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Charles Bonnet syndrome

 Department of Neurology, Dr. D. Y. Patil Medical College, Pune, Maharashtra, India

Date of Submission24-Nov-2019
Date of Decision25-Feb-2020
Date of Acceptance25-Jun-2020

Correspondence Address:
Furqan Mohd Akram Khan,
H-206, Mahindra Royale, Nehrunagar Road, Pimpri, Pune - 411 018, Maharashtra,
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/mjdrdypu.mjdrdypu_321_19


Charles Bonnet Syndrome (CBS) or visual release hallucinations are a type of psychophysical visual disturbance and the experience of complex visual hallucinations (VHs) in a person with partial or severe blindness. We present a case of 73-year-old blind male, who lost his vision due to glaucoma, presented with a history of complex VHs. The investigations for alternative pathological causes of VHs were negative and therefore, the etiology of hallucinations was attributed to CBS. Excellent response to low-dose olanzapine was seen, with complete remission by the end of 5th week after starting olanzapine.

Keywords: Charles bonnet syndrome, visual hallucinations, visual impairment

How to cite this URL:
Akram Khan FM, Dave D, Nirhale S, Rohatgi S, Rao P, Naphade P. Charles Bonnet syndrome. Med J DY Patil Vidyapeeth [Epub ahead of print] [cited 2021 Nov 30]. Available from: https://www.mjdrdypv.org/preprintarticle.asp?id=308720

  Introduction Top

Charles Bonnet Syndrome (CBS) is defined by the occurrence of visual hallucinations (VHs) in the absence of any mental disorder. Elderly patients with reduced visual acuity due to ophthalmic diseases are most affected. Conditions are often associated with the syndrome of age-related macular degeneration, cataract, or glaucoma. The hallucinations are loosely associated with the cause and localization of a cerebral pathology but are strongly correlated with an abnormally activated neuronal network. It is a diagnosis of exclusion, and should be differentiated from the other causes of complex VHs that occur transiently (e.g., hypnogogic hallucinations, epileptic phenomenon, Parkinson's disease,  Lewy body dementia More Details, and migraine) or causes of persistent complex VHs (e.g., Anton's syndrome; peduncular hallucinations that occur due to the thalamic or brainstem lesions, delirium tremens). The diagnosis of CBS is made when these hallucinations occur in patients with vision loss in the absence of psychosis, delirium, or other causes. The accurate diagnosis of this distressing disease is challenging, considering the serious implications of alternative diagnoses.[1],[2],[3]

CBS was considered to be rare, in the past. Only 46 patients had been described as affected with CBS, from 1760 to 1989.[2] In recent years, numerous cases of CBS have been reported, some of which assess the frequency of hallucinatory disorders in case of visual loss. Due to lack of specific diagnostic criteria, it is difficult both to estimate the prevalence of CBS, and to determine whether CBS is more common than is generally appreciated. We emphasize particular clinical aspects and management of this case and present main data published in literature about CBS, in an attempt to educate and help new physicians and patients.

  Case Report Top

A 73-year-old male with a history of blindness in both eyes for 10 years, which started as painless field loss and gradually progressed over 3 years to complete loss of vision, due to Glaucoma, now presented with complaints of distressing complex VHs for 4 months.

Described as, seeing different types of animals mainly snakes which keep changing their size around him in a room, these animals play among them and rearrange themselves in a horizontal line, move from one place to another within the room without producing any sounds. He also sees human couples with disproportionately large heads wearing colorful goggles who vomit out the snake which grows in size and then joins other animals in the room. Frequency and duration of hallucinations varied and gradually increased from once in a day to multiple episodes daily, lasting from minutes to hours. The hallucinations were waxing and waning, more when the patient was sitting quietly alone in a room. The hallucinations were not accompanied by any change in behavior. The patient and his family denied any symptoms indicative of depression. No violent behavior toward himself or others was reported. Insight was completely present, the patient stated, that the hallucinations were unreal. In spite of complete insight, initially, the patient was frightened and perturbed by these hallucinations. The patient had no previous medical or psychiatric history and was in good physical and mental health. Ophthalmological examination revealed blindness in both eyes with raised intraocular pressure and secondary optic atrophy, the rest of the neurological including higher mental fun ctions and general physical examination was normal. His routine laboratory data were within normal ranges. Serological tests were negative. MRI Brain revealed no abnormality except for a few chronic ischemic changes. Electroencephalogram did not show any abnormal findings. Visual evoked response testing showed absent responses in both eyes. After explaining about the benign nature of the illness and reassurance about an absence of a serious medical condition patient was started on olanzapine at 5 mg/day and was increased to 10 mg/day after 2 weeks, after partial improvement in the form of decreased frequency, duration and complexity of VHs, complete remission was seen gradually over 3 weeks. Gradually, over 6 months' dose of olanzapine was reduced to 2.5 mg/day without any recurrence.

