What Causes Impaired Speech While Suffering From Scoliosis?

my mother is 92 yo, in good health,within the last 1-2 years has become difficult to walk, speech has become impaired. Has had CT Scans which show no stroke. Made several attempts at MRI s but she has scoliosis and cannot lay her head all the way back and down therefore making it impossible to perform an MRI. Her doctor wants to give her Sinemet for 5 days before we try an open MRI to try to relax her then an hour before the MRI give her Adovan, am sure I spelled it wrong. She does not shake but holds her left hand closed but will open it if you tell her to. Doctor thinks she has Parkinsons symtoms. She clutches things and is very strong, hard to get her to let go. Takes us about 2-3 time before she will let go of a handle or an object she may be holding. She moves very robotically then sometimes normally. Needs help walking. She has weak vocal cords cannot speak clearly the sometimes she speaks perfectly.Has loss of hearing. Sleeps a lot. Her ability to walk on her own has deteriorated slowly over 1-2 years. Primary Doctor says it is arthritis. I am concerned about her taking Sinemet even for a short period of time. She has her mental faculties still smart alert but verbal and physical mobility deteriorating.