Illusory perceptions are intriguing neuropsychiatric symptoms, largely unrecognized and classically associated with mental disorders, epilepsy or dementia (Tang & Tang, 2020), although they can also occur in healthy individuals (Tien, 1991). Their occurrence in the context of focal brain lesions such as stroke is reportedly rare (Chabwine et al., 2010), most probably because they are overlooked, which increases the difficulty of understanding their underlying mechanisms and anatomical determinants. Hence, careful screening of patients with illusory perceptions remains important, whereas illusory perceptions should be documented and investigated comprehensively. This paper reports the case of an elderly patient presenting with several rare illusory symptoms simultaneously, including the feeling of a presence (FOP) as well as auditory and visual hallucinations associated to palinopsia, in the context of a small right central opercular acute ischemic stroke.

The FOP is defined as the illusory feeling that a person is nearby, without really seeing or hearing them (Hara et al., 2021). Although rare in vascular lesions (Chabwine et al., 2010), it has long been reported in patients with psychiatric and other neurological pathologies (Brugger et al., 1996), but also in healthy subjects undergoing particular experiences, such as physical exhaustion (Blanke et al., 2014) or social isolation (Brugger et al., 1999). Although the neural mechanisms underlying this phenomenon are still to be fully elucidated, some brain regions appear to be anatomically and/or functionally involved, such as the parietal cortex and the temporoparietal junction (Blanke et al., 2014). Palinopsia, which consists of persistent visual perception after the visual stimulation has vanished (Critchley, 1951), encompasses a variety of visual symptoms, classified as illusory (unformed objects) or hallucinatory (well-formed objects). Palinopsia is classically associated with severe visual impairment following occipital brain damage, but also with visual seizures, drug abuse and migraine, etc (Abert & Ilsen, 2010).

Because these symptoms occurred simultaneously (although they were independent and clearly distinct), they were all assumed to be associated with the acute stroke lesion. However, because the complex clinical picture was compatible with multiple lesion locations (frontoparietal, temporal and occipital lobes) according to the literature, we hypothesized that only defects in associative fibers tracts connecting the brain areas of interest (namely the superior longitudinal fasciculus (SLF), the inferior longitudinal fasciculus (ILF) and the arcuate fasciculus (AF)) would be the most plausible and unambiguous explanation for this unique clinical constellation.

No part of the study procedures was pre-registered prior to the research being conducted.