Brachial plexus Flashcards
What is brachial plexus?
A network of nerves innervating muscles of the shoulder, upper chest and arm
Anterior rami of C5 through T1
Where does brachial plexus extend from?
Cervical neural foramina to axilla
What is brachial plexus closely related to?
Scalene muscles
Subclavian artery
Where does the brachial plexus begin?
Root of neck, passes through the axilla and runs through entire upper extremity
What is the brachial plexus formed by?
Anterior rami of cervical spinal nerve C5, C6, C7 and C8 and first thoracic spinal nerve, T1
What are the 5 parts that the brachial plexus is divided into?
- Roots
- Trunks
- Division
- Cord
- Branches
What does the roots refer?
Anterior rami of spinal nerves that comprise the brachial plexus
What are the anterior rami of spinal nerves?
C5, C6, C7, C8 and T1
Where does parties spinal nerves arise?
At each vertebral level
They leave the spinal cord via intervertebral foramina of vertebral column
What does each spinal nerve divide into?
Anterior and posterior ramps
What happens after the formation of the roots?
The nerves pass between anterior and medial scalene muscled to enter base of neck
What happens at the base of the neck?
Roots of brachial plexus converge to form 3 trunks
what are the 3 trunks?
- Superior trunk: combination of C5 and C6 roots
- Middle trunk: combination of C7
- Inferior trunk: combination of C8 and T1 roots
Where does the trunks traverse?
Laterally, crossing posterior triangle of neck
What does each trunk divide into?
2 branches within posterior triangle of the neck
One division moves anteriorly and other posteriorly (anterior and posterior divisions)
3 anterior nerve fibre
3 posterior nerve fibre
Divisions leave posterior triangle and pass into axilla
They recombine into cord of brachial plexus
What happens once the anterior and posterior divisions have entered the axilla?
They combine together to form 3 cords
Baked by their position relative to axillary artery
What are the 3 cords?
- Lateral cord
- Posterior cord
- Medial cord
Lateral cord
- Anterior division of superior trunk
2. Anterior division of middle trunk
Posterior cord
- Posterior division of superior trunk
- Posterior division of middle trunk
- Posterior division of inferior trunk to
Medial cord
- Anterior division of inferior trunk
What do the cords give rise to?
Major branches of brachial plexus
Where does the subclavian artery extend along?
Floor of interscalene triangle between anterior and middle scalene muscles
What does the supraclavicular plexus include?
Roots and trunks
Where is the retroclavicular plexus located?
Costoclavicular space, above subclavian artery and vein
What does the subclavian artery form?
Floor of interscalene triangle
What does the subclavian artery and vein take ?
Name of axillary artery and vein at lateral border of 1st rib
What merges at dorsal root ganglion?
At each vertebral level
Anterior-motor
Posterior-sensory riots exiting from spinal cord within neural foramina
What do both rami include?
A mixture of motor and sensory fibres
What forms brachial plexus?
Anterior rami
Why imaging?
Most brachial plexopathies present with vague and non-specific symptoms
Purely/mostly motor symptoms are generally seen in young patients: usually preganglionic; stretch injury
Mixed sensory and motor plexopathy - usually in older patients, usually post-ganglionic; tumours
Clinical diagnosis: electrodiagnostic studies e.g. ENMG
Brachial plexopathy
A form of peripheral neuropathy
It occurs when there is damage to brachial plexus
Direct injury to the verge; stretching injuries; pressure from Tumours in area or damage that results from radiation therapy
What are specific symptoms of brachial plexopathy?
- Brown-seguards syndrome
- Ipsilateral phrenic nerve involvement
- Ipsilateral scapular singing
- Ipsilateral Horner’s syndrome
Site of injury for brown-seguards syndrome
Spinal cord ipsilateral to avulsion
Site of injury for ipsilateral phrenic nerve involvement
Supraclavicular brachial plexus involving roots, trunks or both
What is site of injury for ipsilateral scapular winging
Proximal branches of C5 through C7
What is site of injury for ipsilateral Horner’s syndrome?
Infraclavicular plexus
What are medications for brachial plexus?
- Mass involving the plexus (intrinsic/extrinsic)
- Traumatic injury (preganglionic/postganglionic)
- Entrapment syndromes (thoracic outlet syndromes: sites of compression)
- Post-treatment evaluation (recurrent tumour vs radiation injury)
- Others (diffuse/focal pathology)
What is magnetic resonance (MR) neurography?
Group of techniques with the potential to allow optimal non-invasive evaluation of many abnormalities of brachial plexus
- Structural
- Microstructural
What MRI is used to observe brachial plexus? I’m
- Coronal STIR sequences - cover both sides
- Sagittal STIR sequences on each side
- Coronal T1w volumetric, isometric with and without gadolinium
What is structural MR neurography?
Evaluation of longitudinal axis of peripheral nerve
What are abnormal findings of brachial plexus?
- Loss of fat planes around all or part of a plexus component
- Diffuse or focal enlargement of a component
- Presence of an eccentric or modular mass
- Marked hyperintensity on STIR
- Enhancement on T1-w images with fat suppression
- Altered fasicular pattern
