Complex visual hallucination [Neurosurgery Wiki]

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====== Complex visual hallucination ======
Complex [[visual hallucination]]s may affect some normal individuals on going to [[sleep]] and are also seen in pathological states, often in association with a sleep [[disturbance]]. The content of these hallucinations is striking and relatively stereotyped, often involving [[animal]]s and human figures in bright colours and dramatic settings. Conditions causing these hallucinations include narcolepsy-cataplexy syndrome, [[peduncular hallucinosis]], treated idiopathic Parkinson's disease, Lewy body dementia without treatment, [[migraine]] coma, [[Charles Bonnet syndrome]] (visual hallucinations of the blind), [[schizophrenia]], hallucinogen-induced states and epilepsy. 

Manfor and Andermann described cases of hallucinosis due to several of these causes and expand on previous hypotheses to suggest three mechanisms underlying complex visual hallucinations. (i) Epileptic hallucinations are probably due to a direct irritative process acting on cortical centres integrating complex visual information. (ii) [[Visual pathway]] lesions cause defective visual input and may result in hallucinations from defective visual processing or an abnormal cortical release phenomenon. (iii) [[Brainstem lesion]]s appear to affect ascending cholinergic and serotonergic pathways, and may also be implicated in Parkinson's disease. These brainstem abnormalities are often associated with disturbances of sleep. They discussed how these lesions, outside the primary visual system, may cause defective modulation of thalamocortical relationships leading to a release phenomenon. We suggest that perturbation of a distributed matrix may explain the production of similar, complex mental phenomena by relatively blunt insults at disparate sites
((Manford M, Andermann F. Complex visual hallucinations. Clinical and neurobiological insights. Brain. 1998 Oct;121 ( Pt 10):1819-40. doi: 10.1093/brain/121.10.1819. PMID: 9798740.))