The document summarizes key information about spinal nerves and the brachial plexus. It describes:
- The anatomy of spinal nerves, including their dorsal and ventral roots and formation of rami.
- The 31 pairs of spinal nerves and their names based on point of issue from the spinal cord.
- How ventral rami branch and join to form the cervical, brachial, lumbar, and sacral plexuses.
- The major nerves of the brachial plexus and their motor and sensory innervation, including the axillary, radial, musculocutaneous, ulnar, and median nerves.
- Common injuries to spinal nerves and the brachial plexus
2. Spinal nerves attach to
Spinal Nerves the spinal cord via roots
Dorsal root
Has only sensory neurons
Attached to cord via rootlets
Dorsal root ganglion
○ Bulge formed by cell bodies
of unipolar sensory neurons
Ventral root
Has only motor neurons
No ganglion - all cell bodies
of motor neurons found in
gray matter of spinal cord
12-2
3. Spinal Nerves
31 pair
each contains thousands of nerve fibers
All are mixed nerves have both sensory and motor
neurons)
Connect to the spinal cord
Named for point of issue from the spinal cord
8 pairs of cervical nerves (C1-C8)
12 pairs of thoracic nerves (T1-T12)
5 pairs of lumbar nerves (L1-L5)
5 pairs of sacral nerves (S1-S5)
1 pair of coccygeal nerves (Co1)
12-3
4. Formation of Rami
Rami are lateral branches of a
spinal nerve
Rami contain both sensory
and motor neurons
Two major groups
Dorsal ramus
○ Neurons innervate the
dorsal regions of the body
Ventral ramus
○ Larger
○ Neurons innervate the
ventral regions of the
body
○ Braid together to form
plexuses (plexi)
12-4
5. Dermatomal Map
Spinal nerves indicated by capital letter and number
Dermatomal map: skin area supplied with sensory
innervation by spinal nerves
12-5
6. Introduction to Nerve Plexuses
Nerve plexus
A network of ventral rami
Ventral rami (except T2-T12)
Branch and join with one another
Form nerve plexuses
○ In cervical, brachial, lumbar, and sacral regions
○ No plexus formed in thoracic region of s.c.
12-6
7. Dorsal Ramus
Branches of Neurons within muscles of trunk and back
Ventral Ramus (VR)
Spinal Braid together to form plexuses
○ Cervical plexus - VR of C1-C4
Nerves ○ Brachial plexus - VR of C5-T1
○ Lumbar plexus - VR of of L1-L4
○ Sacral plexus - VR of L4-S4
○ Coccygeal plexus -VR of S4 and S5
Communicating Rami: communicate
with sympathetic chain of ganglia
Covered in ANS unit
12-7
8. Brachial Plexus
Formed by ventral rami of
spinal nerves C5-T1
Five ventral rami form
three trunks that separate into
six divisions that then form
cords that give rise to nerves
Major nerves
Axillary
Radial
Musculocutaneous
Ulnar
Median
12-8
10. Brachial Plexus: Radial Nerve
Motor components stimulate
Posterior muscles of arm, forearm, and
hand
○ Triceps, supinator, brachioradialis,
extensors
○ Cause extension movements at elbow
and wrist, thumb movements
Sensory components
Skin on posterior surface of arm and
forearm, hand
12-10
11. Brachial Plexus:
Musculocutaneous Nerve
Motor components stimulate
Flexors in anterior upper arm:
(biceps brachii, brachialis)
○ Cause flexion movements at
shoulder and elbow
Sensory: Skin along lateral
surface of forearm
12-11
12. Brachial Plexus: Ulnar Nerve
Motor components
stimulate
Flexor muscles in anterior
forearm (FCU, FDP, most
intrinsic muscles of hand)
Results in wrist and finger
flexion
Sensory: Skin on medial
part of hand
12-12
13. Brachial Plexus: Median Nerve
Motor components
stimulate
All but one of the flexors of the
wrist and fingers, and thenar
muscles at base of thumb
(Palmaris longus, FCR, FDS,
FPL, pronator)
Causes flexion of the wrist
and fingers and thumb
Sensory components
Stimulate skin on lateral part
of hand
12-13
17. Principles of Localization
Certain sites are prone to nerve
entrapments/injuries
Nerve opposing bone
○ Ulnar nerve at the elbow
Closed spaces
○ Carpal tunnel
Adjacent structures
○ Median nerve at the elbow, adjacent to
the brachial artery
18. Principles of localization (cont.)
Order in which branches arise
Movements at specific joints
Single nerve
○ Elbow extension
Radial
Multiple nerves
○ Elbow flexion
Musculocutaneous
Radial
19. Brachial Plexus Injuries
Upper Lesions of the Brachial
Plexus (Erb’s Palsy): resulting from
excessive displacement of the head to
opposite side and depression of shoulder
on the same side.
20. Thiscauses excessive traction or
even tearing of C5 and 6 roots of
the plexus. It occurs in infants
during a difficult delivery or in
adults after a blow to or fall on
shoulder.
