Table 3.

The Prevalence of Preoperative CDAS on Sagittal T1 MRI and Compressing Structural Anomalies

	Type A, N = 20	Type B1, N = 7	Type B2, N = 5	Type B3, N = 12	P
SM, n (%)	10 (50)	3 (43)	4 (80)	8 (67)	0.516
AS posterior fibrous edge, n (%)	10 (50)	5 (71)	2 (40)	9 (75)	0.5
Roos, n (%)	12 (60)	5 (71)	2 (40)	6 (50)	0.39
MRI CDAS, n (%)	1 (5)	7 (100)	3 (60)	7 (58.3)	0.001

More than one structure could be found intraoperatively. The prevalence of each anomaly did not differ significantly between the subgroups.