CHARLES BONNET SYNDROME IN AN ELDERLY PATIENT CONCURRENT WITH ACUTE CEREBELLAR INFARCTION TREATED SUCCESSFULLY WITH HALOPERIDOL

Field: Medicine (Health Sciences)

To the Editor: Charles Bonnet syndrome (CBS) is characterized by its hallmark visual hallucinations in older adults with intact cognition.1, 2 The syndrome is often undiagnosed or misdiagnosed because of patients' fear of being diagnosed with a mental illness and overlapping symptoms with ophthalmological, neurological, and psychiatric mimics. Patients may be referred inappropriately for inpatient psychiatric care or undergo unnecessary and misguided medical interventions upon presentation for CBS, with resultant delayed treatment and unwarranted suffering.1, 3 A 75-year-old man presented to the emergency department with multiple falls, asthenia, and visual hallucinations at home over 1 week. Past medical history included hypertension, surgery for cerebral aneurysm, emphysema, and ischemic cardiomyopathy. Initial computed tomography (CT) scan of the head and spine was unremarkable, and cognition was intact Folstein Mini-Mental State Examination (MMSE) score=28/30). An evolving acute to subacute cerebellar infarction was visualized on follow-up CT scan, and heparin was initiated. Echocardiography and angiography studies were normal. The patient articulated visualizing bothersome, vivid, colorful people, animals, and shapes from the corners of his eyes that he acknowledged were unreal. Physical and neuropsychiatric examinations and laboratory testing further excluded other organic, metabolic, infectious, or toxic etiologies for the hallucinations. The patient had previously presented to his ophthalmologist with visual acuity complaints and was diagnosed with hypertensive retinopathy and bilateral cataracts but neglected to mention these ongoing visual hallucinations for fear of being diagnosed with mental illness. As a diagnosis of exclusion, CBS was confirmed, and the patient was reassured but also treated temporarily with haloperidol nightly until immediate marked resolution of hallucinations. CBS is best described as visual hallucinations in patients with acquired visual loss without cognitive impairment.1-3 These patients retain insight into the unreal nature of the hallucinations, which do not occur in other sensory domains. These self-limited hallucinations occur regularly in clusters, with asymptomatic intervals. The most common characteristics include tessellopsia (regular overlapping patterns), prosopometamorphosia (facial distortions), dendropsia (branching forms), and polyopia (multiple forms of one image).3 The differential diagnosis of new-onset visual hallucinations may be daunting, and a multidisciplinary approach is requisite, including medication review, neuropsychiatric and ocular examinations, and tests to exclude metabolic or toxic encephalopathies, drug and alcohol withdrawal syndromes, and neuropsychiatric etiologies, including tumors, Parkinson's disease, Lewy-body dementia, epilepsy, migraine, infarction, peduncular hallucinosis, psychoses, delirium, schizophrenia, affective disorders, and conversion reactions.1-4 In an analysis derived from the National Comorbidity Survey Replication, an association between visual impairments and visual hallucination was significant (odds ratio (OR)=3.09, 95% confidence interval (CI)=1.06–8.99, P<.04) only in older adults (≥60), whereas a significant association was found with visual impairments and auditory hallucinations in younger adults (18–39, OR=13.25, 95% CI=2.99–58.75, P<.001).5 The prevalence of CBS varies from as low as 0.4% to as high as 12%, which may be due to discrepant exclusion criteria and underrecognition.3 Some argue that the MMSE is not sensitive enough to detect subtle cognitive deficits of a higher order, and thus patients considered for CBS should undergo comprehensive psychiatric evaluation. Recruitment bias exists across subspecialties because CBS spans many disciplines, including ophthalmology, neurology, geriatrics, and psychiatry. To our knowledge, this is the first case of acute cerebellar infarction associated with CBS. A single case of CBS in the hemianopic visual field was described after an occipital infarct in a patient with intact visual acuity.6 A trigger of this syndrome by cerebellar infarction is plausible in this patient because the cerebellum is known to be involved with visuomotor function, through updating internal predictions abut visual consequences of behavior.7 Other than correction of underlying visual impairment, no evidence-based medical treatment guidelines exist in the literature, and most recommendations derive from small-scale case studies. Haloperidol was associated with cessation of hallucinations in one prior case report, whereas olanzapine was beneficial in CBS possibly resultant from serotonergic and dopaminergic effects.4, 8 Anticonvulsants such as carbamazepine, valproate, and gabapentin have also been employed.1-4 Recognition of CBS is essential for geriatricians because its features of comorbid hallucinations, visual impairments, and frailty are more common in older adults. It seems prudent to screen all visually impaired older adults for hallucinations, and conversely, older adults who are referred for psychiatric disorders and hallucinations should be aggressively screened for vision impairments. Prompt recognition of hallucinations as being derived from CBS as opposed to primary neurological or psychiatric diseases can avert inappropriate unnecessary interventions and allay patient anxieties often simply through reassurance of its generally benign nature. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. Author Contributions: Each author contributed to the acquisition of the research articles. The corresponding author contributed the history and physical examination as he was directly involved with patient care. Each author contributed in the preparation, writing, and final review of the discussion. Sponsor's Role: Not applicable.