What is Corticobasal Syndrome (CBS)?

From the Guidelines

Corticobasal syndrome (CBS) is a rare, progressive neurodegenerative disorder characterized by asymmetric motor symptoms and cognitive impairment, typically presenting with stiffness, slowness of movement, and difficulty controlling one side of the body, particularly affecting the arms and hands, as described in the study by 1.

Key Characteristics of CBS

• Asymmetric limb clumsiness in patients between 50 to 70 years of age
• Unilateral limb rigidity and dystonia, including the “alien limb phenomenon”
• Postural imbalance and cortical features, such as apraxia, cortical dementia, cortical sensory deficits, and impaired language production

Diagnosis and Treatment

Diagnosing CBS can be challenging, and imaging remains an essential diagnostic tool, as noted in the study by 1. Treatment focuses on symptom management, as there is no cure.

• Levodopa may provide modest benefit for parkinsonian symptoms in some patients, though response is typically poor
• Baclofen or botulinum toxin injections can help manage muscle rigidity and dystonia
• Antidepressants like SSRIs may be needed for depression or anxiety
• Physical, occupational, and speech therapy are essential components of care to maintain function

Pathophysiology and Prognosis

CBS is caused by abnormal accumulation of tau protein in brain cells, leading to cell death in the cerebral cortex and basal ganglia, as described in the study by 1. The condition typically progresses over 6-8 years, with patients eventually requiring significant assistance with daily activities.

From the Research

Definition and Characteristics of Corticobasal Syndrome (CBS)

• Corticobasal syndrome (CBS) is a neurodegenerative disorder characterized by a combination of cortical and basal ganglia signs 2.
• It is classified as a tauopathy and presents with a unilateral or markedly asymmetric clinical picture, which is rare among parkinsonian syndromes 2.
• The most common presenting cortical features include apraxia, aphasia, parietal lobe sensory signs, frontal dementia, or myoclonus, while basal ganglia signs include rigidity, akinesia, limb dystonia, and postural instability 2.

Clinical Diagnosis and Challenges

• The diagnosis of CBS is often challenging due to the rarity of the full complement of findings at presentation, the subtle nature of some signs, and the overlap with other parkinsonian and dementing illnesses 2.
• The differential diagnosis includes Parkinson's disease, progressive supranuclear palsy, frontotemporal dementia, primary progressive aphasia, and Alzheimer's disease 2.
• The clinical diagnosis is not confirmed pathologically in up to half of cases, leading to the preference for the term corticobasal syndrome over corticobasal degeneration during life 2.

Treatment and Management

• Treatment of CBS is primarily supportive, with most patients dying within 10 years of onset 2.
• Parkinsonian signs may improve with levodopa, while clonazepam can suppress myoclonus and botulinum toxin can relieve dystonia 2.
• Multidisciplinary therapeutic approaches, including low-frequency repetitive transcranial magnetic stimulation (rTMS), pharmacological treatment, rehabilitation, and botulinum toxin injection, may improve symptoms and quality of life 3.

Cognitive Dysfunction and Triggers

• Cognitive dysfunction is a frequent manifestation of CBS, with patients often presenting with cognitive deficits before the onset of motor symptoms 4.
• There is evidence to suggest that potential central or peripheral triggers may initiate neurodegeneration in CBS, with a higher frequency of focal triggers observed in CBS compared to Parkinson's disease 5.
• The heterogeneity of CBS in terms of clinical, radiological, neuropsychological, and pathological aspects poses a significant challenge for evaluation and diagnosis 4.