Vocal cord problem (after partial neck dissection)

Hello all!!

I still come here from time to time to read how everyone is doing.  I still see some old names of wonderful people who are always here for support and help. Bless you all!! 

Well, my Dad is doing ok, he had his rad/onc doctor check-up today. He had partial neck dissection (15 nodec removed - all clear) back in September 2013. Right after that dissection he started to have problem with his voice. It was hoarse and he could not speak for a long time. We all thought it was due to lack of saliva because he still has a big issue with saliva and has to drink a lot of water or eat more moisty food. 

Oh yes, just as a reminder: He had Base of tongue cancer with lymph nodes involved (35 rads and 7 chemos, finished in Sept 2012). Then they did a partial neck dissection on the left side of the neck in September 2013 and all were clear.

Today the doctor examined his mouth and throad, tongue... All looks good, no sign of cancer. But she said that the vocal cord on the left side (where his treatment and neck dissection was) is not mobile. 

Before on previous check-ups both vocal cords were smooth and mobile. But now the left one is not. Also his voice is not ok, so it is logical. He will have PET/CT on January 21st and we will see then. My mom got scared what if it is a tumour, but doctor said that most likely not and that it is probably just damage from radiation or partial neck dissection. But PET/CT will show the truth.

So my question is: Did anyone had similar problem? The first year after treatment his cords were fine and on every doctor appointment they looked good. But this time, 4 months after neck dissection one of them is stiffer and not mobile.Could it be just side effect - as scarred tissue or damage? It is funny that his voice is hoarse since that neck dissection. 

So, can you have problems with vocal cords AFTER partial neck dissection? Can it be related? 

Thank you all for your help and may this 2014 year be a true blessing for all!!

V.