  Discussion Top

CBS is a condition that causes vivid, complex, recurring VHs, usually in older adults with later-life vision loss which cannot be explained by psychiatric, neurological, or medical disorders. VHs are often pleasant or neutral in nature, but can be distressing.[4] CBS usually occurs in elderly people, probably because of the higher prevalence of visual impairment in this group. Younger patients suffering from CBS often present in association with other conditions such as lower cognitive function, cerebrovascular disease, social isolation, and cortical atrophy. The strongest risk factors for CBS include bilateral visual impairment, declining visual acuity, cerebral damage, cognitive defects, social isolation, and sensory deprivation.[2]

The “VHs” associated with CBS can range from animated, colorful, dreamlike images to fewer complex visions of people, animals, vehicles, houses, and similar everyday images. The people who perceive these visions know they're just mirages, of sorts, i. e., the images are illusions, not delusions. Patients with CBS may initially second-guess themselves but they ultimately accept that their perceptions have no substance. In other words, adults with CBS are usually in good mental health and come to understand that these hallucinations are not sensate or real. The awareness of the unreal nature of VHs is a characteristic hallmark of CBS patients.[5]

In 1760, a Swiss philosopher and naturalist Charles Bonnet first described the condition. Bonnet documented the complex VHs experienced by his 90-year-old grandfather, Charles Lullin, and published his findings in an essay. His grandfather underwent cataract surgery in both eyes. The bilateral cataract surgery initially improved his vision, but his vision deteriorated over time. The VHs occurred shortly after his vision loss. Charles Lullin's hallucinations included detailed figures of men, women, birds, animals, buildings, tapestries, and carriages with variations in size, shape, and place. He knew that these VHs were not real, but he was uncertain why he was experiencing them. He was in good overall health without any psychiatric disorders. Ironically, Charles Bonnet also experienced VHs after he suffered from an unknown cause of painful vision loss at 20 years of age, the vision loss progressed to severe visual impairment by the age of 40 years. In 1967, another Swiss scientist, George De Morsier, coined the term, CBS.[6],[7],[8]

Commonly CBS occur in patients with poor bilateral visual acuity, but can also occur in individuals with unilateral or fluctuating visual loss. The most common ocular diseases leading to CBS is age-related macular degeneration, other common ocular diseases leading to CBS are cataracts, post-enucleation, macular photocoagulation, central retinal artery occlusion, Leber's hereditary optic neuropathy, and glaucoma. Reported non ocular causes of CBS includes lesions of diencephalon and also diffuse lesions of cortex such as pseudo-orbital tumor, acute hemorrhage infarct at the right occipital lobe, acute cerebellar infarction, optic chiasmal meningioma, anteromesial temporal lobectomy, optic neuritis associated with multiple sclerosis, occipital lobe resection due to cortical dysplasia, upper quadrantanopia after selective amygdalohippocampectomy, complete hemianopia after resection of a parietal astrocytoma, complete hemianopia after resection of a occipital glioblastoma multiforme, temporal arteritis, optic glioma with extension along optic radiation.[2]

In CBS, when retinal cells no longer receive and relay visual images to the brain, due to eye disease or damage to the optic pathways, resulting in a process of differentiation of the visual association areas of the cerebral cortex the visual system begins creating its own “phantom” images. The cause of this disorder is thought to be a misfire in the brain similar to the neurological mix-up that occurs in patients with phantom limb syndrome. Sensory deprivation due to a visual impairment produces endogenous activation of the visual cortex which then fires spontaneously, mainly in the ventral occipital lobe, within or around the fusiform gyrus (Brodmann area 37).[2],[9],[10] This theory is supported by functional neuroimaging studies, showing increased activity in the fusiform gyrus in an area corresponding to the color center, area V4, in patients who report color VHs during fMRI, or high firing activity in the middle fusiform gyrus in patients who hallucinated objects.[2]

