The term ictal illusion is indebted to the Latin noun ictus, which means blow or thrust. In neurology the term ictus refers to a paroxysmal epileptic seizure. The term ictal illusion is used to denote an "illusion that occurs in the context of an *aura or a related seizure disorder. The term is used in opposition to *ictal hallucination. The distinction between ictal illusions and ictal hallucinations is similar to that between non-ictal illusions and hallucinations. Thus ictal illusions are conceptualized as misperceptions of actually perceived objects or stimuli, whereas ictal hallucinations are considered to be percepts that arise in the absence of an appropriate object or stimulus in the extracorporeal world. Both, however, arise as a consequence of a focal epileptic seizure.
References
Baumgartner, G. (1982). Visuelle Wahrnehmungsstörungen und Halluzinationen bei Epilepsie und anderen Hirnerkrankungen. In: Halluzinationen bei Epilepsien und ihre Differentialdiagnose. Edited by Karbowski, K. Bern: Verlag Hans Huber.
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.
Dictionary of Hallucinations. J.D. Blom. 2010.