Computerized Dynamic Posturography (CDP)

Computerized Dynamic Posturography (CDP) is a unique assessment technique used to objectively quantify and differentiate among the wide variety of possible sensory, motor, and central adaptive impairments to balance control. As such, CDP is complementary to clinical tests designed to localize and categorize pathological mechanisms of balance disorders. CDP can identify and differentiate the functional impairments associated with the pathological processes. By itself, CDP cannot diagnose pathology or site-of-lesion.

Because of the complex interactions among sensory, motor, and central adapting processes, CDP requires separate protocols to adequately differentiate among impairments. To quantify the failure of adaptive mechanisms to select appropriate sensory inputs and movement response patterns, CDP exposes the patient to a variety of controlled visual and support surface conditions.

The benefits of Computerized Dynamic Posturography are well documented in the clinical literature. The contribution of CDP information to positive treatment outcomes has been demonstrated in numerous controlled studies . A thorough overview of CDP methodology and clinical applications can be found in “Practical Management of the Dizzy Patient,” edited by Joel A. Goebel (Lippincott Williams & Wilkins Publishers 2000).

CDP Defined

As defined by the American Academy of Otolaryngology-Head and Neck Surgery and the American Academy of Neurology, CDP includes1:

  1. Isolation and Quantification of orientation inputs from the visual, vestibular and somatosensory systems
  2. Isolation and Quantification of central integrating mechanisms for selecting functionally appropriate orientation sense(s)
  3. Isolation and Quantification of functionally appropriate movement strategy(s) in a variety of controlled task conditions
  4. Isolation and Quantification of motor output mechanisms for generating timely and effective postural movements

As defined, CDP is the only method validated by controlled research studies to isolate the functional contributions of vestibular inputs, visual inputs, somatosensory inputs, central integrating mechanisms, and neuromuscular system outputs for postural and balance control.1

Posturographic methods that do not satisfy the AAO-HNS and AAN criteria cannot be considered equivalent to those that do comply with AAO-HNS and AAN guidelines.1

During CDP testing, the patient stands on a movable, dual forceplate support surface within a moveable surround (enclosure). Under control of a computer, the force platform can either move in a horizontal plane (translate), or rotate out of the horizontal plane.3 Standardized test protocols expose the patient to support surface and visual surround motions, during which the patient’s postural stability and motor reactions are recorded. These test protocols include:

  1. Sensory Organization Test (SOT)
  2. Motor Control Test (MCT)
  3. Adaptation Test (ADT)

During the SOT, the utility of visual, vestibular, and proprioceptive inputs in controlling spontaneous sway is eliminated without provoking motor reactions by moving the support surface and the visual enclosure in response to the patient’s postural movements. During the motor control protocols (MCT and ADT), reactions are provoked by unexpected abrupt movements of the support surface. Because the measures of postural stability, as well as the motions of the support surface and visual surround, are precisely controlled and calibrated relative to the patient’s height and weight, standardized graphical summaries can compare the patient’s results to those of age-matched asymptomatic (normal) individuals.


References:

  1. Black FO (2001). “Clinical status of computerized dynamic posturography in neurotology.” Current Opinion in Otolarynogol Head Neck Surg 2001, 9:314-318.
  2. Nashner LM, Black FO, Wall C (1982). “Adaptation to altered support and visual conditions during stance: patients with vestibular deficits.” J Neurosci 5:117-124.
  3. Monsell EM, et al (1997). “Technology Assessment: Computerized dynamic platform posturography”. Otolarynogol Head Neck Surg 1997, 117:394-398.

Origins

The technique commonly referred to in the clinical literature as Computerized Dynamic Posturography (CDP) was developed though a series of basic research studies on human movement control, which were funded by the National Institutes of Health and NASA in the 1960’s and 1970’s. CDP as a clinical tool for evaluating the sensory and motor components of balance control was first described by Nashner, et al1 in 1982 and the technique became available commercially in 1986 when NeuroCom International, Inc. introduced the EquiTest® system. The specific test protocols consisting of the Sensory Organization Test (SOT), Motor Control and Adaptation Tests (MCT and ADT), which classify a device as CDP, were further described in the 1997 Technology Assessment published in Otolaryngology Head & Neck Surgery.2

CDP, is now considered to be the standard quantitative method for isolating and assessing the sensory and motor components of balance.3


References:

  1. Nashner LM, Black FO, Wall C (1982). “Adaptation to altered support and visual conditions during stance: patients with vestibular deficits.” J Neurosci 5:117-124.
  2. Monsell EM, et al (1997). “Technology Assessment: Computerized dynamic platform posturography”. Otolarynogol Head Neck Surg 1997, 117:394-398.
  3. Black FO (2001). “Clinical status of computerized dynamic posturography in neurotology.” Current Opinion in Otolarynogol Head Neck Surg 2001, 9:314-318.