Visual hallucinations in psychologically normal people: Charles Bonnet's syndrome

Video-evoked neuromarkers of visual function in age-related macular degeneration

Neural markers of visual function in age-related macular degeneration (AMD) allow clinicians and researchers to directly evaluate the functional changes in visual processing which occur as a result of the progressive loss of afferent input from the macula. Unfortunately, few protocols exist that elicit such neural markers, and most of these are poorly adapted to AMD. Here, we propose a novel method of embedding frequency tags into full color and motion videos by periodically manipulating the contrast of visual information of different spatial frequencies at different temporal frequencies. These videos elicit steady-state visual evoked potentials (SSVEPS) in viewers which, when measured using electrophysiological neuroimaging methods, independently represent the responses of populations of neurons tuned to the tagged spatial frequencies. We used electroencephalography (EEG) to record the SSVEPs of 15 AMD patients and 16 age-matched healthy controls watching a 6-min series of natural scene videos filtered with this spatial frequency tagging method. Compared with healthy controls, AMD patients showed a lower SSVEP to high spatial frequency information, and a stronger response to the low spatial frequency information in the video set. The ratio of the SSVEP to lower relative to higher spatial frequency information was strongly predictive of both visual acuity and contrast sensitivity, and the topographic distributions of these responses suggested retinotopic reorganization of the neural response to spatial frequency information.

The prevalence of Charles-Bonnet syndrome in ophthalmic patients: A systematic review and meta-analysis

OBJECTIVES

Charles Bonnet Syndrome (CBS) involves visually impaired yet mentally healthy individuals experiencing visual hallucinations (VH) while being aware of the hallucinations' unreality. Its prevalence varies across different conditions, with low vision, bilateral vision loss and advanced age being established as risk factors. This meta-analysis aims to comprehensively assess CBS literature with regard to CBS prevalence in ophthalmic patients.

METHODS

A comprehensive literature search was conducted on June 11th and June 13th 2023, using the databases PubMed/MEDLINE and Web of Science. Data evaluation and extraction was accomplished by two separate authors. Study analysis was performed qualitatively, thereafter quantitatively by a subsequent meta-analysis, including subgroup assessments for variations among demographic and ophthalmic variables.

RESULTS

49 eligible studies were identified, encompassing data from 20 303 patients. The collective prevalence of CBS in literature was determined to be 10.2 % (95 % confidence interval: 7.23 % - 14.1 %). Vision rehabilitation patients suffer most frequently from CBS (24.6 %). Patients with retinal diseases, low vision, and glaucoma suffer from CBS at similar rates. The prevalence of CBS among these cohorts spans from 11.8 % to 17.7 %. Age (p = 0.0013) and sex (p = 0.003) correlated statistically significantly with the prevalence of CBS.

CONCLUSIONS

CBS is prevalent among ophthalmic patients with various eye diseases, especially in the presence of low vision. Ophthalmologists should consider that about one in six patients with retinal diseases, glaucoma, or low vision they assessed might experience CBS. Awareness among medical professionals should be increased, as education provides patients with relief.

Visual cortical activity in Charles Bonnet syndrome: testing the deafferentation hypothesis

Visual hallucinations in individuals following sight loss (Charles Bonnet syndrome; CBS) have been posited to arise because of spontaneous, compensatory, neural activity in the visual cortex following sensory input loss from the eyes-known as deafferentation. However, neurophysiological investigations of CBS remain limited. We performed a multi-modal investigation comparing visual cortical activity in 19 people with eye disease who experience visual hallucinations (CBS) with 18 people with eye disease without hallucinations (ED-Controls; matched for age and visual acuity) utilising functional MRI, EEG, and transcranial magnetic stimulation (TMS). A pattern of altered visual cortical activity in people with CBS was noted across investigations. Reduced BOLD activation in ventral extrastriate and primary visual cortex, and reduced EEG alpha-reactivity in response to visual stimulation was observed in CBS compared to ED-Controls. The CBS group also demonstrated a shift towards lower frequency band oscillations in the EEG, indicative of cortical slowing, with significantly greater occipital theta power compared to ED-controls. Furthermore, a significant association between reduced activation in response to visual stimulation and increased excitability (in the form of reduced TMS phosphene thresholds) was observed in CBS, indicating persistent visual cortical activation consistent with hyperexcitability, which was found to be significantly associated with increased hallucination severity. These results provide converging lines of evidence to support the role of increased visual cortical excitability in the formation of visual hallucinations in some people following sight loss, consistent with the deafferentation hypothesis.

Charles Bonnet syndrome in patients with geographic atrophy secondary to age-related macular degeneration: a cross-sectional study

Background

Age-related macular degeneration (AMD) is a prevalent cause of irreversible vision loss among the elderly. The prevalence and detailed characteristics of Charles Bonnet syndrome (CBS) remain largely unexplored in patients with geographic atrophy (GA) secondary to AMD.

Objectives

To investigate the prevalence and characteristics of CBS in patients with GA secondary to AMD.

Design

Prospective cross-sectional study.

Methods

A total of 149 patients with GA secondary to AMD were previously screened and examined for clinical studies. These patients were then prospective contacted by telephone for this study, and 120 patients responded and agreed to do an interview on symptoms of CBS. All with CBS were inquired about detailed characteristics of their hallucinations.

Results

Patients with GA secondary to AMD were aged 82.1 ± 6.2 years and 62% were of female biological sex. The prevalence of CBS was 25 in 120 (20.8%). Thirteen (52%) of those with CBS were not previously informed of the disease. We found no difference between those with and without CBS in terms of age, biological sex, hearing difficulties, whether living alone or with others, co-morbidity of psychiatric or neurological diseases, or psychotropic use. Characteristics of the visual hallucinations were reported to occur at various frequencies from daily to less than monthly, occur during various times of the day, and almost always last minutes at most. Ten in 25 (40%) had not told anyone of having CBS.

Conclusion

One in five with GA has CBS, which ranks GA as an eye disease with one of the highest reported prevalences of CBS. The condition presents with a significant variation across the patient group. A very large proportion of those with CBS were not informed of the disease and had never told anyone of their condition by their own initiative.

Is Charles Bonnet Syndrome a Harbinger of Neurocognitive Disorder With Lewy Bodies? A Clinical Conundrum

Charles Bonnet syndrome (CBS) is a clinical condition in which patients with visual impairment experience visual hallucinations (VH) in the presence of clear consciousness. It typically occurs in elderly people and confuses clinicians with multiple differential diagnoses due to VH, which can be present in a variety of clinical conditions ranging from psychosis to neurocognitive disorders (eg, neurocognitive disorder with Lewy bodies). In the latter, the concomitant presence of cognitive decline and parkinsonism aids the diagnosis. Here we report the case of an elderly man with retinitis pigmentosa (and thus significant visual loss), who presented with VH, thus warranting a diagnosis of CBS, but who later also manifested a rapid onset cognitive decline and parkinsonism, which necessitated a new diagnosis of major neurocognitive disorder with Lewy bodies. This case prompted us to consider whether CBS is a harbinger of neurocognitive disorder with Lewy bodies or whether there is a clinical overlap between these 2 clinical constructs. This case report attempts to unravel this clinical conundrum.

