General
- Supraclavicular brachial plexus (SBP) injury, is very rare
- Normally associated with traumatic injury.
Injury classification
Variation
- Prefix: Contribution from C4 can be present
- Postfix: Contribution from T2 is present
Supraclavicular Brachial Plexus (SBP)
- Lies superior to the clavicle
- Includes the
- Roots
- Trunks
- Divisions
- Subdivided into
- Proximal to the dorsal root ganglion (DRG).
- Classification (Birch 2011)
- Distal to the dorsal root ganglion (DRG).
- With avulsion injuries the DRG remains intact and therefore no Wallerian degeneration of the sensory nerve takes place and these patients will not have a positive Tinel’s sign
- Erb’s point
- A point half way along the posterior border of the sternocleidomastoid muscle from which all cutaneous branches of the cervical plexus converge and become superficial.
- Lesser occipital nerve
- Greater auricular nerve
- Transverse cervical nerve
- Supraclavicular nerves
- Is the site where C5 and C6 form the upper trunk of the brachial plexus.
- This is clinically particularly important as it is at this location where forces applied to the upper forequarter and head and neck of a patient converge, commonly causing SBPi (Supracalvicular brachial plexus injury).
- Pressure over this point elicits Duchenne-Erb paralysis
- Electrical stimulation over this area causes various arm muscles to contract.
Preganglionic injuries
Injury type | Avulsion location | Dural sleeve | Roots |
A | Avulsion central to the transitional zone (TZ) | Torn fully | Both |
B1 | Avulsion distal to TZ; | Torn fully | Both |
B2 | Avulsion distal to TZ | Intact until foramen | Both |
B3 | root rupture within the spinal canal without DRG displacement or dural rupture | Intact fully | Both |
B4 | Avulsion distal to TZ | Intact fully | Only one of the dorsal or ventral roots |
Postganglionic injuries
- Horner’s syndrome
- Ptosis, miosis, anhidrosis, and enophthalmos
- Associated with
- Total plexal injury
- SBPi affecting the lower plexus
- Due to the simultaneous injury of the sympathetic trunk with preganglionic injury as well as direct spinal, head, or vascular injuries
Infraclavicular Brachial Plexus (ICBP)
- Include
- Cords
- Branches
Numbers
- Incidence of traumatic brachial plexus injury (Bpi)
- 500 cases / year in the UK
- Principally as a result of road traffic collisions (60%)
- High- energy polytrauma motorcycle accidents in young men and are associated with long- bone fractures and head injuries.
- Motorcyclists
- Account for 1% of road users in the United Kingdom
- Account for 20% of all road fatalities and serious injuries
- 7000 serious injuries per year
- As road safety in general is improving, as shown by Keep in 2013, the amount of high- energy accident survivors in the United Kingdom is increasing.
- Between 1990 and 2012 there has been a 66% decrease in the number of people killed in road traffic accidents and a 62% decrease in severe injury.
- SBPi accounts for only 1% of polytrauma patients
- Incidence: 0.3 to 6.3 cases/ 100 000/ year.
- Narakas’s rule of sevens: Seven ‘70% statistics’ regarding BPis,
- 70% of cases involve road accidents,
- 70% of these accidents are motorcyclists
- 70% of these patients present with combined injuries,
- 70% of these lesions are supraclavicular,
- 70% of these lesions involve at least one nerve root avulsion,
- 70% of these avulsions involve a C7, C8, or T1 level nerve root,
- 70% of patients with avulsions develop chronic pain
Mechanism of injury
- Depends on
- Stretching of more than 12% of a nerve
- Duration of nerve ischaemia:
- > 8 hours of ischaemia will result in severe nerve injury.
- Force required to avulse cervical nerve roots
- 200 newtons
- Nerve root exiting angles
- Different forequarter positions at the time of impact will result in differing force vectors and therefore differing injury.
- Mechanism
- Arm and head or neck being pulled away from each other → arm being pulled below horizontally → upper plexal injury,
- The arm being pulled above horizontally → lower plexal injury.
- Dislocated shoulder
- A significant injury
- Can be a risk factor for supra or infraclavicular brachial plexus, (ICBP), injuries.
- Injury is usually to the upper trunk affecting predominately the suprascapular and axillary nerves.
- Many of those who get combined injuries also have an abnormal band of fascia connecting the pectoralis minor to the thoracic wall.
- This effectively narrows the space for the exiting SBP into the ICBP and means these patients are more susceptible to injury.
- Using an average male of 70 kg as an example and a deceleration period over 1 second, it is easy to calculate the starting speeds to generate the force described.
- In order to avulse a nerve root starting speeds of only 5 mph would be required, if the force is imparted on the SBP.
