Where is the C1 dermatome?
When you pick-up a neurotip or piece of cotton wool to examine sensation, what sections of the skin are innervated by the C1 nerve root?
There is no C1 dermatome.
The C1 root innervates the meninges of the posterior fossa around the foramen magnum and has no cutaneous branch. Neck stiffness is a test of the C1, C2 and C3 roots that innervates the meninges of the posterior fossa. By stretching inflamed or chemically irritated meninges stimulates a reflex that causes the cervical muscles to go into spasm. The spasms are more marked with extension and flexion movements of the cervical spine compared to lateral rotatory movements. The latter can help differentiate meningeal irritation from other potential causes of neck stiffness. This is referred to as meningism.
Self-learning
What is the differential diagnosis for neck stiffness due to meningism?
What is Brudzinski's Sign?
What is Kernig’s Sign?