Table 2:

Coefficients of taper ratios as a function of age for Chiari, IS, and control patients from final multivariate model^a

Parameter	Slope Estimate in Model	Standard Error	P Value
Taper ratio
Chiari	0.01 mm/level	0.188	1.0
Controls	−0.03 mm/level	0.178	.8
Chiari + syrinx	−0.3 mm/level	0.194	.14
IS	0.3 mm/level	0.214	.21
Effect of age on taper ratio
Chiari	−0.03 mm/level/year of age	0.010	.009
Effect of age2 on taper ratio
Chiari	0.0003 mm/level/year of age2	0.0001	.01
Effect of age on taper ratio
Controls	0.003 mm/level/year of age	0.005	.5
Chiari + syrinx	0.0003 mm/level/year of age	0.006	1.0
IS	−0.03 mm/level/year of age	0.010	.003
Effect of age2 on taper ratio
IS	0.0003/level/year of age2	0.0001	.01

^aAge and the presence of a Chiari malformation affect spinal canal taper ratios, with both variables interacting. The multivariate analysis estimates the taper ratio (millimeter/level) for Chiari patients as equal to −0.445–0.009 (age of patient in years), for the controls as −0.114–0.074 (age of the patient in years), and for the IS group as 0.191–0.039 (age of the patient in years).