Visual hallucinations

Visual hallucinations are relatively uncommon, and can be due to a variety of 'organic' brain diseases, affecting a variety of regions of the brain.  The use of the term organic here is by convention, and should not be taken to imply absence of brain dysfunction in psychiatric illness

Clinical presentation

Visual hallucinations can take various forms and should be distinguished from visual distortions or pseudohallucinations. They can be divided into simple and complex forms:

  • simple hallucinations
    • typically due to irritation or stimulation of the primary visual cortex (e.g. tumours, epilepsy) 
    • brief, uniform and stereotyped
    • flashes of light and colour or indistinct forms
  • complex visual hallucinations
    • disruption to the wider visual system
    • complex visual percepts
      • branching or tessellated patterns
      • people and/or animals
      • complex scenes often associated with sensory distortions

Of interest, the patient's insight and response to these hallucinations is variable. In some cases, such as Lilliputian hallucinations (miniature people in lines or groups often performing strange actions), the hallucinations are not distressing, but rather elicit curiosity or wonder.  In other settings, for example those due to psychiatric disturbance, delirium or intoxication/withdrawal are often frightening.

Aetiology

A number of conditions are known to be associated with visual hallucinations including: 

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rID: 29906
Tag: refs
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