Decomposition of spinal cord evoked potentials into propagating and stationary components

Abstract

Spinal cord evoked potentials (SCEPs) recorded from the epidural space allow examination of both the propagating action potentials (PAPs)² and stationary action potentials (SAPs)². PAPs reflect the integrity of the white matter spinal tracts while SAPs reflect the function of synaptic structures in the grey matter. At the segmental level at which the SAPs reach a maximal amplitude^3–5, the PAPs superimposed on the SAPs can be difficult to interpret since their amplitude is of the order of 10 times smaller than the SAPs. The PAPs can be made easier to interpret at the time of data acquisition if a highpass analog filter is used to attenuate the SAPs, which are primarily composed of lower frequency components. However, with this technique the SAPs are not recorded and therefore unavailable for examination. This study examines the utility of a digital filter as a tool to perform decomposition of the PAPs and SAPs after acquisition of SCEPs using wide bandwidth filter settings.