One underlying disease. Different experiences.
Alpha-synuclein disease encompasses several brain conditions, such as Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, and related disorders. These conditions share a common biological process: the accumulation of an abnormal protein known as alpha-synuclein. However, the manifestations of these diseases can vary greatly among individuals.
This variability occurs because the disease affects different brain systems in unique ways and at different times for each person.
The Brain Works Through Networks
The brain functions through networks, groups of interconnected cells that manage functions like movement, thinking, mood, motivation, sleep, blood pressure, and more. Alpha-synuclein disease impacts these networks unevenly. The networks most affected early on typically dictate the initial and most noticeable symptoms. Over time, more networks are usually involved, leading to changes in symptoms as the disease progresses.
Why Dopamine Matters (But Isn't the Whole Story)
Dopamine is a key chemical messenger in the brain, facilitating communication between brain cells. Many visible symptoms of alpha-synuclein disease involve dopamine, which travels along several major brain pathways, each supporting different functions. If alpha-synuclein disrupts a specific dopamine pathway early on, the corresponding symptoms will reflect that disruption.
How Different Dopamine Pathways Shape Symptoms
Movement Pathway
(Controls smooth, automatic movement)
When the movement pathway is affected, common symptoms include:
- Slowness or stiffness
- Shuffling or balance problems
- Tremor
- Smaller handwriting or softer voice
This symptom pattern is often referred to as Parkinson's disease, although it doesn't mean other brain systems are unaffected; it simply indicates that movement changes are initially the most noticeable.
Thinking and Planning Pathway
(Supports attention, organization, and mental flexibility)
If the dopamine pathways involved in thinking and planning are impacted early, individuals may experience:
- Trouble concentrating or multitasking
- Slower thinking
- Difficulty planning or organizing
- Feeling mentally overwhelmed
Movement symptoms might be mild or appear later, and sometimes individuals seek medical attention first for memory or thinking issues rather than movement problems.
Motivation and Mood Pathway
(Supports drive, interest, and emotional balance)
When dopamine pathways related to motivation and emotion are more affected, symptoms may include:
- Apathy or loss of interest
- Depression or anxiety
- Changes in motivation or reward
- Feeling "flat" or disengaged
These changes are not due to personal weakness or a primary psychiatric illness; they reflect alterations in brain circuits that regulate motivation and emotion.
Why Hallucinations or Confusion Can Occur
Some individuals with alpha-synuclein disease may experience visual hallucinations, confusion, or fluctuations in attention. These symptoms are not solely due to dopamine.
They usually result from a combination of changes in:
- Attention and alertness systems
- Visual processing areas of the brain
- Sleep-wake regulation
- Other brain chemicals, notably acetylcholine
This pattern is common in dementia with Lewy bodies, where thinking, perception, and alertness may vary from day to day.
Symptoms Beyond Dopamine
Alpha-synuclein disease also affects brain systems not reliant on dopamine, explaining why some people first notice:
- Acting out dreams during sleep (REM sleep behavior disorder)
- Lightheadedness when standing
- Constipation or bladder changes
- Temperature or sweating changes
- Loss of smell
These symptoms indicate involvement of sleep and autonomic systems, which control automatic body functions.
Why Diagnoses Can Overlap
Alpha-synuclein affects multiple brain networks, and different networks are affected to varying degrees in each person, leading to overlapping and evolving diagnoses.
This explains why:
- Parkinson's disease is not just a movement disorder
- Dementia with Lewy bodies is not simply Parkinson's plus dementia
- Multiple system atrophy is not just a faster version of Parkinson's
These conditions represent different patterns of the same underlying disease, shaped by which brain systems are most affected.
What This Does Not Mean
It's crucial to clarify what this understanding does not imply:
- It does not predict exactly how symptoms will progress
- It does not determine a fixed timeline
- It does not mean everyone will develop the same symptoms
Individuals can remain stable for extended periods, and symptoms often change gradually.
The Big Picture
Alpha-synuclein disease is best understood as a network condition, not a single symptom or diagnosis. The symptoms experienced by a person reflect:
- Which brain systems are most affected
- How those systems interact
- How the brain adapts over time
This understanding aids doctors in explaining symptom variations, selecting safer treatments, and planning personalized care.
What This Means for You
- Differences in symptoms are expected and normal
- Changes reflect biology, not effort or personality
- Care is individualized and adjusted over time
- The goal is understanding, safety, and quality of life
If you or a loved one has alpha-synuclein disease, your care team will focus on which systems are affected now, what support is needed, and how to plan thoughtfully, without assuming the worst.