My kiddo has whispered since the onset of her PANDAS in 12-2011 (after 3 months of no talking). The only time we had normal voice was for one month in 7-2012 and part of one night after I gave her part of an Ambien to help her sleep. My daughter has what appears to be Abductor spasmodic dysphonia (aka whispering .) They are now of the opinion that this originates in the basal ganglia.
"Spasmodic dysphonia is thought to be caused by abnormal functioning in an area of the brain called the basal ganglia. The basal ganglia consist of several clusters of nerve cells deep inside the brain. They help coordinate movements of the muscles throughout the body. Recent research has found abnormalities in other regions of the brain, including the brainstem, the stalk-like part of the brain that connects to the spinal cord."
I have been doing some research on this, and I am interested in anyone elses efforts or input about the whispering. We bought our kiddo a personal voice amplifier and it worked to at least some degree, but before we could really get into it, it broke. I have reorder another, and it is not here yet.
Okay, I will add more links here as I find them, and everyone can feel free to add to this if you have any input:
https://www.nidcd.nih.gov/health/voice/pages/spasdysp.aspx
Overall google search: https://www.google.com/#q=abductor+dysphonia+treatment
A fourth type of dysphonia is:
Whispering dysphonia
A fourth type has also been described. This appears to be caused by mutations in the TUBB4 gene on the short arm of chromosome 19 (19p13.2-p13.3).[3] This gene encodes a tubulin gene. The pathophysiology of this condition has yet to be determined. http://en.wikipedia.org/wiki/Spasmodic_dysphonia#Whispering_dysphonia
I will have to look into if my kiddo has this mutation or not.