A case series of musical hallucinations in psychiatry of old age-in search of the sound of silence

Musical hallucinations (MH) are the subjective experience of hearing music when none is played. They are a rare, understudied area of psychiatry. MH are more common in women and older age and have several underlying aetiologies and predisposing factors such as hearing impairment, mental illness and certain medications. There are no consensus guidelines on treatment; thus, current treatment has two broad approaches: (1) the removal of potential inciting factors (e.g. optimising hearing aids, medications) or (2) pharmacotherapy (antipsychotics, antidepressants, mood stabilisers and cognitive enhancers). This paper presents a case series of patients presenting with MH to a psychiatry of old age service in Dublin City and reviews the current literature of MH. Older age, female gender and hearing impairment are known risk factors for MH. Our findings concurred with the literature-two of three patients were female, and two of three patients suffered from hearing impairment. As this was a psychiatry of old age service, all patients were elderly. One case had a swift resolution of symptoms with a combination of an antipsychotic and antidepressant. The other two cases had limited responses to treatment despite optimising their hearing aids and trials of a number of medications at therapeutic levels. Further research into MH is needed to establish a treatment that is evidence based and symptom focused.

Epidemiology and phenomenology of the Charles Bonnet syndrome in low-vision patients

BACKGROUND

The occurrence of visual hallucinations in visually impaired people without mental impairment is known as Charles Bonnet Syndrome (CBS). To date, the prevalence of CBS has been reported with high variance. The present study aims at evaluating the prevalence of CBS among low-vision patients.

METHODS

From March 2018 to February 2022, 194 patients with a visual acuity ≥ 0.5 logMAR approached the low vision section of the Eye Clinic Sulzbach. Of these, 50 patients were found eligible, agreed to participate in the study and were screened for CBS. The course of the disease, its phenomenology and characteristics, the circumstance of onset, the ability to manipulate and resolve the hallucinations, and the psychosocial aspects of CBS were investigated.

RESULTS

26% of patients with low vision suffered from CBS. Women did not suffer from CBS significantly more often than men. Often, insight into the unreality of the images is not achieved immediately. Patterns or so-called "simple" hallucinations occurred just as frequently as other types of images such as people, body parts or faces. The most frequent images were animals. Visual hallucinations, lasting only for seconds in most cases, occurred more frequently during the day and in bright surroundings. All patients experienced the hallucinations exclusively with their eyes open. The hallucinations generally did not move with the eyes. Many sufferers did neither communicate about their hallucinations nor consult any physician.

CONCLUSIONS

CBS among low-vision patients is common. Its prevalence constitutes clinical relevance. Future management of CBS may benefit from encouraging patients to share their experiences and consult a physician.

Visual hallucinations originating in the retinofugal pathway under clinical and psychedelic conditions

Psychedelics like LSD (Lysergic acid diethylamide) and psilocybin are known to modulate perceptual modalities due to the activation of mostly serotonin receptors in specific cortical (e.g., visual cortex) and subcortical (e.g., thalamus) regions of the brain. In the visual domain, these psychedelic modulations often result in peculiar disturbances of viewed objects and light and sometimes even in hallucinations of non-existent environments, objects, and creatures. Although the underlying processes are poorly understood, research conducted over the past twenty years on the subjective experience of psychedelics details theories that attempt to explain these perceptual alterations due to a disruption of communication between cortical and subcortical regions. However, rare medical conditions in the visual system like Charles Bonnet syndrome that cause perceptual distortions may shed new light on the additional importance of the retinofugal pathway in psychedelic subjective experiences. Interneurons in the retina called amacrine cells could be the first site of visual psychedelic modulation and aid in disrupting the hierarchical structure of how humans perceive visual information. This paper presents an understanding of how the retinofugal pathway communicates and modulates visual information in psychedelic and clinical conditions. Therefore, we elucidate a new theory of psychedelic modulation in the retinofugal pathway.

Musical hallucination or musical obsession? A differential diagnosis between two cases

Musical hallucinations and musical obsessions are distinct phenomena. The first can be understood as a manifestation of the musical ear syndrome, which produces deafferentation auditory hallucinations, while the latter is an obsessive symptom of obsessive-compulsive disorders. Both symptoms are often poorly understood and mistaken for one another or for signs of psychotic disorders. We report two cases, one characterized by musical hallucinations and the other by musical obsessions, both with comorbid hearing impairment, which is the main confounding factor in their differential diagnosis. We critically compare the two cases and their key features, allowing diagnostic differentiation and a targeted therapeutic approach.

Review of Risk Factors, Pathophysiology, Management Principles, and Role of Medications

This is a case report of one patient experiencing psychotic symptoms in the setting of Charles Bonnet syndrome (CBS). Case description is included, and patient has been deidentified. Patient's consent could not be obtained for the submission of the report. The case report focuses on understanding and formulating key psychological issues addressed in this case. It is important to identify that the absence of psychotic illness is classical in patients presenting with psychotic symptoms in CBS and the role of antipsychotic medication is uncertain. A literature review on the management of CBS guidelines published across the world and summarization of the management approach applicable to this case. Visual hallucination is a perception of a visual stimuli when none exists. CBS is characterized by the presence of complex visual hallucinations experienced by the visually impaired, i.e., in an individual with ocular pathology causing vision loss without having true psychosis or dementia. Furthermore, the person having these experiences has a preserved insight into the unreal nature of the perceptions and the absence of mental disorders. An introduction to the terminology "atypical CBS" or "CBS plus" was done to consider visual hallucinations in individuals with low level of insight in a setting of possible cognitive deficits or other hallucinatory modalities.

Modelling phenomenological differences in aetiologically distinct visual hallucinations using deep neural networks

Visual hallucinations (VHs) are perceptions of objects or events in the absence of the sensory stimulation that would normally support such perceptions. Although all VHs share this core characteristic, there are substantial phenomenological differences between VHs that have different aetiologies, such as those arising from Neurodegenerative conditions, visual loss, or psychedelic compounds. Here, we examine the potential mechanistic basis of these differences by leveraging recent advances in visualising the learned representations of a coupled classifier and generative deep neural network-an approach we call 'computational (neuro)phenomenology'. Examining three aetiologically distinct populations in which VHs occur-Neurodegenerative conditions (Parkinson's Disease and Lewy Body Dementia), visual loss (Charles Bonnet Syndrome, CBS), and psychedelics-we identified three dimensions relevant to distinguishing these classes of VHs: realism (veridicality), dependence on sensory input (spontaneity), and complexity. By selectively tuning the parameters of the visualisation algorithm to reflect influence along each of these phenomenological dimensions we were able to generate 'synthetic VHs' that were characteristic of the VHs experienced by each aetiology. We verified the validity of this approach experimentally in two studies that examined the phenomenology of VHs in Neurodegenerative and CBS patients, and in people with recent psychedelic experience. These studies confirmed the existence of phenomenological differences across these three dimensions between groups, and crucially, found that the appropriate synthetic VHs were rated as being representative of each group's hallucinatory phenomenology. Together, our findings highlight the phenomenological diversity of VHs associated with distinct causal factors and demonstrate how a neural network model of visual phenomenology can successfully capture the distinctive visual characteristics of hallucinatory experience.

Explanatory power by vagueness. Challenges to the strong prior hypothesis on hallucinations exemplified by the Charles-Bonnet-Syndrome

Predictive processing models are often ascribed a certain generality in conceptually unifying the relationships between perception, action, and cognition or the potential to posit a 'grand unified theory' of the mind. The limitations of this unification can be seen when these models are applied to specific cognitive phenomena or phenomenal consciousness. Our article discusses these shortcomings for predictive processing models of hallucinations by the example of the Charles-Bonnet-Syndrome. This case study shows that the current predictive processing account omits essential characteristics of stimulus-independent perception in general, which has critical phenomenological implications. We argue that the most popular predictive processing model of hallucinatory conditions - the strong prior hypothesis - fails to fully account for the characteristics of nonveridical perceptual experiences associated with Charles-Bonnet-Syndrome. To fill this explanatory gap, we propose that the strong prior hypothesis needs to include reality monitoring to apply to more than just veridical percepts.

