Tilt Illusions (or Room Tilt Illusion, RTI)

Timothy C. Hain, MDMost recent update: May 16, 2020

Rarely people experience an illusion that the world is tilted. This is not a frequent disturbance and there is little written about it. The perception of tilt depends on integration of sensory input (i.e. eyes, ears, feet, internal estimate from brain), central processing of signals in the brainstem and brain. Thus there are diverse potential causes of the tilt symptom.

In what was probably the largest report on this subject, Sierra-Hidalgo et al (2012) reviewed 130 cases reported in the literature, and indicated that "The most common location of the injury was the central nervous system (CNS) (61.4 %). Supratentorial and infratentorial structures accounted for the same frequency of lesions. The most common aetiology was cerebral ischaemia (infarction or transient ischaemic episode; 27.7 %)."

In a contrary report, Malis and Guyot (2003) reported that "We report here 23 cases of room tilt illusion, all but 2 occurring in patients with either vestibular peripheral abnormalities or normal assessment findings. " Thus they appear to be emphasizing an inner ear origin.

Bottom line: the RTI has been associated with many different problems, including from the ears, eyes, and brain. It is not a specific symptoms.

Structures in inner ear, showing utricle, which senses tilt

Orientation of utricle (horizontal) and saccule (vertical)

 

Abbreviations:

Input side causes of tilt illusions

Starting with the input side, there are multiple redundant inputs for tilt -- the otoliths, the eyes, and somatosensation from the feet. As always, there is also the internal idea of where one is in space that is an "input". Because there is redundant input, tilt perception should be relatively secure. Should (for example), the ear indicate that a person is angled forward, there should also be a corresponding vote from the feet and eyes. If one is wrong, the other inputs should tell the person that one of the signals is wrong. From this framework, individuals with unreliable senses, such as poor inner ear function, poor vision, inability to feel their joints, and poor cognition might all be more vulnerable to tilt illusions.

Otolith or Semicircular canal:

Ocular disturbances: Disorders that alter the torsional position of the eye can produce an illusion of tilt.

Individuals who grow up without binocular fusion, often exhibit a tendency for their eyes to take up unusual torsional positions. This is presumably because they do not fuse vision from both eyes, and "let them go". Lemmos and Eggenberger (2013) reported on ocular torsion in patients with strabismus.

We did not encounter any reports of tilt illusions attributed to somatosensory disturbances.

Central tilt illusions

Otolith processing is largely done in the brainstem. Visual processing is largely done in occipital cortext. Somatosensation widely distributed from spinal cord through the brainstem and parietal cortext. The location of the "internal model" of one's position and trajectory in space, is also likely widely distributed. Laurens et al (2010) discuss the internal model concept. Wang et al (2019) suggested that most tilt illusions are from central causes such as stroke, TIA or vestibular migraine. Lopez Dominguez suggested that room tilt illusions might be due to migraine (in a single case) as they responded to Flunarizine. Clement et al (2001), from studies on astronauts, suggested that tilt perception was the result of multisensory input, that could be reweighted by exposure to microgravity, resulting in an exaggerated sensation of tilt after returning to earth normal gravity. This is a very reasonable hypothesis.

Organized from lower to higher:

Treatment of tilt illusions

Given the diverse causes reported to cause tilt illusions, the most logical approach is to attempt to determine the cause with inner ear testing and CNS testing. If no cause can be identified, we favor treating for migraine.

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