Charles Bonnet Syndrome
Charles Bonnet Syndrome is a fascinating, if not somewhat esoteric, clinical phenomenon. Understanding its core clinical features, especially for clinicians that work with geriatric patients, can add an important component to one’s diagnostic skill set. This practice article covers some of the basics with full references for further reading.
Description and Essential Features
Charles Bonnet Syndrome (CBS) is defined by:
- Formed or complex visual hallucinations
- Pathological visual loss, and
- Normal cognitive functioning[1]
CBS occurs only among older adults, and almost universally concomitantly with vision loss. Prevalence increases with age. Varying degrees of gender prevalence are reported in the literature, although it seems females may outnumber males, overall. Estimates of prevalence among older adults range from 0.4% (Shiraishi, Terao, Ibi, Nakamura, Tawara, 2004) to 27% (Teunisse, Cruysberg, Verbeek, & Zitman, 1995), with the larger estimate representing those with end-stage Age-related Macular Degeneration (AMD).
Neuropathology and Pathophysiology
There is no consensus regarding the cause of CBS. Theories posit that it may represent an interruption in normal vision/sensory input, leading to self-stimulation (recovery or compensation by the visual system; Tan & Sabel, 2006) by the brain. Interruptions, in turn, can be secondary to various pathological events, especially AMD. The social isolation experienced by many older adults can exacerbate this (Fernandez, Lichtshein, Vieweg, Victor, 1997). CBS can occur in patients with normal vision, and may occur in the absence of both pathological processes of the eye and brain pathology (Gold & Rabins, 1989).
AMD is highly correlated with the onset or presence of CBS, and may represent the greatest risk factor or causative process. Other conditions represent both proximal and distal risk factors. CBS may present in patients with diabetic retinopathy, glaucoma, and cataracts (Teunisse, Cruysberg, Verbeek, Zitman, 1995; O’Farrell, Lewis, McKenzie, Jones; 2010). Visual degeneration is not necessary for a diagnosis of CBS (although the lack thereof is rare among those with the diagnosis; Shiraishi, Terao, Ibi, Nakamura, Tawara, 2004, as cited in O’Farrell et al., 2010). CBS can also occur comorbidly with grief and asymptomatic HIV (Fernandez, Lichtshein, Vieweg, Victor, 1997).
Neuropsychological and Clinical Presentation
Visual hallucinations between patients are, as a rule, heterogeneous. Although there are no reported cases of stereotypical forms, those most commonly reported are of people, animals, buildings and scenery. CBS hallucinations may also cause or be exacerbated by panic disorder (Murai & Takagi, 2004).
Once psychosis, dementia and delirium are ruled out, neuropsychological testing should reveal few, if any, deficits (at least on verbal/non-visually loaded tests). Existing literature specifically covering this topic yields mixed findings: Scott, Schein, Feuer, and Folstein (2001) found a nonsignificant relationship between cognitive scores and CBS. Abbot, Connor, Artes, and Abadi (2007) reported a negative association between arousal and outcomes scores (no one was surprised). Diminished scores may also be moderated by a threshold of vision loss. Despite these findings, diminished intellectual capacity is a potential risk factor for the presence of visual hallucinations (Collerton et al. 2005, as cited in O’Farrell et al., 2010). One study (Pliskin, Kiolbasa, Towle, Pankow, Ernest, Noronha, et al., 1996, as cited in O’Farrell et al., 2010) found a significant difference in neuropsychological test scores between those with CBS and controls. These findings were later invalidated, however, as 8 of the 11 patients in the CBS group did not have insight that their hallucinations were not real.
Radiological Findings
CT and MRI scans have not yielded positive clinical correlations, and should be negative; positive findings are likely distal and incidental. fMRI found hallucinations connected with ventral occipital lobe “within or around the fusiform gyrus.” PET scans performed during hallucinatory experiences have implicated temporal regions, the corpus striatum, and thalamus in the creation and mediation of CBS visual hallucinations (Adachi, Watanabe, Matsuda & Onuma, 2000).
Diagnosis and Differentials
Some individuals may report “flashes” of light in their peripheral visual field(s), especially in the dark, which are referred to as Moore’s lightning streaks. Occipitoparietal or Occipitotemporal infarcts, Alzheimer’s and Lewy Body dementia, and withdrawal from Benzodiazepines or chronic alcohol intoxication must be ruled out.
