Vestibular-evoked muscle responses in patients with spinal cord injury

Abstract

The vestibular system was activated by galvanic electrical stimulation in 22 patients with spinal cord injury. Three patients were studied standing and all were studied sitting. Electromyographic responses recorded in soleus (standing patients) and the erectores spinae (all patients) were compared with data from 18 control subjects. The vestibular stimulus polarity and head position were arranged so as to produce excitatory medium latency muscle responses in the controls. Responses in the patient group were present bilaterally, present unilaterally or absent below the level of injury. The amplitude of response recorded in erectores spinae at lumbar levels below the lesion in 21 patients (left and right side responses summed) and five control subjects was positively correlated with American Spinal Injuries Association (ASIA) grade: the smallest amplitudes were found in patients with the most severe impairment (Spearman rank correlation coefficient rs = 0.59; P = 0.002, two-tailed). The latency of response (averaged for both sides) was negatively correlated with ASIA grade in 21 patients: the longest latencies were found in patients with the most severe impairment (rs = -0.57; P < 0.01, two-tailed). Amplitude and latency were negatively correlated (rs = -0.72, P < 0.002, two-tailed). The latencies of responses recorded in the erectores spinae at different vertebral levels were linearly related to the vertical distance from the inion to the recording site in both patient and control groups. The conduction velocities of the spinal pathways activated by vestibular stimulation were 4.6 and 10.4 m/s in patient (recording below lesion) and control groups, respectively. Both clinical status (patients recording below lesion, patients recording above lesion and controls) and distance were significant predictors of latency (general linear model, P < 0.0005). It is concluded that measurement of vestibular-evoked responses could provide information on the level and density of spinal cord lesions.

Vestibular-Evoked Myogenic Potential (VEMP) in the Evaluation of Schistosomal Myeloradiculopathy

“…It is also of interest in SMR to check the integrity of the spinal cord using galvanic methods with electrodes recording impulses in muscles of the legs, because this would permit the evaluation of the whole extent of the spinal cord. 22 One limitation of our study is, of course, the absence of histologic evidence of spinal cord disease in patients who presented abnormal or no response to VEMP. Biopsy of the spinal cord in such cases is out of question and would not be proposed by the investigators nor accepted by Ethical Boards.…”

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.…”

Impaired scaling of responses to vestibular stimulation in incomplete SCI

“…The only published data of GVS in SCI patients showed that patients with more severe impairment had longer latencies and smaller amplitudes of back muscle EMG responses (Iles et al 2004). Even though they cannot simply be related because of diVerent paradigms with standing or sitting subjects, respectively, those Wndings are in line with the present results.…”

“…So far only one study has examined vestibulospinal reXexes in SCI patients (Iles et al 2004). GVS-elicited EMG responses in the back muscles (erectores spinae) of SCI patients had reduced amplitudes and delayed responses compared to control.…”