Samenvatting

The current procedure for assessing nervous activity in the spinal cord is needle ElectroSpinography (needle EMG). This is an invasive and painful approach during which a needle is inserted into the subarachnoid space. It is hypothesised that High-Density surface ElectroMyography (HD-sEMG) is a non-invasive alternative for this. This study was conducted to test the viability of HD-sEMG for monitoring spinal functioning.
Five subjects underwent electro-stimulation of the n. tibialis posterior. Three configurations for a HD-sEMG grid (64 channels) were tested: (1) just lateral of the L4 vertebra (towards side of stimulated limb), (2) on the processus spinosis of L4, and (3) on the processus spinosis of Th12. Each configuration was recorded twice per subject. The stimulation protocol consisted of 1000 stimulations administered pseudo-randomly every ±300 ms, while the HD-sEMG was sampled at 16 kHz.
Epoch 10-300 ms after every stimulation were aligned and averaged. This yielded a single average response per channel, which was compared against a baseline (recording without stimulations).
All channels were assessed to identify significant, stimulus-related potentials. The average power of the peaks was divided by the standard error of mean of the baseline to obtain the signal-to-noise ratio (SNR).
The SNRs of configurations 1, 2, and 3 were 5.23 (±3.56), 3.96 (±1.23), and 3.96 (±2.03) dB, respectively. All three SNRs were found to be sufficiently high to suggest that HD-sEMG is indeed a viable technique for monitoring neurophysiological activity in the spinal cord.