Brachial plexus Flashcards
outline the various components of the brachial plexus
roots
trunks
divisions
cords
branches
what are the spinal nerves part of
the peripheral nerve system
how many pairs of spinal nerves
31 pairs
where of spinal nerves arise from
dorsal and ventral roots
what fibres are from the dorsal root
afferent sensory fibres (body -> brain)
what fibres are from the ventral root
efferent motor fibres (brain -> muscle)
what do dorsal and ventral roots merge into
single spinal nerve
containing sensory and motor fibres (mixed nerve)
what do the spinal nerves exit via
intervertebral foramen
what does the intervertebral formed divide into
dorsal / posterior ramus
venture / anterior ramus
what forms a plexus
some rami (ramus) from different spinal nerves will anastomose into a plexus ( e.g brachial plexus )
what is a plexus
a network of intersecting nerves or vessels (arteries)
what is a nerve plexus
a network of intersecting nerve fibres from different spinal nerves that serve the sam part of the body
terminate distally as individual nerves
what spinal nerves form brachial plexus
Anterior rami
spinal nerve C5 -T1
what are dermatomes
an area of skin in which sensory peripheral nerves derive from a single spinal nerve root
each spinal nerve relays sensation form a particular region of the skin to the brain
cervical nerves
C1-C8
carry sensation from cevical dermatomes (C2-C8)
head neck majority of arm and hand
how come there are only 30 dermatomes but 31 pairs of spinal nerves
C1 spinal nerve does not have a dorsal root so does not carry sensory information from the skin
thoracic nerves
T1-T12
carry sensation from thoracic dermatomes
(torso , inner part of arm )
lumbar nerves
L1-L5
carry sensation from lumbar dermatomes
(groin area, majority of lower limbs)
sacral nerves
S1-S5
carry sensation from sacral dermatomes
(minority of lower limbs, perianal region, genitals)
coccygeal nerve
C0
Carry sensation from coccyx (Co1)
(coccygeal region - around the tailbone)
what are myotomes
muscle innervated by a single spinal nerve
each spinal nerve relays motor information to a particular set of muscles
most muscle = more than one myotomes - receive innervation from more than one spinal nerve
brachial plexus
a complex intercommunicating network of nerves
provides sensory and motor innervation to upper extremity
areas supplied by branchial plexus - Sensory innervation
upper limb except area of the skin near the axilla
areas supplied by branchial plexus - motor innervation
muscles of upper limb
should girdle except trapezius muscle
roots
C5, C6, C7, C8, T1
trunks
superior
middle
inferior
divisions
anterior or posterior
cords
material
posterior
medial
terminal branches
musculocutaneous nerve
axillary nerve
radial nerve
median nerve
ulnar nerve
where do the roots of brachial plexus emerge
anterior rami C5-T1 spinal nerves emerge from respective interveteral foramen
where do the roots of brachial plexus lie
lie in posterior triangle of the neck between anterior and medial scalene muscles
when do roots unite to form trunks
shortly after exiting foramen the roots -> trunks
what part of the trunk do the C5 and C6 roots form
superior upper trunk
what part of the trunk does the C7 root form
middle trunk
what part of the trunk does the C8 and T1 roots form
inferior lower trunk
what muscles does the trunk of brachial plexus pass through
anterior and medial scalene muscles
where is trunk of brachial plexus
cross base of posterior triangle of the neck
passes over apex of lung and first rib towards clavicle
what and where does the trunk divide
at posterior aspect of the middle third of the clavicle trunks split into divisions
how many anterior and posterior divisions are there
3 anterior (superior, middle and inferior trunks)
3 posterior (superior, middle and inferior trunks)
where do the divisions pass
both divisions pass inferiorly behind clavicle
enter axilla and combine to form cords
3 cords
lateral cord
posterior ord
medial cord
lateral cord
anterior divisions from superior and middle trunks
contain fibres from C5, C6,C7
posterior cord
3 posterior divisions
contain fibres from C5 C6 C8 C8 T1
medial cord
anterior division from inferior trunk
contain fibres from C8 T1
first part of axillary artery
posterior and lateral cords - super-lateral to artery
medial cord = posterior to artery
second part of axillary artery
posterior cord = posterior to artery
medial cord = medial to artery
lateral cord = lateral to artery
3rd part of axillary artery
cords terminate by elongating into 5 terminal branches
terminal branches of lateral cord
musculocutaneous nerve
lateral root of median nerve
terminal branches of posterior cord
redial nerve
axillary nerve
terminal branches of medial cord
ulnar nerve
medial root of median nerve
pre sized brachial plexus
plexus is derived from C4-C8
post fixed brachial plexus
plexus is derived from C6-T2
where do pre terminal nerves arise from
roots trunks and cords of the plexus
where does long thoracic nerve originate from
C5, C6, C7
Innervates the serratus anterior muscle
flexion
decrease angle between 2 body parts
extension
increase angle between 2 body parts
abduction
away form midline
adduction
towards midline
supination
palm up
pronation
palm down
route of musculocutaneous nerve
formed in axilla
passes down flexor compartment of the arm
eerges lateral to biceps tendon
continues into forearm as lateral cutaneous nerve
musculoctaneous nerve = sensory (arm)
sensory information
lateral half of anterior forearm
small lateral part of posterior forearm
musculoctaneous nerve motor (arm)
biceps brachii - flexion of arm and forearm
coracobrachialis - flexion of arm
brachial - flexion of forearm
and forearm supination
What happens if musculoctaneous nerve is damaged
affect ..