- Other injuries that can be missed
- Arterial injury to the
- Axillary
- Subclavian
- Vertebral vessels;
- Fractures
- Dislocations
- Muscle injuries of the forequarter.
Clinical presentation
- 3 separate distinct patterns of injury that may occur in isolation or combination, namely:
- Supraclavicular brachial plexus injury with preganglionic injury,
- Severe, crushing, unremitting, shooting pain in an insensate arm.
- Pain is usually along the dermatome of the injured spinal nerve.
- Kato in 2006 described a cohort where more than 50% of avulsion patients had significant pain occurring by 24 hours and 90% by 6 weeks postinjury.
- Negative Tinel’s test.
- Injury to nerves branching at or around the root level
- Long thoracic → Serratus anterior
- Dorsal scapular → Levetor scapulae and rhomboid
- Phrenic nerves → Diaphragm
- Supraclavicular brachial plexus injury with postganglionic injury,
- Positive Tinel’s test,
- No Horner’s syndrome,
- No serratus anterior, rhomboid, diaphragmatic dysfunction
- Absent sensory nerve action potentials, (SNAPs) on nerve conduction studies.
- Upper brachial plexopathy (C5, C6)
- Erb’s palsy
- A characteristic posture referred to as the ‘waiter’s tip’ position, namely, shoulder adduction and medial rotation, elbow extension, and forearm pronation.
- Increase in angle between neck & shoulder.
- Traction (stretching or avulsion) of upper ventral rami (e.g. C5, C6)
- Lower brachial plexopathy (C8, T1)
- Klumpke’s palsy:
- In elbow flexion, forearm supination, extreme wrist extension, and clawing of the hand as a result of weakness in the small muscles of the hand.
- Excessive upward pull of limb.
- Traction (stretching or avulsion) of lower ventral rami (e.g. C8, T1)
- Infraclavicular brachial plexus injury
Investigations
MRI
- Investigation of choice
- Extremely useful in SBPi but interpretation of the SBP portion can be challenging with conventional MRI.
- Special sq to to assess both pre- and postganglionic nerves
- Magnetic resonance neurography (MRN)
- Requires > 3- Tesla
- Provide an excellent form of non-invasive imaging of any peripheral nerve.
- Magnetic resonance myelography (MRM)
- MRM is useful to assess the preganglionic SBP, which is also non- invasive and just as efficient as traditional myelography in detecting injuries at this level.
- MRM does not require contrast medium injection into the spinal canal or radiation.
- Combining these two imaging modalities together can revolutionize the diagnosis and management of SBPi, especially in non- specialist centres.
CT and CT angiography
- Vascular injury and/ or haematomas, which are common in SBPi, will cause a significant fibrotic reaction around the SBP.
- This, on top of the initial injury, can be enough to cause a permanent conduction block, without surgical intervention.
CT myelography
- Require intradural injections.
- Assessing nerve root avulsions
- Meningoceles or pseudomeningoceles. The lower nerve roots of the SBP can be difficult to distinguish due to the artefact created by the lower cervical and upper thoracic spinal vertebrae.
Plain X- rays
- CXR
- Raised hemi- diaphragm → a phrenic nerve injury
- Thoracic trauma
- C spine
- Transverse process fractures = nerve root avulsion injuries.
- Forequarter X- rays
- Humeral, scapula, clavicular fractures, and shoulder girdle injuries
Electrodiagnostic testing
- Good adjunct to sensory and motor examination and imaging.
ㅤ | Conduction velocity | MUAPs | CMAPs | SNAPs | To be aware |
Neuropraxia | Maintained | None | Normal, slight reduction proximally | Reduced | Permanent conduction slowing due to thinner internodes |
Axonotmesis | Reduced | None | Reduced proportional to axonal loss | Reduced | Positive sharp waves and fibrillations |
Neurotmesis | Nil | None | Reduced proportional to axonal loss | Absent | Positive sharp waves and fibrillations |
- EMG and NCS
- Can both be used to demonstrate an injured nerve segment,
- Will not show axonal transection.
- EMG
- Motor unit action potentials (MUAPs)-EMG
- Ask patient to contract muscle
- To evaluate the electrical activity of muscle during rest and during activity.
- Denervated muscle changes can be seen as early as 1 week after an injury and the speed with which this change can be detected is inversely related to the nerve length.
- The longer the axons = the longer the Wallerian degeneration will take → longer it takes for EMG changes
- Distal muscles taking 3– 6 weeks to demonstrate denervation.
- When significant nerve injury has taken place, there will be EMG changes immediately but only a skilled Neurophysiologist will be able to detect this.
