Purpose Craniocervical instability (CCI) is a disabling consequence of ligamentous laxity at the craniocervical junction (CCJ) for some Ehlers-Danlos syndrome (EDS) patients. The purpose of this study was to report craniometric measurements in EDS patients with suspected CCI and provide clinically useful baselines for these measurements.
Methods This descriptive analysis included 50 patients with EDS and suspected CCI. All subjects had dynamic CCJ imaging. The soft-tissue clivo-axial angle (CXA), basion-axial interval (BAI), basion-dental interval (BDI), and Grabb-Mapstone-Oakes measurement (pB-C2) were measured using udMRI. The angular displacement between C1 and C2 (C12-rot) was measured on CT in right and left-axial rotation. Pathological thresholds were collected from existing literature (CXA<135˚, BAI>12mm or ∆BAI>4mm between flexion and extension, BDI>12mm, pB-C2>9mm, C12-rot≥41˚). Data was analysed using descriptive statistics.
Results The mean age of the patients was 34 years, with a male-to-female ratio of 10:1. The mean CXA measurements were 132.85±25.52˚ (±2σ), 129.06±21.23˚, and 152.99±27.96˚ in neutral, flexion, and extension. 77.6% of patients had at least one CXA measurement <135˚. The mean BAI measurements were 3.74±4.71mm, 4.10±4.90mm, 1.70±6.32mm in neutral, flexion, and extension. No patients had a BAI>12mm. 25.6% of patients had a ∆BAI>4mm between flexion and extension. The mean BDI measurements were 4.39±2.88mm, 3.89±2.72mm in flexion, and 6.12±4.05mm in neutral, flexion, and extension. No patients had a BDI>12mm. The mean pB-C2 measurements were 7.57±2.67mm, 7.75±3.19mm, and 6.31±2.66mm in neutral, flexion, and extension. 35.5% of patients had a pB-C2 measurement >9mm. The mean C12-rot in right and left rotation were 33.94±10.40˚ and 33.90±12.06˚respectively. 19.5% of patients had a C12-rot≥41˚. 94% of patients had at least one measurement satisfying a pathological threshold.
Conclusion Disparity between proportions of patients classified as unstable by each parameter supports the use of several parameters in the radiological identification of CCI in EDS patients. Dynamic imaging is needed to appreciate positional derangements of measurements. Further evaluation of the parameters with consideration of patient symptomatology is required.