L16 - BRACHIAL PLEXUS AND NERVE DISTRIBUTIONS Flashcards
List the components and location of the roots of brachial plexus?
Ventral rami of (C4) C5, 6, 7, 8, T1 (T2)
within prevertebral musculature
List the components and location of the Trunks of brachial plexus?
Trunks:
upper (C5, C6), middle (C7), lower (C8, T1)
posterior triangle of neck
List the components and location of the Divisions of brachial plexus?
Anterior, posterior
behind clavicle
List the components and location of the Cords of brachial plexus?
lateral, medial, posterior
upper half of axilla
List the components and location of the Branches of brachial plexus?
Nerve fibres from different spinal levels
Arise from all parts of the plexus, except divisions.
Which part of the arm is supplied by which part of the brachial plexus?
- Anterior divisions: flexor compartment (richer nerve supply)
- Posterior divisions: extensor compartment
What is the anterior wall of the Axilla?
pectoralis major, pectoralis minor (crosses 2nd part of axillary artery)
What is the posterior wall of the Axilla?
Posterior wall: latissimus dorsi, subscapularis, teres major
What is the medial wall of the Axilla?
Serratus anterior
What is the lateral wall of the Axilla?
long head of biceps, short head of biceps, coracobrachialis
List the branches from the Roots of the brachial plexus?
2
- Dorsal scapular nerve (mainly C5)
- Long thoracic nerve (C5,6,7)
List the branches from the upper trunk of the brachial plexus?
2
- Suprascpular nerve (C5,6)
- Nerve to subclavius (C5,6)
List the branches from the lateral cord of the brachial plexus?
- 5
- lateral pectoral n. (C5, C6, 7)
- musculocutaneous n. (C5, 6, 7)
- lateral root of median n. (C6, 7)
List the branches from the Median cord of the brachial plexus?
4½
- medial pectoral n. (C8)
- medial cutaneous n. of arm (T1)
- medial cutaneous n. of forearm (C8, T1)
- ulnar n. ((C7), C8, T1)
- medial root of median n. (C8, T1)
List the branches from the posterior cord of the brachial plexus?
5
- upper subscapular n. (C5, 6)
- thoracodorsal n. (C6, 7, 8)
- lower subscapular n. (C5, 6)
- axillary n. (C5, 6) *
- radial n. (C5, 6, 7, 8, T1) *
Give the course and innervation of dorsal scapular nerve.
Branch from C5 root
Course: Posterior to back, does not pass through axilla
Supply:
- Levator scapulae
- Rhomboid major
- Rhomboid minor
Give the course and innervation of Long thoracic nerve.
Branch from C5,6,7 root
Course: vertically down, then over surface of serratus anterior
Supply:
Serratus anterior
What arises from long thoracic nerve injury?
Winging of scapula
Give the course and innervation of suprascapular nerve.
Branch from upper trunk
Course: Bound by superior transverse scapular ligamnet and converges into hole, Runs with suprascapular artery
Supply:
- Supraspinatus
- Infraspinatus
Give the origin and innervation of lateral pectoral nerve.
Branch from Lateral cord (C5,6,7)
Innervate pectoralis major
Give the course and innervation of musculocutaneous nerve.
Branch from anterior division of lateral cord (C5,6,7)
Course:
From muscle to skin, continues as lateral cutaneous nerve of forearm, 5 main terminal branches
Supply: - Anterior flexor arm muscles: elbow flexors - Coracobrachialis - Biceps brachii - Brachialis Lateral skin of forearm
What is the consequence of damage to musculocutaneous nerve?
Affects flexion (brachioradialis), supination (biceps brachialis) of forearm + decrease sensation at lateral forearm
Compensated by other muscles that can flex the elbow **
Is damage to musculocutaneous nerve likely?
Well-protected (does not pass through any area which is vulnerable to damage), unless stab wound in axilla
What are the 2 parts of the median nerve and their origin?
1) C6,7»_space; Lateral root of median nerve
2) C8, T1»_space; Medial root of median nerve
Give the course of median nerve?
Anterior compartment of arm with no branches in arm
> > Half way down the arm, crosses brachial artery from LATERAL to MEDIAL
> > Carpal tunnel
> > hand
What muscles do the Median nerve innervate?
