Corticobasal Syndrome (CBS) is a progressive neurodegenerative disorder characterized by asymmetric parkinsonism, cortical sensory deficits, alien limb phenomena, and prominent gait and balance disturbances. Vestibular dysfunction is a critical yet under-recognized feature of CBS that contributes significantly to the high fall risk and postural instability observed in affected individuals. This page provides a comprehensive review of vestibular function testing modalities applicable to CBS, their clinical utility, and how findings can differentiate CBS from other atypical parkinsonian disorders such as Progressive Supranuclear Palsy (PSP) and Parkinson's Disease (PD)[1][2].
¶ Pathophysiology of Vestibular Dysfunction in CBS
The vestibular system is vulnerable in CBS due to degeneration of multiple neural structures:
Basal Ganglia: The basal ganglia play a critical role in vestibular processing and balance control. degeneration of the basal ganglia in CBS disrupts the integration of vestibular information with proprioceptive and visual inputs[3].
Parietal Cortex: The posterior parietal cortex integrates vestibular, visual, and somatosensory information for spatial orientation. Cortical dysfunction in CBS affects this integration, leading to vestibular perceptual deficits.
Brainstem: Although less affected than in PSP, brainstem nuclei involved in vestibular processing can be compromised in CBS, particularly in advanced disease stages.
A comprehensive vestibular evaluation in CBS should include:
flowchart TD
A["Comprehensive Vestibular Assessment"] --> B["Bithermal Caloric Testing"]
A --> C["Video Head Impulse Test"]
A --> D["Posturography"]
A --> E["CDP"]
A --> F["VEMP Testing"]
B --> G["VOR Function"]
C --> H["VOR Gain"]
D --> I["Balance Strategy"]
E --> J["Sensory Organization"]
F --> K["Otolith Function"]
flowchart TD
A["Patient with CBS Symptoms"] --> B["Baseline Neurological Exam"]
B --> C["Caloric Testing"]
B --> D["vHIT"]
B --> E["Posturography/CDP"]
C --> F{"Asymmetric Loss?"}
D --> G{"Reduced VOR Gain?"}
E --> H{"Abnormal Sway?"}
F --> I["Supports CBS"]
G --> I
H --> I
I --> J["Compare with PSP/PD patterns"]
J --> K["Final Diagnosis"]