Can a person who has had his voicebox removed due to a tumour,get frontal lobe dysfunction?

the cancer had spread to the lymph nodes in the patient and even though he had radiation treatment,had to have a second operation a few months later to remove a massive tumour from behind his ear.three months after the first operation,when voicebox was removed,the patient started to act strangely and his nature changed,he became childlike and couldnt remember simple things eg:spoon. didnt know what it was called or used for.forgot people that he had known for 25 years.had no control of his bodily functions and was in diapers.this was a highly intellegent man,kindest hearted,good sense of humour,well travelled.with so much pride,in less than one year from the date of the first operation,he sadly passed away.i nursed him to the end and need to know what happened in frans,s brain.The doctor said he had frontal lobe dysfunction.What caused it and why did this happen,{in simple english,please}He also had a stroke when he came out of theatre with the second operation,due to massive blood los

You said he had a stroke when he came out of the theater, which is the reason he had the changes in personality and face recognition (usually the bottom of and the rear portion of the right frontal lobe). It does sound as though he also had left hemisphere damage in the front and upper portion of the parietal lobe, too, since he had difficulty speaking and lost his bodily functions.
The only connection the stroke had with the laryngeal operation was not the laryngectomy (voice box removal) itself, but the stress of the operation on his body.
I have a really hard time with doctors who are not qualified in site-of-brain-lesion diagnosis making statements like that doctor did. I would be more likely to believe the statement of a neurologist.

Well depending on the location of the stroke he had, that certainly could have explained some of his decompensation. And it's possible that he had metastatic cancer to his brain, though this would have been easily detected on CT/MRI. There are also many causes for dementia that are completely unrelated to his cancer - perhaps he had Alzheimer's or diffuse vascular disease in his brain. Unfortunately, without an autopsy, there is no way to know for sure what would have caused his declining mental status.

The frontal lobes have nothing to do with speech