Implications of the Results of Stepping Test in Patients with Unilateral Vestibular Dysfunction

Abstract

The stepping test is a dynamic test for the evaluation of equilibratory function, whose accuracy is so high that it enables us to detect even a slightly compensatory stage labyrinthine disturbance undetectable with static equilibratory function tests. Because it is a equilibrium movement test, it requires a more precise adjustment of the pyramidal and extrapyramidal systems. A stepping test with eyes closed allows us to record and observe even a slightest disturbance of the pyramidal and extrapyramidal tract that cannot be demonstrated with static equilibratory function tests. In patients with unilateral labyrinthine disturbance, a deviation occurs during the stepping test. No publication is available, however, that deals with the time course change in the stepping record.We recorded the center of gravity in the stepping test by KINETOGRAVICORDER and studied time-course change in the recording. Our findings were as follows:Nine patients with unilateral Meniere's disease (in normal phase), selected as subjects, were instructed to face front in the dark. In that position, they performed steppings in an exact rhythm (1.2Hz) with eyes closed, while recordings were taken to examine the onset of deviation. Deviation started with the 8th to 17th step (average 12.4th step), or 6.4sec to 13.6sec (average 9.95sec) after the initiation of steppings.The above results suggest that: (1) A voluntary movement due to central programming is eliminated by approximately about 12 steppings to be replaced by an extrapyramidal reflex. The period during which the said 12 steppings or thereabouts are performed (about 10sec) is the latent time for deviation, (2) a regular rhythm accelerates the manifestation of laterality in the motor reflex, (3) the imposition of regular rhythm has an element of the Jendrassik maneuver, so that it encourages the manifestation of deviation in steppings. We concluded therefore that the stepping test would yield sufficiently meaningful data even if the number of steps to be taken was reduced from that in the past test.