Morphometric analysis of the tentorial notch by magnetic resonance

Introduction The tentorial notch is the aperture between the free edges of the tentorium cerebelli. This complex space varies greatly in dimensions; its study could improve the understanding of the mechanism of brain injuries. The morphometric analysis of the tentorial notch has been analyzed mainly in cadaveric studies. However, the postmortem effect could have an impact in such measures, varying amongst themselves. The aim of this study was to evaluate the morphometry of tentorial notch by Magnetic Resonance Imaging (MRI) in a Hispanic population. Methods A descriptive cross‐sectional study was performed. We analyzed retrospectively 45 MRI in the tentorial notch from asymptomatic patients, age ranging from 18 to 60 years. The images were evaluated intraobservatory by an expert radiologist. We measured: maximum notch width (MNW), the maximum width of the notch in the axial plane; notch length (NL), the length of the tentorial notch from the superoposterior edge of the dorsum sellae to the apex of the notch; interpedunculoclival distance, the distance from the interpeduncular fossa to the superoposterior edge of the dorsum sellae; apicotectal distance, the distance from the tectum in the median plane to a perpendicular line dropped from the apex of the tentorial notch to the cerebellum; cisternal third nerve distance, the distance covered by the cisternal portion of the third cranial nerve; inter‐third nerve angle, the angle between the two third cranial nerves. Results According to the quartile of the MNW, we divided the patients into narrow, midrange and wide groups. Also, quartile groups determined by NL were classified as short, midrange and long. The mean and standard deviation of MNW was of 31.42 ± 2.75 mm; NL, 55 ± 4.91 mm. apicotectal distance, 18.85 ± 3.83; interpedunculoclival distance, 21.03 ± 3.24; inter‐third nerve angle, 54.53 ± 7.25; right and left cisternal third nerve distance, 22.75 ± 4.55 and 21.78 ± 4.36 respectively. Statistical differences was identified only between sexes in the MNW. Conclusion Morphometric changes in cadaveric models in the tentorial notch and its neurovascular relations may have implications for a better understanding of the mechanisms of brain herniation and traumatic lesions. In addition, this data could improve the anatomical knowledge for neurosurgeons for cranial base surgical approaches. Although this data does not replace the image guidance, it improves the orientation for neurosurgeons. Significance/implication Differences in the clinical presentation of some neurological injuries could be related to variations in the space of the tentorial notch and the position of the brainstem. A transtentorial herniation is the movement of the temporal lobe through the tentorial notch. This pathology occurs in vascular disease, tumors, and brain edema. Furthermore, the location of the pressure and the pathological process, the dimensions of the notch could be a factor for the pattern of herniation.