Disturbed egocentric space representation in cervical dystonia.

In addition to visual spatial input, vestibular and proprioceptive signals are used in judging the egocentric space. We asked whether the abnormal head posture of patients with cervical dystonia (CD) is associated with distortions of their internal spatial reference frame. The perception of subjective straight-ahead (SSA) was tested under various conditions in 28 CD patients and in matched controls. They were asked to direct a laser pointer to the position that they believed to be "straight ahead" relative to their bodies' orientation (body-centered spatial perception). Body-independent visual spatial perception was assessed with different neuropsychological tests. CD patients had a greater deviation of the subjective straight ahead, indicating body-centered visual spatial perception, than controls. No effects were seen in body-independent visual spatial perception. Patients with CD are impaired in body-centered, egocentric spatial perception, but not in body-independent, allocentric spatial perception.