Patterns of Disturbed Impulse Propagation in Multiple Sclerosis Identified by Low and High Frequency Somatosensory Evoked Potential Components

Abstract

In human median nerve somatosensory evoked potentials (SSEPs), high frequency (600 Hz) oscillations (HFOs) are superimposed onto the low frequency SSEP component N20. High frequency oscillations are generated both in deep axon segments of thalamo-cortical projection neurons and at the primary somatosensory cortex. The present study aimed to test the hypothesis that HFOs might be more sensitive to temporal dispersion caused by demyelinating lesions in multiple sclerosis (MS) than the N20. The authors recorded HFOs in median nerve SSEPs in 50 patients with definite MS and in 30 healthy controls. Three patterns of SSEP alterations were found: (1) abolished HFOs with either normal (11% of stimulated limbs), or delayed N20 (16% of stimulated limbs); (2) an attenuation of N20 amplitude with preserved HFOs (13%); and (3) a mixture of both patterns (21%). The first pattern--normal N20 with abolished HFOs--indicates that the HFOs are a sensitive marker of slight demyelination. The second pattern is suggestive of a mainly axonal lesion type, while the third pattern points to a combined axonal/demyelinating process or a conduction block. Analysis of HFOs allows identification of slight demyelinating processes in MS patients in whom the N20 SSEP component remains unaffected. The HFOs provide a tool to distinguish different patterns of disturbed impulse propagation.

Auditory spatio-temporal brain dynamics and their consequences for multisensory interactions in humans

“…In strong agreement are the repeated observations in humans of non-linear neural response interactions within the initial 100 ms post-stimulus onset (Giard and Peronnet, 1999;Foxe et al, 2000;Molholm et al, 2002;Lutkenhoner et al, 2002;Fort et al, 2002a,b;Gobbele et al, 2003; see also Murray et al, 2004Murray et al, , 2005aGonzalez Andino et al, 2005) and/or within brain regions traditionally held to be 'unisensory' in their function (e.g. Macaluso et al, 2002;Calvert, 2001;Murray et al, 2004Murray et al, , 2005aMartuzzi et al, 2007;Meylan and Murray, 2007; see also Ghazanfar et al, 2005;Kayser et al, 2005Kayser et al, , 2007 for recent functional evidence from non-human primates).…”

Pain in Parkinson's disease and multiple sclerosis: Its relation to the medial and lateral pain systems

“…In a recent study, it was found by analysis of recordings of somatosensory evoked potentials that the transmission of impulses generated by median nerve stimulation to S I was disturbed in MS patients (Gobbelé et al, 2003). Despite the reduced capacity of S I to process sensory stimuli, S I still retains its plasticity.…”

Classification of the extracellular fields produced by activated neural structures

“…For instance, if recording of traveling potentials far from the axon, is desired, it will be important to keep low frequency (high pass) filters as low as possible. However, if the goal of an experiment is to analyze the changes in the local environment that a nerve impulse encounters, it is best to set the low frequency filter high enough to reduce the amplitude of the traveling potentials [30]. …”