Charles Bonnet Syndrome Adversely Affects Vision-Related Quality of Life in Patients with Glaucoma

PURPOSE

To investigate the impact of Charles Bonnet syndrome (CBS) on vision-related quality of life (VRQoL) in patients with glaucoma.

DESIGN

Cross-sectional cohort study.

PARTICIPANTS

Twenty-four patients with CBS and 42 matched controls without CBS out of 337 patients with open-angle glaucoma (OAG) with visual field (VF) loss.

METHODS

A matching technique was used to identify control patients with similar disease stage, best-corrected visual acuity (BCVA) and age to patients with CBS. Patients' VRQoL was determined using the National Eye Institute Visual Function Questionnaire 25 (NEI VFQ-25). Rasch-calibrated NEI VFQ-25 scores of the CBS group and the control group were compared. Uni- and multivariable regression analysis was used to evaluate the impact of different factors on VRQoL.

MAIN OUTCOME MEASURES

Vision-related quality of life in patients with glaucoma with CBS and without CBS.

RESULTS

Vision-related quality of life scores were significantly lower in the CBS group than in the control group on both the visual functioning scale with 39 points (95% confidence interval (CI): 30-48) vs. 52 points (95% CI: 46-58) (P = 0.013) and on the socioemotional scale with 45 points (95% CI: 37-53) vs. 58 points (95% CI: 51-65) (P = 0.015). Univariable regression analysis showed that integrated visual field mean deviation (IVF-MD) (r2 = 0.334, P < 0.001), BCVA in the better eye (r2 = 0.117, P = 0.003), and the presence of CBS (r2 = 0.078, P = 0.013) were significantly correlated to VRQoL scores on the visual functioning scale. Integrated visual field mean deviation (r2 = 0.281, P < 0.001), age (r2 = 0.048, P = 0.042), and the presence of CBS (r2 = 0.076, P = 0.015) were significantly correlated to VRQoL scores on the socioemotional scale. Multivariable regression analysis showed that IVF-MD and the presence of CBS accounted for nearly 40% of the VRQoL score on the visual functioning scale (R2 = 0.393, P < 0.001) and for 34% of the VRQoL score on the socioemotional scale (R2 = 0.339, P < 0.001).

CONCLUSIONS

Charles Bonnet syndrome had a significant negative association to VRQoL in patients with glaucoma. Presence of CBS should be considered when evaluating VRQoL in patients with glaucoma.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Emotional well-being in Charles Bonnet syndrome: exploring associations with negative affect, loneliness and quality of life

Background

Charles Bonnet syndrome (CBS) is a condition characterised by the occurrence of vivid and complex visual hallucinations in individuals with visual impairment.

Objective

To explore the relationship between emotional distress and the perceived impact of CBS symptoms on participants' lives. We tested the hypothesis that heightened negative affect was associated with a more negative appraisal of CBS symptoms, increased self-reported loneliness, and poorer quality of life (QOL).

Design

Cross-sectional.

Methods

Participants recruited predominantly via vision-related charities rated their hallucinations and their impact on a Likert scale. Loneliness and negative affect were assessed with the Three-Item Loneliness Scale and Positive and Negative Affect Schedule. Health index (EQ-5D-3L) and vision-related QOL (VF-9) were also assessed. Correlation analysis and multi-variable regression determined the relation between survey responses.

Results

The majority of 126 respondents (81%) were aged 65+ years and 84% reported active CBS symptoms. Fifty-five percent of respondents rated impact of CBS as negative and no-one rated the impact as 'very pleasant'. A statistically significant correlation was found between impact of CBS and negative affect (p ⩽ 0.001; rho = -0.34) and impact of CBS and loneliness (p = 0.017; rho = -0.21). The relation between negative affect and CBS impact remained statistically significant when accounting for the impact of loneliness and the relationship between loneliness and CBS effect (p = 0.002, adj R 2 = 0.1). A statistically significant correlation between loneliness and negative affect (p ⩽ 0.001; rho = 0.55) was also found.

Conclusion

Respondents experiencing negative emotions were more likely to perceive the impact of CBS symptoms as negative and report greater feelings of loneliness. Negative affect is an important consideration when assessing people with CBS.

Modelling perception as a hierarchical competition differentiates imagined, veridical, and hallucinated percepts

Mental imagery is a process by which thoughts become experienced with sensory characteristics. Yet, it is not clear why mental images appear diminished compared to veridical images, nor how mental images are phenomenologically distinct from hallucinations, another type of non-veridical sensory experience. Current evidence suggests that imagination and veridical perception share neural resources. If so, we argue that considering how neural representations of externally generated stimuli (i.e. sensory input) and internally generated stimuli (i.e. thoughts) might interfere with one another can sufficiently differentiate between veridical, imaginary, and hallucinatory perception. We here use a simple computational model of a serially connected, hierarchical network with bidirectional information flow to emulate the primate visual system. We show that modelling even first approximations of neural competition can more coherently explain imagery phenomenology than non-competitive models. Our simulations predict that, without competing sensory input, imagined stimuli should ubiquitously dominate hierarchical representations. However, with competition, imagination should dominate high-level representations but largely fail to outcompete sensory inputs at lower processing levels. To interpret our findings, we assume that low-level stimulus information (e.g. in early visual cortices) contributes most to the sensory aspects of perceptual experience, while high-level stimulus information (e.g. towards temporal regions) contributes most to its abstract aspects. Our findings therefore suggest that ongoing bottom-up inputs during waking life may prevent imagination from overriding veridical sensory experience. In contrast, internally generated stimuli may be hallucinated when sensory input is dampened or eradicated. Our approach can explain individual differences in imagery, along with aspects of daydreaming, hallucinations, and non-visual mental imagery.

[Temporary and persistent visual phenomena in neurology]

Temporary and persistent visual phenomena are a frequent reason for a neurological presentation. The diagnosis can usually be made with the help of a structured anamnesis with determination of the time of onset, the course and symptoms as well as the monocular vs. binocular manifestation. The visual aura in migraine is certainly the most frequent entity to be differentiated. In particular, persistent visual phenomena such as visual snow syndrome, hallucinogen persisting perception disorder and the Charles Bonnet syndrome (CBS) seem to be underdiagnosed in clinical practice for various reasons and are probably not that rare. Instrumental diagnostics are mostly used for exclusion diagnostics and are a component of a complete patient education, but can be indicative for certain questions (CBS, epilepsy). This article presents the most frequent visual phenomena from the neurological practice and their differential diagnoses, guided by a case history.

Charles Bonnet syndrome in patients with Stargardt disease: prevalence and risk factors

AIMS

To describe the prevalence of the Charles Bonnet syndrome (CBS) and search for potential CBS risk factors in a Dutch Stargardt disease (STGD1) cohort.

METHODS

Eighty-three patients with STGD1 were screened for CBS. They underwent a full eye examination. All patients completed the social functioning domain of the 36-Item Short Form Health Survey questionnaire. Participants suspected of CBS were interviewed to further evaluate their visual hallucinations.

RESULTS

CBS prevalence was 8.4%. Six out of seven patients with CBS were women. CBS was not associated with age (p=0.279, Mann-Whitney). Patients with CBS had a significant lower social functioning score (p<0.05, Mann-Whitney). All seven patients with CBS were in the category of vision impairment (visual acuity <6/12, but ≥3/60). Moreover, first hallucinations manifested after a drop in visual acuity. The retinal atrophic area of the worst eye tended to be lower in the CBS group (range 0.11-9.86 mm²) as compared with controls (range 0-180 mm²). There was no relation between the position of the scotoma and the location of the visual hallucinations.

