Parkinson’s Spectrum Disorders
Parkinson’s spectrum disorders share features like the abnormal clumping of proteins in the brain and particular problems with movement (slowness, tremor and rigidity).

Parkinson’s spectrum disorders encompass a group of neurodegenerative disorders characterized by the abnormal accumulation of proteins, including tau and α-synuclein. While these disorders differ in their clinical and pathological features, they share important characteristics, including parkinsonian symptoms (slowed movements, tremor and stiff or rigid muscles), cognitive and behavioral decline, and involvement of specific circuits in the brain.

Corticobasal Syndrome

Corticobasal syndrome (CBS) is a condition that causes changes in movement, language skills or both. CBS may start with movement problems, such as stiff muscles on one side of the body involving the arm, leg, or both. People with CBS may describe having a hard time controlling their arm or leg. Some people with CBS have language problems first and may develop movement problems over time. Thinking and behavior changes may happen either at the beginning or later in the disease.

Lewy Body Disease

Lewy body disease includes dementia with Lewy body disease (DLB) and Parkinson’s disease dementia (PDD). DLB is a condition that causes changes in thinking, behavior and movement. DLB usually starts with thinking and behavior changes that are followed by problems with movement. The movement problems in DLB are similar to those seen in people with more classical Parkinson’s disease.

Multiple System Atrophy

Multiple system atrophy (MSA) typically presents as a combination of symptoms that affect both the involuntary (autonomic) nervous system and movement. Along with the parkinsonian symptoms (slow movement, rigid muscles and poor balance), patients may also experience trouble with their blood pressure, breathing, bladder function and muscle control. The symptoms reflect the progressive loss of different types of nerve cells in the brain and spinal cord.

Parkinson’s Disease

Parkinson’s disease is caused by a loss of nerve cells in a specific part of the brain called the substantia nigra. Cells in the substantia nigra communicate with other movement control centers in the brain by secreting dopamine and other neurotransmitters. When substantia nigra cells die, they stop secreting dopamine, and the other movement control centers become unregulated. This disturbance in the movement control centers of the brain cause the main symptoms of Parkinson’s disease (slowness, tremor and gait or balance problems).

Parkinson’s Disease Dementia

Parkinson’s disease dementia (PDD) is defined by changes in thinking and behavior in someone with a diagnosis of Parkinson’s disease (PD). PD is an illness characterized by gradually progressive problems with movement, most commonly involving slowing of movements, a tremor present at rest, and walking instability which can cause falls. PDD is similar to dementia with Lewy bodies (DLB) in that it also causes changes in thinking, behavior and movement, but in DLB, the movement problems start after the thinking and behavior symptoms.

Progressive Supranuclear Palsy

Progressive supranuclear palsy (PSP) is a condition that causes changes in movement, language and behavior. In its typical form, Richardson’s Syndrome, PSP causes difficulties with balance that lead to frequent falls. Eye movement problems are also a characteristic symptom of PSP, although these are often discovered when a doctor examines a person with PSP. Slowed movement, stiffness and difficulty walking are common. People with PSP may also have changes in speaking, thinking or behavior.

Vascular Parkinsonism

The diagnosis of vascular parkinsonism (VaP) is the clinical diagnosis of parkinsonism due to cerebrovascular disease (disease of the blood vessels in the brain). There are two main VaP subtypes: 

  1. Gradual onset, slowly progressive VaP, due to small vessel disease and blood-brain-barrier dysfunction that presents with progressive parkinsonism. Symptoms typically do not respond to dopaminergic therapies.
  2. Post-stroke VaP, defined as the sudden onset of parkinsonism after a stroke. Symptoms typically respond to dopaminergic therapies.

In addition, mixed VaP is parkinsonism due to vascular disease in addition to other neurodegenerative disorders (such as Alzheimer’s diseaseParkinson's disease, or frontotemporal dementia syndromes). In this case, vascular disease is not the sole cause but rather a contributing factor to parkinsonism.