11. Upper limb nerve injuries

Question 1

Approach to a neurological problem

Answer 1

Anatomically localise the lesion
Consider the pathophysiology
Differential diagnosis

Question 2

UMN vs LMN

Answer 2

LMN arises from the anterior horn cell (whereas UMN from motor cortex)

Question 3

UMN disease examination findings

Answer 3

Held in flexed posture if chronic.
Increased tone
Pyramidal weakness (Flexor muscles stronger than extensors)
Brisk reflexes.
Sensory level

Question 4

LMN examination findings

Answer 4

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.

Question 5

UMN problem example

Answer 5

stroke

Question 6

LMN problem example

Answer 6

ALS

polio (rare)

Question 7

Anatomical localisation of upper limb nerve injuries

Answer 7

3 anatomical regions for localising the lesion:

Roots
Brachial plexus
Peripheral nerve

Question 8

Myotome vs dermatome

Answer 8

Myotomes - Relationship between the spinal nerve & muscle
Dermatomes - Relationship between the spinal nerve & skin

Question 9

dermatomes

Answer 9

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

Question 10

C5 root and myotome

Answer 10

Deltoid

Shoulder abduction

Question 11

C6 root and myotome

Answer 11

Biceps, Brachialis, brachioradialis

Elbow flexion

Question 12

C7 root and myotome

Answer 12

Triceps
Superficial forearm extensors
Superficial forearm flexors

Elbow extension
Wrist extension
Wrist flexion

Question 13

C8 root and myotome

Answer 13

Forearm extensors
Deep forearm flexors

Finger extension
Finger flexion

Question 14

T1 root and myotome

Answer 14

Intrinsic hand muscles

Finger abduction

Question 15

Biceps reflexe

Answer 15

Biceps reflex – C5 reflex conveyed through the musculocutaneous nerve.

Question 16

Supinator jerk

Answer 16

Supinator jerk – C6 reflex conveyed through the radial nerve.

Question 17

Triceps jerk

Answer 17

Triceps jerk – C7 reflex conveyed through the radial nerve.

Question 18

Finger jerk

Answer 18

Finger jerk – C8 reflex conveyed through the median and ulnar nerve.

Question 19

Reflexes in lower motor neuron lesions

Answer 19

reflexes depressed

Question 20

Nerve root impingement

Answer 20

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

Question 21

Types of nerve (plexus) injury

Answer 21

avulsion
rupture
neuroma
neurapaxia

(Avulsion / rupture – brachial plexus trauma, neurapraxia blunt injury)

Question 22

Avulsion

Answer 22

Avulsion: Tearing of the nerves from its attachment at the spinal cord. – Require surgical repair

Question 23

Rupture

Answer 23

Rupture: Tearing of the nerves but not from its attachment to the spinal cord – Require surgical repair

Question 24

Neuroma

Answer 24

Neuroma: tumour or growth of the nerve tissue. Can arise from the axon or myeloma – Require surgical repair

Question 25

Neurapraxia

Answer 25

Neurapraxia: Axons remain intact, but myelin damage cause an interruption of the impulse down the nerve fibre – Good prognosis.

Question 26

Flail arm

Answer 26

C5-T1 lesions causing flail arm Left shoulder subluxation Atrophy of the left deltoid, supraspinatous and infraspinatous

Question 27

brachial plexus injury

Answer 27

``` 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 ```

Question 28

Erbs palsy

Answer 28

- 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) ```

Question 29

Symptoms of Erbs palsy aka waiters tip

Answer 29

``` Arm cannot be- Elevated Abducted External rotated Flexed at elbow ``` But fingers unimpaired Hand works but arm does not!

Question 30

Klumpke's palsy

Answer 30

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!

Question 31

Metastatic brachial plexopathy

Answer 31

Pancoast tumour (lung) – infiltration of the lower brachial plexus Pain in shoulder girdle and inner arm. Ipsilateral horners syndrome

Question 32

Radiation induced brachial plexopathy

Answer 32

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

Question 33

Idiopathic brachial neuritis aka Parsonage-Turner syndrome

Answer 33

``` 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 ```

Question 34

Thoracic outlet syndrome

Answer 34

Variations in anatomy cause compression sites: - Between anterior and middle scalene muscles - Beneath clavicle in the costoclarvicular space - Beneath tendon of Pectorlis minor

Question 35

Causes of thoracic outlet syndrome

Answer 35

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.

Question 36

neurogenic thoracic outlet syndrome

Answer 36

Paresthesia, numbness, weakness Not localised to specific nerve distribution Reproducibly aggravated by elevation or sustained use of arms or hands.

Question 37

vascular thoracic outlet syndrome

Answer 37

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.

Question 38

Long thoracic nerve injuries

Answer 38

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

Question 39

Median nerve

Answer 39

2 common sites of compression Wrist (Carpel tunnel syndrome) Elbow

Question 40

Median nerve innervated hand muscles

Answer 40

L ateral 2 lumbricalsO pponens pollicisA bductor pollicis brevisF lexor pollicis brevis

Question 41

Median nerve compression signs

Answer 41

thenar wasting

Question 42

Carpal tunnel syndromes

Answer 42

``` Causes include: Diabetes Pregnancy Hypothyroidism Rheumatoid arthritis Repetitive strain ``` Median N. entrapment at carpal Tunnel (also damaged in wrist fractures)

Question 43

Anterior interosseous nerve

Answer 43

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

Question 44

Anterior interosseous nerve syndrome

Answer 44

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

Question 45

Ulnar claw

Answer 45

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).

Question 46

ulnar nerve branches around medial epicondyle

Answer 46

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

Question 47

Ulnar nerve palsy sign

Answer 47

Froment's sign (crab grip) due to weakness of adductor pollicis

Question 48

ulnar vs c8

Answer 48

C8 All finger extensors (radial nerve) FDP of Index/middle (median nerve) Ulnar nerve d5 and 1/2 d4. Test d5

Question 49

Radial nerve palsy aka Saturday night palsy

Answer 49

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

Question 50

Nerve conduction studies

Answer 50

Useful in determining the amplitude and velocity of a peripheral nerve

Question 51

Axonal vs demyelinating

Answer 51

Axonal loss results in a decrease in amplitude | Demyelinating results in a decrease in velocity

Question 52

Neurogenic vs myogenic

Answer 52

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)