Motion sickness: part I--a theory.

Early reports on space exploration suggested that cosmonauts and astronauts sustained "motion sickness" symptoms described as "dizziness, nausea, vomiting, flashes of light, formed hallucinations or illusions of inversion of image in space." Hallucinations may be due to many causes but most of the above symptoms were similar to those experienced by some patients with expanding intracranial lesions whose symptomatology was referable to the temporoparieto-occipital cortex of the brain. On the basis of our observations, it is suggested that the term "motion sickness" might be applied to earthly symptoms of dizziness, nausea, and vomiting--such as encountered ascending in an elevator or tossing about on the sea--for they are primarily related to the inner ear, the peripheral or end organ. However, when inversion of body image and formed and unformed visual hallucinations are superimposed upon these, there must be interpretation by the temporoparieto-occipital cortex and this might be designed as "motion sickness in space."