Orientation in space and perception of earth-verticality in patients with Parkinson`s disease and Pisa syndrome.

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With this study we plan to investigate orientation in space in patients with Parkinsons disease (PD) and Pisa syndrome (PS). Orientation in space involves the visual, somatosensory and vestibular system. Perception of earth-verticality can be investigated by determining the subjective visual vertical (SVV). SVV tilts are induced in normal subjects when tilted >60° to one side (A effect). Altered verticality perception is also the hallmark of the ocular tilt reaction (OTR), a syndrome caused by lesions of the otolithic pathway between the inner ear and the medial longitudinal fasciculus (riMLF). It is characterized by deviation of the SVV, head tilt, ocular torsion and skew deviation. PD encompasses perceptual deficits including visual, vestibular and proprioceptive information processing. Abnormal axial postures are also frequent findings in PD. One such disorder of posture is PS, characterized by lateral flexion of the spine. Preliminary results show an SVV tilt in PS patients. It is unknown if this SVV tilt in PS is due to the A-effect, given the inner roll-plane deviation of these patients or due to a primary perceptual dysfunction. Could PS be a manifestation of otolithic imbalance or of an asymmetric involvement of the riMLF? Do the alterations in perception of body schema and in the integration of somatosensory information change the OTR classic features to a body lateral deviation? How does dopaminergic medication affect these somatosensory and perceptual deficits? We plan to collect demographic and clinical data of the PD/PS population at the Institute of Neurosciences of the Favaloro Foundation, Buenos Aires, Argentina. These patients will be investigated for signs of an OTR, and the A-effect will be examined by determining the SVV in different degrees of body tilt (with and without dopaminergic stimulation) and compared to PD-patients without PS, PD-patients with lateral deviation not caused by PS, and healthy subjects.