Cranio-cervical abnormalities in moderate-to-severe osteogenesis imperfecta - Genotypic and phenotypic determinants

Abstract

Introduction: Cranio-cervical anomalies are significant complications of osteogenesis imperfecta (OI), a rare bone fragility disorder that is usually caused by mutations in collagen type I encoding genes.

Objective: To assess cranio-cervical anomalies and associated clinical findings in patients with moderate-to-severe OI using 3D cone beam computed tomography (CBCT) scans.

Methods: Cross-sectional analysis of CBCT scans in 52 individuals with OI (age 10-37 years; 32 females) and 40 healthy controls (age 10-32 years; 26 females). Individuals with a diagnosis of OI type III (severe, n = 11), type IV (moderate, n = 33) and non-collagen OI (n = 8) were recruited through the Brittle Bone Disorders Consortium. Controls were recruited through the orthodontic clinic of the University of Missouri-Kansas City (UMKC).

Results: OI and control groups were similar in mean age (OI: 18.4 [SD: 7.2] years, controls: 18.1 [SD: 6.3] years). The cranial base angle was increased in the OI group (OI: mean 148.6° [SD: 19.3], controls: mean 130.4° [SD: 5.7], P = .001), indicating a flatter cranial base. Protrusion of the odontoid process into the foramen magnum (n = 7, 14%) and abnormally located odontoid process (n = 19, 37%) were observed in the OI group but not in controls. Low stature, expressed as height z-score (P = .01), presence of DI (P = .04) and being male (P = .04) were strong predictors of platybasia, whereas height z-score (P = .049) alone was found as positive predictor for basilar impression as per the Chamberlain measurement.

Conclusion: The severity of the phenotype in OI, as expressed by the height z-score, correlates with the severity of cranial base anomalies such as platybasia and basilar impression in moderate-to-severe OI. Screening for cranial base anomalies is advisable in individuals with moderate-to-severe OI, with special regards to the individuals with a shorter stature and DI.

Keywords: cone-beam computed tomography; cranio-cervical abnormalities; genotypic and phenotypic determinants; osteogenesis imperfecta.

Figure 1:. Landmarks and measurements.

A. Cranio-cervical landmarks identified in CBCTs in sagittal view. B. Reference lines to measure angles (Cranial base angle, Clivoaxial angle) or distances between point Dens to the respective line. C. Landmarks and reference line for the Bimastoid-Dens measurement in the coronal view. The two-colored bones represent two different coronal planes. Refer to Table 1 for measurement definitions.

Figure 2:

Cranio-cervical abnormalities in control and OI group. SEM denoted with continuous line among each dataset, dotted line across datasets describes cutoff value for each measurement. p = 0.001*** by T-Test.

Figure 3:

Cranio-cervical abnormalities by OI type. SEM denoted with continuous line among each dataset, gray shadow represents the pathological measurements above or below the cutoff value. p= 0.05*, 0.005**, 0.001***NS: Not significant by ANOVA.