Session 5: The Brachial Plexus Flashcards
Explain the consequences of injury to the upper root nerves of the brachial plexus and explain how to test their functional integrity
Root Injuries: Upper (C5/6):
Erb’s Palsy
Shoulder dystocia
Can resolve on own or need surgery
Features Loss of axillary and musculocutaneous nerve function
Wasted deltoid and biceps/brachialis
Arm is pronated and medially rotated
Elbow extended
Dermatomal sensory loss “Waiters tip”
Explain the consequences of injury to the lower root nerves of the brachial plexus and explain how to test their functional integrity
Lower (C8/T1): Klumpke’s Paralysis
- Traction to abducted arm
- Falls, ladders, motorbikes
- Traumatic childbirth
Features:
- Loss of ulnar (and median nerves)
- Possible Horner’s syndrome (if T1 affected)
- Intrinsic hand muscles paralysed
- “Claw Hand” supinated forearm with flexed wrist and fingers
- Dermatomal sensory loss
Long thoracic nerve injury
Long thoracic nerve innervates Serratus anterior:
- From upper 8/9 ribs to medial margin of scapula
- Acts to protract and stabilise the scapula
- Damage to long thoracic nerve (of bell) causes paralysis
- When patient tries to push forward or throw a punch, it normally moves the scapula around the ribs (anteriorly)
Long thoracic nerve damage after breast cancer surgery can lead to unopposed action of the rhomboids, so the scapula is pushed back –> winging of the scapula
Musculocutaneous nerve injury
- Musculocutaneous nerve is not often injured in trauma as it is well protected by muscles
- May be damaged during surgery for breast cancer shoulder dislocation
- Weight lifters can be prone to this (compression)
Effects
- Weak elbow flexion and supination
- Absent biceps reflex
- Lateral forearm sensory loss
- Terminal branch is called the “lateral cutaneous nerve of the forearm”
Median nerve injury
Causes:
- Elbow: supracondylar humeral fractures
- Wrist laceration
- Carpal tunnel syndrome
Results:
- Loss of sensation lateral 3½ fingers
- Loss of:
- Wrist flexion, elbow pronation
- Flexion of radial ½ of digits
- Presence of “benediction sign”
- Presence of ape hand deformity (Thumb not abductable, nor opposable)
- Tinel’s sign*
Axillary nerve
Axillary nerve supplies 1) Detloid and 2) Teres minor
- Commonly damaged through dislocations of shoulder and fracture of the surgical neck of the humerus
Effects
- Loss of abduction (from >15°)
- Sensory loss on lateral upper arm
- Regimental badge patch
“Flat shoulder deformity”: due to wasting of the deltoid muscle (along with teres minor)
Radial Nerve Injury
- The radial nerve runs closely apposed to the shaft of the humerus, so can be damaged in humeral fractures
- Injury at axilla (Saturday night palsy)
- At arm due to humeral shaft fracture (groove)
- Below elbow in neck of radius fracture
Effects
Wrist drop: cannot extend the wrist, elbow or fingers
Depending on where lesion is
Sensory loss to posterior forearm and dorsum of hand
Depending on where lesion is
Ulnar nerve injury
- Elbow fractures
- Funny bone trauma
- Wrist trauma
Effects:
- Sensory loss in medial 1½ fingers (palmar and dorsal)
- Ulnar claw
- Hyper-extended 4th and 5th digits at MCP
- Hyper-flexed 4th and 5th digits at IPJs
- Inability to abduct/adduct fingers against resistance
- Weak thumb adduction “Froment’s sign”
- Claw worse on extension (unlike median nerve)
Dermatomes, myotomes and reflexes: describe the their anatomical basis
Dermatomes (pic)
Upper limb Myotomes
- Shoulder Abduction – C5 (axillary)
- Shoulder Adduction – C6/7/8
- Elbow Flexion – C5 (musculocutaneous)
- Elbow Extension – C7 (radial)
- Wrist Flexion & Extension – C6/7 (radial)
- Finger Flexion – C8 (median)
- Finger Extension – C7 (radial)
- Finger Abduction – T1 (ulnar)
- Abductor pollicis brevis – T1 (median)
Reflexes
- Biceps jerk: C5/6
- Triceps jerk: C6/7
- Brachioradialis reflex: C6/7
