1st February 2024

Background

This is a rare form of dementia. It is due to progressive neurodegenerative cognitive decline, which constitutes approximately around 2% of all cases of dementia worldwide. Patients with Parkinson’s disease have a higher chance of dementia, although almost 2/3rd do not suffer from dementia. It is a condition characterised by deterioration of cognition and day-to-day tasks. 

It is generally characterised by difficulties in thinking and concentration. They usually present with difficulties in communication (speech and language) and executive functioning.

It is a part of dementia with Lewy bodies. One of the entities is Parkinson’s disease dementia, while the other is Lewy Body dementia. 

Epidemiology

• Like Alzheimer’s dementia, this is a common neurodegenerative illness
• It is seen similarly in both sexes.
• It is a disease of middle-aged and older people.
• It constitutes 2% of all cases of dementia worldwide

Pathophysiology

Lewy body accumulates in vulnerable sites of the central nervous system. It contains a protein called alpha-synuclein. The alpha-synuclein is seen in Alzheimer’s dementia as well. There is also a deficiency of Acetylcholine.

Depending on the deposition of the Lewy body, they can be predominantly Nigral disease, limbic disease or diffuse neocortical disease.

Parkinson’s disease dementia is diagnosed based on the timing of cognitive difficulties and motor symptoms. If dementia was present at the onset of symptoms or within 1 year of motor symptoms, then it is Lewy Body dementia. However, if someone has had Parkinson’s dementia or if they have had motor symptoms for at least 1 year and following that, if they develop memory difficulties, it is diagnosed as Parkinson’s disease dementia.

Risk factors

• No specific risk factors 
• Men and women are equally affected
• More likely to run in families
• The presence of hallucinations in a person without dementia, excessive daytime sleepiness and postural instability can increase the chances of dementia with Parkinson’s disease