Stage 1 Registered Report:  Rationale, design and study protocol for a prospective, exploratory study Predicting Response to image-Guided Cryoneurolysis of the Greater Occipital Nerve (CryoGON) in Chronic Migraine Using a Conventional Greater Occipital Nerve Block.

BACKGROUND

Chronic migraine is frequently refractory to available preventive therapies. Image-guided cryoneurolysis of the greater occipital nerve (CryoGON) may provide longer-lasting relief than conventional greater occipital nerve (GON) blocks. This Stage 1 Registered Report describes a prospective, exploratory study evaluating whether response to a conventional GON block predicts subsequent response to CryoGON, and assesses open-label safety, tolerability, feasibility and efficacy of CryoGON.

METHODS

The study is planned as a single-site, investigator-initiated, open-label clinical investigation. Adults with chronic migraine will complete a ≥28-day electronic baseline diary before receiving bilateral conventional GON blocks, followed by a ≥28-day observation. Eligible participants then undergo navigation-guided CryoGON with 12-week follow-up. The primary endpoint is the association between change in moderate-to-severe headache days after GON block (weeks 1-4) and after CryoGON (weeks 9-12). Key secondary endpoints estimate the diagnostic performance of GON-block response applying a ≥30% reduction threshold for treatment effect to identify CryoGON responders, including sensitivity, specificity and predictive values. Additional endpoints include change in migraine days, patient-reported global impression of change, Migraine-Specific Quality of Life Questionnaire v2.1, procedure tolerability, technical success, and safety (treatment-emergent adverse events and adverse device effects). Women of childbearing potential, including pregnant and breastfeeding participants, are eligible for participation.

DISCUSSION: This study will provide the first systematic evaluation of whether a simple, widely available GON block can guide patient selection for CryoGON and will generate foundational open-label data on its clinical performance and safety. Findings will inform the design and justification of a subsequent sham-controlled trial.

TRIAL REGISTRATION AND APPROVALS: The study will preregister at ClinicalTrials.gov. and obtain all necessary ethical approvals before study initiation.Sponsor: St. Olav's University Hospital, Trondheim, Norway.Funding: Stiftelsen Dam (grant SDAM_FOR701626).