BONE-MINERAL DENSITY OF THE SKULL IN PREMENOPAUSAL WOMEN

Dual-energy X-ray absorptiometry (DXA) of the head has received little attention. We used DXA to measure bone mineral density (BMD) of the e ntire skull including the mandible (BMDHead) and BMD of the cranial va ult (BMDVault) in 91 normal young women. We also measured BMD of the t otal body (BMDTotal body), proximal femur (''total femur''), and lumba r vertebrae (L1-L4). BMD (g/cm(2); mean +/- SE) was 1.032 +/- 0.011 fo r L1-L4, 0.995 +/- 0.011 for total femur, and 2.283 +/- 0.028 for BMDV ault (cranial vault) and the mean body weight of all subjects was 59.8 kg. Correlation between BMDVault and BMDHead was 0.991 and this was n ot different from 1.0 (P = 0.473). The average difference between BMDV ault and BMDHead was -0.004 g/cm(2) suggesting that these two measurem ents of bone mass of the skull were similar. To determine the correlat ion between the different variables after accounting for external sour ces of variation, partial correlation derived from multiple regression was determined. Correlations between BMD at the various locations and with BMDTotal body, were moderate to strong. Although small in magnit ude, the partial correlations of body weight with BMDTotal body, total femur, and L1-L4 were significantly different from zero (P < 0.02). T he results show that BMDVault, total femur, and L1-L4 were of equal va lue in predicting BMDTotal body, and further, BMDVault was not influen ced by body weight. Including body weight in multiple regression in ad dition to total femur or L1-L4 removed the extraneous variation due to body weight, and predictions of BMDTotal body were as reliable as whe n BMDVault was based on goodness of fit tests (P = 0.314). The techniq ue used to measure BMD of the cranial vault is a relatively new variat ion of DXA technology. The precision was as good as other measurements of bone mass of the entire skull (including the mandible). Because th e cranial vault is less sensitive to mechanical influences, it may be a region where response to therapy could be evaluated. The cranial vau lt may be a useful area to study certain heritable diseases that affec t the skeleton, skeletal artifact, or evaluation of oral bone loss.