The main purpose of this study is to establish the various normal measurements of skulls in Koreans, because there has been no sound data available. It is needles to say that for proper X-ray diagnosis of the skull, measurements of our own nationals are indispensable inasmuch as measurements from foreign sources cannot be directly applied to Koreans due to the considerable racial differences in the appearance of the skull that are known to exist.
The various measurements of the skulls in normal Koreans have been newly established, and they were compared with those given by foreign authors in an attempt to bring out salient differences in measurements, if any. Finally, an extensive statistical analysis of data was performed to investigate the correlation
in the various measurements in various age groups.
Materials and methods:
Frontal and lateral radiographs of the radiologically normal skulls of 1,000 patients of Yonsei University Severance Hospital and the Children's Hospital of Seoul City were chosen for measurement , the age distribution of the patients being from new-born to 70 yeats.
An experimental study was made using a dry skull to determine the radiographic magnification factor(enlargement factor) in various focus film distances(F.F.D) and object-film-distances(O.F.D.). Knowing the F.F.D and O.F.D on filming, one can readily calculate the enlargement factor and real dimensions of the object by measuring the dimensions of the reoentgenogram. It was proved by this experiment that the angles of the skull film is constant regardless of the differences of F.F.D or O.F.D.
A. Various measurements:
1) Measurement of the base of the skull for basilar invagination:
a) Chamberlain's measure: The odontoid process should not project more than 1.6mm(2 S.D.) above the Chamberlain's line(Line form the posterior margin of the hard palate to the posterior margin of the foramen magnum).
b) McGregor's measure: When the tip of the odontoid process lies 5.6mm(2 S.D.) above the base line(Line from the posterir margin of the hard palate to the most caudal point of the occipital curve), the measurement lies on the extreme edge of
normality and strongly indicative of basilar invagination.
3) Bull's measure:
In any individual case the Bull's angle(The angle formed by twe lines, one drawn along plane of the hard palate and the other drawn along plane of atlas.) is more than 18 degrees(3 S.D.), the pathology must be seriously considered.
2) Measurement of the base of the skull for platybasia:
The basal angle(The angle formed by two lines drawn from the center of the sella turcica, one to the nasion, the other to the anterior margin of the foramen magnum.) is not a measurement of degree of impression of the base but is an impression of one part ;of the base relative to another. The base may be impressed with or without disturbance of this relationship.
The normal range of the basal angle in Korean adults is 133±10 degrees.
3) Nasal angle:
The normal range of the nasal angle(the angle formed by two lines, one drawn from the nasion to the base of the anterior nasal spine and the other to the anterior margin of the foramen magnum.) in all age groups lies in between 54.3 and 68.3
degrees, its mean value being 61.3. The nasal angle of human being is the smallest of all mammalians according to Welcker.
4) Facial angle(Angle of Weisbach)
The facial angle of Weisbach is the angle formed by two lines drawn from the mental point, one to the nasion, the other to the anterior margin of the foramen magnum. this angle4 in 100 normal adults averages about 51 degrees.
Almost all of the author's series belong to orthognathic group according to Dyke's classifications.
5) Size of sella turcica:
The average A-P diameter(length) of the sella turcica over 16 years of age is 11.4mm, the S.D. being 1.47mm. the depth of the sella turcica averages 10.33mm with the S.D. of 1.46mm.
6) Size of skull in three dimensions:
The breadth, height, length, and modulus of th skull in various age groups have been measured and tabulated in 4 charts. A comparison study with the Haas' series (U.S.A.) is shown is graphic forms. The cephalic index(Br/L×100) of Koreans is
considerably high, indicative of brachycephaly.
7) Thickness of calvarium:
The average thickness of the frontal and parietal bones are 5.2m and 5.3mm, respectively.
8) Pineal localization:
It was found that neither Vastine-Kinney charts not Fray's cranio-angle method could directly applied to Koreans without proper modification due to the fact that the majority of Koreans are brachycephalic in type.
9) Physiological intracranial calcificatins:
The incidence and distribution of physiological calcification by sex and decades were tabulated studying 1,000 skull films. the incidence of pineal and habenullar calcifications in individuals over 21 years of age is approximately 13%, and not a
single calcified pineal gland was seen in individuals under 10 years of age.
Calcification in the falx cerebri is common, the incidence being 9.5% in entire group.
B. Comparison studies with foreign series:
Comparison study in each category was made with foreign series to a great extent.
1. Chamberlain's measurement: Average Korean adults are 2 to 5mm smaller than in Poppel and Bull's series.
2. McGregor's measurement: No significant difference is present between British and author's series.
3. Basal angle: No significant racial difference is noted.
4. Nasal angle: Somewhat smaller is Korean than is Welcker's series.
5. Size of sella turica: As compared with Camp's series, the length of the sella turcica is slightly longer(0.8mm) and the depth is considerably deeper(2.2mm) in Koreans.
6. Cephalic index is considerably greater in Koreans than in American, and the modulus (Br+L+H)/3 is slightly larger in Koreans.
7. No significant difference is present in the thinness of the calvarium and basal angle, as compared with Orley's series.
8. The incidence of pineal calcification in Koreans is considerably lower than in Americans, the ratio being approximately 1/4 in individuals over 21 year's of age.
C. Correlation in the various measurements in various age groups:
1. Close correlation is observed in Chamberlain's and McGregor's measurements with the correlation coefficient of 0.898.
2. Inverse correlation is present in the basal angle with increasing age, and C.C.(Correlation Coefficient) of -0.729 is present in the younger age group from new born to 2 years of age.
3. Size of sella turcica increases proportionately with increasing age up to 20 years, and C.C. between the size of the sella turcica and age is slightly over 0.7.
4. The nasal angle does not show significant difference in the various age groups, and has no correlation with the basal angle. According to Welcker, both basal and nasal angles decrease with advancing age, and his data does not correspond with ours.
The various roentgenorgraphic measurements of the skulls in 1000 normal Koreans have been established for the first time. The study includes the following:
Chamberlain's measurement, McGregor's measurement, Bull's angle, base angle, nasal angle, facial angle, size of the sella turcica, thickness of the skull, pineal localization, and physiological intracranial calcification.
Each measurement is compared wit that from foreign sources.
The correlation factors in the various measurement s and age groups have been investigated to a great extent.
Considerable difference in the values of various measurements in different age groups is noted, therefore, one should use the proper measurements for the different age groups.
As far as the authors know, this is the first attempt to establish extensive measurements of the skull in various age groups.
(This article includes 25 tables, 31 graphs, 15 drawings 3 roentgenograms and 2 charts.)
Presented at the 14th Korean Radiological Society meeting in 1962.