Parietal foramen in modern Japanese calvaria, its frequency and location

Abstract

To examine the frequency and location of the parietal foramen, a total of 117 calvariae of 63 male, 13 female and 41 sex-unknown Japanese cadavers were studied. The results obtained were as follows.1) Frequency of the parietal foramenBy a total number of the parietal foraminaon both sides, the calvariae were classified into five categories: type A (with a single foramen), type B (with a double foramen), type C (with three foramina), type D (with four foramina) and type E (without any foramen). Furthermore, the calvariae of types A and C were, by a number of the foramina on either side, divided into two subtypes, and those of type D into three.The percentages of occurrence of the calvariae of types A, B, C, D and E were 26, 48, 16, 1 and 9, respectively. The calvariae of types A-2 and B-3 in which there was no foramen on the left side only was found in 17% of the whole, while those of types A-1 and B-1 where no foramen was present on the right side only occurred in 14%. The highest frequency of occurrence of the foramen in males was 48% in the case of type B-1 (a single foramen on each side), whereas that in females was 39% in the case of type A-2 (a single foramen on the right side only). The lowest frequency of occurrence of the foramen in males was, on the other hand, 7% in the cases of types B-3 (a double foramen on the right side only) and D (a double foramen on each side), while that in females was 5% in the cases of type B-3, C-1 (a single foramen on the left and a double on the right), D and E.2) Location of the parietal foramenFor measuring, a perpendicular line to the midsagittal plane was drawn from the parietal foramen on the external surface of the calvaria, and the foot of the perpendicular was designated as a point "P". Either antero-posterior or transverse location of the parietal foramen was expressible as a percentage of the lambda-P length to the lambda-bregmatic distance or a percentage of the length of the perpendicular line to the same distance.The parietal foramen was located antero-posteriorly at about 30%'s distance from the lambda in the case of types A-1, A-2 and B-1 in both sexes. The foramen was transversely at 5% away from the mid-sagittal plane in males, while it was 3% away from this plane in females without distinction of calvarian type.