Posturography: A Test for Balance and Dizziness

Posturography is a technique used to quantitatively assess a person’s balance and postural control. It provides objective data on how an individual maintains stability under various conditions, making it valuable for managing health issues that cause dizziness, unsteadiness, or falls. By measuring the body’s subtle movements, posturography helps identify which parts of the balance system may not be functioning correctly.

The Body’s Balance Control Systems

Maintaining an upright posture relies on the interplay of multiple sensory systems and the central nervous system (CNS). The visual system provides information about our body’s position relative to the surrounding environment. The vestibular system, located in the inner ear, acts like a gyroscope, sensing head movements and gravity to help the brain understand our orientation in space.

These systems work with the somatosensory system, which includes a network of sensors in our skin, muscles, and joints. These receptors provide proprioceptive feedback, which is the sense of our body’s own position and movement. This information, along with inputs from the visual and vestibular systems, is sent to the CNS.

The brain and spinal cord integrate these signals to create an internal model of the body’s posture. Based on this information, the CNS generates precise motor commands sent to muscles throughout the body. These commands result in continuous, subtle adjustments that allow us to maintain our balance.

Methods and Technology in Posturography

Posturography assessments fall into two categories: static and dynamic. Static posturography evaluates a person’s ability to maintain balance while standing still on a fixed surface. This is done using a force platform, a plate equipped with sensors that measure the tiny shifts in body weight and pressure. These measurements help quantify the body’s natural sway.

Dynamic posturography challenges balance under changing conditions. The most common form is Computerized Dynamic Posturography (CDP), which uses a movable force platform and a visual enclosure. During a CDP test, the platform can be tilted unexpectedly, and the visual surround can be altered to create a sense of motion. This allows clinicians to systematically disrupt the sensory information a person relies on for balance.

A widely used protocol in CDP is the Sensory Organization Test (SOT). In the SOT, a person undergoes a series of trials under different conditions, such as with eyes open or closed, on a stable or moving platform, and with a stable or moving visual background. A safety harness is worn throughout the test to prevent falls.

Interpreting Posturography Results

The data collected from posturography provides several metrics for analyzing balance. A primary measurement is the Center of Pressure (COP), which represents the point where the body’s total force is exerted on the support surface. The amount and speed of COP movement, or postural sway, is a direct indicator of stability; less sway indicates better postural control.

From these sway measurements, an overall equilibrium score can be calculated for each test condition. In the Sensory Organization Test, these scores are used to generate sensory analysis ratios. These ratios compare performance across different conditions to pinpoint which sensory system—visual, vestibular, or somatosensory—the individual may be over-relying on or which may be impaired.

For instance, if a person sways significantly more when the visual surround moves, it might suggest an over-reliance on visual cues. If they struggle when both visual and surface inputs are unreliable, it points toward how well they use their vestibular system for balance. These patterns help create a detailed picture of an individual’s balance strategy and potential deficits.

Uses of Posturography in Diagnosis and Rehabilitation

Posturography is a clinical tool for diagnosing and managing conditions affecting balance. It is used to investigate the causes of chronic dizziness, vertigo, and general imbalance by objectively assessing the function of the different balance systems. The results help clinicians differentiate between issues originating from the inner ear, the CNS, or other sensory deficits.

The technique is useful in evaluating balance impairments associated with specific neurological conditions. Patients often undergo posturography to quantify their stability and assess fall risk, especially those with:

• Parkinson’s disease
• Multiple sclerosis (MS)
• Peripheral neuropathy
• Recovery from a stroke
• Traumatic brain injury

Beyond diagnosis, posturography plays a part in rehabilitation. By identifying specific sensory or motor control deficits, therapists can design targeted balance training programs. The test can then be used to monitor a patient’s progress, providing objective feedback on the effectiveness of the therapy and allowing for adjustments to the rehabilitation plan.