Brachial plexus Flashcards
What is the brachial plexus?
Plexus of nerves formed by the
anterior (ventral) rami of lower four cervical and the first
thoracic (i.e., C5, C6, C7, C8, and T1) spinal nerves (with
little contribution from C4 to T2 spinal nerves).
What is a prefixed and a Postfixed brachial plexus?
Prefixed - is when the contribution from C4 is large and that from T2 is absent.
Postfixed - contribution from T2 is large and that from C4 is
absent.
Identify the 4 components of the brachial plexus and their location.
The brachial plexus consists of four components:
(a) roots - The roots (five) are constituted of anterior primary rami of
C5 to T1 spinal nerves. They are located in neck, deep to
scalenus anterior muscle.
(b) trunks - The trunks (three) are formed as follows:
The C5 and C6 roots join to form the upper trunk; the C7
root alone forms the middle trunk and, C8 and T1 roots join
to form the lower trunk. They lie in the neck occupying the
cleft between scalenus medius behind and the scalenus
anterior in front.
(c) divisions - Each trunk divides into anterior and posterior divisions.
They lie behind the clavicle.
(d) cords - The cords (three) are formed as follows: the anterior
divisions of the upper and middle trunks unite to form the
lateral cord and the anterior division of the lower trunk
continues as the medial cord. The posterior divisions of the
three trunks unite to form the posterior cord.
Identify the branches from the brachial plexus, from the roots to cords.
A. From roots
1. Long thoracic nerve/nerve to serratus anterior (C5, C6,
and C7).
2. Dorsal scapular nerve/nerve to rhomboids (C5).
B. From trunks
1. Suprascapular nerve (C5 and C6)
2. Nerve to subclavius (C5 and C6)
The branches arising from roots and trunks are
supraclavicular branches of brachial plexus.
From cords
1. From lateral cord
(a) Lateral pectoral nerve (C5, C6, and C7).
(b) Lateral root of median nerve (C5, C6, and C7).
(c) Musculocutaneous nerve (C5, C6, and C7).
From medial cord
(a) Medial pectoral nerve (C8 and T1).
(b) Medial cutaneous nerve of arm (T1).
(c) Medial cutaneous nerve of forearm (C8 and T1).
(d) Medial root of median nerve (C8 and T1).
(e) Ulnar nerve (C7, C8, and T1).
3. From posterior cord
(a) Radial nerve (C5, C6, C7, C8, and T1).
(b) Axillary nerve (C5 and C6).
(c) Thoraco-dorsal nerve/nerve to latissimus dorsi (C6,
C7, and C8).
(d) Upper subscapular nerve (C5 and C6).
(e) Lower subscapular nerve (C5 and C6).
Where is the Erb’s point located?
It is the region of upper trunk of
brachial plexus where six nerves meet as follows: 5th and
6th cervical roots join to form the upper trunk, which gives
off two nerves—suprascapular and nerve to subclavius, and
then divides into anterior and posterior divisions.
Identify the various spinal segments of the brachial plexus which control the following movements of the upper limb.
(i) Adduction of the shoulder
(ii) Abduction of the shoulder
(iii) Flexion of the elbow
(iv) Extension of the elbow
(v) Flexion of the wrist and fingers
(i) Adduction of the shoulder is controlled by C5 segment.
(ii) Abduction of the shoulder is controlled by C6 and C7
segments.
(iii) Flexion of the elbow is controlled by C5 and C6
segments.
(iv) Extension of the elbow is controlled by C6 and C7
segments.
(v) Flexion of the wrist and fingers is controlled by C8 and
T1 segments.
What is Erb’s paralysis? Explain the cause, nerve roots involved and the description of the deformity.
Erb’s paralysis/palsy (upper plexus injury) is a deformity caused by an injury to the brachial plexus nerves in the neck which may occur by a fall from a height and landing on shoulder or traction of the arm
during birth of a child, causing weakness or paralysis in the arm.
It involves the upper trunk (C5 and C6 nerve roots).
In this deformity, the arm
hangs by the side, adducted and medially rotated, and
forearm is extended and pronated.
– Adduction of arm due to paralysis deltoid muscle.
– Medial rotation of arm due to paralysis supraspinatus,
infraspinatus, and teres minor muscles.
– Extension of elbow, due to paralysis of biceps
brachii.
– Pronation of forearm due to paralysis of biceps
brachii.
– Loss of sensation (minimal) along the outer aspect
of arm due to involvement of roots of C6 spinal
nerve.
What is klumpke’s paralysis? Explain the cause, nerve roots involved and the description of the deformity.
Klumpke’s palsy (lower plexus injury) is characterized by paralysis or weakness in the muscles of the forearm and hand, leading to a claw-like deformity of the hand and fingers.
It is caused by the hyperabduction of the arm, which may occur when
one falls on an outstretched hand or an arm is pulled into
machinery or during delivery (extended arm in a breech
presentation).
The nerve roots involved in this injury are C8 and T1 and sometimes C7.
The clinical
features of Klumpke’s paralysis are as follows:
– Claw hand, due to paralysis of the flexors of the wrist and fingers (C6, C7, and C8), and all intrinsic muscles of the hand (C8 and T1).
– Loss of sensations along the medial border of the forearm and hand (T1).
– (Autonomic involvement) Horner’s syndrome, (characterized by partial ptosis, miosis, anhydrosis, and enophthalmos) due to involvement of sympathetic fibres supplying head and neck, which leave the spinal cord through T1.