21. Effects:
Motor: paralysis of
the supraspinatus,
infraspinatus,
subclavius,
biceps brachii,
part of brachialis,
coracobrachialis;
deltoid
teres minor.
Sensroy: sensory loss on the lateral side
of the arm.
22. Deformity:
waiter tip postion
c. limb will hang by the side,
d. medially rotated by sternocostal part
of the pectoralis major;
e. pronated forearm (biceps paralysis)
24. Lower Lesions of the Brachial Plexus
(Klumpke Palsy)
traction injuries by excessive abduction of
the arm
i.e. occurs if person falling from a height
clutching at an object to save himself or
herself.
Can be caused by cervical rib.
T1 is usually torn (ulnar and median
nerves)
25. Motor Effects: paralysis of all the
small muscles of the hand.
Sensory effects: loss of sensation
along the medial side of the arm.
deformity: claw hand caused by
hyperextension of the
metacarpophalangeal joints and
flexion of the interphalangeal
joints.
26.
27. Axillary Nerve injury
Causes:
crutch pressing upward into the
armpit,
Downward shoulder dislocations
fractures of the surgical neck of the
humerus.
28. Motor effects:
Deltoidparalysis
teres minor paralysis.
Sensory effects:
lossof sensation at lower ½ of
deltoid
Deformity:
Wasting of deltoid
29.
30. Radial Nerve injury
Injury in axilla :
crutch pressing up into armpit
drunkard falling asleep with
one arm over the back of a
chair.
fractures of proximal humerus.
31. Motor effects:paralysis of
triceps
Anconeus
extensors of the wrist
Extensors of fingers.
Brachioradialis
supinator muscle
Deformity: Wrist and finger
drop
32. Sensory effects :
small area of sansation
loss at arm and forearm
sensory loss over lateral
part of the dorsum of the
hand (lat. 3.5 fingers
without distal phalynges)
33. Injuries at Spiral Groove
Caused by fracture shaft of humerus.
Motor effects: paralysis of
extensors of the wrist
Extensors of fingers
34. Deformity:
Wrist and finger drop
Sensory effects:
anesthesia is present over the
dorsal surface of the hand (lat.
3.5 fingers)
35.
36.
37. Median Nerve
injury
Motor effects: paralysis of
pronator muscles
long flexor muscles of the wrist
and fingers,
Exception:
e. flexor carpi ulnaris
f. medial half flexor digitorum profundus.
38. Deformity:
apelike hand
3.thenar muscles wasted
4.thumb is laterally rotated and
adducted.
5.index and to a lesser extent
the middle fingers tend to
remain straight on making
6.Weakening of lat. 2 fingers
39. Sensory:
Sensory loss on the lat. 3.5
fingers on palmar side
Sensory loss over distal
phalynges of lat. 4 fingers on
dorsal surface
40.
41.
42.
43. Ulnar nerve injury
Motor effects: paralysis of
flexor carpi ulnaris
medial half of the flexor digitorum
profundus
All interossei
3-4 lumbricals
loss of abduction and adduction of
fingers
Wasting of hypothenar
44. Deformity:
partial
claw hand
Sensory effects :
Sensory loss over 1.5 fingers on
both surfaces
45.
46.
47.
48. CARPAL TUNNEL
TUNNEL FORMED BETWEEN THE CONCAVITY OF THE
CARPAL BONES AND A LIGAMENT THAT COVERS
THIS( FLEXOR RETINACULAM)
TENDONS OF THE FLEXORS PASS THROUGH
MEDIAN NERVE ALSO PASSES THROUGH
CROWDED TUNNEL
CARPAL TUNNEL SYNDROME
- CAUSED DUE TO COMPRESSION OF THE NERVE IN THE
TUNNEL
- CAUSES-
- 1. SWELLING OF THE TEDONS( OVERUSE)
- 2. PREGNANCY( EDEMA)
- 3. ARTHRITIS
SYMPTOMS- TINGLING OR NUMBNESS-LATERAL PART OF HAND,
WEAKNESS IN THUMB MOVEMENT
TREATMENT- REST, SPLINTING,ANTI-INFLAMMATORY DRUGS,
SURGERY
49. Diagnosis
Relies mainly on clinical examination
No specific lab. Studies
CT myelography
MRI
Nerve conduction studies
50. Treatment
Most injuries recover without any Rx
Rx is done in very highly specialized
centers
Surgical options
d. nerve transfers
e. nerve grafting
f. muscle transfers
g. free muscle transfers
h. neurolysis of scar around the brachial
plexus in incomplete lesions.
51. Advances in nerve injury Rx
Carlstedt obtained promising initial
results with the repair of preganglionic
lesions by replanting nerve rootlets
directly into the spinal cord.
This is a dramatic advance because
preganglionic lesions were previously
thought to be irreparable
52. End-to-side radial sensory to
median nerve transfer has
been reported to improve
sensation and to relieve pain
in C5 and C6 nerve root
avulsion