Treatment, Intervention and Rehabilitation
In some cases, anticonvulsants and SSRIs have been reported as effective (Adachi, Watanabe, Matsuda & Onuma, 2000; Murai & Takagi 2004). In other cases, progression of eye disease severity and time cause remission. For some patients, the hallucinations become sufficiently disturbing, in which case low-dose antipsychotics may offer symptom relief. Environmental interventions may be more useful, including increased social contact and improved home lighting (Adachi, Watanabe, Matsuda & Onuma, 2000).
Visual hallucinations occur as normal (or even expected) phenomena in some cultures, as part of bereavement, or during withdrawal from benzodiazepine abuse, to name a few examples. Given this, their occurance is relatively common compared to what the general populace believes. Yet, they remain highly stigmatized, and are associated with being “crazy.” As such, prevalence rates of CBS may be artificially depressed with stigma as a moderating variable.
In almost all cases, the first step in symptom relief seems to be creating an open channel of communication between clinician and patient regarding the nature of visual hallucinations and CBS (if present). In one study, of the 60 patients surveyed, the only common clinical feature between them was that 100% were glad to hear that the disorder had a name, and that it was not associated with mental illness (Teunisse, Cruysberg, Hoefnagels, Verbeek, Zitman, 1996).
References
Abbot, E. J., Connor, G. B., Artes, P. H. & Abadi, R. V. (2007). Visual loss and visual hallucinations in patients with age-related macular degeneration (Charles Bonnet syndrome). Investigative Ophthalmology & Visual Science, 48, 1416–1423.
Adachi N., Watanabe T., Matsuda H., Onuma T. (2000). Hyperperfusion in the lateral temporal cortex, the striatum and the thalamus during complex visual hallucinations: Single photon emission computed tomography findings in patients with Charles Bonnet syndrome. Psychiatry & Clinical Neuroscience. 54,157–162.
Fernandez, A., Lichtshein, G., Vieweg, W., Victor R. (1997). The Charles Bonnet syndrome: A review. The Journal of Nervous and Mental Disease. 185 (3), 195–200.
Gold K., Rabins, P. V. (1989). Isolated visual hallucinations and the Charles Bonnet Syndrome: A review of the literature and presentation of six cases. Comprehensive Psychiatry 30, 90–98.
Murai, T., Takagi, S. (2004). Charles Bonnet Syndrome and panic disorder. The Journal of Neuropsychiatry and Clinical Neurosciences. 16(3), 382–383.
O’Farrell, L., Lewis, S., McKenzie, A., Jones, L. (2010). Charles Bonnet Syndrome: A review of the literature. Journal of Visual Impairment & Blindness. 104(5), 261–274.
Tan, C. S. H. & Sabel, B. A. (2006) Dynamic changes in visual acuity as the pathophysiologic mechanism in Charles Bonnet syndrome (visual hallucinations). European Archives of Psychiatry and Clinical Neuroscience. 256 (1) 62–63.
Scott, I. U., Schein, O. D., Feuer, W. J., & Folstein, M. F. (2001). Visual hallucinations in patients with retinal disease. American Journal of Ophthalmology, 131, 590–598.
Shiraishi Y, Terao T, Ibi K, Nakamura J, Tawara A (2004). The rarity of Charles Bonnet syndrome. Journal of Psychiatric Research 38, 207–13.
Teunisse, R. J., Cruysberg, J. R., Verbeek, A., & Zitman, F. G. (1995). The Charles Bonnet Syndrome: A large prospective study in the netherlands: A study of the prevalence of the Charles Bonnet Syndrome and associated factors in 500 patients attending the university dept of opthamology at nijmegen. British Journal of Psychiatry, 166 (2), 254–257. doi:10.1192/bjp.166.2.254
Teunisse, R. J., Cruysberg, J. R., Hoefnagels, W. H., Verbeek, A. L., Zitman, F. G. (1996). Visual hallucinations in psychologically normal people: Charles Bonnet’s syndrome. Lancet 347 (9004), 794–797.
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Which means that there is an absence of a dementing disorder or delirium, and that the patient has insight that the hallucinations are not real. There is some disagreement about whether or not insight is an important diagnostic criteria for CBS. ↩
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