Irreversable serotonin neurotoxicity symptoms?

[JackiesBabyy]

What are the signs of serotonin-based neurotoxicity once it's gotten to the point of being beyond repair? Such as what a heavy long term MDMA user would get.

 

[xxxyyy]

i got a constant tremor in my hands, that will not go away even with heavy doses of muscle relaxants (e.g. diazepam). my memory's also gone from superb to just about average, although which part the MDMA played in that and what the alcoholism i cannot say.