Impaired scaling of responses to vestibular stimulation in incomplete SCI

Abstract

Patients with incomplete spinal cord injury (iSCI) have impaired postural control leading to a high danger of falling. Clinically, it is impossible to assess the extent to which postural instability due to sensorimotor deWcit is inXuenced by a disturbance in the vestibulospinal pathways. Galvanic vestibular stimulation (GVS) was applied to investigate changes in the vestibular spinal responses and their potential inXuence on postural stability in iSCI patients. Six chronic iSCI patients and age-matched controls were stimulated with a bipolar binaural stimulus. The centre of pressure (CoP) and soleus EMG responses during free standing with closed eyes on Wrm and compliant ground were measured. The impairment in postural stability was assessed by the mean amplitude of CoP deXections during two minutes undisturbed standing. Although iSCI patients were signiWcantly less stable than controls, direct GVS responses of the soleus EMG and postural sways tended to be increased on Wrm ground. The GVS responses increased when changing from Wrm to compliant ground, showing a close correlation between the extent of postural instability and the response amplitudes. Therefore, challenging proprioceptive feedback induced a signiWcant up-modulation of the GVS responses. However, when we took the postural instability in iSCI patients into account, the EMG and CoP responses to GVS were reduced compared to controls. The combined assessment of EMG and CoP responses to GVS complements the clinical examination and permits evaluation of the preservation and modulation of vestibulospinal responses in iSCI.

Age-related differences in cognitive and postural dual-task performance

“…We also calculated the mean amplitude (MA) and speed (MV) of CoP displacement. MA was the average distance of CoP displacement to its mean and was a global measure allowing to estimate overall postural stability [26]. MV was the sum of the displacement scalars over the sampling period divided by the sampling time [27] and has been suggested to represent the amount of activity required to maintain stability [28].…”

Cortical and vestibular stimulation reveal preserved descending motor pathways in individuals with motor-complete spinal cord injury

“…While most studies focus on the preservation of corticospinal pathways due to its role in volitional movement, other descending motor pathways, such as vestibulo-spinal and reticulo-spinal pathways, may also contribute to preserved motor function below the level of injury. Galvanic vestibular stimulation (GVS) has been studied previously as a means to test the integrity of vestibulospinal pathways in motorincomplete SCI (14,15). However, GVS requires subjects to…”

Use of galvanic vestibular feedback to control postural orientation in decerebrate rabbits

“…It was shown that normal reaction to GVS (the lateral body sway) persisted in a part of SCI patients (Iles et al 2004;Liechti et al 2008;Wydenkeller et al 2006). This finding implies that the spinal pathways responsible for the effect of GVS (which descend in the ventral part of the spinal cord, Muto et al 1995) were not damaged in these patients.…”