Comparison of cortical potentials evoked by mechanical and electrical stimulation of the human oesophagus

Abstract

BACKGROUND: The pathways mediating Cortical Evoked Potentials (CEP) obtained by mechanical (MS) and electrical (ES) stimulation of the oesophagus remain controversial. Whilst CEP have been recorded with either stimuli, the longer latency of CEP to MS has led to the suggestion that these responses are mediated via unmyelinated C-fibres whereas the shorter latency CEP to ES are mediated via myelinated A-6 fibres. However, a direct comparison of the CEP characteristics in the same subject have not been reported. Aim: To compare oesnphageal CEP obtained by MS and ES. Methods: CEP were recorded from the vertex (Cz) in 6 male subjects (age 25-31) using surface electrodes connected to a signal averager via an amplifier. Stimulation was applied 5cm above the LOS. Electrical Stimulation: Was performed using a bipolar ring electrode connected to a stimulator. Stimulation Intensity (SI) was 75% of the subjects maximum tolerated intensity. A grand average of 200 stimuli were recorded. Mechanical Stimulation: Was performed using a 2cm silicone balloon connected to a pump. SI was set at a level which produced a strong, non-painful sensation. A grand average of 200 stimuli were recorded. The rise time to maximum balloon inflation was constant (165ms). Peak latencies were measured from the onset of inflation. Results: Reproducible, triphasic CEP were evoked in all subjects by ES and MS of the oesopha ~us. Values given as group mean _+ SD.