There is no doubt my FIL has Parkinson's. He has a neurologist and he has all the classic symptoms. Recently his psychiatrist diagnosed him with Alzheimer's. Wondering how one can tell the difference between the two when getting the diagnosis is so difficult to begin with.
This is certainly a huge challenge to diagnose!
My heart goes out to you. It is a long and difficult journey. God bless your FIL and you and your family.
The "Lewy Bodies" can cause not only the familiar physical symptoms of PD, but cognitive problems as well. If someone with PD develops dementia, particularly with certain characteristics, he is usually diagnosed with having Parkinson's Disease with Dementia (PDD).
The Lewy Body clumps don't always start out by causing PD symptoms. Sometimes dementia (with particular characteristics) comes first, and the Parkinson symptoms may appear much later or only very mildly. Such people are said to have Dementia.with Lewy Bodies.
Both caused by the clumps in the brain named for Lewy, PDD and DLB are basically the same pathology just differentiated by which symptoms came first and are strongest. Together both diseases are called Lewy Body Dementia (LBD).
Brain autopsies often reveal both clumps and tangles -- evidence of both LBD and AD.
So you are right; it is very difficult to accurately diagnose different types of dementia. It can be important to get an early diagnosis by someone who has experience and expertise in this field. For examples, some drugs developed for AD are even more effective for LBD. Some drugs that are OK when given to an AD patient can cause permanent damage or death to someone with LBD.
I would ask the psychiatrist why she or he came up with AD instead of the more expected PDD. Does your FIL have characteristics that fit the AD profile better? (And don't be surprised if the doctor just doesn't know much about LBD -- that is unfortunately not uncommon, even among specialists.)
You might want to do a little research on the Lewy Body Dementia Association web site, particularly on the subject of the characteristics of LBD that distinguish it from other forms of dementia.
Best of luck to you and your family. Whatever the specific kind of dementia, it is a heartbreaking disease.
There are some drugs that treat both, most have varying results and some carry serious side effects. Each patient is different.
PD and Alz are different illnesses. Your father could have both. PD effects mainly motor skills. Alz. effects cognitive abilities. Although there is a form of Alz. that some PD patients develop.