Dementia in Parkinson’s Disease

Dementia is an umbrella term that is defined by a decline in memory and cognitive, or thinking, skills to a level that interferes with normal function. It is normal for older people to have more problems remembering names and faces than they had before, but this does not interfere with normal activities in most cases. People with dementia will misplace things much more than they used to. They will forget appointments, get lost driving, even in relatively familiar places. They may wake up during the night and think they need to go to work even though they retired years ago. They may ask to go home even though they are at home, mistake their wife for their mother, and sometimes get agitated when they are certain there is something wrong and no one else takes this seriously. Patients with dementia often cause problems because they wake up at night and try to go outside, or they may try to cook something and then forget they’ve left the burner or oven on. More commonly they ask the same question repeatedly, driving their family crazy.

Causes of Dementia

There are many causes of dementia. In the western world, Alzheimer’s disease is the most common cause. Dementia with Lewy bodies, a variant of Parkinson’s disease, is a distant second. Most important for our readers, dementia is more common in people with Parkinson’s disease (PD) than in people the same age who do not have PD. Dementia, when it occurs in PD is part of the disease itself and not from the medications used to treat PD. That is, there are brain changes that occur in parts of the brain involved in memory and thinking. Having dementia does not mean having Alzheimer’s disease. While there are some connections between the two disorders, Parkinson’s Disease patients with dementia generally do not have Alzheimer’s disease.

Before diagnosing dementia, one must be careful to exclude other factors that might impair memory or cognition, and might be reversed. There are rare metabolic causes, like underactive thyroid, low vitamin B12, and rare brain infections, that can be easily checked for. Most importantly, certain medications, particularly medications used for over active bladder, that block the same brain chemical, acetylcholine, that is at very low levels in both Alzheimer’s disease and Parkinson’s Disease dementia, may make the patient appear to have dementia, and simply stopping the medication may reverse the problem.

Beyond the simple blood tests for B12, thyroid, syphilis and a few other conditions, it will be up to the doctor, based on the clinical picture, as to whether formal neuropsychological tests, which are sophisticated tests of memory and problem solving, and are expensive and time consuming, or brain imaging with CAT scan or MRI are worthwhile.

Dementia progresses at different rates for different people

Dementia is, unfortunately, progressive but, like the motor features of MD, progresses at very different rates in different people. It not only causes poor memory and thinking, but also is frequently associated with depression, sleep disorders, loss of motivation, loss of interest and pleasure in activities that had previously enriched or even defined their life. Patients with dementia are often apathetic, showing reduced happiness and unhappiness. They are more likely to develop problems with sleeping too much or developing challenging sleep habits brings with it an increased sensitivity to the side effects of all the drugs used in treating Parkinson’s Disease itself. People with dementia are more likely to develop hallucinations or confusion. Therefore the motor problems of Parkinson’s Disease cannot be treated as aggressively in a patient with dementia as compared to the patient without dementia.

Dementia does not kill people. It is not a death sentence. It is true that dementia is associated with a reduced life expectancy, but this is likely due to the greater difficulty involved in treating the motor problems of PD. As noted above, this is because of the increased likelihood of drug side effects in patients with dementia. Unfortunately, more bad things happen to people with dementia. They may forget to use their cane or walker, increasing the risk of falls. They may take their medications unreliably or incorrectly or ignore warning signs of other medical problems.

Dementia can be treated through medication, but its progression will continue

Some of the problems caused by dementia are treatable, but there are no medications that slow the progression of this problem, just as there are no treatments that slow the progression of the rest of the Parkinson’s Disease syndrome. We often use the same medications that are used in Alzheimer’s disease to improve concentration and memory, although only one, rivastigmine, has been approved by the Food and Drug Administration for dementia in PD. Most experts believe that each of the Alzheimer drugs are about as useful in dementia in Parkinson’s Disease as they are in Alzheimer’s, which, unfortunately, is not great. As with all medications used in PD, whether for slowness, stiffness, tremor, depression or sleep disorders, if the medication is not helpful, one should either try a higher dose or stop it. Since the drugs used to treat dementia take several weeks to work, and the dose often requires increases, the family needs to allow a reasonable time period, usually around two months, to decide if it is helpful or not. Obviously this needs to be discussed with the prescribing doctor.

There is a lot of research being done to better understand and better treat dementia in PD.

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