Density spectral array of BIS VISTA™ monitoring system in a functional hemispherectomy.

We present the case of an adult patient with drug-resistant epilepsy caused by extensive inflammation in the right cerebral hemisphere. She was scheduled to undergo right functional hemispherectomy, which is common in pediatric surgery, but about which few studies have been published with respect to adult patients. During the intraoperative period, the density spectral array of the bilateral bispectral index (BIS) VISTATM monitoring system was used. We observed a power increase in low frequency (0.1-4Hz) and alpha bands (8-12Hz) in the right hemisphere, where the epileptogenic focus was. During disconnection from the frontal lobe, there was a marked decrease of power in low frequency and alpha bands on the right side, with no changes during disconnection from other areas of the brain. We think that further studies are needed to determine whether the density spectral array can be a useful tool for monitoring the effectiveness of functional hemispherectomy.