Table 3.

Head motion during scans.

Movement	Task	Plane	Controls		CD
			Mean	SD	Mean	SD
Translation (mm)	Rest	x	0.08	0.07	0.12	0.10
		y	0.11	0.12	0.16	0.15
		z	0.33	0.31	0.36	0.24
	Hand	x	0.08	0.06	0.15	0.15
		y	0.11	0.11	0.17	0.16
		z	0.32	0.30	0.46	0.32
	Head	x	0.10	0.08	0.13	0.10
		y	0.13	0.14	0.17	0.15
		z	0.37	0.33	0.38	0.26
Rotation (mm)	Rest	x	0.28	0.26	0.40	0.34
		y	0.16	0.17	0.19	0.17
		z	0.21	0.17	0.34	0.29
	Hand	x	0.26	0.23	0.44	0.35
		y	0.15	0.14	0.23	0.20
		z	0.21	0.16	0.42	0.37
	Head	x	0.31	0.31	0.39	0.31
		y	0.19	0.17	0.19	0.17
		z	0.24	0.18	0.39	0.34

A three-way MANOVA (task × plane × group) was conducted to analyze translational and rotational head movements. There was a significant main effect for group on both translation (F = 744) and rotation (F = 2173), suggesting the CD group moved more than the control group overall. However, the actual magnitude of the difference was small and well below the 1.75 cutoff. There was a significant main effect for task on both translation (F = 140) and rotation (F = 128), suggesting one task was associated with greater motion. Post hoc analyses indicated that head tasks showed significantly more head motion than rest (p = 0.00) and hand tasks (p = 0.00). There was a significant main effect of plane on both translation (F = 8026) and rotation (F = 1644). Post hoc analyses indicated that z translation showed significantly more head motion than x (p = 0.00) and y translation (p = 0.00). For rotational movements, post hoc analyses indicated that rotation in the x plane showed significantly more head motion than the y (p = 0.00) and z (p = 0.00) planes.

CD, cervical dystonia.