Hi and welcome to the Chiari forum.
Yes, I had dealt with a few issues concerning my voice...hoarseness is one of them, I have had my voice leave when I attempt to sing and my throat hurts, I had always attributed it to PND. But after years of Drs and getting the many different Diagnosis....I now know it was more likely related to Chiari or my Ehlers-Danlos/MAST Cell diagnosis.
Has your son been tested for ALL related conditions such as EDS, POTS, SYRINGOMYELIA...?