Screening for unilateral intracranial abnormalities using near infrared spectroscopy. A preliminary report

Near infrared spectroscopy (NIRS) is being increasingly used for medical applications, including neurosurgical care. This preliminary report describes the use of a low cost, indigenous, non-invasive system where NIRS is used to identify superficial unilateral intracranial abnormalities. The optical density (OD) over each hemisphere was initially studied in 50 normal volunteers. The specificity, sensitivity, reliability and reproducibility of the NIRS generated from the developed equipment in detecting OD were thus confirmed. The OD over each hemisphere was then measured in 71 other individuals, immediately after a computed tomography (CT) scan of the brain was performed. Data was statistically analysed to find the average OD difference (compared to the opposite side) of the various intracranial compartments. Differences in OD suggested a unilateral intracranial abnormality. All those in whom OD differences were detected with the NIRS system had unilateral abnormalities on the CT scan. None of the 53 patients who had a normal CT scan had significant differences in OD.