14 - Brachial Plexus Flashcards
What nerve roots does the brachial plexus contain, where does it start and terminate?
- Anterior rami of C5 to T1
- Starts in neck and terminates in axilla
How is the brachial plexus divided into five parts?
- Roots
- Trunks
- Divisions
- Cords
- Branches
What do the posterior rami of C5-T1 innervate?
The skin of the back and the muscles of the back
How do the roots of the brachial plexus pass to where they converge to form trunks?
- Pass between anterior and middle scalene muscles to enter posterior triangle of neck
- At base of neck they form three trunks: superior, middle and inferior
What nerve root does each trunk contain?
- Superior: C5 and C6
- Middle: C7
- Inferior: C8 and T1
Where do the trunks of the brachial plexus go next and what do they combine to form?
- Posterior triangle of neck
- Form divisions, anterior and posterior, which leave posterior traingle and go into axilla
Where do the divisions of the brachial plexus go and what do they form?
- From posterior triangle into the axilla where they form cords
- Named by position relative to axillary artery
- Lateral, posterior and medial
What are each of the three cords made from?
- Lateral cord: anterior divisions of superior and middle trunks
- Posterior cord: Posteriors of all three trunks
- Medial cord: Continuation of inferior trunk
How do the cords then form branches in the brachial plexus and what do they supply?
- Musculocutaneous, median and ulnar from anterior divisions supply the flexor muscles
- Axillary and radial from posterior divisions supply the posterior arm, the extensors
How can you remember the spinal nerve roots for the 5 major brachial plexus branches?
What is the common cause of injury of the upper brachial plexus?
- Excessive increase in angle between neck and shoulder, e.g trauma and birth
- C5 and C6 myotomes will be lost
What muscles will be paralysed with an upper brachial plexus injury?
Any nerve with root C5 or C6
What is the physical symptoms of an upper brachial plexus injury?
- Limb hanging by side in medial rotation, adducted arm and extented elbow
- Erb’s Palsy
What is the typical mechanism of injury to the lower brachial plexus?
- Forced hyperextension or hyperabduction
e. g falling from height and grabbing tree, pulling baby in delivery - C8 and T1 affected so issues with those myotomes
What muscles will be affected with a lower brachial plexus injury?
- Intrinsic muscles of hand, flexors of forearm supplied by ulnar nerve
- Muscles supplies by C8 and T1 within median and radial nerves
What is the physical signs of lower brachial plexus injury?
- Klumpke’s palsy
- Claw hand: hyperextension of all metacarpophalangeal joints, flexion of interphalangeal, thumb abduction and wasting of interossei
Label the following nerves on the brachial plexus.
Label the following diagram.
What are the contents of the axilla?
What are the contents of the fibrous axillary sheath?
Axillary artery, axillary vein and cords & branches of the brachial plexus
How can you remember the branches of the brachial plexus and the nerve roots that supply them?
