Investigating Type B Basilar Invagination Through Cephalic Indices.

OBJECTIVE: We sought to compare the diagnostic accuracy of cephalic indices for type B basilar invagination (BI). METHODS: This retrospective study examined head and neck magnetic resonance imaging sequences of 31 Group B BI cases and 96 controls. Two examiners blinded to diagnostic data evaluated the cephalic indices of each magnetic resonance imaging sequence, described as width/length (WLI) and height/width (HWI). The distance of the odontoid process apex to Chamberlain line and clivus canal angle were measured. The interexaminer and intraexaminer reproducibility of the cephalic indices was calculated using intraclass correlation coefficient. The diagnostic accuracy was discerned by the receiver operating characteristic (ROC) curve. All analyses were scrutinized with a 95% confidence interval. RESULTS: Cephalic indices showed interexaminer and intraexaminer reproducibility ≥94%. The areas under the ROC curve were 0.639 (WLI) and 0.874 (HWI) (95% confidence interval: P < 0.05). The HWI showed a sensitivity of 74.7% and a specificity of 85.5% for the cutoff criterion ≤58. The WLI presented a sensitivity of 53.3% and a specificity of 66.7% for the cutoff criterion ≥86. CONCLUSIONS: The HWI showed the largest area under the ROC curve in comparison with the WLI, with robust sensitivity and specificity values, indicating that the proportions between cranial height and width can help clinicians in investigating type B BI.

Reliability and Agreement in the Cerebellar Tonsil Tip Localization: Two Methods Using the McRae Line Concept in MRI.

BACKGROUND: The cerebellar tonsil tip position (TP) is a common parameter used for the radiologic diagnosis of Chiari malformation type 1 (CM1). However, these paramedian structures are usually not properly visualized in the midsagittal section. Such mismatch may be a source of bias in TP measurements based on the McRae line (ML) traced between median craniometric points. This study aims to evaluate the intraoperator and interoperator reliability and agreement of 2 protocols to trace the ML in magnetic resonance imaging (MRI) for the cerebellar tonsil tip localization, adding a 3-dimensional multiplanar reconstruction (MPR) approach to the midsagittal plane. METHODS: Sixty-two T1-weighted head MRIs were obtained for 32 CM1 patients and 30 controls. Two operators independently applied 2 TP measurement protocols, one considering only the visualization of the sagittal plane and the other using MPR. The intraclass correlation coefficient was used to assess intraoperator and interoperator reliability, and the Bland-Altman graphical method was used to evaluate the agreement between the measurement protocols. RESULTS: The sagittal method significantly underestimated ML and tonsillar herniation when compared with the MPR method. The MPR method provided better reliability of the ML measurement when compared to the sagittal method, but this did not influence the reliability of the TP. Analysis of the Bland-Altman plot showed that the limits of agreement were close to acceptable for the ML, but not for measures of TP. CONCLUSIONS: The standardization of the LM tracing by the MPR method improves the acquisition of data regarding the position of the tonsils.

Foramen Magnum Angle: A New Parameter for Basilar Invagination of Type B.

OBJECTIVE: To describe the foramen magnum angle (FMA) as a new parameter for basilar invagination (BI) type B. METHODS: The FMA was performed on sagittal slice of magnetic resonance imaging (MRI) as a line from the hard palate to the opisthion (angle vertex), and another line from the opisthion to the basion. The MRIs from 31 participants with BI type B and 96 controls were used. Intraclass correlation coefficient, descriptive data, and receiver operating characteristic (ROC) curve were used for statistical analysis at the 95% confidence interval. RESULTS: The interobserver agreement of the FMA was 0.952. Patients with BI type B had a FMA significantly greater (25.9° ± 9.3°) than control participants (11.6° ± 4.9°) (P < 0.001). The area under the ROC curve showed a diagnostic value of 0.947. The FMA showed sensitivity 0.900 and specificity 0.854 for the cutoff criterion 17° (P < 0.001). CONCLUSIONS: The FMA had an optimal diagnostic value that provided complementary evidence to investigate BI type B.

Relationship between basilar invagination and brachycephaly in Northeastern Brazil.

BACKGROUND: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.