ENVIRONMENTAL TILT

   Also referred to as visual tilting, tilting illusion, upside-down reversal of seeing, and floor-on-ceiling phenomenon. All five terms denote a transient illusory percept in which the extracor-poreal environment assumes a tilted or upside-down position. Environmental tilt typically lasts for several seconds, and usually no longer than an hour. The tilting tends to take place through a variable arc between 90° and 180°, sometimes slowly, but mostly paroxysmally. The perceived spatial relationships within the environment remain intact. The phenomenon tends to be accompanied by dizziness. Environmental tilt usually presents as a binocular illusory phenomenon, but monocular cases have been reported as well.The return to a normal orientation of the perceived objects tends to be abrupt. Restoration of normal orientation may be followed by an episode of "diplopia. In 1983 the expression "tortopia was suggested by the American neurologist Allan H. Ropper to denote the symptom complex of tilting of the visual environment. Pathophysiologically, environmental tilt is attributed primarily to functional disturbances affecting connections between cerebel-lar and cerebral vestibular-otolithic pathways. Less frequently, it is attributed to pontomedullary or cerebral cortical (especially parieto-occipital) dysfunction. Etiologically, environmental tilt is associated with a variety of neurological conditions, including the lateral medullary syndrome of Wallenberg, labyrinthine disorders, transient ischaemic attacks (TIAs) affecting the vertebro-basilar artery territory, multiple sclerosis, trauma, and encephalitis. After lateral medullary infarction, environmental tilt may last up to several days. In a conceptual and phenomenologi-cal sense, environmental tilt is closely related to " plagiopsia.

   References

   Ropper, A.H. (1983). Illusion of tilting of the visual environment. Report of five cases. Journal of Clinical Neuro-ophthalmology,3, 147-151.

   Vaphiades, M.S. (2000). Disorders of visual integration. American Orthoptic Journal, 50, 101-106.