Template:Short description Template:Infobox medical condition (new) Visual release hallucinations, also known as Charles Bonnet syndrome or CBS, are a type of psychophysical visual disturbance in which a person with partial or severe blindness experiences visual hallucinations.
First described by Charles Bonnet in 1760,<ref name="deMorsier1967">Template:Cite journal</ref><ref name="Vukicevic/Fitzmaurice">Template:Cite journal</ref> the term Charles Bonnet syndrome was first introduced into English-speaking psychiatry in 1982.<ref>Template:Cite journal</ref> A related type of hallucination that also occurs with lack of visual input is the closed-eye hallucination.
Signs and symptomsEdit
People with significant vision loss may have vivid recurrent visual hallucinations (fictive visual percepts).<ref name=":1" /> One characteristic of these hallucinations is that they usually are "lilliputian" (hallucinations in which the characters or objects are smaller than normal).<ref>Template:Cite journal</ref> Depending on the content, visual hallucinations can be classified as either simple or complex.<ref name=":1" /> Simple visual hallucinations are commonly characterized by shapes, photopsias, and grid-like patterns.<ref name=":0">Template:Cite journal</ref> Complex visual hallucinations consist of highly detailed representations of people and objects.<ref name=":0" /> The most common hallucination is of faces or cartoons.<ref name="ted">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Those affected understand that the hallucinations are not real, and the hallucinations are only visual.<ref>Template:Cite journal</ref><ref name="Mogk/Riddering/Dahl/Bruce/Brafford">Template:Cite book</ref> Visual hallucinations generally appear when the eyes are open, fading once the visual gaze shifts.<ref name=":1" /> It is widely claimed that sensory deprivation is instrumental in the progression of CBS.<ref name=":2" /> During episodes of inactivity, hallucinations are more likely to occur.<ref name=":1" /> The majority of those with CBS describe the duration of hallucinations to continue for up to a few minutes, multiple times a day or week.<ref name=":1" />
Even though people of all ages may be affected by Charles Bonnet syndrome, those within the age range of 70 to 80 are primarily affected.<ref name=":1" /> Among older adults (> 65 years) with significant vision loss, the prevalence of Charles Bonnet syndrome has been reported to be between 10% and 40%; a 2008 Australian study found the prevalence to be 17.5%.<ref name="Vukicevic/Fitzmaurice" /> Two Asian studies, however, report a much lower prevalence.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> The high incidence of underreporting this disorder is the greatest hindrance to determining the exact prevalence.<ref name="Mogk/Riddering/Dahl/Bruce/Brafford" /> Underreporting is thought to be a result of those with the condition being afraid to discuss the symptoms out of fear that they will be labeled of unsound mind.<ref name="Mogk/Riddering/Dahl/Bruce/Brafford" />
PathophysiologyEdit
There is no general consensus on the definition of CBS.<ref name=":0" /> Predominant factors correlated with CBS are a decrease of visual acuity, visual field loss, and elderly age.<ref name=":1" /> While characteristic features of visual hallucinations are not specifically linked to the anatomical site of the ocular injury, they usually match to the location of visual loss.<ref name=":1" /> The most commonly accepted theory for Charles Bonnet syndrome proposes that extreme visual impairment promotes sensory deafferentation, leading to disinhibition, thus resulting in sudden neural firings of the visual cortical regions.<ref name=":1" /> A few studies record that visual hallucinations are likely to be concentrated in the blind regions.<ref name=":2">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Functional magnetic resonance imaging (fMRI) of Charles Bonnet syndrome patients displays a relationship between visual hallucinations and activity in the ventral occipital lobe.<ref name=":1" /> A connection between age-related macular degeneration (AMD) and colored visual hallucinations has been presented.<ref name=":0" /> Color vision signals travel through the parvocellular layers of the lateral geniculate nucleus (LGN), later transmitting down the color regions of the ventral visual pathway.<ref name=":0" /> Due to cone photoreceptor damage located in the macula, there is a significant reduction of visual input to the visual association cortex, stirring endogenous activation in the color areas and thus leading to colored hallucinations.<ref name=":0" /> Patients with CBS alongside macular degeneration exhibit hyperactivity in the color areas of the visual association cortex (as shown in fMRIs).<ref name=":0" /> Those who have significant ocular disease yet maintain visual acuity may still be susceptible to CBS.<ref name=":0" />
