Brachial Plexus Flashcards
What is the most common mechanism for brachial plexus injuries?
Closed injury (traction, compression, or combination of the two).
What is the most common location of brachial plexus injuries?
Supraclavicular, root and trunks.
What is the typical mechanism of a C8-T1/lower trunk traction injury?
Forceful abduction of the arm overhead.
What brachial plexus injury is typically produced by violent lateral bending of the head and neck?
Traction injury of C5, C6/upper trunk.
What is a common site for brachial plexus compression injuries?
Between clavicle and first rib, near the coracoid process.
What are the demographics of the majority of patients with brachial plexus injuries?
Male, aged 15 to 25.
What proportion of brachial plexus injuries occur in motor vehicle accidents?
70%.
What type of vehicle is most commonly implicated in brachial plexus injuries?
The motorcycle (70% of motor vehicle accidents). Snow mobiles in colder climates.
At what level do most root avulsions occur?
Lower roots (C7, C8, T1)
How many nerve roots form the brachial plexus?
Five (C5–8, T1).
What term describes a contribution of the C4 nerve root to the brachial plexus?
Prefixed plexus
What phenomenon is described by the term “postfixed” brachial plexus?
T2 contribution to the plexus
What are the five separate sections of the brachial plexus?
Roots, trunks, divisions, cords, terminal branches.
(Robert Taylor Drinks Coffee Black)
What structure is formed by coalescence of the ventral and dorsal rootlets?
The nerve root.
What vascular structure is associated with the C7 root in the exposure of the cervical region of the brachial plexus?
Transverse cervical artery.
The medial cord of the brachial plexus receives contributions from which nerve roots?
C8 and T1.
Where does the nerve root leave the spinal canal?
Through the neuroforamen.
What is contained in the dorsal root ganglion?
The cell bodies of the sensory nerves.
Where do the motor nerves travel?
In the volar root ganglion. (V-volar, Vroom!!)
What is described by the term preganglionic brachial plexus lesion?
- lesion proximal to the dorsal root ganglion
- intradural rupture of the rootlets
- avulsion from spinal cord
How are the upper, middle, and lower trunk typically formed?
Upper trunk by C5 and C6.
Middle trunk by C7.
Lower trunk by C8 and T1.
What is Erb point?
Point where C5 and C6 merge to form upper trunk.
What structures join to become the posterior cord?
All three posterior divisions.
What is formed by the anterior divisions of the upper and middle trunk?
The lateral cord.
(Imagine a football announcer, “Number 34 runs up [upper trunk] the middle [middle trunk] and throws a lateral [lateral cord]!”)
What continues as the medial cord?
The anterior division of the lower trunk.
The cords are named after their location in relation to which structure?
The axillary artery.
What part of the brachial plexus crosses underneath the clavicle?
The divisions.
What muscles are innervated by the dorsal scapular nerve?
Rhomboid major/minor and levator scapulae.
What are the terminal branches of the posterior cord?
Proximal to distal:
1. upper subscapular n. 2. thoracodorsal n.
3. lower subscapular n. 4. axillary n.
5. radial n.
What branches originate at the C5 root level?
- phrenic n. contribution
- long thoracic n. contribution
- dorsal scapular n. (levator scapulae, rhomboids)
What are the terminal branches of the medial cord?
Four “medial (or median)” structures and the ulnar nerve.
Medial pectoral n.
medial brachial cutaneous n. medial antebrachial cutaneous n. contribution to the median n. ulnar n.
What are the branches of the lateral cord?
- lateral pectoral n.
- contribution to the median n. 3. musculocutaneous n.
What branches originate from the upper trunk?
Suprascapular n. nerve to the subclavius.
Where is the inferior cervical sympathetic ganglion located?
In proximity of the T1 nerve root.
What is Horner syndrome?
- ptosis
- miosis
- anhydrosis
- enophthalmos
This constellation indicates a lesion of the cervicothoracic sympathetic ganglion (adjacent to C8, T1) disrupting the oculosympathetic pathway.
How is muscle strength graded?
By the British Medical Research Council grading system:
M0: no evidence of contractility
M1: evidence of contractility but no motion
M2: complete range of motion with gravity eliminated M3: complete range of motion against gravity
M4: complete range of motion against some resistance M5: normal power
Examination of which upper extremity functions will test for the condition of the posterior cord?
