The perception of head rotation in Parkinson's disease.

The accuracy in detecting angular displacements of the head and the neck was investigated in 14 patients with idiopathic Parkinson's disease (PD) and 16 age matched normal controls by the technique of vestibular and cervical "remembered" saccades. It was found that although the remembered saccades in PD patients were multiple-step and showed low initial saccadic gain, the final eye position of the eyes matched the rotational stimulus as accurately as in normals. This indicates that perception of head/neck rotation is normal in PD which is inconsistent with views that vestibulo/proprioceptive dysfunction contributes to the postural disorder in PD. The presence of multiple-step remembered vestibular and cervical saccades agrees with reported abnormalities in visual remembered saccades in PD and indicates that the difficulty in generating saccadic movements based on memorized sensory information is not confined to visual-memory.