Enlargement of the frontal sinus.

The enlargement of the frontal sinus has been analysed in a longitudinal study of 49 males and 47 females for whom a first lateral cephalogram was available at from 2 to 5 years of age for 88 subjects and from 6 to 11 years for 8 subjects. Thereafter the cephalograms were taken at approximately yearly intervals and in 28 subjects a last cephalogram was taken at 24 years or older. In only six subjects was enlargement of the sinus still proceeding at the time of the last cephalogram . The enlargement was assessed by a standardized measurement of the maximum vertical height of the sinus. The median age for the first appearance of the frontal sinus was 3 X 25 years for the boys and 4 X 58 years for the girls. It enlarged on average to 32 X 60 mm (SD 9 X 10) in the males and 26 X 60 mm (SD 7 X 50) in the females. The median age at which the main increase in size of the sinus ceased was 15 X 68 years for boys and 13 X 72 years for girls, thus suggesting that the enlargement of the frontal sinus, a mainly osteoclastic activity, follows very closely the trends for growth in bone lengths.