[Quantifying the stimulus parameters in the neck torsion test].

Abstract

Cervically induced eye movements can be observed when the trunk is rotated and the head fixed. In most test situations, rotating chair motion and head fixation are carried out manually. As a result, specific and non-specific sources of error are involved in these procedures that hamper the reproducibility of test conditions. A system is described that provides quantifiable and reproducible, electronically controlled movements of the rotating chair. Ramp and rectangular stimulus profiles are achieved by infrared optical gate devices on the chair axis. Various processor-controlled sequences of angular displacement and duration can be programmed and monitoring of chair movement is available to the operator during testing, which is otherwise performed in complete darkness. Individual casts of the upper jaw connected with a telescope wall clamp facilitate optimal head fixation. Since great caution is required when using an electronically controlled chair for such tests, and the possibility of damage to the vertebral column is increased by head fixation, several devices have been incorporated into the equipment to fulfil safety requirements such as release mechanism in the head fixation system, besides other safety devices. This system enables cervically induced eye movements which can be related to amplitude, acceleration and velocity of trunk rotation. The results are important for direction and extent of eye shifts, nystagmus and circular-vection.