Friday, July 5, 2013

Pyschotic Hallucination and Charles Bonnet syndrome



An interesting video lecture from TED Talks. Mr. Sacks in this lecture differentiated Pyschotic Hallucination from that of Charles Bonnet syndrome.

Some notes from his talk:

1) There is a special form of visual hallucination which may go with deteriorating vision or blindness. This was originally described in the 18th century, by a man called Charles Bonnet.

2) Charles Bonnet syndrome

A lot of elderly people  are hearing impaired or visually impaired and about 10 percent of the hearing impaired people get musical hallucinations. And about 10 percent of the visually impaired people get visual hallucinations. You don't have to be completely blind, only sufficiently impaired.

Repetition of perception is sometimes called palinopsia.

 As you lose vision,  the visual parts of the brain are no longer getting any input, they become hyperactive and excitable, and they start to fire spontaneously. And you start to see things. The things you see can be very complicated indeed.

Some had very mobile hallucinations as well. A lot of them had to do with a car.

Those not having  trouble with their eyes, but the visual parts of the brain such as little tumor in the occipital cortex can cause problem like seeing cartoons.

Something like 10 percent, visually impaired people get  Charles Bonnet Syndrome. But no more than one percent of the people acknowledge them, because they are afraid they will be seen as insane or something. And if they do mention them to their own doctors they may be misdiagnosed.

There is also a rare thing called temporal lobe epilepsy, and sometimes, if one has this, one may feel oneself transported back to a time and place in the past. You're at a particular road junction. You smell chestnuts roasting. You hear the traffic. All the senses are involved. And you're waiting for your girl. And it's that Tuesday evening back in 1982. And the temporal lobe hallucinations are all-sense hallucinations, full of feeling, full of familiarity, located in space and time, coherent, dramatic. The Charles Bonnet ones are quite different.


So in the Charles Bonnet hallucinations, you have all sorts of levels, from the geometrical hallucinations -- the pink and blue squares the woman had -- up to quite elaborate hallucinations with figures and especially faces. Faces, and sometimes deformed faces, are the single commonest thing in these hallucinations. And one of the second commonest is cartoons.

 Think of the number of blind people. There must be hundreds of thousands of blind people who have these hallucinations, but are too scared to mention them. So this sort of thing needs to be brought into notice, for patients, for doctors, for the public. Finally, I think they are infinitely interesting and valuable, for giving one some insight as to how the brain works.


3) Psychotic hallucinations, whether they are visual or vocal, they address you. They accuse you. They seduce you. They humiliate you. They jeer at you. You interact with them.  There is none of this quality of being addressed with these Charles Bonnet hallucinations. There is a film. You're seeing a film which has nothing to do with you, or that's how people think about it.



 

 Source link: http://www.ted.com/talks/oliver_sacks_what_hallucination_reveals_about_our_minds.html


More on hallucination - http://en.wikipedia.org/wiki/Hallucination