vs LMN
LMN arises from the anterior horn cell (whereas UMN from motor cortex)
UMN disease examination findings
Held in flexed posture if chronic. Increased tone Pyramidal weakness (Flexor muscles stronger than extensors) Brisk reflexes. Sensory level
LMN examination findings
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.
UMN problem example
stroke
LMN problem example
ALS
polio (rare)
Anatomical localisation of upper limb nerve injuries
3 anatomical regions for localising the lesion:
Roots
Brachial plexus
Peripheral nerve
Myotome vs dermatome
Myotomes - Relationship between the spinal nerve & muscle
Dermatomes - Relationship between the spinal nerve & skin
dermatomes
A dermatome is an area of the skin supplied by nerve fibres originating from a single dorsal nerve root.
However, there is considerable overlap of innervation between adjacent dermatomes and
there is also considerable anatomical variation
Dermatome landmarks: Middle finger is C7 and either side is C6 and C8 Nipple T4 Umbilical T10 Groin L1
C5 root and myotome
Deltoid
Shoulder abduction
C6 root and myotome
Biceps, Brachialis, brachioradialis
Elbow flexion
C7 root and myotome
Triceps
Superficial forearm extensors
Superficial forearm flexors
Elbow extension
Wrist extension
Wrist flexion
C8 root and myotome
Forearm extensors
Deep forearm flexors
Finger extension
Finger flexion
T1 root and myotome
Intrinsic hand muscles
Finger abduction
Biceps reflexe
Biceps reflex – C5 reflex conveyed through the musculocutaneous nerve.
Supinator jerk
Supinator jerk – C6 reflex conveyed through the radial nerve.
Triceps jerk
Triceps jerk – C7 reflex conveyed through the radial nerve.
Finger jerk
Finger jerk – C8 reflex conveyed through the median and ulnar nerve.
Reflexes in lower motor neuron lesions
reflexes depressed
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
Types of nerve (plexus) injury
avulsion
rupture
neuroma
neurapaxia
(Avulsion / rupture – brachial plexus trauma, neurapraxia blunt injury)
Avulsion
Avulsion: Tearing of the nerves from its attachment at the spinal cord. – Require surgical repair
Rupture
Rupture: Tearing of the nerves but not from its attachment to the spinal cord – Require surgical repair
Neuroma
Neuroma: tumour or growth of the nerve tissue. Can arise from the axon or myeloma – Require surgical repair
Neurapraxia
Neurapraxia: Axons remain intact, but myelin damage cause an interruption of the impulse down the nerve fibre – Good prognosis.
Flail arm
C5-T1 lesions causing flail arm
Left shoulder subluxation
Atrophy of the left deltoid, supraspinatous and infraspinatous
brachial plexus injury
Trauma Erb-Duchenne type paralysis: Avulsion of C5,C6 roots. Klumpke paralysis: Avulsion of C8, T1 roots. Cancer Lung cancer: Pancoasts tumour Radiotherapy Inflammatory Brachial neuritis Structural Thoracic outlet syndrome
Erbs palsy
- upper plexus palsy
C5/C6 innervated muscles
Superior trunk of brachial plexus
(adults- blow to shoulder)
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)
Symptoms of Erbs palsy aka waiters tip
Arm cannot be- Elevated Abducted External 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
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 aka Parsonage-Turner syndrome
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: 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 costoclarvicular space
- Beneath tendon of Pectorlis minor
Causes of thoracic outlet syndrome
Neurogenic and vascular
Neurogenic: predominantly affects the median-innervated abductor pollicis brevis muscle (thenar wasting)
Vascular: High rib causes area of stenosis with a poststenotic dilatation. Clots may form in the dilated vessel with small fragments that then become detached and pass down the brachial artery into the hand. Acute ischaemic changes lead to Raynaud’s phenomenon.
neurogenic thoracic outlet syndrome
Paresthesia, numbness, weakness
Not localised to specific nerve distribution
Reproducibly aggravated by elevation or sustained use of arms or hands.
vascular thoracic outlet syndrome
Forearm fatigue within minutes of use.
Swelling and cynaosis
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.
Long thoracic nerve injuries
Long thoracic nerve
may be injured by blows or pressure
in the posterior triangle of the neck
or during a radical mastectomy.
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
Impairment of the long thoracic nerve leads to “winging” of the scapula
Median nerve
2 common sites of compression
Wrist (Carpel tunnel syndrome)
Elbow
Median nerve innervated hand muscles
L ateral 2 lumbricalsO pponens pollicisA bductor pollicis brevisF lexor pollicis brevis
Median nerve compression signs
thenar wasting
Carpal tunnel syndromes
Causes include: Diabetes Pregnancy Hypothyroidism Rheumatoid arthritis Repetitive strain
Median N. entrapment at carpal Tunnel (also damaged in wrist fractures)
Anterior interosseous nerve
arises 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 policis longus)
& dip joints of index and middle fingers – (flexor digitorum profundus)
weakness of pronation
Ulnar claw
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)
hyperextention at the MCP (lubricals are paralysed).
ulnar nerve branches around medial epicondyle
superficial sensory branch comes
off in distal forearm above wrist)
Deep ulnar branch
Guyon’s canal motor only to intrinsic hand muscles
Occupation, cycling, rheumatoid arthritis
Ulnar nerve palsy sign
Froment’s sign (crab grip) due to weakness of adductor pollicis
ulnar vs c8
C8
All finger extensors (radial nerve)
FDP of Index/middle (median nerve)
Ulnar nerve d5 and 1/2 d4. Test d5
Radial nerve palsy aka Saturday night palsy
Radial nerve damage rarely causes extensive sensory loss
Extensive overlap with median/ulnar excepting anatomical snuff box
Radial nerve dorsum of hand thumb and proximal par of index and quarter of d3
Nerve conduction studies
Useful in determining the amplitude and velocity of a peripheral nerve
Axonal vs demyelinating
Axonal loss results in a decrease in amplitude
Demyelinating results in a decrease in velocity
Neurogenic vs myogenic
Needle EMG measures the 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)
