Characterization and processing of surface recorded spinal somatosensory evoked potentials.

Somatosensory evoked potentials were recorded from the skin surface overlying the spinal cord, from the lower lumbar to the lower cervical regions. The recorded responses did not vary over time in any one individual and at each level a consistent wave shape was obtained across all individuals tested. Since the initial signal-to-noise ratio (SNR) for the evoked response recorded at any cord level is very low, the signal data must be processed. In this study, bandpass filtering or matched filtering was used together with ensemble averaging to obtain a usable signal in a reasonable processing time. SNR was improved approximately 1.5 X with bandpass filtering and 2 X with matched filtering. Although the output of the matched filter is a distorted version of the input signal, detection of information is enhanced and processing time using the matched filter and ensemble averaging can be reduced to 1/4 that required for ensemble averaging alone.

[1]  P. Nelson,et al.  Intraoperative loss of somatosensory-evoked potentials predicts loss of spinal cord function. , 1982, Anesthesiology.

[2]  P. Maccabee,et al.  Evoked potentials recorded from scalp and spinous processes during spinal column surgery. , 1983, Electroencephalography and clinical neurophysiology.

[3]  J Debecker,et al.  The system bandpass required to avoid distortion of early components when averaging somatosensory evoked potentials. , 1974, Electroencephalography and clinical neurophysiology.

[4]  J A Sgro,et al.  Phase synchronized triggering: a method for coherent noise elimination in evoked potential recording. , 1985, Electroencephalography and clinical neurophysiology.

[5]  S. Jones,et al.  Spinal and sub-cortical evoked potentials following stimulation of the posterior tibial nerve in man. , 1978, Electroencephalography and clinical neurophysiology.

[6]  Matched Filters in Nerve Conduction Velocity Estimation , 1983, IEEE Transactions on Biomedical Engineering.

[7]  J R Boston,et al.  Effects of analog and digital filtering on brain stem auditory evoked potentials. , 1980, Electroencephalography and clinical neurophysiology.

[8]  A J Gabor,et al.  The human posterior tibial somatosensory evoked potential: synapse dependent and synapse independent spinal components. , 1985, Electroencephalography and clinical neurophysiology.

[9]  R. Cracco,et al.  Spinal evoked response: peripheral nerve stimulation in man. , 1973, Electroencephalography and clinical neurophysiology.

[10]  G. Klem,et al.  A New Technique for Intraoperative Monitoring of Spinal Cord Function: Multichannel Recording of Spinal Cord and Subcortical Evoked Potentials , 1982, Spine.

[11]  N. P. Thomas,et al.  A system for the electrophysiological monitoring of the spinal cord during operations for scoliosis. , 1983, The Journal of bone and joint surgery. British volume.

[12]  E R John,et al.  Application of digital filtering and automatic peak detection to brain stem auditory evoked potential. , 1982, Electroencephalography and clinical neurophysiology.