Corticobasal syndrome

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Corticobasal syndrome (CBS) is a rare progressive neurodegenerative disease that causes parts of a person’s brain to change over time. As a result of these changes, people living with CBS can experience increased difficulty with their coordination, movement, thinking and speech.

Société Alzheimer Society

Overview

Corticobasal syndrome (CBS) is usually caused by an overproduction of a protein in the brain called tau. This overproduction causes areas of the brain to become increasingly damaged and to shrink over time.

The parts of the brain that are most affected in CBS are:

  • The outer “thinking” layer of the brain, known as the cortex, and
  • The deeper areas of the brain, called the basal ganglia, which helps with movement.

Other names used for CBS include:

  • Corticobasal Degeneration (this term refers to the brain pathology),
  • Corticobasal Ganglionic Degeneration, and
  • Cortical-basal Ganglionic Degeneration.

Symptoms

Symptoms are most commonly seen in people between the ages of 60 and 80, but may begin in some people in their 40s.

CBS can be confused with Parkinson’s disease and Progressive Supranuclear Palsy because some symptoms, like stiffness or rigid movements, can resemble some of the common characteristics of these other neurodegenerative diseases.

Early symptoms of this disease are often related to difficulties with the person’s movement or can present as changes with planning, multitasking, speech, or language.

Difficulties with movement

A person may only experience difficulties with movement in one of their hands, arms or legs. It is also not uncommon for the early physical symptoms to appear only on one side of the body. As the disease progresses, both sides of the body will become affected.

Similar to symptoms of Parkinson’s disease, people with CBS can experience movement difficulties such as rigidity, lack of coordination, and ‘limb dystonia’ (involuntary tightening of the affected limb). People with CBS may complain that a limb affected by the disease does not feel like part of their body. This is known as the “alien limb” sensation.

Tremors

Unlike people with Parkinson’s disease, tremors have been found to be less common in those who are living with CBS.

Changes in cognitive abilities

Changes in cognitive abilities may be experienced early or as the disease progresses. People with the cognitive symptoms of CBS typically experience difficulties with:

  • Recalling words,
  • Simple calculations, and
  • Carrying out a plan, praxis and slow or slurred speech.

Visual spatial disorientation

Visual spatial disorientation can be seen as a symptom of CBS.

If you're finding it difficult to "sense" yourself relative to the earth, your surroundings and objects around you, you may be experiencing spatial disorientation.

For example, you might see an object near you and perceive it to be located closer or farther to you than where it actually is. Think of the effect when you look at a passenger side mirror in a car, where "objects may be closer than they appear" – this is a mild way of experiencing visual spatial disorientation.

Diagnosis

It can be challenging to diagnose early-stage CBS as a number of symptoms are shared with similar neurodegenerative diseases, including:

  • Parkinson’s disease
  • Alzheimer’s disease
  • Frontotemporal dementia
  • Dementia with Lewy bodies
  • Progressive supranuclear palsy, and
  • Multiple system atrophy.

People who show signs of cognitive difficulties prior to movement symptoms may be misdiagnosed with Alzheimer’s disease or frontotemporal dementia. It is usually not until movement symptoms develop that CBS is considered.

CBS may take several months or even years to diagnose. Making a diagnosis of CBS becomes easier for physicians when the person presents with both cognitive and physical symptoms.

There is no single test to diagnose CBS. Physicians assess patterns and types of symptoms to help rule out other conditions that could be causing the symptoms, such as Parkinson’s disease, stroke or motor neuron disease.

Brain imaging (MRI) is often used to help detect any abnormal changes in the brain that are features of CBS, such as the shrinkage of the brain’s cortex. A thorough assessment may also include neuropsychological testing to evaluate the impact of symptoms on the person’s mental abilities.

Risk factors

At present, there is no known cause of CBS and common risk factors have not been identified. However, similar to other types of dementia, CBS is characterized by an excess amount of the tau protein in the brain. It is still unknown what causes this surplus of the tau protein, and why it results in the deterioration of brain cells.

Treatment

Currently, there is no known cure for CBS. Medications that are often used to manage symptoms of Parkinson’s disease can be tried in CBS but are usually not as effective.

Cholinesterase inhibitors used to improve alertness and cognition in people with Alzheimer’s disease do benefit some people with CBS.

Therapeutic approaches

Therapeutic approaches can support people living with CBS to manage symptoms of their disease:

  • Occupational and physical therapies that provide passive range of motion may help to maintain physical functioning throughout the progression of the disease.
  • Early speech therapy has also been found to help delay difficulties with verbal communication.