Introduction to Posturography & Vestibular Testing

Computerized dynamic posturography (CDP) is the gold standard for objectively quantifying balance. Within CDP, the Motor Control Test (MCT) and the Adaptation Test (ADT) are two critical protocols that assess automatic postural responses. These motor tests are often performed alongside sensory organization tests to differentiate between VESTIBULAR, visual, and somatosensory deficits. The scoring of these tests provides crucial data for clinicians managing patients with dizziness and imbalance.

The Motor Control Test (MCT): Scoring Automatic Responses

The MCT measures a patient's ability to recover from an unexpected, forward or backward translation of the support surface. The primary scoring metrics include:

• Latency (ms): The time between the platform movement and the initiation of the patient's corrective response. Prolonged latencies are a hallmark of central or peripheral VESTIBULAR pathology.
• Amplitude (deg/s): The strength of the muscle response needed to stabilize the body. High amplitudes may indicate poor efficiency or co-contraction.
• Weight Symmetry (%): The distribution of force between the left and right legs during the recovery. Scores significantly different from 50% suggest unilateral compensation or orthopedic limitations.

Normative data is used to generate a composite score. A score of "0" or a negative value often indicates a severe VESTIBULAR loss, whereas a score of 100 represents perfect performance relative to age-matched controls.

The Adaptation Test (ADT): Measuring Long-Loop Plasticity

The ADT assesses the patient's ability to adaptation to a continuously tilting platform (toes up or toes down). Unlike the MCT, which measures a reactive "stumble" response, the ADT measures the central nervous system's capacity to modify the response over repeated trials.

Scoring focuses on the sway energy (the integrated area of the center of pressure path) over the course of 5 trials. A healthy score shows a decay in sway energy (negative slope), indicating rapid adaptation. A flat or rising slope indicates poor habituation, often seen in patients with persistent dizziness and maladaptive VESTIBULAR compensation.

Clinical Interpretation: From Scores to Treatment

When scoring these POSTUROGRAPHY tests, clinicians must look for patterns. An abnormal MCT latency with a normal SOT (Sensory Organization Test) suggests a cerebellar or brainstem lesion. An abnormal ADT score, particularly with high initial sway energy, is very common in patients with dizziness due to phobic postural vertigo or PPPD. The ultimate goal of these motor tests is to guide treatment—such as habituation exercises or VESTIBULAR rehabilitation—to retrain the brain's adaptation mechanisms.