Hello Kay! I read your question carefully and understand your concern. I think that your father may have a peripheral facial palsy, which in most of the cases is caused by a viral infection or the cause is not found. I would like to know if he has had problems with expressing himself and answering the questions before , from Alzheimer disease , or it has started now with the face problem. Does he have a slurred speech or he can t express words. A peripheral face palsy can be caused by a possible stroke in the brainstem , but it is not associated with difficulty expressing , only with slurred speech from the dysfunction of the muscles involved in speech. Other symptoms like paralysis or dizziness would be present in case of a possible stroke. So, I would advise you to consult with a neurologist, have a good physical examination . If it is just a peripheral face palsy no other examinations are needed and he can try treatment with steroids and antiviral therapy for some weeks if no contraindications. If other signs are present a brain MRI would be helpful to exclude a possible stroke. Hope to have been of help! Thank you for using HCM! Greetings! Dr. Abaz Quka