CONCLUSION

The relative high CBS prevalence in STGD1 suggests that CBS may be more prevalent in younger ophthalmic patients than currently presumed. In this specific group of patients, we established social isolation and acquired vision impairment as risk factors for CBS. There was a female preponderance among patients with CBS. Age and retinal pigment epithelium atrophy were not identified as significant risk factors. We should actively diagnose CBS in patients of any age who fulfil the criteria for the category vision impairment, especially in cases where social isolation is suspected.

The presenting visual symptoms of optic chiasmal disease

Recognising optic chiasmal disease early is important in order to avoid irreversible visual loss and the potential risk of mortality for patients. Yet, there is frequently a delay in the initial diagnosis. Whilst the signs of optic chiasmal disease, particularly the perimetric findings, are well documented in the recent literature, the symptoms have been less well reported. Whilst some patients with optic chiasmal disease will be asymptomatic, many will complain of visual symptoms including symptomatic field defects, problems with central vision, difficulty with near tasks, binocular visual disturbances, colour vision disturbances, photophobia, phosphenes, glare, and rarely, oscillopsia and visual hallucinations. Others may have headache or the severe and sudden visual symptoms associated with pituitary apoplexy. The visual symptoms may be vague or non-specific, even when there are significant bitemporal visual field defects. We aim in this review to describe the presenting visual symptoms of optic chiasmal disease, and to illustrate these with selected qualitative descriptions from the literature. Our hope is that this will aid clinicians in eliciting a careful history of the sometimes subtle symptoms that may be present.

Transcranial Direct Current Stimulation in the Treatment of Visual Hallucinations in Charles Bonnet Syndrome: A Randomized Placebo-Controlled Crossover Trial

OBJECTIVE

To investigate the potential therapeutic benefits and tolerability of inhibitory transcranial direct current stimulation (tDCS) on the remediation of visual hallucinations in Charles Bonnet syndrome (CBS).

DESIGN

Randomized, double-masked, placebo-controlled crossover trial.

PARTICIPANTS

Sixteen individuals diagnosed with CBS secondary to visual impairment caused by eye disease experiencing recurrent visual hallucinations.

INTERVENTION

All participants received 4 consecutive days of active and placebo cathodal stimulation (current density: 0.29 mA/cm²) to the visual cortex (Oz) over 2 defined treatment weeks, separated by a 4-week washout period.

MAIN OUTCOME MEASURES

Ratings of visual hallucination frequency and duration following active and placebo stimulation, accounting for treatment order, using a 2 × 2 repeated-measures model. Secondary outcomes included impact ratings of visual hallucinations and electrophysiological measures.

RESULTS

When compared with placebo treatment, active inhibitory stimulation of visual cortex resulted in a significant reduction in the frequency of visual hallucinations measured by the North East Visual Hallucinations Interview, with a moderate-to-large effect size. Impact measures of visual hallucinations improved in both placebo and active conditions, suggesting support and education for CBS may have therapeutic benefits. Participants who demonstrated greater occipital excitability on electroencephalography assessment at the start of treatment were more likely to report a positive treatment response. Stimulation was found to be tolerable in all participants, with no significant adverse effects reported, including no deterioration in preexisting visual impairment.

CONCLUSIONS

Findings indicate that inhibitory tDCS of visual cortex may reduce the frequency of visual hallucinations in people with CBS, particularly individuals who demonstrate greater occipital excitability prior to stimulation. tDCS may offer a feasible intervention option for CBS with no significant side effects, warranting larger-scale clinical trials to further characterize its efficacy.

Charles Bonnet Syndrome Associated With Recurrent Hypertensive Crisis

Charles Bonnet syndrome (CBS) is a disorder of visual hallucinations in psychologically normal patients with ocular disease or damage to visual pathways. The etiology of CBS is not fully understood. It is associated with various triggers, with age-related macular degeneration the most common; other triggers are systemic diseases such as stroke, multiple sclerosis, and anemia as well as lighting issues, fatigue, and medical or surgical eye treatments. Visual disturbances such as decreased visual acuity, visual field deficits, or visual hallucinations are common in association with hypertensive encephalopathy. We describe a patient with episodic CBS triggered by recurrent hypertensive crises, which resolved with blood pressure management in the hospital setting.

Investigation of structural brain changes in Charles Bonnet Syndrome

•

Reduced grey matter in the occipital cortex in eye disease groups.

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Widespread altered diffusivity in eye disease groups.

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No cortical or white matter changes associated with presence of visual hallucinations.

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Negative association between hippocampal volume and Hallucination severity.

Background and objectives

In Charles Bonnet Syndrome (CBS), visual hallucinations (VH) are experienced by people with sight loss due to eye disease or lesional damage to early visual pathways. The aim of this cross-sectional study was to investigate structural brain changes using magnetic resonance imaging (MRI) in CBS.

Methods

Sixteen CBS patients, 17 with eye disease but no VH, and 19 normally sighted people took part. Participants were imaged on a 3T scanner, with 1 mm resolution T1 weighted structural imaging, and diffusion tensor imaging with 64 diffusion directions.

Results

The three groups were well matched for age, sex and cognitive scores (MMSE). The two eye disease groups were matched on visual acuity. Compared to the sighted controls, we found reduced grey matter in the occipital cortex in both eye disease groups. We also found reductions of fractional anisotropy and increased diffusivity in widespread areas, including occipital tracts, the corpus callosum, and the anterior thalamic radiation. We did not find any significant differences between the eye disease participants with VH versus without VH, but did observe a negative association between hippocampal volume and VH severity in the CBS group.

Discussion

Our findings suggest that although there are cortical and subcortical effects associated with sight loss, structural changes do not explain the occurrence of VHs. CBS may relate instead to connectivity or excitability changes in brain networks linked to vision.

Associations between Age-Related Eye Diseases and Charles Bonnet Syndrome in Participants of the Age-Related Eye Disease Study 2: Report Number 26

Eyecare professionals should be aware of Charles Bonnet Syndrome (CBS), a phenomenon involving visual hallucinations in people with visual impairments. We examined prevalence of CBS among AREDS2 participants and its associations with age-related eye diseases.

[Causes of visual hallucinations in Parkinson's disease]

BACKGROUND

Visual hallucinations (VH) have mainly been considered as late symptoms of Parkinson's disease (PD); however, minor forms of VH also occur in early stages of the disease. Initially dopaminergic overstimulation was discussed as the cause and later on VH have been considered as an early red flag of dementia in PD.

OBJECTIVE

The present study analyzed whether the pathophysiological concept of VH has been enlarged in recent years.

MATERIAL AND METHODS

Clinical, pharmacological, neuropathological as well as functional magnetic resonance imaging studies dealing with VH were reviewed. A systematic classification in monomodal and multimodal models of VH is proposed. The applicability to various forms of VH and various triggering situations is critically examined.

RESULTS

Reduction of the visual information input, erroneous visual processing, attention deficits, and dysfunctional connectivity between various cerebral networks have been shown. There is partial overlapping with the Lhermitte syndrome and the Charles Bonnet syndrome. No model is able to fully explain all VH variants. Not all VH have the same pathogenesis and the same poor prognosis.

CONCLUSION

The chain of causes underlying VH is complex and can vary from patient to patient. So far the therapeutic applications are largely unexplored; however, there is preliminary evidence that beside adjustment of the medication, improvement of visual acuity, active involvement of the partner, and possibly, individually adaptable coping strategies could be successfully implemented.

