In the May 2009 edition of ENT Journal, Dr. Chang has published a paper titled "A Survey of Current Practices of Physicians Who Treat Adductor Spasmodic Dysphonia in the US." The paper was published online instead of the print magazine and can be read here for free after registration.
The paper reports on a variety of factors considered when treating patients with adductor spasmodic dysphonia including surgery (what kind), botox type (A or B or both), how much botox, what concentration of botox, whether botox that has been frozen is used, etc. Interestingly, though most physicians treat spasmodic dysphonia with botulinum toxin type A, there is great variation in the concentration and amount of botox utilized.
Dr. Chang treats patients with Spasmodic Dysphonia with botox injection every Friday afternoon.
Books on voice therapy found to be a useful ADJUNCT to botox injections: