Upper limb nerve injuries Flashcards
Where does the lower motor neuron arise?
Anterior horn
Describe the characteristics of an upper motor neuron pathology
Held in flexed posture if chronic. Increased tone Pyramidal weakness (Flexor muscles stronger than extensors) Brisk reflexes. Sensory level
Describe the characteristics of a lower motor neuron pathology
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.
Name the 3 anatomical regions for localizing a lesion
Roots
Brachial plexus
Peripheral nerves
What are myotomes
Relationship between spinal nerve and muscle
What are dermatomes?
Relationship between spinal nerve and skin
area of the skin supplied by nerve fibres originating from a single dorsal nerve root.
Where is there a lot of anatomical variation?
In dermatomes
What is the myotome of C5?
Deltoid
What is the myotome of C6?
Biceps
Brachialis
Brachioradialis
What is the myotome of C7?
Triceps
Superficial forearm extensors
Superficial forearm flexors
What is the myotome of C8?
Forearm extensors
Deep forearm flexors
What is the myotome of T1?
Intrinsic hand muscles
What muscle action does the C5 myotome perform?
Shoulder abduction
What muscle action does the C6 myotome perform?
Elbow flexion
What muscle action does the C7 myotome perform?
Elbow extension
Wrist extension
Wrist flexion
What muscle action does the C8 myotome form?
Finger extension
Finger flexion
What muscle action does T1 myotome form?
Finger abduction
What is the name of the C5 reflex?
Biceps reflex
Which nerve conveys the biceps reflex?
Musculocutaenous
What is the name of the C6 reflex?
Supinator jerk
Which nerve conveys the supinator jerk
Radial nerve
What is the name of the C7 reflex?
Triceps jerk
Which nerve conveys the triceps jerk?
Radial nerve
What is the name of the C8 reflex?
Finger jerk
Which nerve conveys the finger jerk?
Median and ulna nerve
What happens to reflexes in lower motor neuron lesions?
Reflex is depressed
What does nerve root impingement cause?
Pain which radiates or is aggravated by neck movement
Sensory loss
Weakness
Reflex loss
What causes nerve root impingement?
Hyperflexion and extension
What is an avulsion?
Tearing of the nerves from its attachment at the spinal cord.
What is a rupture?
Tearing of the nerves but not from its attachment to the spinal cord
What is a neuroma?
tumour or growth of the nerve tissue. Can arise from the axon or myeloma
What is a neurapraxia?
Axons remain intact, but myelin damage cause an interruption of the impulse down the nerve fibre
What is flail arm?
Cervical root avulsion
Name some conditions as a result of trauma to the brachial plexus
Erb-Duchenne type paralysis: Avulsion of C5,C6 roots.
Klumpke paralysis: Avulsion of C8, T1 roots.
Name a tumour affecting the brachial plexus
Pancoasts tumour - lung cancer
Which cancer treatment may cause injury to the brachial plexus?
Radiotherapy
Name an inflammatory injury of the brachial plexus
Brachial neuritis
Name a structural injury to the brachial plexus
Thoracic outlet syndrome
Name the muscles weakened in erbs palsy
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)
What is erbs palsy?
- upper plexus palsy
C5/C6 innervated muscles
Superior trunk of brachial plexus
What causes erbs palsy?
Infants - birth and getting shoulder stuck
Adults - blow to the shoulder
What is another name for erbs palsy lesion?
Waiters tip
What actions can and cannot a person with erbs palsy perform?
Elevated
Abducted
External rotated
Flexed at elbow
But fingers unimpaired
Describe 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!
Describe a pancoast tumour
infiltration of the lower brachial plexus
Pain in shoulder girdle and inner arm.
Ipsilateral horners syndrome
Describe 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
Describe Idiopathic brachial neuritis (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.
Give the treatment of Idiopathic brachial neuritis (Parsonage – Turner Syndrome)
Analgesia, physiotherapy
Limited evidence for the use of steroids
Describe 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
List some neurogenic symptoms of thoracic outlet syndrome
Paresthesia, numbness, weakness
Not localised to specific nerve distribution
Reproducibly aggravated by elevation or sustained use of arms or hands.
List some vascular symptoms of 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.
When may the long thoracic nerve be injured?
Long thoracic nerve
may be injured by blows or pressure
in the posterior triangle of the neck
or during a radical mastectomy.
What can injury of the long thoracic nerve lead to?
‘winged scapula’
Describe how injury to the long thoracic nerve results in winged scapula
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
List 2 common sites of nerve compression
Wrist (Carpel tunnel syndrome)
Elbow
Which hand muscles does the median nerve innervate?
L ateral 2 lumbricals
O pponens pollicis
A bductor pollicis brevis
F lexor pollicis brevis
List some 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.
Describe how damage to the anterior interosseous nerve may occur
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
Describe 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
Describe the ulnar claw of a 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.
Describe the ulnar claw of a lower lesion in the upper limb
Flexion at the DIP (FDP is intact)
Flexion at the PIP (interossei are paralysed)
hyperextention at the MCP (lubricals are paralysed).
Where is the deep ulnar nerve?
Guyon’s canal
What does the deep ulnar nerve do?
motor only to intrinsic hand muscles
How can the deep ulnar nerve be injured?
Occupation, cycling, rheumatoid arthritis
What leads to the Froment’s sign?
Weakness of adductor pollicis
Describe radial nerve palsy?
Radial nerve damage rarely causes extensive sensory loss
Extensive overlap with median/ulnar excepting anatomical snuff box
What are nerve conduction studies useful for?
Useful in determining the amplitude and velocity of a peripheral nerve
What does axonal loss lead to?
decrease in amplitude
What does demyelinating lead to?
decrease in velocity
What does needle EMG measure
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)