Charles Bonnet Syndrome in patients with open-angle glaucoma - prevalence and correlation to visual field loss

PURPOSE

To determine the prevalence and characteristics of Charles Bonnet Syndrome (CBS) and its relation to visual field loss (VFL) in patients with open-angle glaucoma (OAG).

DESIGN

Prospective, cross-sectional study.

PARTICIPANTS

Adult patients (n=337) with manifest OAG with verified VFL and without significant macular disease or extraocular conditions known to cause visual hallucinations.

METHODS

Patients attending the glaucoma outpatient department of the Skåne University hospital, Malmö, Sweden, between April 1^st 2018 and December 31^st 2018 were consecutively evaluated for inclusion. Potentially eligible patients admitting to having complex visual hallucinations were interviewed to explore the characteristics of their hallucinatory experiences. Recent automated visual field examinations were available for all participants and swept source optical coherence tomography was performed in participants with CBS to rule out previously undiagnosed macular pathology. The correlation between potential risk factors and CBS was evaluated with logistic regression analysis.

MAIN OUTCOME MEASURE

Prevalence of CBS in patients with OAG.

RESULTS

CBS was found in 7.1% (95% CI: 4.7% - 10.6%) of patients with OAG. Participants with CBS were more likely to have at least one eye with a visual field index (VFI) of ≤ 30% compared to those without CBS (71% vs. 34.2%; P = 0.001). Although the best-corrected visual acuity (BCVA) in the worse eye was significantly lower in participants with CBS (decimal equivalent of Snellen BCVA: 0.25 vs. 0.6, P = 0.003), 33% of these participants had a BCVA of ≥ 0.5 in the worse eye. In multivariable analysis, CBS was correlated to the VFI of the better eye (odds ratio 0.984; 95% CI: 0.969 - 0.998, P = 0.030) and the BCVA of the worse-seeing eye (odds ratio 0.210; 95% CI: 0.046 - 0.952, P = 0.043).

CONCLUSIONS

CBS was not a rare condition in patients with glaucoma. Patients with a combination of advanced VFL and low BCVA had the highest risk of CBS; however, one out of three patients with CBS had a BCVA of ≥ 0.5 in both eyes. These findings emphasize the importance of being attentive to symptoms of CBS in patients with glaucomatous VFL even when visual acuity is preserved.

Schankin C, Straube A. Visual Phenomena Associated With Migraine and Their Differential Diagnosis

BACKGROUND

Visual phenomena are of many different kinds; their differential diagnosis is usually possible with directed history-taking. In this review, we describe common visual phenomena that must be distinguished from a migraine aura.

METHODS

This review is based on publications retrieved by a selective search in PubMed and the Web of Knowledge/Science, with special attention to the current classification of the International Headache Society and the recommendations of the German Migraine and Headache Society. The following search terms were used: "visual phenomena/phenomenon," "migraine aura," and "persistent/complication/ long-lasting/ongoing."

RESULTS

The most helpful questions for differential diagnosis are whether the symptoms are present in one eye only or in both, whether their onset was sudden or over minutes or days, and whether the phenomenon has occurred only once or repeatedly, or is persistently present. A visual aura associated with migraine must be distinguished, in rare cases, from an isolated epileptic aura, from cerebral/retinal ischemia, or from visual snow. Further differential diagnoses include a persisting perceptual disturbance after hallucinogen use (HPPD, "hallucinogen persisting perception disorder") and the Charles Bonnet syndrome (CBS); the latter arises as a consequence of severely impaired vision. Posterior reversible encephalopathy syndrome (PRES) is rare and generally reveals itself over its further course through the appearance of additional clinical manifestations. Primary ophthalmological causes can usually be readily identified and classified by ophthalmological examination.

CONCLUSION

Patients with visual phenomena typically consult physicians from various medical specialties. A correct differential diagnosis can be made based on the history if the physician views the symptoms in their overall context to determine the particular disease entity that is responsible.

Closed-Eye Visual Hallucinations Preceding Severe Alcohol Withdrawal

Few existing cases of closed-eye visual hallucinations have been reported. These rare perceptual disturbances are distinct from open-eye visual hallucinations, as observed in Charles Bonnet syndrome. This case report discusses a 35-year-old male who presented with closed-eye visual hallucinations 24 hours before severe alcohol withdrawal. On initial presentation, the patient denied auditory or visual hallucinations. The day before the onset of severe alcohol withdrawal, the patient reported vivid, colorful, and lifelike visual hallucinations with his eyes closed which disappeared with eyes open. The hallucinations consisted of cartoon characters such as Daffy Duck, a lifelike blond woman with curly hair, and a tree-covered landscape. The patient endorsed awareness that the hallucinations were not real. The next day, the patient became acutely delirious with rapid onset of agitation, space-time disorientation, open-eye visual hallucinations, and emotionally disturbing illusions. The patient was promptly transferred to the intensive care unit (ICU) to manage severe alcohol withdrawal, including administration of intravenous sedation. During follow-up evaluation, the patient retained a clear memory of the closed-eye hallucinations. However, he had no recollection of the ICU course. Several etiologies were considered, including alcohol withdrawal complicated by polysubstance withdrawal and acute hepatitis, which resolved following pharmacological treatment. To the best of our knowledge, this is the first case report of its kind. Additional research is required to elucidate the etiology, mechanism, and clinical implications of closed-eye visual hallucinations.

Nonpsychotic Hallucinations and Impaired Vision: The Charles Bonnet Syndrome

Charles Bonnet syndrome is a clinical entity that presents with visual hallucinations in patients with worsening visual acuity and no underlying neuropsychiatric disorder. A 93-year-old male presented to the emergency department complaining of complex visual hallucinations. He had been without his prescription glasses as they were being repaired. After work-up and medication review, no underlying drug or neuropsychiatric disease was found. Moreover, the hallucinations resolved after his vision improved. This case illustrates a frequently missed clinical entity in our practice. Clinical suspicion and reassurance are paramount for adequate patient care.

Knowledge domain and emerging trends in visual hallucination research: A scientometric analysis

BACKGROUND

Visual hallucination (VH) refers to a spontaneous visual perception without corresponding external stimuli and often occurs in ophthalmological and neuropsychiatric disorders. It is associated with poor quality of life, and increased patient hospitalization and nursing home admission. To date, a scientometric analysis of research on VH is lacking.

AIM

To objectively summarize the features of VH research and gain insights into the emerging trends in research on VH.

METHODS

CiteSpace V was used in this article. Publication outputs, document types, geographic distributions, co-authorship status, research hotspots, and co-citation status were analyzed. A total of 2176 original articles and 465 reviews were included in the database downloaded from the Web of Science Core Collection. We selected the top 50 most cited or occurring articles or items to create a visualized network with a 1-year interval. In the document co-citation analysis stage, we performed clustering analysis on co-cited references, and log likelihood tests were used to name the clusters.

RESULTS

The results showed that most publications can be classified into neurology, sports, and ophthalmology studies. In addition, North America, Europe, Asia and Australia published the most documents. Some well-known authors have always had a leading role in this field; meanwhile, new authors keep emerging. A relatively stable cooperation has been formed among many authors. Furthermore, neuropsychiatric symptom and functional connectivity are the top hotspots. Research on VH in dementia with Lewy bodies and Parkinson’s disease (PD) have received much attention. Studies on VH in PD are likely to be the new emerging trends in the future, especially the mechanisms of VH.

CONCLUSION

Research on VH has formed a complete system. More large-scale clinical and in-depth basic research are required to better understand the mechanisms underlying VH, which will contribute to our understanding of the pathophysiology and therapeutic options for VH.

