Stimulation artefact on EEG trace with BIS monitoring during D-wave recording.

The D-wave reflects the corticospinal fibre potentials and is frequently recorded intraoperatively for intramedullary spinal tumours to ensure maximum safe resection. A 38-year-old male had an intramedullary spinal cord tumour surgically removed while being monitored with D-wave from a single distal electrode technique. Total intravenous anaesthesia (TIVA) with propofol (without a muscle relaxant and with intermittent intravenous fentanyl boluses) was used for the maintenance of anaesthesia guided by processed electroencephalography (EEG) using a bispectral index (BIS) monitor. Regular spike artefacts were observed in the EEG signal recorded by the BIS® monitor during the application of the single-pulse transcranial electrical stimulus and were used as a visual indicator of stimulus delivery. Finally, we propose a novel method of confirming stimulus delivery during D-wave recording based on stimulation artefacts in the EEG signal recorded by the BIS® monitor.