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THE ENIGMA BEHIND CHARLES BONNET SYNDROME

THE ENIGMA BEHIND CHARLES BONNET SYNDROME

Dr mrs Netranee Anju Ramdinny-Purryag

Psychiatrist, BSMHCC-Mauritius

 

Introduction

Charles Bonnet Syndrome, also known as visual release hallucinations, is the experience of complex visual hallucinations in a person with partial or severe blindness. It was first described by Charles Bonnet in 1760.1,2

As Douwe Draaisma remarks, the ‘enormous variation in the type of images’ seen by Charles Bonnet Syndrome patients is striking.3

Once regarded as extremely rare, it is now known that up to 40% of people with impaired vision develop Charles Bonnet Syndrome 4 although up to 60% may keep the experiences to themselves.5

Misdiagnosis as psychosis, delirium and early dementia is common5 and some people with Charles Bonnet Syndrome have been almost confined to mental institutions. So, clinicians need to remain vigilant for this intriguing condition.

History

Charles Lullin was a distinguished and well loved magistrate in Geneva for many years. He was the grandfather of Charles Bonnet, who documented the experiences of the old man when the latter was 89 years of age; the old man experienced visual hallucinations. The elderly man was seeing things that were not there. He developed a variety of hallucinations, ranging from simple to complex forms. The simplest hallucinations he described were an infinity of whirling atomic particles swirling around his field of view. He also had hallucinations of simple lines and dots, coloured blobs and geometrical patterns. He saw figures in his room, typically females in elaborate flowing silk robes, but, bizarrely, wearing inverted tables or caskets on their heads. In his room, the walls would become adorned with paintings in beautiful golden frames, landscapes, portraits; things that he had never seen before.6

Charles Lullin was normal sighted until about 80 years of age, after which his vision began to deteriorate. At first this was partly attributed to a cataract in one eye. In the late 80s’, Lullin’s vision deteriorated further and a second cataract operation did not help. By the age of 89 years, he was unable to read because he had lost his central vision, but with a preserved peripheral field. In that state, he suddenly developed a variety of hallucinations, ranging from simple to complex forms.6

In the 1930s, the medical community decided to honour Charles Bonnet with the naming of Charles Bonnet Syndrome to reflect that Bonnet had been the first person ever to realize that visual hallucinations in eye disorders were something rather different to the visual hallucinations encountered in mental illness and Alzheimer’s disease.6

Explanations for this Mysterious Disease

An early psychoanalytical interpretation suggested that ‘the ego defends itself by creating a substitute world full of entertaining scenes to compensate for the visual loss.3 However, far from being entertained, the hallucinations leave some people distressed.

A widely supported theory suggests that the hallucinations are a mental equivalent of a phantom limb.7 Half of the afferent neuronal fibres projecting to the brain begins in the eyes 8 and so, the brain expects a considerable perceptual input. According to the deafferentation theory, lack of stimuli to the visual association areas of the cerebral cortex causes a release phenomenon similar to phantom limb symptoms.7,9 As Draaisma points out, the images often appear when vision begins to decline and then disappear when blindness occurs. According to the release theory, the vision should then be at their clearest when vision starts to decrease, as he notes.

Sensory deprivation offers another possible explanation. The hallucinations developed by sufferers of Charles Bonnet Syndrome develop when some sufferers shut their eyes.10 In one study, 10 of 13 normally sighted patients report hallucinations while being blindfolded for 5 days.7 This is however contradictory to Draaisma’s view that the images disappear when blindness occurs.

Another theory proposes a dysfunction in the brain’s censors. A psychoanalytic theory published in 1962 suggested that the failing eyesight decreases the perception of reality, which makes room for the products of imagination.3

A neurophysiological version suggests that the brain’s censorship mechanism continually removes irrelevant sensory impulses from conscious perception. However, this depends on normal sensory input. If the input falls below a certain threshold, the brain allows subconscious perceptions to surface producing visual hallucinations.10

Different views

There have been various prevalences reported for Charles Bonnet Syndrome. A 1989 review identified just 46 cases of Charles Bonnet Syndrome. More recent prevalence estimates range from less than 1% to 40% of patients with impaired vision. Several reasons account for this variation in prevalence: differences in history taking, the definitions used and patients’ willingness to report their hallucinations.7

Some definitions of Charles Bonnet Syndrome do not include visual loss.7

Furthermore, researchers do not agree whether certain images, for example bright lights and diffuse colours or auditory hallucinations are part of Charles Bonnet Syndrome.7

Treatment

There is no specific treatment for Charles Bonnet Syndrome.

