Dermatomes with key points
Sensibility C2 dermatome
1 cm lateral to external occipital protuberance
nerve root involvement
C2 nerve root involvement is rare, but can be seen with trauma to the upper cervical spine, tumor, or vascular anomaly that can lead to pressure on the C2 nerve root
Sensation in the C3 dermatome
In the supraclavicular fossa mid-clavicular
nerve root involvement
C3 nerve root involvement is rare, but can be seen with degenerative changes in the facet joints causing narrowing of the nerve root canal and swelling of the C3 nerve root. Cervical disc prolapse at this level is extremely rare.
Sensation in the C4 dermatome
Just above the acromioclavicular joint
nerve root involvement
C4 nerve root involvement is rare, but can be seen in degenerative conditions (spondylosis of the facet joints) if the osteoarthritis leads to narrow neuroforamina for the C4 nerve root. However, it is more common that extensive degenerative changes at this level rather cause myelopathy than nerve root involvement.