An overview of psychological and social factors in Charles Bonnet syndrome

Charles Bonnet syndrome (CBS) is a condition where cognitively normal individuals with sight impairment experience simple and/or complex visual hallucinations. The exact pathogenesis of CBS is unknown; however, deafferentation is often recognised as a causal mechanism. Studies have provided insight into the multifaceted impact of CBS on wellbeing. Onset of CBS may cause distress among those believing visual hallucinations are indicative of a neurological condition. Hallucinatory content is often congruent with the emotional response. For example, hallucinations of a macabre nature typically result in a fearful response. Visual hallucinations may be highly disruptive, causing everyday tasks to become challenging. Clinical management relies on forewarning and pre-emptive questioning. Yet, knowledge and awareness of CBS is typically low. In this review, we provide a summary of the social and psychological implications of CBS and explore recent developments aimed at raising awareness and improving patient management.

Three cases of Charles Bonnet Syndrome in patients with advanced glaucomatous visual field loss but preserved visual acuity

Purpose

To describe three cases of Charles Bonnet syndrome (CBS) in glaucoma patients with preserved visual acuity.

Methods

Three glaucoma patients who had taken part in a recent CBS study were interviewed about their hallucinations. The patients underwent macular optical coherence tomography (OCT) of both eyes. The visual function was evaluated with visual field measurement (Humphrey visual field analyser) and visual acuity testing (Snellen scale).

Results

All three patients had preserved visual acuity (≥0.5 in both eyes) and at least one eye with advanced visual field defect (Mean Deviation worse than −12.00 decibel). They all reported vivid visual hallucinations with insight into the unreal nature of the hallucinations.

Conclusion

Charles Bonnet syndrome can occur in glaucoma despite preserved visual acuity. Awareness of this relation is desirable among clinicians, as it will improve communication with patients.

How do the blind 'see'? The role of spontaneous brain activity in self-generated perception

Spontaneous activity of the human brain has been well documented, but little is known about the functional role of this ubiquitous neural phenomenon. It has previously been hypothesized that spontaneous brain activity underlies unprompted (internally generated) behaviour. We tested whether spontaneous brain activity might underlie internally-generated vision by studying the cortical visual system of five blind/visually-impaired individuals who experience vivid visual hallucinations (Charles Bonnet syndrome). Neural populations in the visual system of these individuals are deprived of external input, which may lead to their hyper-sensitization to spontaneous activity fluctuations. To test whether these spontaneous fluctuations can subserve visual hallucinations, the functional MRI brain activity of participants with Charles Bonnet syndrome obtained while they reported their hallucinations (spontaneous internally-generated vision) was compared to the: (i) brain activity evoked by veridical vision (externally-triggered vision) in sighted controls who were presented with a visual simulation of the hallucinatory streams; and (ii) brain activity of non-hallucinating blind controls during visual imagery (cued internally-generated vision). All conditions showed activity spanning large portions of the visual system. However, only the hallucination condition in the Charles Bonnet syndrome participants demonstrated unique temporal dynamics, characterized by a slow build-up of neural activity prior to the reported onset of hallucinations. This build-up was most pronounced in early visual cortex and then decayed along the visual hierarchy. These results suggest that, in the absence of external visual input, a build-up of spontaneous fluctuations in early visual cortex may activate the visual hierarchy, thereby triggering the experience of vision.

Benefit of psychiatric evaluation on anxiety in patients with Charles Bonnet syndrome

Objective

Charles Bonnet syndrome (CBS) is defined as an occurrence of visual hallucinations (VHs) in the absence of any psychiatric/neurological disorder. Significantly reduced vision due to age-related macular degeneration (AMD), cataract or glaucoma is the most common cause for CBS. Aim of this randomized controlled study was to assess whether additional treatment by a psychiatrist is beneficial for patients with CBS.

Methods and Analysis

Patients with visual acuity of 0.5 LogMAR or worse in the better eye were screened. Instruments used were an interview asking about details of the VH, a mental test and a questionnaire on quality of life. Patients with CBS were randomised into two groups: in group 1, a patient-doctor consultation was performed by an ophthalmologist, and in group 2 a consultation and, if needed, additional medical assessment and treatment was given by a psychiatrist.

Results

4900 patients were screened. 390 patients met the inclusion criteria and among these a CBS prevalence of 34 patients (8.7%) was found. The female-to-male ratio was 4:1 and the average age was 79.3 ± 9.7 years. Four different types of VH were observed: 41% humans (n=14), 32% geometrical shapes/patterns (n=11), 15% plants (n=5) and 12% animals (n=4). The change in quality of life in patients with CBS was not significantly different in both groups (p=0.727, ophthalmologist: n=18, psychiatrist: n=16).

Conclusion

It is essential for medical staff involved with patients suffering from severe vision loss to be aware of CBS. This will help to better identify and interpret symptoms and could also lead to a more adequate treatment for affected patients.

Discussion

It is essential for medical staff involved with patients suffering from severe vision loss to be aware of CBS. This will help to better identify and interpret symptoms and could also lead to a more adequate treatment for affected patients.

Exacerbation of visual hallucinations in Charles Bonnet syndrome due to the social implications of COVID-19

Objective

Charles Bonnet syndrome (CBS) occurs secondary to sight loss, characterised by spontaneous visual hallucinations. Symptom manifestation can be influenced by social isolation. This research aims to evaluate the effect of the COVID-19 pandemic lockdown on patients with CBS.

Methods and analysis

A prospective cross-sectional survey of 45 individuals with active CBS. Open and closed ended questions were used to measure patient-reported features of hallucinatory experiences during the COVID-19 lockdown and perceived episode triggers. Analysis comprised of descriptive statistics, analysis of variance and associations, supplemented with qualitative descriptions.

Results

The survey was operational for 31 days during the COVID-19 pandemic (June–July 2020). The mean (±SD) age of respondents was 69.3 (±18) years and the majority (42.2%) had macular disease. Loneliness during the lockdown was associated with changes in the nature of visual hallucinations (p=0.04). Individuals experiencing greater loneliness were, on average, older than those with no changes to their feelings of loneliness (mean age 73.3±17 vs 60.2±19 years; p=0.03). Despite experiencing greater feelings of loneliness (67%), most individuals (60%) had not accessed support services for this reason.

Conclusions

Around half of respondents in this survey experienced exacerbation of visual hallucinations during the COVID-19 pandemic, which may partly be explained by loneliness and/or environmental triggers. We provide suggestions to promote effective patient self-management of symptoms.

Hallucinations on demand: the utility of experimentally induced phenomena in hallucination research

Despite the desire to delve deeper into hallucinations of all types, methodological obstacles have frustrated development of more rigorous quantitative experimental techniques, thereby hampering research progress. Here, we discuss these obstacles and, with reference to visual phenomena, argue that experimentally induced phenomena (e.g. hallucinations induced by flickering light and classical conditioning) can bring hallucinations within reach of more objective behavioural and neural measurement. Expanding the scope of hallucination research raises questions about which phenomena qualify as hallucinations, and how to identify phenomena suitable for use as laboratory models of hallucination. Due to the ambiguity inherent in current hallucination definitions, we suggest that the utility of phenomena for use as laboratory hallucination models should be represented on a continuous spectrum, where suitability varies with the degree to which external sensory information constrains conscious experience. We suggest that existing strategies that group pathological hallucinations into meaningful subtypes based on hallucination characteristics (including phenomenology, disorder and neural activity) can guide extrapolation from hallucination models to other hallucinatory phenomena. Using a spectrum of phenomena to guide scientific hallucination research should help unite the historically separate fields of psychophysics, cognitive neuroscience and clinical research to better understand and treat hallucinations, and inform models of consciousness. This article is part of the theme issue 'Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation'.

