I was reading up on this too. Neuroleptic drugs may have extrapyrimidal side effects including dystonias! This side effect is usually temporary and ceases after the drug is discontinued but in very, very rare cases has been permanent. I have not found an article about SD induced by neuroleptics in my searches.I've been trying to figure out what may have caused my SD and the only culprit I can think of is a drug that I was being treated with shortly before the onset of my SD symptoms. It was not a neuroleptic, rather an SSRI. I did find one article detailing a woman with spasmodic dysphonia due to SSRI's but her SD went away after the SSRI was discontinued.
http://www.thefreelibrary.com/Dysphonia+induced+by+selective+serotonin+reuptake+inhibitors.-a0136387735