- wrist extension (radial n.)
- elbow extension (radial n.)
- shoulder abduction (axillary n. via deltoid)
How can the condition of the suprascapular n. be tested?
- shoulder elevation (supraspinatus)
- external rotation (infraspinatus)
What is a strong indicator for a preganglionic lesion at the C8 and T1 nerve roots?
Presence of a Horner syndrome (indicating a lesion of the cervicothoracic sympathetic ganglion [adjacent to C8,
T1]).
Dysfunction of which nerve will result in scapular winging with forward elevation of the shoulder?
Long thoracic nerve via serratus anterior (SALT—serratus anterior long thoracic).
What is the significance of transverse process fractures on the cervical spine x-rays in brachial plexus patients?
May indicate root avulsion.
What findings on a chest x-ray may point toward a brachial plexus lesion?
Fractures of the first and second rib.
What is the significance of pseudomeningoceles on a cervical CT myelogram?
Indicates root level injury.
What finding would be expected on the chest x-rays of patients with phrenic nerve injury?
Elevation of ipsilateral hemidiaphragm.
What do fibrillation potentials in the EMG indicate?
Denervation of the tested muscles (just like the heart fibrillates when it is dying).
After acute brachial plexus injury, how soon would muscles exhibit fibrillations in the EMG?
10 to 14 days for proximal muscles and 3 to 4 months for distal muscles.
What evidence can be found in electrodiagnostic studies of preganglionic lesions?
Preservation of sensory nerve action potentials (SNAPs).
What is the significance of the appearance of nascent potentials in follow-up EMGs?
Early sign of reinnervation.
What does the presence of intraoperative nerve action potentials (NAPs) across a lesion indicate?
Intact axons.
How many patients with detectable NAPs across a lesion will make a clinically useful recovery?
90%.
What pattern of NAPs would be expected in a preganglionic plexus lesion?
Accelerated conduction velocity with increased amplitude.
What do motor evoked potentials assess?
Integrity of motor pathway via the ventral root (remember Vroom)
How can the integrity of the sensory pathway via the dorsal roots be tested?
Somatosensory evoked potentials.
When is immediate exploration and primary repair of brachial plexus injuries indicated?
Sharp, open injuries.
What is the preferred treatment for low-velocity gunshot wounds of the brachial plexus?
Observation, local would management.
What type of nerve injury is typically associated with low-velocity gunshot wounds?
Neuropraxia.
What is the recommended time frame for brachial plexus exploration in stretch injuries that fail to recover?
3 to 6 months.
What is the order of priority for restoration of function to the flail extremity?
- elbow flexion
- shoulder abduction/stability
- hand sensibility
- wrist extension/finger flexion
- wrist flexion and finger extension
What type of injury is preferably addressed with primary nerve repair?
Sharp laceration, not possible in stretch injuries.
What procedure needs to be performed to facilitate intraoperative nerve conduction studies?
External neurolysis.
What is the treatment for electrically silent ruptures or neuromas of the brachial plexus that are electrically
silent?
Interpositional nerve grafting (eg, sural cable graft).
What upper extremity function should be targeted if interpositional nerve grafting from a functioning C5 nerve root is performed?
Shoulder abduction (suprascapular, axillary nerves).
What nerve root (when available) should be used to restore elbow flexion by interpositional sural nerve grafting?
C6 (musculocutaneous n.).
How can triceps function be restored in a patient with a brachial plexus injury at the trunk level?
By interpositional grafting from C7 across the zone of injury.
What is the likely etiology of neuropathic pain after brachial plexus reconstruction?
Regenerating axons from non-avulsed nerve roots.
What type of brachial plexus injuries requires the use of nerve transfer (neurotization) to restore function?
Preganglionic injuries.
How can a nerve transfer accelerate recovery of function?
By decreasing the distance between the nerve repair site and the end organ (muscle).
What is the Oberlin transfer?
Transfer of select ulnar nerve fascicles in the upper arm to motor branches of the musculocutaneous nerve to the
biceps to restore elbow flexion.
What nerve has been used successfully to neurotize the serratus anterior muscle to address scapular winging?
Thoracodorsal nerve.
