Characteristics of patients with cervical pain originating from the lateral atlanto-axial joint (C1-C2)

Background The lateral C1-C2 joint is an understudied source of upper cervical pain and is typically investigated only after negative work-up at C2-C3 and C3-C4. The clinical profile of patients with presumed C1-C2 pain remains poorly defined, and the relationship between diagnostic block response and medium-term corticosteroid benefit is unclear. Objective To characterize the clinical profile of patients with persistent upper cervical pain after negative C2-C3 and C3-C4 work-up who underwent C1-C2 intra-articular injection, and to identify factors associated with immediate diagnostic block response and with 3-month response to therapeutic intra-articular corticosteroid injection. Methods In this prospective study, fifty participants were recruited from a tertiary/quaternary physiatry clinic between 2022 and 2025. All had persistent upper cervical pain after negative C2-C3 and C3-C4 medial branch blocks. Participants underwent fluoroscopy-guided intra-articular C1-C2 injection with lidocaine and dexamethasone. A positive response at T0 was defined as ≥50% pain relief at 30 min. A positive response at T3 was defined as ≥50% pain reduction and/or ≥5-point improvement on the Neck Disability Index. Results Forty-nine participants were analyzed at T0 and forty-eight at T3. At T0, 22/49 participants (44.9%) responded to the diagnostic block. Facial pain was associated with lower odds of response, whereas predominant neck pain or combined neck and head/face pain was associated with greater odds of response. At T3, 16/48 participants (33.3%) met responder criteria. Electric shock-type pain was associated with lower odds of response, whereas reported pain on touch was associated with greater odds of response. Response at T0 did not predict response at T3. Conclusion In patients with persistent upper cervical pain after negative C2-C3 and C3-C4 work-up, lateral C1-C2 pain may be more likely in those with predominant neck pain or combined neck and head/face pain. Factors associated with immediate diagnostic response differed from those associated with 3-month therapeutic benefit, suggesting that diagnostic and therapeutic phenotypes may not be equivalent at this level.