PSYCHOGERIATRIC NOTE Atypical Charles Bonnet Syndrome in a patient with hemianopia and cognitive impairment after right occipitotemporal stroke Charles Bonnet Syndrome (CBS) is characterized by recurrent simple and complex visual hallucina- tions (VH) in patients with visual impairments due to ophthalmological conditions but with normal mental status and full insight. A deafferentation theory that explains CBS assumes that a loss of visual inputs results in compensatory cortical hyperexcitability and spontaneous neuronal firing of the occipital visual cortices. 1 VH might also be explained by cortical release phenomena, where visual loss disinhibits endogenous activation of the visual cortex, mainly the fusiform gyrus. 2 The con- tent of the complex VH depends on the aberrant activation of those specific regions of the ventral visual stream involved in the perception of faces, figures, animals, or objects. 1,2 Additionally, CBS has been observed in patients with normal visual acuity but with visual field defects after occipital or occipitotemporal strokes, and it has a slight prevalence after right-sided lesions. Among these patients, a small number experience VH restricted to the hemianopic field. VH usually occurred immediately after the stroke onset and lasted from 1 week to 3 months, usually resolving spontaneously. 3 Recently some authors reported that CBS might coexist with mild cognitive impairment, raising the possibility that CBS might mask a cognitive decline. 4 However, few studies have explored cognitive func- tioning in CBS, and the relationship between CBS and cognitive impairment is still debated. Further- more, an atypical CBS or a CBS plus variant has been proposed to include patients with multimodal hallucinations, dementia, and low insight. 5 We report a unique case of a patient with right occipitotemporal stroke and cognitive impairments without dementia who developed CBS in the hemianopic field 1 year after the stroke. An extensive neuropsychological assessment was administered. The patient was a right-handed 62-year-old man with left hemiparesis, left hemianopia, and cognitive deficits after an ischaemic stroke in the territory of the right posterior cerebral artery. Neuropsychologi- cal assessment showed mild left neglect, construc- tional apraxia, visual agnosia, and visuo-spatial and episodic memory impairments. Screening tests ruled out a dementia condition, and at 1-year follow-up, no signs of cognitive decline were reported (Table 1). One year after the stroke, the patient suddenly started to experience VH for which he was admitted to the hospital. VH were confined to the left hemianopic field; they were initially simple (‘I see psychedelic flies.’ ‘The wall is waving like a flag.’) but then became more complex (‘A health assistant gave me his jacket.’‘A child is eating an ice cream.’‘They are following me into the bathroom.’). He showed emotional distress over the hallucinations but was aware of their inexis- tence. Brain magnetic resonance imaging ruled out recent strokes and showed the previous ischaemic lesion that encompassed the right inferior temporal gyrus, posterior hippocampus and parahippocampal regions (part of the ventral visual stream), and calcarine region (Fig. SS1). Ophthalmological examinations showed no ocular diseases. The patient underwent standard and dynamic 24-h electroencephalographic examinations that showed mild theta abnormalities in the right temporal and posterior areas and no epileptic activities. He was initially treated with levetiracetam 500 mg twice daily, later replaced by valproic acid 500 mg twice daily after the onset of aggressive verbal behaviour. One week after onset, the hallucinations dis- appeared, and the patient was dismissed with no psy- chotropic treatment. To our knowledge, this is the only case reported in the literature involving late-onset CBS in the hemianopic field after right posterior stroke, with extensive neuropsychological assessment showing visuo-perceptual and visuo-spatial deficits. A © 2020 Japanese Psychogeriatric Society 1 doi:10.1111/psyg.12548 PSYCHOGERIATRICS 2020