Reassurance about the nature of the illness, that is not being a mental illness, could be highly comforting and all that may be needed.

Although antidepressants and anticonvulsants have been used for Charles Bonnet Syndrome with good effect in previous reports,11, 12 the efficacy of these drugs in the treatment is somewhat questionable and should be reserved for those who exhibit high levels of distress and have not responded to conventional intervention.13

The treatment approach would also depend on other comorbid physical or mental disorders.13,14 Combination of medications and programmed blinking or intermittent closing and opening of the eyes have been reported as helpful.2 The techniques used in the treatment of Charles Bonnet Syndrome are enumerated in the table which follows:

Techniques in the treatment of Charles Bonnet Syndrome

1.      A change is made to see if hallucinations disappear. For example, switch on a light to see if they disappear.

2.      The eyes are moved from left to right every second for up to 30 seconds without moving the head.

3.      Staring at the image, blinking rapidly or reaching out to touch the vision. For some, these methods help the vision to fade.

4.      Moving around or performing a task, such as getting up to make a cup of tea may help

5.      Hallucinations may be worse when a person is stressed out or tired. So, enough sleep is required to prevent hallucinations from worsening.

 

The best solution is however, finding the effective treatment to the eye disorder because Charles Bonnet Syndrome has been reported to regress with effective treatment of the cause of visual loss and improvement of visual activity.15,16

Conclusion

In conclusion, doctors and relatives are advised to seek for hallucinatory experiences by asking the visually impaired about it. Doing this would go a long way at ameliorating the suffering of the usually impaired from this syndrome that could possibly be passed off as a mental disorder. It would also strengthen the consultation liaison services between psychiatry and ophthalmology.

References

1.      .Morsier G. Le syndrome de Charles Bonnet: Hallucinations visuelles des viellards sans deficience mentale (in French). Ann Med Psychol 1967;125: 677-701.

2.      Vukicevic M, Fitzmaurice K. Butterflies and black lacy patterns: the prevalence and characteristics of Charles Bonnet hallucinations in an Australian population. Clinical and Experimental Ophthalmology 2008; 36:659-65.

3.      Draaisma D. Disturbances of the Mind. Cmbridge University Press 2009;11-39.

4.      Singh A, Subhi Y, Sorensen TL. Low awareness of Charles Bonnet Syndrome in patients attending a retinal clinic. Danish Med J 2014; 61: A4770.

5.      Jan T, Del Castillo J. Visual Hallucinations. Charles Bonnet Syndrome. Western J Emerg Med 2012; 13: 544-7.

6.      Dominique F. Charles Bonnet Synd. MDS Digest 27-32.

7.      Jackson ML, Ferencz J. Charles Bonnet Syndrome: visual loss and hallucinations. Can Med Assoc J 2009; 181:175-6.

8.      Grunda T, Marsalek P, Sykorova P. Homonymous hemianopia and related visual defects: Restoration of vision after a stroke. Acta Neurobiologiae Experimentalis 2013; 73: 237-49.

9.      Singh A, Subhi Y, Sorensen TL. Low awareness of the Charles Bonnet Syndrome- elderly people and visual hallucinations. BMJ 2004; 328: 1552-4.

10.  O’ Farrell L, Lewis S, Mckenzie A, et al. Charles Bonnet Syndrome. A review of the literature. J Visual Impairment Blindness 2010; 104: 261-72.

11.  Terao T. Effects of Carbamazepine and Clonazepam combination on Charles Bonnet Syndrome. A case report. Hum Psychopharmacol Clin Exp 1998;13: 451-3.

12.  Lang UE, Stokowski D, Schulze D, Domula M, Schmidt E, Linat JG, et al. Charles Bonnet Syndrome: Successful treatment of visual hallucinations due to vision loss with SSRIs. J Psychopharmacol 2007; 21: 553-7.

13.  Hartney KE, Catalano G, Catalano M. Charles Bonnet Syndrome: Are medications necessary? J Psychiatr Pract 2011; 17: 137-41.

14.  Teunisse RJ, Cruysberg JR, Hoefnagels WH, Verbeek AL, Zitman FG. Visual hallucinations in psychologically normal people: Charles Bonnet Syndrome. Lancet 1996; 347: 794-7.

15.  Singh A, Sorensen TL. Charles Bonnet Syndrome improves when treatment is effective in age related macular degeneration. British Journal Ophthalmol 2011; 95: 291-2.

16.  Meyer CH, Fleckensstein M, Rodrigues EB, Mennel S. Incidence and regression of Charles Bonnet Syndrome in vascular age-related macular degeneration. British Journal Ophthalmol 2011; 95: 1137-74.