The Usefulness of Near-Infrared Spectroscopy in Monitoring the Location of Eloquent Area and Function Preservation in Brain Surgery

The extent of resection has been shown to influence the outcome of brain tumours. The concept of brain plasticity is to prevent damage to the eloquent areas while maximizing the extent of tumor resection. The present case report describes the usefulness of the near-infrared spectroscopy (NIRS) in evaluation of the possibility of functional preservation for surgeries in eloquent areas. We present a 46-year-old woman, who had previously undergone four sessions of internal decompression surgery for left frontal anaplastic ependymoma. She later underwent radical tumor resection surgery involving the superior and middle frontal gyri, anterior parietal gyrus, corpus callosum, coronal radiation and basal ganglia. Postoperatively, her right hemiparesis did not deteriorate and she could ambulate without much aid. Multichannel NIRS system revealed that hot spot location was in the right superior frontal gyrus and parietal lobe by the same task of right knee joint movement. We judged that her right brain motor function shifted to the contralateral hemisphere by the long course of her illness. It might be possible that if the NIRS was used earlier around the third or fourth perioperative period, with a reliable confirmation of migration of the right motor function to opposite side, the option of a more aggressive tumor resection may have been attempted. NIRS can be a useful and sensitive tool for predicting the location of eloquent areas and monitoring the extent of brain plasticity between surgeries.