Peripheral Nerve Lesions - Brachial Plexus Injuries

Question 1

What are the contributions to the axillary nerve?

Answer 1

C5 and C6 only

Question 2

What are the contributions to the musculocutaneous nerve?

Answer 2

C5-C7

Question 3

What is a dermatome?

Answer 3

an area of skin supplied by a single spinal nerve

Question 4

Label the anterior dermatomes

Answer 4

Question 5

Label the posterior dermatomes

Answer 5

Question 6

What is a myotome?

Answer 6

a muscle (or group of muscles) that is innervated by a single spinal nerve

Question 7

What types of trauma/injury to the nerves is possible?

Answer 7

1. stretching of nerves
2. tearing of nerves
3. laceration of nerves
4. avulsion of nerves from the spinal cord

Question 8

What is meant by avulsion of nerves?

Answer 8

when the nerves are torn out of the spinal cord during injury

Question 9

What are the 4 categories of brachial plexus pathology?

Answer 9

1. injuries at birth
2. blunt trauma
3. penetrating trauma (wounds to the neck or axilla)
4. disease e.g. tumour at apex of lung that can impact on the plexus

Question 10

What is more likely; a brachial plexus or a peripheral nerve injury?

Answer 10

peripheral nerve injury

the brachial plexus is higher up and is much more protected from injury than the peripheral nerves

Question 11

What are the 2 types of Brachial Plexus injury and the differences between them?

Answer 11

Erb’s Palsy:

this is an upper brachial plexus injury affecting C5 and C6

(sometimes C7)

Klumpke’s palsy:

this is a lower brachial plexus injury affecting C8 and T1

(sometimes C7)

Question 12

What types of injuries will affect the roots and trunks of the brachial plexus?

Answer 12

Roots:

affected by cervical cord injuries and traction injuries

Trunks:

affected by injuries to the 1st rib

Question 13

What are the 2 most common causes of brachial plexus injury?

Answer 13

1. during delivery (obstetric)
2. through adult trauma

Question 14

What happens if there is an injury to the whole brachial plexus?

Answer 14

the entire innervation of the upper limb is lost

Question 15

What is the most common cause of whole plexus injuries?

Answer 15

motorbike accidents

when people are thrown from bikes, as they hit the ground their head turns in the opposite direction to their shoulder

this stretches the brachial plexus and pulls the nerve roots out of the spinal cord

Question 16

Why may the skin look different after a whole plexus injury?

Answer 16

the skin requires an autonomic nerve supply (T1) for vasoconstriction and vasodilation

Question 17

How may the pupil look different after a whole plexus injury?

Answer 17

constriction of the pupil is due to injury to T1 and loss of autonomic function

Question 18

When may Erb’s palsy (upper BP injury) happen in children?

Answer 18

when there is excessive stretching of the neck during delivery

this leads to damage to C5 and C6 nerve roots

Question 19

What is the most common cause of excessive stretching of the neck during delivery, leading to Erb’s palsy?

Answer 19

shoulder dystocia

this is when the baby’s shoulders are too large for the birth canal so there is tugging on the neck during delivery

Question 20

What is the result of Erb’s palsy in children?

Answer 20

The arm is medially rotated and hangs limply by the side

There is loss of ability to flex the elbow

Question 21

Why is there medial rotation of the arm in Erb’s palsy?

Answer 21

medial rotation is unopposed as the lateral rotators are not functioning

teres minor and infraspinatus (lateral rotators) are innervated by C5 and C6

Question 22

Why is there loss of elbow flexion in Erb’s palsy?

Answer 22

Biceps brachii and brachialis are not functioning due to injury ot C5, 6 and 7

Supination of the forearm by biceps cannot occur

Question 23

Why does the arm hang limply by the side in Erb’s palsy?

Answer 23

Damage to the axillary nerve (C5, C6) means that there is loss of the abductors (deltoid)

Question 24

What happens to the muscles in Erb’s palsy later on in life?

Answer 24

Muscular atrophy as they cannot be used

They appear smaller and less well developed than normal

Question 25

What causes upper brachial plexus injuries in adults?

Answer 25

violent falls on the side of the head and shoulder, which force the two apart usually motorbike accidents

Question 26

What investigations are conducted and what is the prognosis in an upper brachial plexus injury in adults?

Answer 26

**Investigations:** MRI shows nerve root damage **Prognosis:** depends upon the degree of damage function may return or there may be permanent damage

Question 27

What causes Klumpke's Palsy (lower BP injury) in children?

Answer 27

During delivery, the baby's upper limb is pulled excessively This leads to damage of the inferior trunk of the BP (C8, T1 - ulnar nerve)

Question 28

How is Klumpke's palsy caused in adults?

Answer 28

excessive force is applied to an abducted shoulder the upper limb is suddenly pulled superiorly e.g. grasping to prevent a fall

Question 29

What are the investigations and prognosis for Klumpke's Palsy in adults?

Answer 29

**Investigations:** MRI shows nerve root damage **Prognosis:** depends upon the degree of nerve damage function may return or there may be permanent damage

Question 30

What muscles are innervated by the ulnar nerve (affected in Klumpke's palsy)?

Answer 30

**Arm:** nothing **Forearm:** flexor carpi ulnaris (FCU) medial half of FDP **Hand:** hypothenar eminence adductor pollicis all the interossei the medial 2 lumbricals

Question 31

What areas of the skin are innervated by C8 and T1?

Answer 31

the medial side of the hand and forearm

Question 32

What is the result of Klumpke's palsy in the hand and why?

Answer 32

there is paralysis of the majority of the intrinsic hand muscles an imbalance between the ongoing function in some intrinsic & extrinsic muscles but weakness in others leads to "claw hand"

Question 33

What syndrome is Klumpke's palsy associated with? Why?

Answer 33

Horner's syndrome Sympathetic neurones supplying the head originate from T1 and may also be damaged by traction

Question 34

What are the 4 features of Horner's syndrome?

Answer 34

1. ptosis (drooping of upper eyelid) 2. miosis (constriction of pupil) 3. anhidrosis (inability to produce sweat) 4. vasodilation