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Background: Tonsillar herniation is a condition that manifests as herniation of the brain parts, originating from the hindbrain and progressing through the foramen magnum into the cervical vertebral canal. Although the etiology of tonsillar herniation is unclear, it has been suggested that it may be congenital or acquired. In particular, there is speculation that primary mesodermal insufficiency may affect the size of the posterior cranial fossa.

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SummaryBackgroundWe assessed retrospectively the reference values of pelvic dimensions by 3D CT performed for non-obstetrical indications in non-pregnant multiparous women with a successful vaginal delivery. We further aimed to evaluate the impact of maternal short stature on these parameters.Material/MethodsThe 3D CT pelvimetry was performed retrospectively in 203 non-pregnant women selected consecutively if they had at least one singleton term delivery with head presentation and if there was no history of maternal or fetal birth trauma or cerebral palsy after childbirth. With standard sagittal and reformatted axial-oblique views, anteroposterior including three conjugates of pelvic inlet, transverse, posterior sagittal diameters of pelvic inlet, the plane of greatest diameter, the plane of least diameter, and pelvic outlet were measured. Selected obstetric parameters were collected.ResultsOverall, the pelvises had transverse oval appearance in inlet and size of the female pelvis. The diagonal conjugate was at least 15 mm longer than the obstetric conjugate. Women with short stature had lower maximal birth weight, and this was in accordance with their somewhat lower pelvic diameters.ConclusionsThe findings of this study present the reference values of the main planes of the true pelvis by 3D CT pelvimetry in a relatively large group of multiparous women who passed a trial of labor successfully. Overall, the pelvises had features of female pelvic bony structure although pelvic diameters were somewhat lower in multiparous women with short stature. The 3D pelvimetry with CT applications may be used as an adjunct to clinical and ultrasonographic examinations to rule out cephalopelvic dystocia in selected cases.

Radiologically recognising pneumatisation and anatomical variations of the ACP may be helpful in decreasing the incidence of surgical complications during anterior clinoidectomy.