What function can be restored by neurotizing the suprascapular nerve with spinal accessory or phrenic nerve?
Shoulder abduction/external rotation.
What nerve can be targeted in addition to suprascapular nerve to further improve shoulder abduction?
Axillary nerve.
What nerve transfers are commonly used for restoration of biceps function after upper trunk disruption?
Medial pectoral nerve to musculocutaneous nerve or the biceps motor branch Oberlin transfer.
What is the advantage of the Oberlin transfer over interpositional nerve grafts from C6 to regain biceps
function?
Faster and more predictable recovery of function.
In the Oberlin transfer fascicles of the ulnar nerve transmitting which function should preferably be used?
Fascicles that stimulate wrist flexion (FCU).
What modification of the Oberlin transfer is available to improve recovery of elbow flexion strength?
Double fascicular nerve transfer described by MacKinnon et al.
What additional muscle is targeted in the double fascicular nerve transfer of the Oberlin transfer?
Brachialis muscle.
What donor fascicles are used to neurotize the brachialis muscle in the double fascicular nerve transfer?
FCR or FDS fascicles of the median nerve.
What donor nerves are available for neurotization to restore elbow flexion in a “panbrachial” plexopathy without signs of recovery?
- intercostal nerves
- spinal accessory via nerve grafts
- phrenic nerve with interpositional grafts
Comparing intercostal and partial ulnar nerve transfers to the biceps branch of the musculocutaneous nerve, which restores elbow flexion more successfully?
Partial ulnar nerve (Oberlin).
What is the advantage of a vascularized nerve graft?
Reinnervation at a faster rate (theoretically)
What contralateral nerve root can be used as a donor of large amounts of motor axons?
C7—usually half of it.
What function is addressed by contralateral C7 transfer via vascularized ulnar nerve to the median nerve?
Finger flexion.
What overall success rate can be expected with nerve transfers to the musculocutaneous nerve?
71% flexion strength > M3, 37% > M4.
What is the success rate of the Oberlin transfer?
97% for >M3, 94%>M4.
How much shoulder abduction can be expected in a good result after nerve transfer?
45◦ .
What options are available for restoration of elbow flexion in patients that present late (>12 months after
injury)?
- free functioning muscle transfer
- tendon transfer of available, expendable muscles
- Steindler flexorplasty (transposition of flexor-pronator origin to anterior humerus) 4. pectoralis major transfer
- latissimus dorsi transfer
- triceps transfer
What are the risk factors for obstetrical brachial plexus palsy?
- increased birth weight
- vertex presentation
- births that require instrumentation for delivery 4. shoulder dystocia
What are causes for obstetric brachial plexus injury (birth palsy)?
Traction injury secondary to
fetal malposition cephalopelvic disproportion forceps use
What are the three distributions observed in obstetric brachial plexus palsy?
- Erb palsy
- Panplexus palsy 3. Klumpke palsy
What nerve roots are involved in Erb palsy?
C5-6—upper roots.
What nerve roots are involved in Klumpke palsy?
C5-T1—lower roots.
What is considered an indication for surgery in obstetric brachial plexus injuries?
Absent biceps recovery at age 3 months.
What does the Mallet classification assess?
Upper extremity function
Which root levels are more likely to be affected by root avulsions?
Lower levels C8, T1.
What is the mainstay for treatment of children with partial lesions?
- Conservative treatment
- ROM exercises
- Prevention of contractures
What is the typical pattern of contracture of the shoulder in children with brachial plexus birth palsy?
Internal rotation
Adduction.
What is a common complication due the internal rotation contracture in children with brachial plexus birth palsy?
Posterior shoulder dislocation.
What nonsurgical treatment can be used to treat early posterior shoulder dislocation due to internal rotation contracture?
Closed reduction and Botulinum toxin A injection into the shoulder internal rotators.
What tendon transfer can be used to improve external rotation of the shoulder and prevent the development of internal rotation contracture?
Transfer of latissimus dorsi and teres major to the humeral greater tuberosity.
What deformity of the elbow will frequently develop in children with obstetric brachial plexus palsy?
Posterior radial head dislocation. Typically by age 5 to 8 years.
What is a typical finding at the forearm in children with obstetric palsy?
Supination contracture.
