Medial branch blocks
One spinal nerve (spinal cord nerve) is assigned to each spinal cord segment or section side.
The pair of the two uppermost spinal nerves emerges directly below the occiput, i.e. above the first cervical vertebra. Since the pair of spinal nerves (C8) exiting below the seventh cervical vertebra is also assigned to the cervical region, there are eight pairs of spinal nerves of the cervical spine (cervical spine) with only seven cervical vertebrae.
The following spinal nerves then have the same names and numbers as the vertebral body above.
In humans, a total of 31 pairs of spinal nerves are therefore usually present
(cervical spine 8, thoracic spine 12, lumbar spine 5, sacrum 1).
The spinal nerves are created by the union of the anterior and posterior roots. The spinal nerves divide into a dorsal and ventral (posterior and anterior) branch. The dorsal branch itself divides into a medial and lateral (inner and outer) branch.
The sensitive nerve supply of a facet joint is provided by 2 adjacent medial (inner) branches.
Therefore 2 medial nervous branches have to be blocked for one facet joint.
The illustration shows the area, where the medial branch originates from the dorsal branch (blue arrow) on the left using the example of the cervical spine. This intervention is performed in prone position under C-arm or CT control.