Cervical receptors and the direction of body sway.

A study was performed to determine whether the predominant direction of body sway is influenced by changes of head-to-trunk position. A group of ten patients suffering from acute unilateral vestibular loss was compared with a group of ten healthy subjects. Body sway was assessed by measurement on a posture platform. Center-of-force stabilograms were recorded with the subjects' eyes closed. After a baseline interval in the normal head-to trunk orientation, the head was torsioflexed with respect to the trunk and the locus of the center-of-force further assessed over a defined interval. It was observed that the patient group manifested a systematic translation of the direction of body sway that was associated in a consistent manner with the unilateral deficit. This translation occurred synchronously with head torsioflexion and could also be reproduced when turning the trunk with the head fixed, so that a semicircular canal influence could be excluded. It appears that cervical proprioceptive input to the central vestibular system is responsible for the effect observed.