Postural instability on one foot in patients with loss of unilateral peripheral vestibular function

The vestibular system is a major contributor to postural control and the vestibular nuclei are closely connected to the limb spinal motor neurons. Acute loss of unilateral peripheral vestibular function results in, among others, postural instability which improves with time due to central compensatory processes. It has been shown, however, that a number of processes, such as sensorimotor restriction, drugs, and so forth, may affect the speed and the quality of compensation. Due to the difference of ipsilateral vs contralateral connectivity between the vestibular nuclei and the limb spinal motor neurons, and the peculiarities of compensatory processes, the ipsilateral may not compensate as well as the contralateral foot to lesion in patients who lost unilateral peripheral vestibular function. To explore this possibility, the sway, while standing on each foot, was recorded in normal subjects (N = 30) and compensated (except three) patients (N = 37) with loss of unilateral peripheral vestibular function and the percentage difference between the two sways was calculated. No difference was found between patients swaying more on the ipsilateral vs patients swaying more on the contralateral foot to lesion (p > .80). There was, however, a statistical difference between patients as a group vs normal subjects as a group (p = .005). These data suggest, although not evident in all patients of the group, that sway on the contralateral foot was less than the sway on the ipsilateral foot to lesion, as initially speculated. They may, however, signify that one foot compensates better than the other. This is a preliminary report and more testing is on-going to confirm these results.