Upper limb nerve injuries Flashcards
How do you approach a neurological problem?
- anatomically localise the lesion
- consider the pathophysiology
- differential diagnosis
Where do LMN arise from?
Anterior horn of spinal cord
How does pathology in UMN present?
Consider tone, strength, abnormal movements, anatomy affected
- Held in flexed posture if chronic
- Increased tone
- Pyramidal weakness (flexor muscles stronger than extensors)
- Brisk reflexes
- Sensory level
How does pathology in LMN present?
Consider tone, strength, abnormal movements, anatomy affected
- Wasting/fasciculations
- Decreased tone (flaccid)
- Weakness in either a myotomal distribution or a peripheral nerve distribution
- Reduced reflexes
- Dermatomal or peripheral nerve distribution of sensory loss
What are the three anatomical regions for localising a lesion?
- Roots
- Brachial plexus
- Peripheral nerve
What is a dermatome?
An area of skin supplied by nerve fibres originating fro a single dorsal nerve root
- Overlap with adjacent dermatoms
- Anatomical variation
For each root, give the myotome and muscle action
- C5
- C6
- C7
- Deltoid: shoulder abduction
- Biceps, brachialis, brachioradialis: elbow flexion
- Triceps, superficial forearm extensors and flexors: elbow extension, wrist extension, wrist flexion
For each root, give the myotome and muscle action
- C8
- T1
- Forearm extensors, deep forearm flexors: finger extension, finger flexion
- Intrinsic hand muscles: finger abduction
For the following reflexes state the nerve being tested:
- Biceps reflex
- Triceps jerk
- Supinator jerk
- Finger jerk (Hoffmans)
- C5 reflex through musculocutaneous nerve
- C7 reflex through radial nerve
- C6 reflex through radial nerve
- C8 reflex thorugh median and ulnar nerve
How does nerve root impingement present?
How does this happen?
- Pain which radiates/aggravated by neck movement
- Sensory loss
- Weakness
- Reflex loss
Cervical spine may be injured during hyper flexion/extension –> injury of neural structures
- Protected from fractures or dislocation due to its flexibility
Define the following terms
- Avulsion
- Rupture
- Neuroma
How do these occur?
How are these managed?
Brachial plexus trauma
- Tearing of the nerves from its attachment at spinal cord.
- Tearing of the nerves but not from its attachment to spinal cord
- Tumour or growth of nerve tissue. Can arise from axon or myeloma
All require surgical repair
What is neurapraxia?
- Axons remain intact but myelin damage cause an interruption of the impulse down nerve fibre
- Caused by blunt injury
- Good prognosis
John has a motor cycle injury resulting in a left flail arm
What type of nerve injury is this?
Lesions in which area cause this?
Presentation?
- Cervical root avulsion
- C5-T1 lesions
- Left shoulder subluxation, atrophy of left deltoid, supraspinatous, infraspinatous
Give two examples of brachial plexus injury resulting from trauma
- Erb-Duchenne type paralysis: avulsion of C5,C6 roots
- Klumpke paralysis: avulstion of C8, 71 roots
What cancers/aspects of treatment can cause brachial plexus injury
- Lung cancer: Pancoasts tumour
- Radiotherapy
Give an example of brachial plexus injury resulting from inflammation
Brachial neuritis
Give an example of brachial plexus injury resulting from structural abnormality
Thoracic outlet syndrome
Consider ERBS PALSY aka “Waiters tip”
- How does it occur?
- Which nerves are affected?
- Which muscles are affected?
- Presentation
- To baby during labour, or to adults following a blow to shoulder
- Upper plexus palsy , superior trunk of brachial plexus
- Muscles innervated by C5/C6: biceps, brachioradialis, deltoid, supraspinatous, supinator
- Arm cannot be elevated, abducted, externally rotated or flexed at elbow. Hand works
Consider KLUMPKES PALSY
- How does it occur?
- Which nerves are affected?
- Which muscles are affected?
