vestibular hallucinatory state

   Also referred to as vestibularly evoked visual hallucination. Both terms refer to the vestibu-lar organ, a term which is indebted to the Latin noun vestibulum (forecourt, entrance hall). They areusedtodenotea * simple or * geometric visual hallucination that can be evoked by means of ear irrigation with warm or cold water. As the Bulgarian otoneurologist Ognyan Kolev notes, vestibular calorization with fluids between 20° and 44°C in healthy individuals, especially when placed in a dark environment, may give rise to * photoptic phenomena consisting of dots, lines, circumferences, arcs, circles, stars, triangles, quadrangles, clouds, columns, and so on. These hallucinations may appear to be stationary or moving, and to be approaching or receding, while they may also undergo changes in colour and brightness. As to the neurophysio-logical correlates of vestibularly evoked visual hallucinations, Kolev suggests that the anatomo-functional connections between the vestibular and optical systems may play an important role, as well as the haemodynamic effects of vestibular calorization on the microcirculatory blood flow of the visual system. In 1953, the Scottish psychiatrist Alistair Sutherland Livingston Rae (1912-2006) described a case in which vestibular calorization with the aid of cold water entailed a displacement ofpre-existent visual hallucinations to the left, followed by their disappearance.

   References

   Kolev, O.I. (1994). Visual hallucinations evoked by caloric vestibular stimulation in normal humans. Journal of Vestibular Research,5, 19-23.

   Rae, A.S.L. (1953). A recurrent vestibular hallucinatory state. Stereotactic and Functional Neu-rosurgery, 13, 96-102.