Multisensory hallucinations in visually impaired elderly subjects

Abstract

We present two case studies that illustrate the classical Charles Bonnet Syndrome and a patient with multisensory hallucinations and delusion in a visually impaired elderly subject. These cases highlight diagnostic complexity and underscore the need for a multidisciplinary approach in management.

Charles Bonnet Syndrome (CBS) was first described in 1760 by Swiss naturalist Charles Bonnet, based on the vivid visual hallucinations experienced by his grandfather, Charles Lullin, who had bilateral cataracts. Lulin remained cognitively intact and aware that his hallucinations were not real.[1] The term CBS was formally introduced by neurologist Georges de Morsier in 1967, who differentiated CBS from hallucinations due to psychiatric or neurodegenerative illnesses and hypothesized a lesion in the pulvino-cortical pathways as a possible cause.[2] The diagnostic criteria for CBS was outlined by the world Health organization in 2018 as under: complex visual hallucinations; partial or complete vision loss; and absence of mental disorders.[3] Clearly, auditory hallucinations are excluded from this definition. However, the literature also contains a growing number of cases of auditory hallucinations which have been described as the auditory variant of CBS.[4] While extensively documented globally, CBS remains underreported in India. Furthermore, hallucinations in modalities beyond vision (e.g., auditory, olfactory) are rarely discussed.[1] Among the cases mentioned below two cases show typical features of CBS, while the third case presented with multisensory hallucinations and delusion in a visually impaired elderly subject.

CASE SERIES

Case 1

A 55-year-old woman with a history of retinal detachment and macular hole since July 2024 presented with complaints of seeing snakes on her bed and floor and holding persecutory delusions since August 2024. She described vivid, colorful, and detailed images of green snakes with fangs and shadowy human figures. She believed neighbors were planting the snakes to kill her and monitoring her via hidden cameras.

Physical examination was normal. Ophthalmologic evaluation revealed bilateral cataracts, macular degeneration, and reduced vision (Right: 20/100, Left: 20/200). Neurological exam and MRI brain were normal. Mental state exam showed anxious affect, visual hallucinations, persecutory beliefs, and partial insight. Cognition was intact (MMSE: 28/30). Based on complex visual hallucinations, intact cognition, and visual impairment, CBS was diagnosed despite the presence of paranoid delusions. She responded well to Risperidone 2 mg, and symptoms resolved. Medications were tapered and discontinued after 4 months, with no recurrence.

Case 2

A 68-year-old woman with advanced age-related macular degeneration (AMD) and bilateral cataracts reported well-formed visual hallucinations (unfamiliar people, animals, flashing lights) along with phantom smells of burning rubber and rotting garbage. She recognized these experiences as unreal. Ophthalmologic exam revealed visual acuity of 6/60 bilaterally with advanced AMD. Neurological examination was normal. Cognitive evaluation showed intact function (MoCA: 28/30). MRI and EEG were normal, ruling out seizures or structural abnormalities. Diagnosed with CBS with multisensory hallucinations, she was started on Risperidone 2 mg daily, which led to symptom improvement. Medication was tapered after 6 months without symptom recurrence.

Case 3

A 64-year-old woman with progressive, painless bilateral visual loss due to nuclear sclerosis cataracts presented after the left-eye cataract surgery. Postoperatively, her unaided vision improved in the left eye; right eye remained impaired (6/60). A few days later, she reported auditory hallucinations, hearing unfamiliar male and female voices, mostly at night. These voices were persecutory and commanding, causing significant distress. Neurological and general examinations were unremarkable. MRI brain was normal. Mental state examination revealed auditory hallucinations with partial insight and intact cognition (MMSE: 28/30). Given her visual impairment, post-operative status, intact cognition, and lack of neurological or psychiatric illness, a variant CBS diagnosis was made. She was started on Risperidone 2 mg daily and Risperidone Consta 25 mg IM biweekly, showing gradual symptom improvement.

DISCUSSION

CBS is a diagnosis of exclusion, characterized by complex visual hallucinations in individuals with significant visual impairment and preserved cognitive function. Although traditionally associated with visual hallucinations, these cases demonstrate multisensory manifestations (auditory, olfactory) that challenge conventional diagnostic frameworks.[1] CBS is often misdiagnosed as a psychiatric disorder, particularly when hallucinations are distressing or elaborate. However, the key differentiating features of CBS include, Presence of complex hallucinations (typically visual), intact cognition and insight, Absence of psychiatric or neurological illness, Underlying visual impairment

CBS is explained by the deafferentation hypothesis, where damage to the visual system leads to disinhibition of the visual association cortex, causing spontaneous neuronal firing and hallucinations. Another explanation is the release phenomenon, where reduced visual input releases intrinsic visual activity in the brain—analogous to phantom sensations in amputees.[2] Risk Factors include advanced age, visual sensory deprivation (due to cataracts, AMD, retinal diseases), cerebral lesions (rare) and social isolation.[1] CBS prevalence varies widely, from 0.4% to 40%, depending on diagnostic criteria, population studied, and clinician awareness.[1]

The first line of management is non-pharmacological. Explaining the benign nature of CBS can significantly reduce distress. Many patients find comfort in knowing these hallucinations are not a sign of psychosis or dementia.[5] Whenever feasible, correcting the visual deficit (e.g., cataract surgery, low-vision aids) can reduce hallucinations.[6] Used when hallucinations are distressing or disabling. Options include Atypical Antipsychotics: Risperidone (0.5–2 mg/day) is most used. Antidepressants (SSRIs): Occasionally used when hallucinations coexist with depression/anxiety. Anticonvulsants have been tried in refractory cases, though evidence is limited.[7] One study reported spontaneous remission in 28% of the patients 1 year after diagnosis, although visual measures did not change.[8] In this series, all three patients responded to low-dose Risperidone, with resolution of hallucinations within 5–6 months and no relapse after medication discontinuation (after 6–9 months).

CONCLUSION

These cases highlight the typical and atypical presentations of CBS, including auditory and olfactory hallucinations, and even paranoid delusions—challenging the traditional view that CBS is strictly visual. They emphasize the need for a broad, multidisciplinary approach, especially in patients with visual impairment presenting with hallucinations. Early recognition, patient education, and, short-term pharmacologic treatment can lead to good outcomes and prevent misdiagnosis.

Authors’ contributions

Concept, design, literature search: RM, MAP. Data acquisition: MAP. Manuscript preparation: MAP, CP. Manuscript editing and manuscript review: RB, NS.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for 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.

Data availability

Data can be made available on reasonable request.

Conflicts of interest

There was no conflict of interest.

Funding Statement

Nil.