Craniocervical instability is not always evaluated with one simple scan. A standard MRI is often part of the workup, but specialists also use flexion-extension imaging, CT, upright MRI, dynamic motion X-ray imaging (DMX), or cone beam CT when symptoms suggest instability at the skull and upper spine.

The measurements matter as much as the scan itself. The literature references the clivo-axial angle, Harris measurement, Grabb-Mapstone-Oakes measurement, and C1-C2 angular displacement, among others. These measurements name what the scan is showing. Without them, the imaging is just a picture.

My own imaging sequence required DMX first, then upright MRI, then cone beam CT. Each scan answered a different question. DMX captured the cervical spine in motion. The upright MRI showed the spine under the load of gravity. The cone beam CT gave a high-resolution view of the bony anatomy at the craniocervical junction. By the time I had all three studies, the instability that had been invisible on the standard supine MRI was documented across multiple modalities.

Many patients spend years being told their imaging is normal before someone orders studies designed to evaluate instability in motion or under load. The body does what it does in the position the scan is taken in. If that position does not provoke the instability, the instability does not appear.

The 2022 systematic review on craniocervical instability in Ehlers-Danlos syndrome (link) outlines the imaging measurements and positional findings specialists currently use when evaluating CCI in connective tissue disorders.