Bias-probe rotation test of vestibular function

Abstract

Apparatus and methods for rotation test stimulus and analysis methods overcome many of the limitations of traditional clinical tests of peripheral vestibular function. An embodiment includes a rotational stimuli applied to the rotational motion for testing that includes two separate components, a bias component and a probe component. The bias component for rotational motion is designed to temporarily turn off vestibular responses in one ear while the responsiveness in the opposite ear is simultaneously evaluated using the probe component of the stimulus. Responses from application of these stimuli are analyzed by isolating and separating the bias response from the probe response. The bias and probe component responses are parameterized by applying curve fits of mathematical functions to the isolated bias and probe component responses. These parameters characterize the patient's vestibular function.

1 . A system comprising:
 a device that rotates a subject; and   a motion control to control motion of the device, the motion control adapted to provide a stimulus to the device, the stimulus being a multiple component stimulus to control motion of the device to temporarily turn off vestibular responses in one ear of the subject and to modulate the motion of the device while the vestibular responses in the one ear are turned off to evaluate responsiveness in another ear of the subject.   
   
   
       2 . The system of  claim 1 , wherein the stimulus includes a bias component of sufficient magnitude to stimulate motion of the device to temporarily turn off vestibular responses in the one ear of the subject, and a probe component to modulate the motion of the device while the vestibular responses in the one ear are turned off to evaluate responsiveness in another ear of the subject. 
   
   
       3 . The system of  claim 2 , wherein the probe component has a frequency higher than that of the bias component and an amplitude lower than that of the bias component 
   
   
       4 . The system of  claim 2 , wherein the bias component of the stimulus includes a sinusoidal waveform and the probe component of the stimulus includes a sinusoidal waveform. 
   
   
       5 . The system of  claim 2 , wherein the bias component of the stimulus includes a pulse waveform and a step waveform and the probe component of the stimulus includes a sinusoidal waveform. 
   
   
       6 . The system of  claim 5 , wherein the probe component of the stimulus is added to the step waveform of the bias component. 
   
   
       7 . The system of  claim 5 , wherein the bias component of the stimulus includes an acceleration pulse waveform of a first duration and a step waveform of a second duration, the second duration longer than the first duration. 
   
   
       8 . The system of  claim 2 , wherein the device is a clinical rotation chair. 
   
   
       9 . The system of  claim 2 , the system further includes eye movement recording equipment to record eye movement of the subject. 
   
   
       10 . The system of  claim 2 , the system further includes a diagnostic tool to analyze a bias response related to the bias component of the stimulus and a probe response related to the probe component of the stimulus. 
   
   
       11 . The system of  claim 10 , wherein the diagnostic tool separately analyzes the bias response and the probe response. 
   
   
       12 . The system of  claim 11 , wherein the diagnostic tool includes a bandpass filter to filter a slow phase eye velocity to isolate the probe response providing a bandpass slow phase eye velocity, and tools to parameterize the probe response. 
   
   
       13 . The system of  claim 12 , wherein the diagnostic tool is adapted to average the bandpass slow phase eye velocity over a number of cycles of the bias component and to parameterize the averaged bandpass slow phase eye velocity. 
   
   
       14 . The system of  claim 10 , wherein the diagnostic tool includes:
 a low pass filter to filter a slow phase eye velocity to remove the probe response to provide a low pass slow phase eye velocity; and   
     a low pass filter to filter the stimulus velocity to remove the probe component to provide a low pass bias velocity, wherein the diagnostics tool is adapted to provide an input-output function correlated to the low pass phase eye velocity versus the isolated bias component. 
   
   
       15 . The system of  claim 14 , wherein the diagnostic tool is adapted to average the low pass slow phase eye velocity and the low pass bias velocity over a number of cycles of the bias component and the diagnostic tool is adapted to estimate a phase for the averaged isolated bias component and a phase for the averaged low pass slow phase eye velocity at a frequency of the bias component, and to time shift the averaged isolated bias component and the averaged low pass slow phase eye velocity such that the two are aligned with a 180° phase shift between them after estimating the phase for the averaged isolated bias component and the phase for the averaged low pass slow phase eye velocity. 
   
   
       16 . The system of  claim 15 , wherein the diagnostic tool is adapted to determine a curve fit to the averaged low pass slow phase eye velocity related to the averaged low pass bias velocity and to fit parameters related to gain behavior of the input-output function and related to a saturation behavior of the input-output function.