Effects of Unilateral Loss of Vestibular Function on the Vestibulo-Ocular Reflex and Postural Control

Abstract

Long-term recovery from surgically induced unilateral loss of vestibular function was studied in 14 patients. Seven patients underwent surgical extirpation or section of the vestibular nerve, and seven patients underwent labyrinthectomy without vestibular nerve section. The vestibulo-ocular reflex (VOR) and postural control were evaluated preoperatively and monitored for up to 4 years postoperatively with use of pseudorandom rotation (combined sinusoidal frequencies from 0.009 to 1.5 Hz) and moving platform posturography. Immediately following surgery all patients showed minimal reductions in the VOR gain constant, but marked reduction in the time constant, and marked increase in slow eye velocity bias. Bias returned to normal values within about 10 days, but time constants never returned to normal values. Results of standard Romberg tests in these patients were normal throughout the preoperative and postoperative periods. However, all patients showed marked postural control abnormalities in tests of the ability to maintain balance in unusual sensory environments in the immediate postoperative period. Seventy-five percent of the patients eventually recovered normal postural control. Postural control returned to near baseline performance with a time course similar to that of the VOR bias. However, postural control also continued to improve after the recovery of VOR bias was complete.

Dynamic Posturography Findings Predict Balance Status in Vestibular Schwannoma Patients

“…These two scores best represent the vestibular part of the overall balance system as tested by CDPP in various vestibular disorders (6Y9). Moreover, previous studies of CDPP in VS patients had shown preoperatively reduced C5S and/or C6S in this patient population (4,10).…”

“…As a result, an objective, reliable, and valid (3) assessment of postural stability as well as of the relative contribution of the separate systems (i.e., vestibular, visual, and somatosensory) that control postural stability is achieved. Although there are reports of preinterventional (preoperative) CDPP findings of VS patients in the literature (4,5), to our knowledge, there has been no effort to correlate subjective vestibular symptoms to objective preinterventional CDPP findings in this patient population.…”

Comparison of electronystagmography results with dynamic posturography findings in patients with vestibular schwannoma

“…Each of the three trials of every condition of the SOT lasts 20 s. These two scores best represent the vestibular part of the overall balance system as tested by CDPP in various vestibular disorders [3 Á6]. Moreover, previous studies of CDPP in patients with VS had shown preoperatively reduced C5S and/or C6S in this patient population [7,8].…”

The Role of Vestibular Testing in the Evaluation of Patients Engaged in Occupations in Non-Terrestrial Conditions

“…Although of limited value in vestibular diagnosis, CDP is an important tool for the evaluation of VSR function. Discordance has been shown between posturography and rotational test results, suggesting that the compensatory processes of the VSR and VOR may have independent courses [69,70]. As CDP provides unique information about balance function and sensory interactions, it is of significant value in monitoring patient progress and compensation processes [71].…”