Normal Value of Skull Base Angle Using the Modified Magnetic Resonance Imaging Technique in Thai Population

Purpose: To determine the normal value of basal angle measured using the modified MR imaging technique in Thai population compared with the standard value obtained from the Western population. Material and Methods: We retrospectively evaluated midline sagittal SE T1 weighted MR images in 200 adults and 50 children. The basal angle of the skull base was measured using the modified MR imaging technique described by Koenigsberg et al. The angle was formed by a line extending across the anterior cranial fossa to the tip of the dorsum sellae and another line drawn along the posterior margin of the clivus. The mean values of the basal angles among different age groups and sex were calculated and analyzed. Results: The mean skull base angle of our adult population was 115° (range 100.5°-130°, SD=5.7) with an inter-observer agreement of 0.85, slightly smaller than the previous study from the USA which was 117°. There was no significant difference between the male and female groups. The mean skull base angle in our children population was 114.7° (range 102- 130.5°, SD=6.3) with an inter-observer agreement of 0.89, quite similar to the previous USA study which was 114°. There was no significant difference between adult and children. Conclusion: The mean adult skull base angle measured using the modified MR imaging technique in Thai population was slightly smaller than the Western population, while the mean skull base angle of children was quite similar. The basal angle range of 103.6°-126.4° may be used as a guide for the potential range of normal skull base angles in Thai population and possibly also the Southeast Asian population