Another hypothesis of VHs formation is based on the failure inhibition in occipital cortex of irrelevant impulses from the conscious perception of images in visually impaired patients, releasing previously subconscious perceptions into consciousness.[9]

Spontaneous remission of VHs may occur if the underlying vision deficit is corrected, as with cataract removal, after the resolution of orbital pseudotumor. Spontaneous remission of VHs may also occur in patients with static or progressive visual impairment, as acute cerebral injury, lasting several days to a week.[2],[11]

In patients with continuous and disturbing hallucinatory episodes, a specific treatment might become necessary. All patients require assurance about the benign and self-limiting nature of the disease. Nonpharmacological interventions to lessen or manage images and hallucinations by reducing the visual pathway deprivation includes: Alternate closing and opening eyes, moving the eyes in rapid back-and-forth and up-and-down movements, looking away or walking away from the images or hallucinations, staring at or fixating on the images, turning on a light (good illumination), distraction or concentrating on something else and reducing social isolation.[12],[13]

Pharmacological treatment is to be reserved only for those patients who are very distressed by the hallucinations because of the inconclusive results in the effectivity. At low doses, olanzapine and venlafaxine have shown beneficial effects. Antipsychotics, anticonvulsants, anti-anxiety, and selective serotonin reuptake inhibitors have been shown, albeit with inconsistent results, in the literature to reduce or eliminate hallucinations.[2]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Menon GJ, Rahman I, Menon SJ, Dutton GN. Complex visual hallucinations in the visually impaired: The Charles bonnet syndrome. Surv Ophthalmol 2003;48:58-72.  Back to cited text no. 1
Lerario A, Andrea Ciammola Charles bonnet syndrome: Two case reports and review of the literature. J Neurol 2013;260:1180-6.  Back to cited text no. 2
Burke W. The neural basis of Charles bonnet hallucinations: A hypothesis. J Neurol Neurosurg Psychiatry 2002;73:535-41.  Back to cited text no. 3
Cox TM, ffytche DH. Negative outcome Charles Bonnet syndrome. Br J Ophthalmol 2014;98:1236-9.  Back to cited text no. 4
Teunisse RJ, Cruysberg JR, Hoefnagels WH, Verbeek AL, Zitman FG. Visual hallucinations in psychologically normal people: Charles Bonnet's syndrome. Lancet 1996;347:794-7.  Back to cited text no. 5
de Morsier G. The Charles bonnet syndrome: Visual hallucinations in the aged without mental deficiency. Ann Med Psychol 1967;2:678-702.  Back to cited text no. 6
Bonnet C. Analytical essay on the faculties of the soul. The brothers C. and A. Philibert, Copenhagen; 1760.  Back to cited text no. 7
Kester EM. Charles Bonnet syndrome: Case presentation and literature review. Optometry 2009;80:360-6.  Back to cited text no. 8
Cogan DG. Visual hallucinations as release phenomena. Arch Clin Exp Ophthalmol 1973;188:139-50.  Back to cited text no. 9
Berrios GE, Brook P. The Charles Bonnet syndrome and the problem of visual perceptual disorders in the elderly. Age Ageing 1982;11:17-23.  Back to cited text no. 10
Holroyd S, Rabins PV. A three-year follow-up study of visual hallucinations in patients with macular degeneration. J Nerv Ment Dis 1996;184:188-9.  Back to cited text no. 11
Eperjesi F, Akbarali N. Rehabilitation in Charles Bonnet syndrome: A review of treatment options. Clin Exp Optom 2004;87:149-52.  Back to cited text no. 12
Plummer C, Kleinitz A, Vroomen P, Watts R. Roman chariots and goats in overcoats: The syndrome of Charles Bonnet. J Clin Neurosci 2007;14:709-14.  Back to cited text no. 13


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