Room tilt illusion in Parkinson's disease: loss of spatial reference frames?

Room tilt illusion, a misperception that the entire room is tilted, is a rare but nonspecific neurological symptom. We report a patient with Parkinson's disease who developed typical room tilt illusion. Single photon emission computed tomography demonstrated hypoperfusion of the posterior area of the right intraparietal sulcus, which is related to discriminating the surface orientation of three-dimensional objects. Therefore, it is possible that dysfunction of this region of the intraparietal sulcus may have disrupted the integration of spatial reference frames for internal representation of the surrounding space in our patient, and thus may have caused room tilt illusion.