C5 nerve root
Roots · C5
The highest root of the plexus. Joins C6 to form the upper trunk, gives the dorsal scapular nerve directly, and sends a branch to the phrenic nerve — which is why an interscalene block paralyses the ipsilateral hemidiaphragm, and why a raised hemidiaphragm after plexus trauma means a proximal C5 avulsion.
Detail
- Motor
- Contributes to deltoid, biceps, supraspinatus and infraspinatus
- Sensory
- Lateral shoulder and upper lateral arm (C5 dermatome)
When it goes wrong
Cervical disc herniation at C4/5
Weak shoulder abduction, reduced biceps reflex, numbness over the lateral shoulder.
Practise this structure
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