- Nerve conduction studies (NCS)
- SNAPs
- SNAPs are preserved in lesions proximal to the dorsal root ganglion therefore preganglionic injuries will have normal SNAPs with abnormal MUAPs
- Compound motor action potentials (CMAPs)
- Important for distinguishing pre- and postganglionic nerve injuries.
Histamine test
- Not routinely performed due to the improvements in BPi imaging and diagnosis.
- An intradermal injection of histamine will normally cause a triple response as follows,
- A red reaction due to direct capillary dilatation → a wheal due to fluid extravasation from increased permeability of vessels → a flare of redness in the surrounding area which is caused by arteriolar dilatation mediated by the axon reflex in the sensory nerve distribution.
- On the left side of the picture, a positive test can be seen (yellow arrows: secondary hyperemia). On the right side, absence of neurogenic inflammation can be observed.
- The histamine test can be used to distinguish between pre- and postganglionic lesions.
- Preganglionic lesion the afferent axons remain intact therefore a normal triple response with flare will be seen.
- Postganglionic lesion the sensory cell body and axon are not connected, and the afferent axons are degenerated therefore only the initial redness and the wheal are seen, the flare response is absent.
Images
Q&A
- What muscles does the brachial plexus pass between?
- The anterior and middle scalene.
- The C5 root is usually adherent to the lateral border of what muscle?
- The anterior scalene muscle.
- What muscle does the musculocutaneous nerve pass through?
- The coracobrachialis. The nerve enters the muscle from the medial side 5 cm distal to the coracoid process. The musculocutaneous nerve has only motor innervation above the elbow and sensory innervation below the elbow.
- How can one differentiate a C6 root lesion from a lesion of the musculocutaneous nerve?
- A C6 root lesion affects the biceps, brachioradialis, and brachialis muscles; a musculocutaneous nerve lesion spares the brachioradialis.
- What findings would indicate that a brachial plexus lesion is very proximal?
- Rhomboid paralysis and winging of the scapula due to loss of serratus anterior muscle function
- Phrenic nerve paralysis
- Cervical spine fracture with or without myelopathy
- Extensive paraspinal denervation
- Presence of meningoceles at multiple levels as shown on myelography
- Presence of a Horner syndrome
- Peripheral sensory potentials or positive results for multiple nerves on histamine injection tests
- What types of arm abduction are affected in a C5 root injury compared with an axillary nerve injury?
- A C5 root injury affects Deltoid and supraspinatous muscle (180° of shoulder abduction); an axillary nerve injury affects Deltoid muscle (only the second 90° of movement).
- Which first branch from the posterior cord supplies the “cough muscle”?
- The thoracodorsal nerve supplying the latissimus dorsi, which contracts when one coughs.
- What can cause a lower root injury, and why are these roots more susceptible to injury?
- A lower root injury (C8 and T1) may be caused by forceful abduction of the shoulder. A lower root injury produces weakness in intrinsics of the hand as well as long flexors and extensors of the fingers. Sensory deficit is along the medial aspect of the arm, forearm, and hand. There may be an associated Horner syndrome if there is a T1-associated preganglionic injury due to disruption of the first sympathetic ganglion. The reason why the lower roots are more susceptible is because the upper roots are secured in their respective vertebrae; the lower roots are not as well secured.
- How can one differentiate ulnar palsy from T1 root lesion?
- The abductor pollicis brevis (invariably median nerve innervated) is spared in ulnar neuropathy, but involved in a T1 lesion.
- What is the thoracic outlet?
- A space bounded by the clavicle, first rib, subclavius muscle, costoclavicular ligament, and anterior scalene muscle.
- What are some C7 muscle movements that are not involved with the radial nerve?
- Shoulder adduction and wrist flexion.
- What are the types of entrapment that result in weakness specific to the supraspinatus and/or infraspinatus muscles?
- Compression at the scapular notch by the suprascapular ligament (or a cyst) results in weakness of the supraspinatus and infraspinatus muscles. If compression occurs at the spinoglenoid notch (after branches have left for the supraspinatus), then only the infraspinatus muscle is affected. The supraspinatus is involved with glenohumeral joint stability and abduction of the humerus. The infraspinatus is mainly involved with external rotation of the upper arm.
- Where is the site of entrapment of the suprascapular nerve?
- Within the suprascapular notch beneath the transverse scapular ligament. Entrapment results in atrophy of the infra- and supraspinatus muscles as well as deep, poorly localized shoulder pain. This is due to the fact that this nerve carries sensation from the posterior joint capsule, but has no cutaneous representation.
- Which nerve roots are usually affected in true neurogenic thoracic outlet syndrome?
- The C8 and T1 nerve roots. Thoracic outlet syndrome is most commonly due to a cervical rib or to an elongated C7 transverse process.
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