Supply all the muscles in the front of the forearm (except flexor carpi ulnaris and the medial half of the flexor digitorum profundus)
Supply 1st & 2nd lumbricals, and thenar muscles (except adductor of thumb).
What skin does Median nerve innervate?
Lateral 2/3 of palm; palmar surfaces and nail-beds of lateral 3½ digits + dorsal surface of the distal 2 phalanges
Where is the median nerve susceptible to damage?
Vulnerable at front of wrist
Damaged by:
1) Compression / swelling at carpal tunnel
2) Cuts at wrist
What are the consequences of median nerve damage at the wrist ?
- Sensory loss
- Loss of muscular and joint proprioception
- Wasting of thenar eminence + Thumb adducted and laterally rotated (unopposed ADduction)
- Ulnar deviation of the wrist
3+4 = ape hand deformity
What is Ape Hand deformity?
Median nerve palsy
Caused by wasting of thenar eminence
Thumb adducted and laterally rotated because Opponens pollicis muscle is paralyzed»_space; no ABDUCTION
What is the course of the ulnar nerve?
From anterior divisions of C8, T1, branch of medial cord
Travel down medial side of anterior compartment of arm, no branch in arm
> > pierce medial intermuscular septum to reach posterior compartment behind medial epicondyle of humerus
> > BACK to anterior compartment of forearm, superficial at wrist
Where is the ulnar nerve suceptible to damage?
Behind medial epicondyle
or
Front of wrist: medial to ulnar artery, lateral to flexor carpi ulnaris tendon and pisiform bone
What is Claw Hand deformity?
Damage to ulnar nerve, leading to motor loss involving fine movement of fingers
- Wasting of Hypothenar muscles, Interosseous muscle (guttering)
- Paralysis of lumbricals
- unopposed long extensors at MCP joint (hyperextensions) & unopposed Long flexors at IP joints (flexion)
What muscles are innervated by the ulnar nerve?
Not anything in the arm
Supplies 1½ muscles in forearm:
- Flexor carpi ulnaris
- Medial part of flexor digitorum profundus
+ most intrinsic muscles of the hand:
- Hypothenar
- 3rd, 4th lumbricals
- Interosseous
What skin regions are innervate by ulnar nerve?
1) Dorsal branch»_space; Medial dorsum of hand
2) Superficial branch»_space; Palmar aspect of medial 1½-2½ fingers
Superficial ulnar nerve innervates the dorsal aspect of the medial 1½-2½ fingers. True or False?
False
Superficial ulnar nerve supplies the palmar aspect
dorsal aspect of the same fingers are supplied by a separate branch given off in the distal third of the forearm
Give the origin and the innervation of Upper subscapular nerve?
Origin = Posterior cord (C5,6)
Supply: Subscapularis
Give the origin and the innervation of Thoracodorsal nerve?
Posterior cord (C6,7,8)
Supply: Latissimus dorsi
Give the origin and the innervation of Lower subscapular nerve?
Posterior cord (C5,6)
Supply Subscapularis
What is the origin and course of the axillary nerve?
Origin = Posterior division C5,6 of posterior cord
Course: Leaves axilla by passing backward through the quadrilateral space»_space; winds around the posterolateral aspect of surgical neck of humerus (may be affected by shoulder dislocation)
What does axillary nerve innervate and what results from injury?
Supplies deltoid and teres minor, and a small area of skin on the lateral side of the arm near the insertion of the deltoid
Injury (from dislocation or swelling in quadrangular space): cannot abduct the arm beyond 45° (abduction initiated by supraspinatus)
Give the origin and innervation of the Radial nerve?
Origin = Posterior division of C6,7,8 + T1 of posterior cord
Supply: All posterior muscles in arm and forearm (extensors)
Cutaneous branches to supply skin of the posterior and lateral surfaces of arm, back of forearm and a small area on dorsum of hand
What is the course of the radial nerve?
