Ventral innervation of the lateral C1-C2 joint: an anatomical study.

Objective: Clinical observation has suggested the presence of ventral cervical extra-articular pain pathways in patients with C1-C2 joint pain. However, the existence of ventral innervation to the C1-C2 joint has not been documented. The objective of this study was to determine whether ventral innervation to the lateral C1-C2 joint exists, and to describe its relational anatomy.

Design: Gross and microscopic dissection was performed on 11 embalmed human cadavers. Wire segments were placed on identified ventral plexus nerves and radiographic imaging obtained in multiple planes. Histologic staining of prevertebral plexus nerves was performed with Osmium and compared with tissue controls.

Results: A superficial and deep cervical prevertebral plexus was identified terminating in the ventral joint capsule of the C1-C2 joint in all cadavers examined (21 sides). The location of the deep cervical prevertebral plexus was consistent within the C2 ventral gutter. Osmium staining confirmed the presence of myelin in plexus specimens.

Conclusion: In this study, two cervical prevertebral plexuses (superficial and deep) were identified that have not previously been described. Terminal branches of the plexuses entered the ventral joint capsule of the lateral C1-C2 joint and were seen approaching the dens. Findings provide and explanation for the clinical observation that electrical stimulation in the C2 ventral gutter can reproduce headache in patients with C1-C2 joint pain.