visual aura

   Formerly known as suffusio. The term visual aura is indebted to the Greek noun aura, which means wind, breeze, or smell. It is used to denote an *aura experienced in the visual modality. The earliest known written account of a visual aura stems from the classical physician Aretaeus of Cappadocia (c. AD 150): "... flashes of purple or black colours before the sight, or all mixed together, so as to exhibit the appearance of a rainbow expanded in the heavens." Visual aurae may present as isolated * visual hallucinations or *illusions of a *simple, *geometric, or *complex nature. Occasionally, * lilliputian hallucinations have been reported in the context of visual aura. The visual aura may also present in the form of visual loss (i.e. as a *scotoma or as tunnel vision). Some examples of visual aurae are *photopsias, * visual snow, and * scintillating sco-tomata. Pathophysiologically, such simple visual phenomena are associated primarily with aberrant neuronal discharges in the primary visual cortex, although other parts of the visual system may be involved as well. The occurrence of complex visual hallucinations, as well as the occurrence oftunnel vision, is associated primarily with occipitotemporal or anteromedial temporal activity. Etiologically, visual aurae are associated primarily with paroxysmal neurological disorders such as migraine and epilepsy. When they constitute the initial or sole ictal manifestation of epilepsy, they are referred to as * visual epilepsy. When visual aurae occur in conjunction with hallucinations in other sensory modalities or with * déjà experiences, they may under certain conditions be designated as *psychic aurae. Vague or poorly defined alterations of visual perception such as 'blurring' are not customarily regarded as aurae. They rather tend to be relegated to the class of 'unclassifiable auras'. Conceptually as well as phenomenologically, visual aurae would seem to be related to * dream scintillations.

   References

   Bien, C.G., Benninger, F.O., Urbach, H., Schramm, J., Kurthen, M., Elger, C.E. (2000). Localizing value of epileptic visual auras. Brain, 123, 244-253.

   Lüders, H., Acharya, J., Baumgartner, C., Ban-badis, S., Bleasel, A., Burgess, R., Dinner, D.S., Ebner, A., Foldvary, N., Geller, E., Hamer, H., Holthausen, H., Kotagal, P., Morris, H., Meencke, H.J., Noachtar, S., Rosenow, F., Sakamotot, A., Steinhoff, B.J., Tuxhorn, I., Wyllie, E. (1998). Semiological seizure classification. Epilepsia, 39, 1006-1013.

   Podoll, K., Robinson, D. (2001). Recurrent Lilliputian hallucinations as visual aura symptom in migraine. Cephalalgia, 21, 990-992.

   Sacks, O. (1992). Migraine. Revisedandexpanded. New York, NY: Vintage Books.