sensation of innervated skin
flexion at shoulder and elbow
supination of forearm
route of axillary nerve
Ford in axilla
exits axilla at inferior border of subscapularis muscle
divides into 3 terminal branches at surgical neck of humerus
- anterior terminal branch
- posterior terminal branch
- articular branch
axillary nerve sensory function
provides sensory information from
inferior lateral deltoid region ( regimental badge area)
axillary nerve motor function
innervates
teres minor - later / eternal rotation of arm
deltoid - arm abduction (15 degrees onward )
what happens if the axillary nerve is damaged
sensation of innervated skin
arm abduction from 15 degrees onwards
route of median nerve
Axilla -> descends down arm alongside brachial artery (laterally then medially halfway down arm ) -> enters forearm at cubital fossa -> travels down forearm -> gives of 2 main branches en route through forearm -> enter hand via carpal tunnel -> 2 terminal branches in the hand
sensory function of median nerve
Proximal part of palm
Palmar surface and fingertips of lateral 3 ½ digits
motor function of median nerve
Innervates
Majority of muscle in anterior forearm
Remaining 2 muscles supplied by ulnar nerve
Thenar muscles (movements of the thumb)
Lateral 2 lumbrical muscles (flexion at metacarpophalangeal joints and extension at interphalangeal joints of the index and middle fingers)
damage at elbow - medial nerve
Damage at elbow
cubital fossa
Lack of sensation over palmer surface and fingertips of lateral 31/2 digits
Weakness of pronation of forearm and wrist flexion
Weakness in flexion of index and middle fingers
Weakness in thumb flexion
damage at wrist - medial nerve
Damage at wrist
Lack of sensation over distal palmer surface and fingertips of lateral 31/2 digits
Weakness in flexion of index and middle fingers
Weakness in thumb flexion
route of radial nerve
Axilla -> exits axilla and travels in radial /spiral groove of humerus -> travels on the lateral part of the elbow through cubital fossa -> enters the forearm and terminated by dividing into 2 branches
sensory function of radial nerve
Arm branches prior to radial groove
Posterior surface of the arm
Arm branches coming off in groove
Lateral surface of arm
strip of skin down middle of posterior forearm
Terminal branches
dorsal surface of lateral 31/2 digits (not fingertips) + associated area on dorsum of hand
motor function of radial nerve
Innervates
Branches in arm (triceps brachii – extends arm at elbow)
Terminal branches ( muscles in posterior compartment of forearm – extend at the wrist and finger joints and supinate the forearm)
damage at arm - radial nerve
Damage at arm (spiral groove)
Lack of sensation in lateral and posterior arm , posterior forearm , dorsal surface of later 31/2 digits and associated area of dorsum of hand
inability to extend at forearm , extend at wrist and fingers
Wrist drop = as wrist flexors are unopposed
damage at forearm - radial nerve
Damage at forearm
Lack of sensation on dorsal surface of the lateral 31/2 digits and associated area of dorsum of hand
Weakness in extension at wrist and fingers
NO wrist drop
route of ulnar nerve
Axilla -> Exits axilla and descends down the arm -> Mid way down the arm it enters posterior compartment of the arm -> travels posterior to the elbow through cubital (ulnar) tunnel -> travels alongside ulna in forearm + gives of 3 main branches -> enters hand via ulnar canal (guyons canal) -> terminates in superficial and deep branches
sensory functions of ulnar nerve
Sensory information
Medial 11/2 fingers and the associate dorsal and palmar area of hand
motor function of ulnar nerve
Sensory information
Medial 11/2 fingers and the associate dorsal and palmar area of hand
Innervates
2 muscle of forearm – flexes and adducts hand at wrist
The major of the intrinsic hand muscles - abduction and adduction of fingers – movement of 4th and 5th digits – thumb adduction
damage at elbow ulnar nerve
Damage at elbow
Less clawing
Affects all the sensory and motor branches of the ulnar nerve results in –
Loss of sensation in medial 1 ½ digits and the associated dorsal and palmar area of hand
Impaired ability to flex and adduct wrist
Impaired movement of the 4th and 5th digits and thumb adduction
Loss of abduction and adduction of the fingers
damage at wrist ulnar nerve
Damage at wrist
More clawing
Loss of sensation over palmar side of medial 11/2 digits and distal palm area
Only the intrinsic muscle of the hand are affected
Impaired movement of the 4th and 5th digits and thumb adduction
Loss of abduction and adduction of the finger
Hyper extension of the 4th and 5th metacarpophalangeal joints and flexion at the interphalangeal
More prominent in distal (wrist) as opposed to proximal (elbow) ulnar nerve damage
what is the test for ulnar nerve damage
forments sign test
* patient asked to grip a piece of paper between thumb and index finger
* positive front sign= patient hyper flexes thumb and can’t grip paper = ulnar nerve damage
cubital fossa
elbow pit - a small triangular area located on the anterior surface of the elbow
cubital fossa
elbow pit - a small triangular area located on the anterior surface of the elbow
Why is there wrist drop in radial nerve damage at the axilla and the arm but not the forearm?
