Dynamic Posturography Sensory Organization Motor Control Testing Posture Evoked Response

Computerized Dynamic Posturography Sensory Organization Test—measurement of sway energy under various visual and support conditions. Motor Control Test—measurement of sway in response to tilt or translation in the support surface. Posture Evoked Responses—EMG recordings during the Motor Control Test.

Measuring Sway Energy Pt stands on force plates (pressure transducers) pick up vertical forces weight distribution front-back left-right Pick up horizontal sheer forces

LIMITS OF STABILITY The furthest distance in any direction a person can lean away from midline (vertical) without altering the original base-of-support (by stepping, reaching, or falling)

Muscle Contractile Patterns Dynamic Equilibrium Sensory Organization Motor Coordination Determination of Body Position Choice of Body Movement Compare, Select & Combine Senses Select & Adjust Muscle Contractile Patterns Visual System Vestibular System Somato- Sensation Ankle Muscles Thigh Muscles Trunk Muscles Environmental Interaction Generation of Body Movement

Equilibrium Score Maximum sway compared to calculated limits of stability 1 – (Max sway/LOS) 100 % = No Sway 0% = Sway reaches LOS Normed for age and height

Sensory Organization Test Normal Vision Eyes Closed Sway-Referenced Vision Fixed Surface Sensory Organization Test SOT 3 1 2 Sway-Referenced Surface 4 5 6

Equilibrium Scores For each of the 6 conditions Composite of all 6 Derived Sensory Analysis

Ratio Conds. Functional Relevance Somatosensory (SOM) 2/1 Visual (VIS) Pt’s ability to use input from the somatosensory system to maintain balance. Visual (VIS) 4/1 Pt’s ability to use input from the visual system to maintain balance. Vestibular (VEST) 5/1 Pt’s ability to use input to the vestibular system to maintain balance. Preference (PREF) 3+6/2+5 The degree to which pt relies on visual info to maintain balance, even when the info is incorrect.

Sensory Analysis

Strategy Analysis Hip vs. Ankle Dominant Hip–high frequency, greater effect in horizontal shearing force Ankle–low frequency, greater effect in vertical forces.

COG Alignment Average weight distribution Displayed for each conditions Offsets may reflect: peripheral sensory neurogenic musculoskeletal adaptation

Motor Control Test Support Surface Translations Sway amplitude Latency Forward Backward Sway amplitude Latency Weight symmetry

Motor ControlTest (MCT) Amplitudes - Threshold/Small - Mid-range/Medium - Saturating/Large Directions - Forward - Backward Measures - Latency - Strength - Symmetry

MCT: Normal Latencies Latencies Slightly Shorter For Large vs Medium Displacements Latencies Symmetrical Between Left & Right Sides

MCT: Latencies Prolonged Possible Deficits: - Extremity/Spinal Orthopedic Injury - Output Pathways Problem Conditions: - Minor If Isolated - Major If Combined Possible Treatments: - Rehabilitation? - Lifestyle Unilaterally

MCT: Latencies Prolonged Possible Deficits: - Neuropathy - Multiple Sclerosis - Spinal Orthopedic - Brainstem/Cortical Problem Conditions: - Minor If Isolated - Major If Combined Possible Treatments: - Lifestyle Bilaterally

Adaptation Test (ADT) Slow Toes Up (Down) Rotations - 8 degrees/sec Sequences of 5 Trials measure response time

ADT: Adaptation Test Normal Adaptation Sway Energy Scores Higher During Initial Trials Sway Energy Decreases Progressively With Repeated Rotations Normal Adaptation

ADT: Adaptation Test Possible Deficits - Mal Adaptation - Ankle Weakness - ROM impairments Problem Conditions - Irregular Surfaces Possible Treatments - Rehabilitation Failure to Adapt

Elderly Fallers: Fail Toes-Up Adaptation Whipple & Wolfson, Balance, 1990 Age-Matched Groups of Fallers & Non-Fallers Compared Toes-Up Adaptation Failure Significantly Higher in Faller Group

Posture Evoked Responses EMG from: Gastrocnemius Tibialis anterior

PERs Short Latency approx 30 ms Mid Latency approx 73 ms Monosynaptic stretch reflex Mid Latency approx 73 ms Polysynaptic segmental reflex Long Latency approx 104 ms Postural response – possibly automatic?