Spike-monitoring of anaesthesia for corpus callosotomy using bilateral bispectral index.

During corpus callosotomy for intractable epilepsy, the electrocorticogram is commonly recorded from electrodes placed on the brain surface to monitor of epileptic activity and assess the synchronisation of epileptic signals between the left and the right hemispheres. We evaluated the usefulness of bilateral bispectral index monitoring using two monitors and two sensors placed above the frontal region. Spikes were readily detected on the electroencephalogram on the bispectral index monitor, and the frequency of their occurrence increased or decreased in response to adjustment of the sevoflurane concentration. The disappearance of synchronisation between the left and the right hemispheres was observed with use of the bispectral index - in concordance with the electrocorticogram. Thus, 'spike-monitoring anaesthesia' using bilateral bispectral index was useful in assessing both the effect of anaesthetics on the electroencephalogram signals and the surgical therapeutic effect.