Frightening Complex Visual Hallucinations in an Elderly Patient with Ophthalmological Pathology and Vascular Dementia

A lady in her 90s was referred to the Later Life Team (LLT) in a rural area of the United Kingdom with complex visual hallucinations (VH). She had significant ophthalmological pathology, including cataracts, a branch retinal vein occlusion, and vitreous haemorrhage. The hallucinations included seeing monkeys ripping the heads off of her cats and lions prowling the garden. The patient was distressed by the hallucinations and believed them to be real events. Her management involved low dose olanzapine and requesting that her ophthalmological surgery be expedited. The surgery resulted in a significant reduction in VH. A diagnosis of vascular dementia went on to be made following cognitive testing and imaging. The cognitive impairment may have contributed to the patient's inability to identify her experiences as hallucinations and thus render her without insight. A review of the computed tomography (CT) scans performed prior to the patient's presentation to our service confirmed significant vascular pathology including small vessel disease and lacunar infarcts. Cognitive testing confirmed a cognitive impairment which had gone unnoticed by her family. This case leads to an interesting discussion regarding diagnosis in complex VH in cases of significant ophthalmological pathology but a lack of insight. Various authors have proposed theories to explain VH; cortical release and the Perception and Attention Deficit (PAD) model are explored as possible explanations for the experiences of this patient.

Case Report: Effect of a Retinal Prosthesis System on Charles Bonnet Visual Hallucinations

SIGNIFICANCE

Charles Bonnet syndrome is commonly encountered and diagnosed in low-vision patients. It can be distressing for some of them, as there is no known effective treatment of this condition. Although there is a growing interest in retinal implants for blind patients with severe retinal diseases, the effect of these devices on Charles Bonnet syndrome visual hallucinations remains undocumented.

PURPOSE

The aim of this study was to report changes in the Charles Bonnet syndrome of a patient with retinitis pigmentosa after implantation of the Argus II retinal prosthesis.

CASE REPORT

A 65-year-old patient with retinitis pigmentosa and no light perception was frequently experiencing Charles Bonnet syndrome. In the hope of improving his vision, he received an Argus II retinal prosthesis in 2018 and participated in a 10-week rehabilitation program at the Institut Nazareth et Louis-Braille. The nature and the frequency of his Charles Bonnet syndrome were documented with the Questionnaire de repérage du syndrome de Charles Bonnet (a French questionnaire used to screen for Charles Bonnet syndrome) before the surgery and for 70 weeks after it. The patient's visual acuity and visual fields were monitored during the same period. Additional tests were administered to document the visual, psychological, and cognitive states of the patient throughout the study.

CONCLUSIONS

Although this case report confirmed that Argus II retinal prosthesis improves the performance of blind patients in visual tests, the improvement was not associated with a decrease in the symptoms of Charles Bonnet syndrome.

UnReal? Investigating the Sense of Reality and Psychotic Symptoms with Virtual Reality

Distortions of reality, such as hallucinations, are common symptoms of many psychiatric conditions. Accordingly, sense of reality (SoR), the ability to discriminate between true and false perceptions, is a central criterion in the assessment of neurological and psychiatric health. Despite the critical role of the SoR in daily life, little is known about how this is formed in the mind. Here, we propose a novel theoretical and methodological framework to study the SoR and its relation to psychotic symptoms. In two experiments, we employed a specialized immersive virtual reality (VR) environment allowing for well-controlled manipulations of visual reality. We first tested the impact of manipulating visual reality on objective perceptual thresholds (just noticeable differences). In a second experiment, we tested how these manipulations affected subjective judgments of reality. The results revealed that the objective perceptual thresholds were robust and replicable, demonstrating that SoR is a stable psychometric property that can be measured experimentally. Furthermore, reality alterations reduced subjective reality judgments across all manipulated visual aspects. Finally, reduced sensitivity to changes in visual reality was related to self-reported prodromal psychotic symptoms. These results provide evidence for the relevance of SoR in the assessment of psychosis and other mental disorders in which reality is distorted.

Deafferentation as a cause of hallucinations

PURPOSE OF REVIEW

The association between hallucinations and sensory loss, especially vision- and hearing-impairment, has been firmly established over the past years. The deafferentation theory, a decrease of the threshold for activation in the brain and the consequential imbalance between excitatory and inhibitory brain networks, is hypothesized to underly this relationship. Here we review the studies investigating this theory with a focus on the most recent literature to better understand the contribution of sensory loss to hallucinations.

RECENT FINDINGS

A large cross-sectional study has recently confirmed the relationship between auditory impairment and deafferentation. However, the underlying mechanisms of deafferentation are still under debate, with hyperexcitability and deviations in bottom-up and top-down processes being the most likely explanations. Social isolation following sensory impairment increases the risk for hallucinations. Better knowledge and awareness about the contribution of deafferentation and loneliness would benefit diagnosis and treatment of hallucinations.

SUMMARY

Studies imply activity in higher order areas, corresponding to the functional mapping of sensory system, and a general state of higher excitability as neurobiological explanation. Auditory deafferentation, tinnitus and other auditory hallucinations, likely lie on a continuum. Social isolation mediates psychotic symptoms in sensory-impaired individuals. Currently, there is no standard treatment for deafferentation hallucinations.

Neuroanatomic correlates of visual hallucinations in poststroke hemianopic patients

OBJECTIVES

Homonymous hemianopia (HH) is the most frequent visual-field defect after a stroke. Some of these patients also have visual hallucinations, the origin and frequency of which remain largely unknown. The aims of this work were to determine the occurrence of visual hallucinations among poststroke hemianopic patients in function of the location (Brodmann areas) of the brain lesion, as determined by MRI, and to study the neuroanatomic correlates of these hallucinations by nature, frequency, and type.

METHODS

One hundred sixteen patients with HH who had had a stroke in the posterior region, including the occipital lobe, participated in the study. We evaluated the frequency and nature of visual hallucinations with the Questionnaire for Hallucinations in Homonymous Hemianopia. The volume of each patient's brain lesion was modeled in 3 dimensions.

RESULTS

Of 116 patients with an HH from a cortical infarction, 85 were excluded due to confounding factors associated with hallucinations. In the final cohort of 31 patients matched for lesion location and etiology, 58% had experienced hallucinations. A significant inverse correlation between lesion size and the frequency of visual hallucinations emerged. The presence of visual hallucinations in poststroke hemianopic patients requires a relatively small lesion that includes, at the very least, loss of the striate cortex but that spares Brodmann area 19, 20, and 37.

CONCLUSION

Our results suggest that visual hallucinations might be due to complex interactions between damaged areas and intact areas of the visual cortex. We discuss these findings regarding models of perception and of visual recognition. Our results also have implications for the clinical care of patients with HH who have had a stroke.

Reversible Charles Bonnet Syndrome After Oculoplastic Procedures

Individuals with Charles Bonnet syndrome (CBS) typically have severe visual loss and experience visual hallucinations yet have no psychiatric disease. Visual impairment often is due to end-stage glaucoma or macular degeneration. We report 3 cases of CBS in patients who underwent an oculoplastic surgical procedure. One patient experienced binocular visual distortion due to excessive topical ophthalmic ointment, and 2 patients experienced monocular visual impairment from patching. Visual hallucinations resolved once vision returned to baseline. We highlight the possibility of transient CBS in postoperative patients who have temporary iatrogenic vision impairment in one or both eyes.