From axilla to posterior side through triangular interval
> > Wind around back of humerus @ radial groove
> > Enter anterior compartment by piercing Lateral Intermuscular Septum above lateral epicondyle
> > Divide into deep and superficial branches at lateral epicondyle
> > Deep branch (dorsal interosseous nerve) pierces the supinator muscle and wraps around neck of radius (vulnerable here) to reach the posterior compartment of the forearm
> > Superficial branch (cutaneous) emerges in the snuff-box and gives off digital branches
What is Wrist Drop syndrome?
Radial nerve damage
Paralysis of extensors of wrist and digits
Median nerve lesions is the least severe. True or False?
False
Radial nerve damage is less disabling compared to median and ulnar nerve lesions
What forms the boundaries of the carpal tunnel?
Roof = flexor retinaculum
Lateral = Hypothenar and Thenar muscles
Inferior = carpal bones
What goes through the carpal tunnel? Does ulnar nerve go through it?
superficial to deep:
- flexor digitorum superficialis tendons (four) (middle and ring finger more superficial to the index and little finger)
- median nerve
- flexor pollicis longus tendon
- flexor digitorum profundus tendons (four)
Ulnar nerve passes outside
Define dermatome. Define myotome.
An area of skin supplied by a single spinal (segmental) nerve
The amount of muscle supplied by a single spinal nerve, or the nerve roots responsible for particular movements
Is the dermotomes of the limb the same as cutaneous innervation fields?
No
List 3 ways to damage the radial nerve?
Humerus fracture
Prolong use of crutches
Saturday Night Syndrome
What are axial lines and how are they arranged? What is the clinical use?
Line of junction of two dermatomes supplied from discontinuous spinal levels
not arranged segmentally in the limbs
Use in test for dermatome response to trace affected spinal level
What are the 5 Areas where dermatomes can be tested for sensation with minimal overlap?
C5 (upper lateral side of arm) C6 (pad of thumb) C7 (pad of index finger) C8 (pad of little finger) T1 (medial aspect of elbow)
Do skin prick tests work for testing myotomes?
No
More complex and merged myotomes in limbs, no distinct areas
What is the use of dermatomes and myotomes?
Test integrity of spinal nerves and level of a neurological lesion
Test integrity of segmental innervation across axial lines (checking for sensation to pin-prick and light touch) and testing which joint movements are impaired
What is the ROM of the shoulder? Which nerves are responsible?
C5 > abduction& lateral rotation
C6,7,8 > adduction & medial rotation
C5,6,7,8 > flexion & extension
What is ROM of elbow? Which nerves are responsible?
C5,6 > flexion
C7,8 > extension
What is ROM of Forearm? Which nerves are responsible?
C6 > supination
C7,8 > pronation
What is ROM of Wrist? Which nerves are responsible?
C6,7 > flexion & extension
What is ROM of Fingers? Which nerves are responsible?
C7,8 > flexion& extension
What is ROM of Intrinsic hand muscles? Which nerves are responsible?
T1 > abduction/adduction of digits II-IV
What is the nerve damage from upper trunk lesion (e.g. from traction injury involving violent separation of head and neck)?
Upper roots C5, 6 commonly affected»_space; Erb’s palsy
- Injury of C5 causes shoulder to be medially rotated and adducted»_space; No abduction and No lateral rotation
- elbow flexion is weakened, forearm becomes pronated (“tip-taking position”)»_space; Cannot supinate
- Sensory loss on lateral aspect of upper arm (C5 dermatome)
What is the nerve damage from lower trunk lesion?
Lower roots C8, T1 affected: Klumpke’s paralysis
- Paralysis & wasting of intrinsic muscles of hand (T1).
- Weakness in flexion of wrist and fingers (C8).
- Loss of sensation on medial side of arm (T1), forearm and hand (C8).
- Interruption of sympathetic outflow to orbit (T1)
> > Similar to ulnar paralysis + thenar muscle and digit flexor paralysis»_space; Combined claw-hand and ape hand
What are some possible causes of Lower trunk lesion?
breech presentation at birth»_space; pull legs during birth causing damage
neurovascular compression by cervical rib
What are the consequences of Interruption of sympathetic outflow to orbit due to T1 damage? (Klumpke’s paralysis)
Horner’s syndrome
constriction of pupil,
drooping of upper eyelid,
sinking in of the eyeball,
lack of sweating on the affected side of the face
