Can you have perm brain/cns damage or neurlogical damage from serotonin syndrome left untreated or not recognized and left on drugs. ?

Rarely, but yes: It's not specifically 'brain' damage but there are some forms of possible permanent critical damage. Read here: http://www.progressivehealth.com/serotonin-syndrome.htm Your awareness is good as it is likely to protect you from such inattention. Definitely discuss w/ Dr and try to find safe expert psychotherapy to avoid unneeded Rx or minimize it. Best wishes!

Serotonin syndrome: resolves completely when you go off the drug or drugs and does not cause brain or neurological damage. However, the immediate effect of the syndrome itself can be lethal. Here's a good source of information: http://www.mayoclinic.org/diseases-conditions/serotonin-syndrome/basics/definition/con-20028946 If you seriously think you may have it, stop all of the possible drugs and get evaluated now.