Spinal Nerves
There are 31 pairs of spinal nerves, named and numbered according to the region and level of the spinal cord from which they emerge. All spinal nerves are mixed (motor and sensory) except C1. At each vertebral body, nerve roots exit from the spinal cord bilaterally, and specific skin areas (dermatomes) are innervated by single or groups of spinal nerves.
Assessing the dermatomes assists in determining the region of the block (numbness).
Important Dermatomes and Anatomical Landmarks
- L1-L2: front of thigh
- T10: Umbilicus
- T6: Xyphisternum
- T4: Nipple
- C6: thumb
- C7: middle finger
- C8: little finger
Note: To avoid complications, the level of the block should be at T4 with no numbness in the upper limbs or fingers.
