Table 2.

Comparison of relevant parameters before and after FVSS ($\overline{x}\pm s$).

	Maximum diameter of syringo (mm)	JOA	Foramen magnum		Central segment of mesencephalic aqueduct
			Systolic peak flow velocity (cm/s)	Diastolic peak flow velocity (cm/s)	Systolic peak flow velocity (cm/s)	Diastolic peak flow velocity (cm/s)
Before FVSS	10.50 ± 2.55	9.86 ± 2.20	7.06 ± 1.56	7.18 ± 2.86	6.82 ± 2.25	6.22 ± 2.15
After FVSS	5.08 ± 2.43	12.67 ± 3.95	5.50 ± 1.22	5.92 ± 1.62	5.41 ± 1.86	5.24 ± 1.12
t	5.29	3.69	4.03	4.33	5.73	6.32
P	P < 0.001	P < 0.001	P < 0.01	P < 0.05	P < 0.05	P < 0.05