Supplemental Table 1. Comparison of center of pression performance between HSP group and Control group with eyes open and closed.; and between SPG4 subgroup and control group.

Variable	HSP G.                (n=17)	CONTROL G.          (n=17)	P-value	Difference
(HSP – Control)	SPG4 SG.                           (n=9)	P-value	Difference
(SPG4 – Control)	
Velocity-ML/ EO 	8.6 (9.5)	3.5 (3.4)	<0.001	5.2 mm/s	8.1 (3.5)	<0.001	4.7 mm/s	
Velocity-ML/ EC 	12.8 (20.4)	3.1 (3.5)	<0.001	9.6 mm/s	11.0 (8.8)	<0.001	7.9 mm/s	
Median of the Difference EO - EC of the VML 	4.9 (9.6)	0.2 (1.2)	0.026	4.7 mm/s	4.9 (8.3)	0.095	4.7 mm/s	
Velocity-AP/ EO 	8.5 (7.9)	4.6 (3.0)	0.001	3.8 mm/s	6.7 (3.3)	0.039	2 mm/s	
Velocity-AP/ EC 	14.2 (18.7)	7.4 (2.6)	0.001	6.8 mm/s	10.8 (11.8)	0.021	3.4 mm/s	
Median of the Difference EO - EC of the VAP	5.9 (9.8)	2.8 (3.3)	0.009	3.2 mm/s	4.4 (6.5)	0.016	1.6 mm/s	
Amplitude-ML/ EO 	7.7 (9.2)	2.2 (3.9)	<0.001	5.5 mm	7.6 (2.1)	<0.001	5.4 mm	
Amplitude-ML/ EC 	13.9 (14.7)	1.8 (4.3)	<0.001	12.1 mm	13.4 (7.3)	<0.001	11.6 mm	
Median of the Difference EO - EC of the AML	6.12 (9.34)	0.02 (0.6)	<0.001	6.1 mm	6.1 (8.4)	0.011	6.1 mm	
Amplitude-AP/ EO 	7.8 (6.6)	3.5 (3.1)	<0.001	4.3 mm	6.59 (3.06)	0.013	3.1 mm	
Amplitude-AP/ EC 	13.9 (15.3)	4.51 (2.54)	<0.001	9.4 mm	8.01 (9.69)	0.001	3.5 mm	
Median of the Difference EO - EC of the AAP	7.4 (9.2)	0.89 (2.22)	0.005	6.5 mm	3.19 (6.72)	0.009	2.3 mm	

Note: Data are shown as median and interquartile range of Mann-Whitnney Test. VML: Velocity mediolateral (mm/s); VAP: Velocity anteroposterior (mm/s); AML: Amplitude Mediolateral (mm); AAP: Amplitude Anteroposterior (mm); EO: Eyes Open; EC: Eyes Closed.