because damage to the radial nerve that occurs before the forearm will result in wrist drop, but the muscles innervation branches off prior to the forearm , so that muscle maintains extension at the wrist
Why are only the intrinsic muscles of the hand affected by ulnar nerve damage at the wrist?
because the 2 forearm muscles supplied by the ulnar nerve are not affected because their branches come off before the wrist.
what is claw hand
hyperextension of the 4th and 5th metacaropophalageal joints and flexion at the interphalageal
What type of ulnar damage gives rise to more prominent claw hand?
more prominent in distal distal (wrist) as opposed to proximal (elbow) ulnar nerve damage
what are the types of brachial plexus injuries
avulsion, rupture, stretching, compression
common symptoms of brachial plexus injury
- reduced/absent sensation in arm or Hand
- weakness/paralysis of shoulder, arm, wrist or hand
- mild severe pain in shoulder or arm
treatment of a brachial plexus injury
- may resolve
- non surgical - physiotherapy steroid
- surgery - nere repair/ graft/ transfer
What nerves are damages in Erbs palsy and what does this cause
to injury of C5-C6
Paralysis of upper brachial plexus
what is Erbs Palsy caused by
Excessive increase in angle between neck and shoulder due to trauma or birth
what nerves are affected due to Erbs palsy
Axillary
Impact musclocutaneous, radial and median
what motor (myotomes) are affects by Erbs palsy
C5 and C6 myotomes
what sensory (dermatomes) are affected by Erbs palsy
C5 and C6 dermatomes
what are the symptoms / signs of Erbs Palsy
Arm extended and wrist fully flexed (waiters tip)
what part of brachial plexus is damaged in Klumpke palsy
Paralysis of upper brachial plexus due to injury to C8-T1
what can cause Klempke palsy
Hyper abduction of arm (trauma)
birth
what is more common at birth Erbs or Klumke palsy
Erbs palsy is more common at birth
what nerves are affected by klumpkes palsy
Ulnar
Radial and median
what causes carpal tunnel syndrome
compression of the median nerve within the carpal tunnel
what risk factors cause carpal tunnel syndrome
repetivitive weist movement
obesity
autoimmune disease
what are the sensory clinical features of carpal tunnel syndrome
numbness
tingling
pain in distribution of skin supplied by distal median nerve
distal palmer surface and fingertips of lateral 3 1/2 digits
what are the motor clinical features of carpal tunnel syndrome
weakness of first and second lumbricals and thenar muscles
weakness in flexion of index and middle finger and thumb
what can cause humeral shaft fracture and radial nerve damage
fractured of shaft often from trauma
why is the radial nerve at increased risk of damage
as radial nerve travels through radial groove
increase risk of damage
what are the sensory clinical features of humeral shaft fracture/radial nerve damage
numbness, tingling pain in distribution of skin supplied by radial nerve
dorsal surface of lateral 31/2 digits and associated area on dorm of hand
sensory loss of forearm
what are the motor clinical features of humeral shaft fracture/ radial nerve damage
weakness of muscles in posterior forearm
weakness in forearm extension
unable to extend at wrist and fingers
wrist drop
what nerve is most likely to be damages if a fracture is at the proximal humerus / scapula such as a (glenohumeral dislocation)
axillary nerves (glenohumeral dislocation)
what is th most common cause of axillary damage
(glenohumeral dislocation)
what nerve is most likely to be damages if a fracture is at supracondylar
median nerve
the radial nerve
rare= ulnar nerve
what nerve can be compressed in cubital tunnel syndrome
ulnar nerve
= ulnar neuropathy
what are the risk factors of capital tunnel syndrome/ulnar neuropathy
prolonged elbox flexion
leaning on elbows
what are the sensory clinical features of cubital tunnel syndrome/ulnar neuropathy
numbness tingling pain in distribution of skin supplied by ulnar nerve
medial 11/2 digits and associated area on palm of hand
what are the motor clinical features of cubital tunnel syndrome/ulnar neuropathy
weakness of 2 muscle of forearm and majority of intrinsic hand muscle
loss of abduction and adduction of fingers
weakness of movement of 4th and 5th digits and thumb adduction
minimal ulnar claw
