Clinical neurophysiology Flashcards
What are the different sections of the brachial plexus?
- roots
- trunks
- divisions
- cords
- nerves (median, ulnar and radial)
What three nerves does the brachial plexus end in?
Musculocutaneous axillary radial median ulnar
What does the median nerve supply?
thumb, index, middle and half ring finger
What does the ulnar nerve supply?
pinky and half ring finger
What does the radial nerve supply?
dorsal hand
What motor fibres does the median nerve supply?
median muscle forearm (proximal and distal) and hand
What nerve root fibres make up the median nerve?
C5 + C6 (lateral cord)
C8 + T1 (medial cord)
What is the primary function of the lateral and medial cord of the median nerve?
lateral is mainly sensory
medial is mainly motor
What nerve branches of the median nerve at the elbow?
anterior interosseous nerve
What is the most common median nerve pathology?
Carpal tunnel syndrome (entrapment neuropathy)
Who is entrapment of median nerve most common in?
females
45-65 yrs
What would be the main differential diagnosis of carpal tunnel syndrome?
Lesion of:
- C6-7
- Brachial plexus
- Proximal median nerve lesion
- motor neurone disease (shouldnt have sensory disturbance)
What are the symptoms of carpal tunnel syndrome?
- paraesthesia in median distribution (can present as whole hand)
- worse during sleep/ on wakening
- loss of dexterity
- can present in dominant hand first
What are the risk factors for carpal tunnel?
- small carpal tunnel
- diabetes mellitus
- inflammatory conditions
- pregnancy, menopause and obesity
- hypothyroidism or renal disorder
- occupational (farmers)
Where will sensation often be spared in carpal tunnel?
thenar eminence as supplied by palmar cutaneous sensory branch
What are the tests for the hand?
Tinels (hand tapping)
Phalens (pushing dorsal aspect of hands against each other, hold at shoulder level for 60s)
What would motor examination of carpal tunnel syndrome show?
wasting thenar eminence
weakness thumb abduction and opposition
What muscles are supplied by the anterior interosseous nerve?
flexor digitorum profundus (flex distal phalanx or index and middle finger)
flexor pollicus longus (flexes distal phalanx thumb)
Pronator quadratus
How would weakness of anterior interosseous nerve present?
- weakness of flexor pollicus longus
- no sensory symptoms
- normal abductor pollicus brevis
- can’t work lighter or take photo on camera
Where is Ulnar nerve most commonly trapped?
elbow
Which roots is ulnar nerve derived from?
C8-T1
What are the branches of the ulnar nerve?
- dorsal cutaneous branch (dorsal part of hand on ulnar border)
- palmar cutanoues branch (palmar area on ulnar border)
- superficial terminal branches (pinky and half ring finger)
What is the most common ulnar neuropathy?
compression
stretch
elbow injury
What are the motor symptoms of ulnar neuropathy?
- decreased grip and pinch
- atrophy of hypothenar eminence and intrinsic hand muscles
- claw hand
If Ulnar damage is at the wrist which branches will be spared?
- dorsal cutaneous and palmar cutaneous
- meaning only sensory disturbance at fingers not at rest of hand
What will lesion at medial cord result in?
finger, hand and forearm
What will ulnar lesion at elbow affect?
finger and hand (forearm not affected)
What causes wrist drop?
CNS lesion C7/8 radiculopathy brachial plexopathy spiral groove PIN
Why do you get wrist drop?
weakness of wrist muscles
What does sensory involvement of wrist drop tell us?
lesion must be above where posterior interosseous nerve branches off (elbow)
If there is no sensory involvement with wrist drop what is the cause?
damage to the posterior interosseous nerve
What nerve does the posterior interosseous nerve branch from?
Radial
