Basilar invagination (BI) is an abnormality characterized by a superior projection at the craniovertebral junction (CVJ). The high prevalence of BI in Northeastern Brazil associated with brachycephaly, which is measured by the cranial index (CI), has been widely reported by several neurosurgeons and radiologists from that region since the 1950s. However, strong evidence for this relationship is still pending. The aim of this study is to investigate whether there is a relationship between BI and CI in a sample with participants from Northeastern Brazil.
The study used magnetic resonance images (MRIs) from 34 patients with BI and 92 controls. These participants had the CI correlated with radiological measurements used in BI diagnosis: Welcker's basal angle (WBA), clivus-canal angle (CCA), apex distance of the odontoid process to Chamberlain's line (DOCL), and Boogaard's angle (BOA). Craniometry was performed using the software Osirix, version 3.9.2 and statistical analysis by SPSS. We used Pearson's test for correlation analysis and the ROC curve was used for depicting CI accuracy related to BI diagnosis. All tests were calculated at the 95% confidence interval.
The BI group showed a moderate correlation between CI and CVJ measurements (P < 0.05). The control group had a weak correlation between CI and DOCL, and no statistical significance was verified for other correlations (P > 0.05). The area under the ROC was 0.659 and a CI greater than 86 had a specificity of approximately 80% for BI (P = 0.002).
The results indicated a greater cephalic projection of the CVJ in patients with high CI in the BI group. Moreover, a CI above 86 has a good diagnosis specificity for BI, showing evidence of a relationship between hyperbrachycephaly and CVJ anomalies in Northeastern Brazil.