What is the likely diagnosis, work‑up, and management for a patient with persistent left‑visual‑field hallucinations and vision loss that began two years after an ischemic stroke?

Diagnosis: Charles Bonnet Syndrome Secondary to Stroke-Related Visual Field Loss

This patient most likely has Charles Bonnet syndrome (CBS), a cortical-release phenomenon causing visual hallucinations in the setting of stroke-induced left visual field loss. 1

Diagnostic Criteria and Confirmation

CBS is characterized by four essential features that must all be present 1:

• Recurrent, vivid visual hallucinations (which this patient has in the left visual field)
• Preserved insight that the hallucinations are not real (patient must recognize unreality)
• No other neurological or medical diagnosis to explain the hallucinations
• Some degree of vision loss (this patient has left visual field loss from stroke)

Critical Red Flags Requiring Alternative Diagnosis

You must immediately pursue neurological evaluation if any of these atypical features are present 1, 2:

• Lack of insight into the unreal nature of hallucinations despite CBS education
• Interactive hallucinations where images respond to or engage with the patient
• New or progressive neurological signs beyond the original stroke deficits
• Cognitive decline or behavioral changes suggesting dementia with Lewy bodies, Parkinson's disease, or Alzheimer's disease 1

Work-Up Strategy

Initial Assessment (If Not Already Completed)

Verify the stroke diagnosis and rule out alternative causes 3:

• Brain MRI with DWI sequences to confirm the stroke location and exclude new lesions, tumors, or progressive disease 3
• Formal visual field testing with automated perimetry (more sensitive than confrontation testing) to document the exact field defect 1
• Medication review to identify drugs that can cause hallucinations: anticholinergics, steroids, dopaminergic agents, or other psychoactive medications 1, 2

Neuroanatomic Correlation

The hallucinations occurring specifically in the left visual field suggest right occipital cortex damage 3, 4. Research demonstrates that CBS hallucinations after stroke require 4:

• Relatively small lesions involving at minimum the striate cortex (V1)
• Sparing of Brodmann areas 19,20, and 37 (extrastriate visual cortex)
• Inverse correlation between lesion size and hallucination frequency (smaller lesions more likely to cause hallucinations)

Psychiatric and Cognitive Screening

Screen for depression and anxiety, as vision loss significantly increases mental health risks 1, 2:

• Use validated depression screening tools
• Refer for professional psychiatric assessment if severe mood changes, daily life interference, or suicidal ideation present 1, 2
• Assess for cognitive impairment that might suggest alternative diagnoses like dementia with Lewy bodies 1

Management Approach

First-Line: Education and Reassurance (Therapeutic in Itself)

Education is the primary treatment and provides significant symptom relief 1, 2:

• Explain to the patient and caregivers that CBS hallucinations are a common, benign phenomenon affecting 15-60% of visually impaired patients 1, 2
• Emphasize the cortical-release mechanism: hallucinations result from lack of visual input causing spontaneous activity in intact visual cortex 1
• Reassure that this does not indicate psychiatric illness or dementia 1, 2
• Document that discussion alone leads to significant anxiety reduction 1

Second-Line: Non-Pharmacological Self-Management Techniques

Recommend these safe behavioral strategies that may reduce hallucination frequency 1, 2:

• Eye movements (rapid saccades or blinking)
• Changing lighting conditions (increasing or decreasing ambient light)
• Distraction techniques (engaging in conversation, listening to music, tactile stimulation)
• Increasing socialization and decreasing stress 3

Vision Rehabilitation Referral (Strongly Recommended)

Refer to comprehensive vision rehabilitation services 1, 2:

• Optimize remaining vision through lighting modifications, magnification devices, and contrast enhancement 2, 3
• Provide psychological support through support groups, which have moderate-quality evidence for improving vision-related quality of life and depression 1, 2
• Address social isolation and functional limitations from the visual field defect 1

Pharmacological Treatment (Reserved for Severe Cases Only)

Do NOT use pharmacological treatment as first-line therapy 1, 2:

• No significant evidence of efficacy for any pharmacological agent in typical CBS 1
• Consider only if severe distress persists despite education and non-pharmacological measures 2
• Atypical antipsychotics (risperidone, olanzapine, quetiapine) have only anecdotal evidence 2, 3
• Avoid reflexive antipsychotic prescription in patients with preserved insight, as CBS hallucinations are benign 2

Prognosis and Follow-Up

Visual hallucinations after stroke typically improve or resolve with time 5:

• Most stroke-related hallucinations are temporary and disappear spontaneously 5
• However, chronic cases persisting beyond 2 years (as in this patient) may represent permanent changes in white matter connectivity and cortical remapping 6
• Schedule regular ophthalmology follow-up to monitor vision and provide ongoing support 3

Common Pitfalls to Avoid

Do not misdiagnose CBS as primary psychiatric illness 2, 3:

• Patients may not report hallucinations due to fear of being labeled "crazy" 3
• Low physician awareness leads to missed diagnosis and inappropriate psychiatric referrals 3

Do not overlook medication-induced causes 2:

• Always review anticholinergics, steroids, dopaminergic agents before diagnosing CBS 2

Do not dismiss the psychological impact of vision loss itself 1, 2:

• Vision loss independently causes depression and requires rehabilitation services 1, 2
• Stepped-care vision rehabilitation reduces depression, dysthymia, and anxiety by 17% over 2 years 1