Prevalence of Charles Bonnet syndrome in patients with age-related macular degeneration: systematic review and meta-analysis

Age-related macular degeneration (AMD) is the most common cause of visual impairment in the developed world. A number of patients experience complex lifelike visual experiences-Charles Bonnet syndrome (CBS). In this systematic review, our aim was to provide an overview of the CBS literature in relation to AMD, to determine the prevalence of CBS in patients with AMD and to provide an overview of associated demographical and clinical aspects. We searched the literature databases PubMed/MEDLINE, EMBASE, Web of Science, the Cochrane Central, and PsycINFO on 22 March 2019 for studies evaluating the prevalence of CBS in patients with AMD. Two independent authors extracted the data and evaluated risk of bias. Studies were reviewed qualitatively in the text and quantitatively in a meta-analysis including subgroup analyses for differences between demographic and clinical factors. We identified 18 studies with data on >4303 patients with AMD. We found an overall prevalence of CBS of 15.8% (95% confidence interval: 11.0%-21.2%). When looking at consecutively recruited patients with neovascular AMD from the clinic, prevalence of CBS was 7.2% (95% confidence interval: 4.3%-10.6%). Among visitors to visual rehabilitation centres, prevalence of CBS was 31.6% (95% confidence interval: 21.7%-42.3%). Taken together, we find that CBS is rather common in patients with AMD.

Functional MRI study in a case of Charles Bonnet syndrome related to LHON

INTRODUCTION

Charles Bonnet syndrome is characterized by simple or complex visual hallucinations (VH) due to damage along the visual pathways. We report a functional MRI study of brain correlates of VH in the context of a severe optic atrophy in a patient with Leber's Hereditary Optic Neuropathy (LHON).

CASE REPORT

A 62-year-old man was diagnosed with LHON (11778/ND4 mtDNA mutation) after subacute visual loss in left eye (right eye was amblyopic). One month later, he experienced VH of a few seconds consisting in "moving red and blue miniature cartoons". One year later VH content changed in colored mosaic (10-15 s duration), usually stress-related, and blue and white flashes (2-5 s), triggered by unexpected auditory stimuli. Audiometry revealed mild sensorineural hearing loss. Three block design functional MRI paradigms were administrated: 1) random "clap", 2) "checkerboard" and 3) non-random "beep". After random "claps" simple flashes were evoked with bilateral activation of primary and secondary visual cortex, cuneus, precuneus and insula. Neither hallucinations nor cortex activation were registered after "checkerboard" stimulation, due to the severe visual impairment. Primary and secondary auditory cortices were "beep"-activated, without eliciting VH by non-random "beep".

CONCLUSIONS

The peculiarity of our case is that VH were triggered by random auditory stimuli, possibly due to a cross-modal plasticity between visual and auditory networks, likely influenced by the sensorineural deafness. Functional alterations of both networks in resting conditions have been demonstrated in LHON patients, even without an auditory deficit. Finally, the absence of VH triggered by expected stimuli is consistent with the "expectation suppression theory", based on increased neural activations after unexpected but not by predicted events.

The elephant in the room: understanding the pathogenesis of Charles Bonnet syndrome

PURPOSE

Charles Bonnet syndrome (CBS) is a syndrome characterised by complex visual hallucinations in individuals who are cognitively normal, though often elderly and visually impaired. Although first described over 250 years ago, the condition remains poorly understood and difficult to treat.

RECENT FINDINGS

Our understanding of CBS pathogenesis has advanced little since it was first described, and much of the recent literature consists of case studies strikingly similar to the first published account of CBS. However, imaging studies have provided some indication as to the cortical areas implicated in the genesis of complex visual hallucinations, and the existence of similar hallucinatory syndromes in other sensory modalities suggests a common underlying mechanism.

SUMMARY

This review begins by describing what is currently known about CBS, focusing on epidemiology, clinical presentation and diagnosis. It then explores potential starting points for better understanding the pathogenesis of CBS, namely the existence of similar conditions in other sensory modalities and the reproduction of complex visual hallucinations in sensory deprivation scenarios. Finally, it discusses how CBS should be approached in clinical practice.

Screening for Charles Bonnet syndrome: Should the definition be reconsidered?

Purpose

Charles Bonnet syndrome (CBS) is a condition in which individuals with visual impairment (VI) and with no cognitive deficits experience visual hallucinations, typically with no other sensory hallucinations. Although few isolated case reports of CBS from India have been published, the prevalence for CBS in India is largely unknown. The primary aim of this study was to estimate CBS prevalence in patients with vision impairment visiting a tertiary eye care center.

Methods

The study was conducted in two phases. In phase 1, patients with VI, age ≥40 years with presenting visual acuity worse than 20/63 were enrolled. In phase 2, patients with presenting visual acuity worse than 20/63 and/or with binocular visual field loss, age ≥18 years were recruited. A CBS survey was administered only to those who passed a screening test for cognition impairment.

Results

A total of 218 patients were screened (phase 1 = 113 and phase 2 = 105). Two-hundred ten patients (mean age ± standard deviation = 49.2 ± 17.3 years, males = 139) were found eligible to complete the CBS survey. Fourteen patients were found to have visual hallucinations. In addition, three other patients had visual hallucinations with associated auditory input to the visual imagery. All patients had complete insight about their hallucinations.

Conclusion

Depending on the inclusion criteria, we found the prevalence for CBS in patients with VI to vary between 6.7% to 8.1% (if including patients with auditory input). More investigation is needed to assess the associated role of other sensory inputs (e.g. auditory) with the visual imagery experienced in CBS.

Reversible Charles Bonnet syndrome secondary to upper lid ptosis

Complex visual hallucinations can occur in visually impaired individuals with no underlying psychiatric disorder. This phenomenon is known as Charles Bonnet syndrome (CBS). It is more common in elderly patients who are suffering from impaired vision due to ocular or neurological disease processes, resulting in sensory deprivation. We report a case of CBS in an elderly female with marked ptosis, which was exacerbated following a knee replacement surgery under general anaesthesia. Her CBS symptoms persisted until surgical correction of the ptosis, with a rapid and dramatic resolution of her hallucinations. Although CBS is typically a chronic condition, unusually in this case it was acute and reversible.

Resting-state functional connectivity and cortical thickness characterization of a patient with Charles Bonnet syndrome

Charles Bonnet syndrome (CBS) is a rare condition characterized by visual impairment associated with complex visual hallucinations in elderly people. Although studies suggested that visual hallucinations may be caused by brain damage in the visual system in CBS patients, alterations in specific brain regions in the occipital cortex have not been studied. Functional connectivity during resting-state functional magnetic resonance imaging (rs-fMRI; without hallucinations) in CBS patients, has never been explored. We aimed to investigate brain structural and functional changes in a patient with CBS, as compared with late blind (LB) and normally sighted subjects. We employed voxel-based morphometry and cortical thickness analyses to investigate alterations in grey matter characteristics, and rs-fMRI to study changes in functional brain connectivity. Decreased grey matter volume was observed in the middle occipital gyrus and in the cuneus in the CBS patient, and in the middle occipital gyrus and in the lingual gyrus within LB subjects, compared to their respective control groups. Reductions in cortical thickness in associative and multimodal cortices were observed in the CBS patient when comparing with LB subjects. The precuneus exhibited increased functional connectivity with the secondary visual cortex in the CBS patient compared to the controls. In contrast, LB patients showed decreased functional connectivity compared to sighted controls between the DMN and the temporo-occipital fusiform gyrus, a region known to support hallucinations. Our findings suggest a reorganization of the functional connectivity between regions involved in self-awareness and in visual and salience processing in CBS that may contribute to the appearance of visual hallucinations.