What are Lilliputian hallucinations?

Lilliputian Hallucinations: Definition and Clinical Significance

Lilliputian hallucinations are visual or multimodal hallucinations of human, animal, or fantasy figures that appear abnormally small in size (micropsia), most commonly occurring in patients with vision loss as part of Charles Bonnet syndrome, but also seen in alcohol use disorder, schizophrenia, and various neurological conditions. 1

Core Characteristics

Lilliputian hallucinations have distinct features that help identify them clinically:

• Size distortion: The hallucinated figures appear miniature or "Lilliputian" (named after Jonathan Swift's tiny people in Gulliver's Travels), with patients experiencing micropsia where characters or objects are much smaller than normal 2
• Sensory modality: 61% are purely visual, while 39% are multimodal (involving other senses) 1
• Environmental grounding: In 97% of cases, the hallucinations are perceived as existing within the actual physical environment, indicating involvement of higher-level perceptual networks that fuse sensory and hallucinatory content 1
• Formed content: These are complex, well-defined, organized hallucinations with clear images, as opposed to simple unformed hallucinations like lights or geometric patterns 3

Etiological Distribution

The underlying causes are remarkably diverse, requiring careful diagnostic evaluation:

• Vision loss conditions (Charles Bonnet syndrome): Age-related macular degeneration, cataracts, glaucoma, or other causes of significant visual impairment account for a substantial portion, with CBS prevalence ranging from 10-60% among visually impaired patients depending on the population studied 4, 2
• Alcohol use disorder: Along with schizophrenia spectrum disorders and vision loss, these three conditions account for 50% of all cases 1
• Neurological disease: Comprises 36% of cases, including dementia (AIDS-dementia complex, post-traumatic dementia), Parkinson's disease, brain tumors, epilepsy, normal pressure hydrocephalus, and migraine 1, 5, 6
• Other causes: Delirium, drug intoxication, sleep deprivation, Epstein-Barr virus infection, and narcolepsy 2

Distinguishing Charles Bonnet Syndrome from Other Causes

When Lilliputian hallucinations occur in the context of vision loss, CBS should be suspected if four criteria are met 4:

• Recurrent, vivid visual hallucinations
• Preserved insight that what is seen is not real (the patient recognizes the unreality of the experience)
• No other neurological or medical diagnosis to explain the hallucinations
• Some degree of vision loss

Red flags indicating an alternative diagnosis include: lack of insight despite education about CBS, hallucinations that interact with the patient, or accompanying neurological signs, which should prompt comprehensive neurological evaluation with brain MRI and consideration of dementia with Lewy bodies, Parkinson's disease, or primary psychiatric disorders 7, 8

Underlying Mechanisms

The pathophysiology involves:

• Perceptual release and deafferentiation: The most likely mechanisms, representing "phantom vision" due to lack of afferent visual information reaching the visual association areas of the cerebral cortex 1, 2
• Cortical release phenomena: Loss of normal visual input leads to spontaneous activity in visual processing areas 4
• Contributing factors: Cognitive deficits, social isolation, and sensory deprivation may also play roles 2

Clinical Course and Prognosis

The natural history varies significantly by etiology:

• Recovery rate: 62% of cases achieve recovery with appropriate treatment of the underlying condition 1
• Chronicity: 18% of cases become chronic 1
• Mortality: 8% of cases end in death, typically related to the underlying neurological disease rather than the hallucinations themselves 1

Management Approach for CBS-Related Lilliputian Hallucinations

Education is therapeutic in itself: Discussion with patients and caregivers about the benign nature of CBS hallucinations leads to significant relief and decreased anxiety, as experiencing these hallucinations without understanding their cause generates fear 4, 7

Self-management techniques that may reduce hallucinations include eye movements, changing lighting conditions, and distraction techniques, which have limited evidence from case series but are safe and can be recommended 4, 7

Vision rehabilitation referral should be made to optimize remaining vision through lighting modifications, magnification, and contrast enhancement, while also addressing psychological aspects through support groups 7

Pharmacological treatment is NOT first-line and should be reserved for patients with severe distress despite education and non-pharmacological measures, as there is limited evidence of efficacy for any pharmacological agent in typical CBS; atypical antipsychotics (risperidone, olanzapine, quetiapine) have been used in case reports but lack robust evidence 4, 7

Critical Clinical Pitfalls

• Do not reflexively prescribe antipsychotics for CBS-related Lilliputian hallucinations, as typical CBS patients maintain insight and the hallucinations are benign 7
• Do not overlook medication-induced causes: Review anticholinergics, steroids, dopaminergic agents, and other drugs that may contribute to hallucinations 7
• Screen for depression and anxiety at follow-up visits, as vision loss significantly increases risk of mental health deterioration; recommend professional psychiatric assessment for patients reporting severe mood changes, interference with daily life, or suicidal ideation 4, 7
• Consider concurrent mechanisms: In cases with both vision loss and neurological disease (such as cataract plus normal pressure hydrocephalus), treating only one mechanism may leave persistent symptoms 6