Symptoms & Causes of CBS

What are the Symptoms?

Symptoms of corticobasal syndrome vary from individual to individual and will change as the disease progresses. While traditional descriptions of CBS focus on the motor aspects of the presentation, the features of CBS are heterogeneous. The first symptoms can be quite varied. The changes associated with CBS can be grouped in the following way.  

• Motor: Often the motor changes begin in one limb or on one side of the body. These changes include slowed movements, stiffness, sustained muscle contractions, involuntary jerking, tremor, and difficulty carrying out learned skilled movements. Patients with CBS can also experience difficulty controlling the movements of an arm or leg; in some cases, patients report that these movements are seemingly generated by someone or something else. Gait changes and a propensity to fall may emerge. 
  
• Speech: Speech can become softer in volume, monotonous, and slowed. Some patients develop speech apraxia, in which the coordination of oral movements that produce syllables, words, and phrases becomes impaired. In speech apraxia, speech sounds become distorted and erroneously generated.  

• Cognitive: For some, the first symptom of CBS is a change in language. There can be difficulty manipulating and comprehending grammatical structures. Written and oral output can become groping and halting. Word-finding issues can become pronounced. Others may initially demonstrate difficulty with attention, planning, problem-solving, or visual perception. 
   
• Behavior: Mood and behavioral changes are often seen in CBS. Patients can become impulsive and/or apathetic. New fads or obsessions can emerge. There can be dietary changes and predilection for sweets. CBS can also affect an individual’s mood, resulting in depression, anxiety, irritability, or withdrawal from usual social interactions. 

CBS can be caused by a number of neurodegenerative diseases. These diseases include but are not limited to: 

• Corticobasal degeneration (CBD) 
• Progressive supranuclear palsy (PSP
• Alzheimer’s disease (AD).  

In CBD and PSP, there is an abnormal build-up of a protein called tau in the brain. In AD, different protein deposits called neurofibrillary tangles and neuritic plaques form. In all cases, these deposits destroy healthy brain cells and, depending on their location in the brain, give rise to the motor, cognitive, and behavioral symptoms of CBS. 

The absolute diagnosis of these is made on the basis of a brain autopsy performed by a neuropathologist.  

Autopsy-confirmed cases of CBD are almost always sporadic, which means they randomly occur in the population at large without a specific genetic mutation. In sporadic CBD, genetic and environmental risk factors do play a role but do not directly cause disease.  

In the exceedingly rare genetic form of CBD, disease is transmitted from one generation to the next by a mutation in the MAPT gene. Individuals with this form of CBD come from families in which as many as half of the members are affected.