Clinical Sciences/Health Conditions
Natan Bensoussan, MD, MSc candidate
Physiatrist
Université de Montréal / Hôpital du Sacré-Cœur de Montréal
Montreal, Quebec, Canada
Jean-Marc Mac-Thiong, MD, PhD
Orthopedic Surgeon, Principal Investigator
Université de Montréal / Hôpital du Sacré-Cœur de Montréal / Centre Hospitalier Universitaire Sainte-Justine
Montreal, Quebec, Canada
Andréane Richard-Denis, MD
Physiatrist
Hôpital du Sacré-Coeur de Montréal
Montreal, Quebec, Canada
Neuro-sacral dysfunction is common after spinal cord injury (SCI) and is traditionally evaluated using digital rectal examination, a subjective and qualitative method. To provide a more objective bedside assessment, we developed the electrosacrogram (ESG), a surface EMG technique that quantifies resting anal tone and voluntary anal contraction (VAC). Although ESG can identify sacral deficits, small fluctuations in signal amplitude could affect interpretation. This study aimed to determine whether the number and placement of surface electrodes influence ESG signal variability, with the goal of optimizing electrode configuration for clinical use.
Design:
A prospective pilot cohort study of adults with traumatic motor-incomplete SCI (AIS C/D) during outpatient follow-up. ESG recordings were obtained using a standardized protocol across five configurations: unilateral perianal placement; bilateral perianal electrodes; posterior reference placement; reference over the ischial tuberosity; and an intrarectal EMG probe. Participants completed five trials of alternating resting tone and maximal VAC. EMG amplitude envelopes (22 Hz sampling) were segmented into 1-second epochs, and variability was quantified using sample variance. Differences across configurations were assessed with Levene’s test and Holm correction.
Results:
Across all participants and electrode configurations, no statistically significant differences in signal variability were observed for either resting anal tone or maximal VAC. Variance distributions remained comparable between unilateral and bilateral surface placements. Alternative reference positions, including posterior and ischial placements, did not produce significant changes in variability. The intrarectal probe also showed no significant advantage in reducing signal fluctuations. Overall, electrode number and placement did not affect ESG signal stability.
Conclusion:
These findings indicate that electrode number and placement do not significantly influence ESG signal variability. Bilateral electrode placement may be clinically indicated in certain assessments or clinical SCI syndromes. The absence of variability differences allows for flexibility in electrode configuration without compromising signal stability.