- Presentation
- Clutching for an object when falling from height
- Inferior trunk plexus injury involving C8/T1. Involves trunk that supplies median and ulnar nerves
- Weakness of all small muscles of hand,
- Arm works, hand doesnt (cant flex wrist or fingers) + sensory loss of hand and inner border of forearm
- May lead to clawed hand
Describe metastatic brachial plexopathy
Cause, presentation
- Pancoast (lung) tumour
- Infiltration of lower brachial plexus
- Pain in shoulder girdle and inner arm
- Ipsilateral horners syndrome
Describe radiation induced brachial plexopathy
- 6 years post radiation
- associated with cancer treatment (breast, lung, lymphoma)
- Pain not necessarily seen
- Preferentially affects upper brachial plexus
What is idiopathic brachial neuritis?
- Cause
- Presentation
- Investigative findings
- Treatment
- Idiopathic, infection
- Severed pain for days, as it diminishes, followed by wasting and weakness. Monophasic and usually unilateral
- MRI shows thickening and enhacement. NCS/EMG useful for prognostication
- Analgesia, physio, steroids?
What are the variation in anatomy that cause compression sites (thoracic outlet syndrome)?
- Between anterior and middle scalene muscles
- Beneath clavicle in constoclavicular space
- Beneath tendon of pec minor
How do the presentations of neurogenic and vascular thoracic outlet syndrome differ?
NEUROGENIC
- predominantly affect median innervated abductor pollicis brevis (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.
Describe neurogenic thoracic outlet syndrome
- Parasthesia, numbness, weakness
- Not localised to specific nerve distribution
- Aggravated by elevation or sustained use of arms/hands
Describe vascular thoracic outlet syndrome
- Forearm fatigue within minutes
- Swelling and cyanosis
- Collateral venous patterning over the ipsilateral shoulder, chest wall and neck
- Rarely painful. Pallor and colnedd due to arterial involvement
- Lower BP on affected arm, diminished distal pulses
How is the long thoracic nerve injured?
Resulting presentation
Why?
- Blows or pressure in posterior triangle of neck or during a radical mastectomy
- Winged scapula
- Supplies serratus anterior which pulls the medil border of the scapula to posterior thoracic wall to stabilise it
What are the common sites of compression of median nerve?
- Wrist (Carpal tunnel)
- Elbow
Which muscles are innervated by median nerve?
Lateral 2 lumbricals
Opponens pollicis
Abductor pollicis brevis
Flexor pollicis brevis
Causes of carpal tunnel syndrome
- Pregnancy
- Diabetes
- Hypothyroidism
- RA
- Repetitive strain
Origin of anterior interosseous nerve?
Becomes compressed between which structures?
Damaged in ?
- Median nerve above elbow (pure motor branch)
- 2 heads of pronator teres
- Gripping tightly with forced pronation- prolonged use of screwdriver?
- Careless blood taking
Presentation of anterior interosseous nerve syndrome
- Weakness in flexor pollicis longus, FDP
- Weakness of pronation
Which muscles does this ulnar nerve supply?
- Medial 2 lumbricals
- 3rd and 4th flexor digitorum profundi
- Interossei
(Intrinsic muscles of the hand)
If there is a higher lesion of the upper limb what is the presentation
How does this differ to a lesion at the wrist?
- Ring and little fingers are not flexed
- FDP intact so flexion at DIP,
- Flexion at PIP (interossei muscles paralysed)
- Hyperextension at MCP (lumbricals paralysed)
What causes froments sign?
Weakness of adductor pollicis
Saturday night palsy aka…
Presentation
Radial nerve palsy
Rarely causes extensive sensory loss due to overlap withmedian/ulnar nerve
- Pain in anatomical snuffbox
What is the use of nerve conduction studies?
How does axonal loss and demyelnation present?
- Determining the amplitude and velocity of a peripheral nerve
- Axonal loss –> decrease in amplitude
- Demyelinating –> decrease in velocity
What kind of study differentiates between neurogenic and myopathic lesions?
- Needle EMG
- measures electrical activity of muscle during voluntary contraction
