CT-determined intracranial volume for a normal population

Intracranial volume comparisons of patients with craniosynostosis and norma l have been contrary to expectations, leading to questioning of the validit y of the current normal reference material. Computed tomography-determined intracranial volume is presented for a white normal population. Specificall y, intracranial volumes for 157 subjects (82 female and 75 male) were measu red from computed tomography data using the Cavalieri estimator: volume det ermination was based on measuring the area in each computed tomography sect ion. Monomolecular and Gompertz models were applied to find curves of best fit to the intracranial Volume as a function of the age. The best fit was o btained using the monomolecular model when the response variable was the lo garithmically transformed intracranial volume, and the independent variable was the logarithm of the age from conception. For example, the mean (stand ard deviation) for male subjects at 1 year and 20 years were 1,125.6 (89.6) mi and 1,472.9 (117.2) mi, respectively, and for female subjects 1,024.9 ( 84.0) mi and 1,321.7 (108.3) mi, respectively. Although the shape and rate of increase of the female and male curves is similar, the female mean is 1. 3 standard deviations below the male mean at 20 years. These curves were co mpared with the commonly referenced curves of Blinkov (1941), Lichtenberg ( 1960), and Dekaban (1977). Our male curve is substantially higher than thes e curves in the age range 8 months to 4 years. Our female curve, however, i s approximately 1 standard deviation below Lichtenberg's curve from birth t o 7 months. There are then only minor differences between our female curve and Lichtenberg's curve until his curve crosses ours at 41 months, where th ey significantly diverge from approximately 4.5 years. Our curves indicate that 95% of the final intracranial volume has been attained by 42 months fo r girls and 46 months for boys.