Neurology of upper limb Flashcards
What is the brachial plexus?
One of the somatic plexuses that supplies the upper limb.
Which spinal nerve roots form the brachial plexus?
The anterior rami of C5-T1.
Which spinal nerve root is associated with shoulder abduction?
C5
Which spinal nerve roots are associated with elbow extension?
C7/8
Which spinal nerve root is associated with finger abduction?
T1
Which spinal nerve roots are associated with wrist extension?
C5/6
Which spinal nerve roots are associated with wrist flexion?
C6-8
What forms the apex of the axilla?
The cervico-axillary inlet.
what forms the base of the axilla?
The axillary fossa.
Which muscles form the anterior wall of the axilla?
Pectoralis major and pectoralis minor.
What structures form the medial wall of the axilla?
Serratus anterior and ribcage.
Which muscles form the posterior wall of the axilla?
Subscapularis, teres major, latissimus dorsi, and the long head of triceps brachii.
what structure forms the lateral wall of the axilla?
The humerus.
What is the origin of the axillary nerve?
It is a branch of the posterior cord of the brachial plexus (root values C5, C6).
Through which space does the axillary nerve exit the axilla?
The quadrangular space.
Which muscles does the axillary nerve innervate?
Deltoid
Teres minor
Long head of triceps brachii
It also innervates the glenohumeral joint.
How can the axillary nerve be injured?
It can be injured in shoulder dislocations.
What are the effects of an axillary nerve injury?
Loss of abduction
Weakened flexion, extension, and rotation
‘Flat shoulder deformity’
Sensory loss over the lateral upper arm
What is the origin of the musculocutaneous nerve?
It is a branch of the lateral cord of the brachial plexus (root values C5-C7).
Which muscle does the musculocutaneous nerve pierce?
It pierces the coracobrachialis.
What is the function of the musculocutaneous nerve in the anterior compartment of the arm?
It provides motor innervation to the flexors of the arm.
Which bone does the musculocutaneous nerve give a branch to?
It gives a branch to the humerus at the nutrient foramen.
What does the musculocutaneous nerve continue as in the forearm?
It continues as the lateral cutaneous nerve of the forearm (sensory only).
What can cause musculocutaneous nerve injury?
Muscular compression or stretch
Shoulder injury
Direct trauma
What are the effects of musculocutaneous nerve injury?
Reduced and tingling sensation in the lateral skin of the forearm
Reduced strength of elbow flexion
What is the origin of the median nerve?
The lateral and medial cords of the brachial plexus (root values C6-T1).
What does the median nerve innervate? (motor and sensory)
Motor innervation: Muscles of the anterior forearm (except flexor carpi ulnaris and medial ½ of flexor digitorum profundus) and hand
Sensory innervation: Lateral palm of the hand and three digits
What is the origin of the ulnar nerve?
The medial cord of the brachial plexus (root values C8, T1).
What does the ulnar nerve innervate? (motor and sensory)
Motor innervation: Flexor carpi ulnaris, medial ½ of flexor digitorum profundus, and hand
Sensory innervation: Medial palm of the hand and 1½ digits
What is the origin of the radial nerve?
The posterior cord of the brachial plexus (root values C5-T1).
What does the radial nerve innervate? (motor and sensory)
Motor innervation: Posterior compartment of arm and forearm (extensors)
Sensory innervation: Skin on the posterior arm, forearm, and dorsolateral hand
What are the 4 effects of median nerve damage above the elbow?
Weak wrist flexion
Loss of forearm pronation
Ape hand deformity
Benediction sign
What 2 conditions can cause median nerve damage at the wrist?
Wrist laceration
Carpal tunnel syndrome
What are the 2 effects of ulnar nerve damage at the elbow?
Cubital tunnel syndrome → Claw hand
Benediction sign
What are the 2 effects of ulnar nerve damage at the wrist?
Guyon’s canal cyst → Claw hand
Benediction sign
What are the effects of radial nerve damage in the axilla?
Saturday night/honeymoon palsy
Wrist drop
Weak forearm extension and supination
What is Wartenberg syndrome?
Nerve entrapment beneath brachioradialis tendon.
What causes Erb-Duchenne’s palsy?
damage to C5/C6 roots, often caused by:
- Shoulder dystocia during a difficult birth
- Head/shoulder stretch injuries
Which 3 nerves are most affected in Erb-Duchenne’s palsy?
Suprascapular nerve
Axillary nerve
Musculocutaneous nerve
What 3 muscles are paralyzed in Erb-Duchenne’s palsy?
Deltoid
Biceps brachii
Brachialis
What is the characteristic arm position in Erb-Duchenne’s palsy?
‘Waiter’s tip’ position → The arm hangs medially rotated and cannot be abducted.
What sensory loss occurs in Erb-Duchenne’s palsy?
There is a loss of sensation in areas supplied by the affected nerves.
What causes Klumpke’s paralysis?
Damage to the lower roots (C8/T1).
What sensory symptoms are present in Klumpke’s paralysis?
C8/T1 dermatome numbness.
What motor deficits occur in Klumpke’s paralysis?
Atrophy of the arm and/or hand
Paralysis of intrinsic hand muscles
what additional symptom can occur in Klumpke’s paralysis?
Persistent pain.
What happens if T1 is affected in Klumpke’s paralysis?
It can lead to Horner’s syndrome (ptosis/miosis).
What are the 3 branches of the thoracoacromial artery?
Acromial branch
Deltoid branch
Pectoral branch
