Cervical proprioception is sufficient for head orientation after bilateral vestibular loss

The aim was to investigate the relative importance of cervical proprioception compared to vestibular input for head movements on trunk. Subjects with bilateral vestibulopathy (n = 11) were compared to healthy controls (n = 15). We studied their ability to move the head accurately to reproduce four specified target positions in the horizontal yaw plane (neutral head position, 10 degrees target, 30 degrees target, and 30 degrees target with oscillating movements applied during target introduction). Repositioning ability was calculated as accuracy (constant error, the mean of signed differences between introduced and reproduced target) and precision (variable error, the standard deviation of differences between introduced and reproduced targets). Subjects with bilateral vestibulopathy did not differ significantly from controls in their ability to reproduce different target positions. When the 30 degrees target position was introduced with oscillating movements, overshoot diminished and accuracy improved in both groups, although only statistically significantly when performed towards the right side. The results suggest that at least in some conditions, accurate head on trunk orientation can be achieved without vestibular information and that cervical somato-sensory input is either up-regulated as a compensatory mechanism after bilateral vestibular loss or is important for such tasks.