The Deep Boltzmann Machine (DBM) is a way of utilizing an undirected probabilistic process in a neural framework.<ref name=":2" /> Researchers argue that the DBM has the ability to model features of cortical learning, perception, and the visual cortex (the locus of visual hallucinations).<ref name=":2" /> Compelling evidence details the role homeostatic operations in the cortex play in regards to stabilizing neuronal activity.<ref name=":2" /> By using the DBM, researchers show that when sensory input is absent, neuron excitability is influenced, thus potentially triggering complex hallucinations.<ref name=":2" />
A short-term change in the levels of feedforward and feedback flows of information may intensely affect the presence of hallucinations.<ref name=":2" /> In periods of drowsiness, CBS related hallucinations are more prone to arise.<ref name=":2" /> Disrupting cortical homeostatic processes after vision has been lost may prevent or setback the emergence of hallucinations.<ref name=":2" /> At varying stages of the cortical grading, acetylcholine (ACh) may impact the balance of thalamic and intracortical inputs as well as the balance in between bottom-up and top-down.<ref name=":2" /> Particularly in CBS, a shortage of acetylcholine at cortical locations should correspond to the onset of hallucinations.<ref name=":2" />
The syndrome can also develop after bilateral optic nerve damage due to methyl alcohol poisoning.<ref>Template:Cite journal</ref>
DiagnosisEdit
A variety of disciplines including optometry, ophthalmology, geriatric medicine, psychiatry, and neurology play a part in securing the diagnosis of CBS.<ref name=":0" /> Since CBS is not commonly recognized by all clinicians, it oftentimes goes misdiagnosed and identified as psychosis, delirium, or dementia.<ref name=":1" /> As a result of this, it is estimated that almost 60% of CBS patients hesitate to notify their physicians.<ref name=":1" /> By focusing on the specific type of visual hallucination, one may find an accurate diagnosis.<ref name=":1" /> If a patient presents symptoms indicative of Charles Bonnet syndrome, basic laboratory examinations like metabolic panel and blood count tests, as well as neuroimaging, may aid in an accurate diagnosis.<ref name=":1" />
TreatmentEdit
There is no treatment of proven effectiveness for CBS.<ref name=":0" /> For those experiencing CBS, knowing that they have this syndrome and not a mental illness seems to be the most comforting treatment so far, as it improves their ability to cope with the hallucinations.<ref name=":0" /> Pharmacologic management including antipsychotics, antidepressants and mood stabilizes have been used in cases with varying results. Due to inconsistent results and associated medication side effects, non-pharmacologic management such as reassurance is currently preferred.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Furthermore, treatment of underlying conditions that caused the visual loss could also remove or improve CBS associated symptoms.<ref>Template:Cite journal</ref><ref name=":4">Template:Cite journal</ref> Those experiencing severe symptoms can also utilize behavior techniques such as repeated blinking during hallucinations, rapid eye movement from one object to another and bright lighting to engage the visual neural pathways.<ref name=":4" /><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Lastly, social isolation, especially in the elderly has also been postulated as a possible etiological factor for CBS and therefore engaging with other individuals could also help alleviate CBS related symptoms.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
PrognosisEdit
As time passes from the initial onset of visual hallucinations, studies show that around 60% of those living with CBS feel that visual hallucinations have no effect on their lives, 33% of people feel that the hallucinations are disruptive to their lives, and 7% of people even find pleasure in the hallucinations.<ref name=":0" />
