Types and Symptoms of Dementia

Types and Symptoms of Dementia

Changes in the structure and chemistry of the brain cause memory and thinking problems in Parkinson’s disease (PD). The protein alpha-synuclein is central to Parkinson’s. This protein forms sticky clumps, called Lewy bodies, that disrupt normal brain functioning. Parkinson’s dementia is thought to be related to Lewy bodies.

Types of Dementia

Lewy body dementia (LBD) is a term that includes two different types of related dementias, distinguished by which symptoms start when: 

  • Parkinson’s disease dementia (PDD) – diagnosed when a person living with PD experiences significant cognitive decline after a year or more of motor symptoms (most typically, after many years of experiencing motor symptoms).  
  • Dementia with Lewy Bodies (DLB) – diagnosed when cognitive decline is the earliest symptom, or when cognitive decline and motor symptoms begin and progress together. This can also be referred to as Dementia with Lewy Bodies (DLB).

Symptoms of Dementia

Potential thinking, memory and behavior changes among people with Parkinson’s disease dementia can be wide-ranging.

Memory changes and confusion

  • Signs can range from forgetting how to do simple tasks, such as making coffee, to difficulty concentrating, learning, remembering or problem-solving. 
  • People with PDD can become disoriented and confused.
  • People with PDD can experience short- and long-term memory impairment.  

Mood changes, hallucinations and paranoia

  • People with PDD can become agitated, irritable or even aggressive. 
  • PDD can cause hallucinations. People may see, hear or feel things that are not real. 
  • PDD can cause delusions. People may have strange or unrealistic beliefs including paranoid thinking, suspicion or distrust.

Visual perception difficulties

PDD can cause subtle visual-perceptual problems. These problems can contribute to visual misperceptions or illusions. This can include difficulty finding objects in a busy space or trouble navigating familiar or unfamiliar places. Night-time low light or macular degeneration can increase these challenges.

Language challenges

  • As PDD advances, people with the disease may experience problems naming objects or may misname them.
  • It can be difficult for people with PDD to comprehend complex sentences where a question or information is included with other details.
  • People with PDD can experience speech problems, such as trouble producing words even when they can think of the word they want to say. Movement symptoms can cause slowed or slurred speech.

Page reviewed by Dr. Jori Fleisher, MSCE, Assistant Professor, Department of Neurological Sciences at Rush University Medical Center, a Parkinson’s Foundation Center of Excellence.


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