Synaesthesia

Synaesthesia is a fascinating phenomenon. As Eagleman (1) says,
patients do get mistakenly diagnosed to have schizophrenia. Synaesthesia
has also been associated with use of hallucinogens like Lysergic acid
diethylamide (LSD) and mescaline(2).

Perceptual experiences in patients may present in any field of
medicine and awareness can help in early diagnosis.

For example, in ‘Hallucinogen Persisting Perception Disorder’,
patients re-experience, following having stopped using the hallucinogen,
one or more of the perceptual symptoms that were experienced while
intoxicated with the hallucinogen (e.g., geometric hallucinations, false
perceptions of movement in the peripheral visual fields, flashes of
colours, intensified colours, trails of images of moving objects, positive
afterimages, halos around objects, macropsia, and micropsia(3). Some
patients report persistence of episodes for many years after having
discontinued the hallucinogen.

In Charles Bonnet syndrome, people with visual impairment present
with complex visual hallucinations. Reassurance to the patient that it is
a benign condition and not mental illness has powerful therapeutic
effect(4).

We are once again reminded that there is no short cut to
taking a good history.

References

1. Eagleman DM. Editorial.Synaesthesia .BMJ 2010;340:b4616 (Jan 8)

2. Ramachandran V.S.1; Hubbard E.M.Synaesthesia -- A window into
perception, thought and language. Journal of Consciousness Studies, Volume
8, Number 12, 2001 , pp. 3-34(32)

3. Diagnostic and Statistical Manual of Mental Disorders. (DSM-
IV)American Psychiatric Association.1994

4.Menon G, Rahman I, Menon.S,Dutton.G.Complex Visual Hallucinations
in the Visually Impaired The Charles Bonnet Syndrome.Survey of
Ophthalmology, Volume 48, Issue 1, Pages 58-72,2003

Competing interests:
None declared