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Foramen Magnum Angle: A New Parameter for Basilar Invagination of Type B
José J C Nascimento1, Leandro M Silva1, Elayne C O Ribeiro2
1Postgraduate Program in Neuropsychiatry, Federal University of Pernambuco, Recife, Brazil.
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.
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