Development of a vibrotactile tasking device for use in vestibular assessment.

The purpose of this study was to design an automated mental alerting task that could be utilized when performing vestibular testing on a broad range of patient populations, including certain difficult-to-test populations, such as the hard-of-hearing. A device was developed that utilized vibrotactile stimuli output to two vibrators placed on the subject's left leg, and responded to activation of two momentary pushbuttons controlled by the subjects. Fourteen normal-hearing subjects without history or symptoms of vestibular involvement participated. Each participant underwent three mental-alerting conditions, defined as no task, verbal task, or vibrotactile task. Each condition involved four irrigations of the ear canals, two with warm water and two with cool water. The resultant nystagmus was recorded and analyzed using four measures to compare the effect of the mental alerting task condition. No significant difference was found between verbal and vibrotactile alerting both of which provided better responses than the no alerting task (F=8.443; df=2,13; p=0.001). Between-subjects analysis showed that the number of gaps, which are undesirable periods of absent nystagmus during test recordings, was smallest for the verbal and vibrotactile tasks, and largest for the no task condition. Overall, the results showed that the vibrotactile tasking device (VTD) is an effective alternative means of providing mental alerting during vestibular testing, specifically that of caloric examination.