Parkinson’s disease dementia is often difficult to differentiate from dementia due to other causes and it may be due to the disease itself or as a result of the drugs taken for the disease. Dementia is a state where there is loss of previously learnt functions, or progressively impaired memory, or a marked change in personality and may be accompanied by hallucinations or depression. In Parkinson’s disease the development of dementia is a late phenomenon, often occurring 10 to 15 years after onset of the disease, and it develops in about 20% of patients. Dementia is less likely to develop in early onset of Parkinson’s disease was below 50 and more likely if it symptoms of Parkinson’s disease started after the age of 70.
Other causes of Dementia
These two are the most common causes of dementia are :
- Alzheimer’s disease
- Diffuse vascular disease
The other causes of dementia may be :
- Lewy body disease
- Cerebral tumor
- Chronic subdural hematoma
- Alcohol or drug abuse
- Vitamin B12 deficiency
Since diseases like Alzheimer’s and Parkinson’s occur in the older age group, they may co-exist and symptoms often overlap.
Symptoms of Parkinson’s Disease Dementia
The symptoms of dementia in Parkinson’s disease occur late in the disease, developing slowly over the years. There may be
- Progressive loss of memory
- Incompetence in doing daily routine tasks
- Change in personality
- Slow and repetitive speech
- Problem with concentration
- Unable to use or understand complex language
- Difficulty in learning new tasks
- Unable to take decisions
- Problems in adapting to change
- Slow response to questions
- Increasing dependency on others.
Diagnosis of Parkinson’s Disease Dementia
Whether the dementia is due to Parkinson’s disease or any other cause is very difficult to diagnose since there are no definite tests available. If the person is known to be suffering from long term Parkinson’s disease and there is gradual change in his mood, in personality, decision making capability, or memory, dementia has to be considered. Brain scans such as CT scan or MRI are not diagnostic for Parkinson’s disease dementia but Positron emission tomographic (PET) scan may be done to differentiate dementia caused by depression from that due to Parkinson’s disease. Neuropsychological testing involving assessment of cognitive abilities such as concentration, memory, reasoning or ability to carry out various tasks is a better method of diagnosing the cause of dementia.
Treatment of Parkinson’s Disease Dementia
There is no definite cure for dementia due to Parkinson’s disease but certain drugs, like cholinesterase inhibitors, may give temporary relief. Antidepressants such as the tricyclic agents nortriptyline or desepramine can be used for depression and mood fluctuation, as also certain selective serotonin reuptake inhibitors like fluoxetine and citalopram. Atypical antipsychotics are preferred such as clozapine for the psychotic symptoms, since the older antipsychotics tend to worsen Parkinson’s disease, but the various side effects of the newer drugs have to be taken into consideration too. Quetiapine or olanzapine may be better tolerated than clozapine.