A large proportion of those with CBS develop the visual hallucinations as vision begins to deteriorate and stop hallucinating once vision is entirely gone.<ref name=":2" /> Complex hallucinations may progress over time if the primary loss of vision is due to damage of the early cortical areas.<ref name=":2" /> If activation of the early cortical areas is suppressed when CBS symptoms have already been exhibited, hallucinations may temporarily terminate.<ref name=":2" /> Also, interrupting vision for a short time by closing the eyes or blinking may be helpful.<ref name="Vukicevic/Fitzmaurice" />
It is possible for a stressful life event to alter the disposition of hallucinatory experiences as well as the emotional experiences (from unconcerning to concerning) in CBS.<ref name=":3">Template:Cite journal</ref> As expressed in some patients, an interplay between CBS and an acute or post-traumatic stress disorder may exist.<ref name=":3" /> The role that trauma plays in CBS may affect how and when a hallucinatory episode is triggered.<ref name=":3" />
HistoryEdit
The disease was first noted by the Swiss naturalist Charles Bonnet, who described the condition in 1760.<ref name=":1" /> He documented it in his 90-year-old grandfather<ref>Bonnet Charles (1760) Essai Analytique sur les facultés de l'âme. Copenhagen: Philibert, pp. 426–428</ref> who was nearly blind from cataracts in both eyes.<ref name="ted" /> After Bonnet's grandfather received bilateral cataract surgery, his vision evolved from slightly better to complete deterioration over time.<ref name=":0" /> It was around this period that his visual hallucinations started.<ref name=":0" /> His hallucinations consisted of perceptions of men, women, birds, carriages, buildings, tapestries, physically impossible circumstances and scaffolding patterns.<ref name="ted" /><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Even though his health was in good shape and he had an absence of any psychiatric disorders, the source of the hallucinations remained unknown.<ref name=":0" /> At forty years old, Charles Bonnet himself developed an unrevealed cause of severe vision loss and experienced the hallucinations.<ref name=":0" />
In 1936, Jean Lhermitte and Julian de Ajuriaguerra, concluded that visual hallucinations consist of thalamic lesions as well as ocular pathology.<ref name=":0" />
In 1967, French-Swiss neurologist, Georges de Morsier, coined the term Charles Bonnet syndrome in Bonnet's honor.<ref name = deMorsier1967/><ref name=":1">Template:Cite journal</ref> De Morsier's description of CBS implies a concentrated neurodegeneration, usually occurring in the elderly with typical cognition.<ref name=":0" /> In psychiatric literature, the most commonly accepted interpretation of CBS is that of Gold and Rabins'.<ref name=":0" /> In 1989, they detailed that the hallucinations associated with CBS are not affecting other sensory modalities.<ref name=":0" /> They believed that the visual hallucinations are oftentimes stereotyped, persistent, and/or repetitive in nature.<ref name=":0" />
Society and cultureEdit
The syndrome is discussed in:
- Vilayanur S. Ramachandran's book Phantoms in the Brain. Ramachandran suggests that James Thurber, who was blinded in one eye as a child, may have derived his extraordinary imagination from the syndrome.<ref>Template:Cite book</ref>
- Vikram Chandra's book Sacred Games (2006)
- David Eagleman's book Incognito: The Secret Lives of the Brain
- Oliver Sacks' 2012 book Hallucinations
- The Indian movie Jawan of Vellimala, released in 2012, in which Mammootty is a victim of the syndrome
- The Black Canvas (2014), a chamber opera by the Greek composer Spyros Syrmos, is about a celebrated painter whose visions are caused by CBS.
- Margaret Atwood's short story "Torching the Dusties"
- Deborah Lawrenson's novel The Lantern (2011)
- Gareth Brookes' graphic novel A Thousand Coloured Castles (2017)
- Dealt, 2017 documentary about notable card mechanic Richard Turner
- The 2019 Netflix film Velvet Buzzsaw
- The Doc Martin episode "One Night Only" (2022, Season 10, Episode 2) depicts Dr. Ellingham diagnosing a patient with Charles Bonnet syndrome.
See alsoEdit
- Template:Annotated link
- Template:Annotated link
- Template:Annotated link
- Template:Annotated link
- Template:Annotated link
ReferencesEdit
External linksEdit
- Information on Charles Bonnet syndrome from RNIB
- National Public Radio article with an audio segment about Charles Bonnet syndrome
- Oliver Sacks: What hallucination reveals about our minds Template:Webarchive Ted Talk, Feb 2009.
- Fortean Times article on Charles Bonnet syndrome
- 'Damn Interesting' article on Charles Bonnet syndrome
- Template:Cite journal