Frontal near-infrared spectroscopy patch sticks to the brow and measures blood oxygen. Source: Mayo Clinic, Jacksonville, Fla.

Researchers have found that a small device worn on a patient’s brow, called frontal near-infrared spectroscopy (NIRS), can be useful in monitoring stroke patients in the hospital, according to a study published in the Feb. 1 issue of Neurosurgical Focus.

The device measures blood oxygen by sticking to a patient’s eyebrows, similar to a pulse oximeter clipped onto a finger, and could offer hospital physicians a safe and cost-effective way to monitor patients who are being treated for a stroke, in real time. NIRS emits near-infrared light that penetrates the scalp and underlying brain tissue, and has been used in animals to study brain blood.

“About one-third of stroke patients in the hospital suffer another stroke, and we have few options for constantly monitoring patients for such recurrences,” William Freeman, MD, associate professor of neurology at the Mayo Clinic in Jacksonville, Fla., said in a statement. “This was a small pilot study … but we plan to study this device more extensively and hope that this bedside tool offers significant benefit to patients by helping physicians detect strokes earlier and manage recovery better.”

To test the effectiveness of NIRS, Freeman and colleagues retrospectively reviewed eight cases from the Mayo Clinic in Florida in which NIRS measurements were obtained while a CT perfusion test was simultaneously performed. The goal was to validate the accuracy of NIRS by testing the correlation with CT perfusion with respect to regional cerebral blood flow (CBF) measurements.

Results showed that both tests offer statistically similar results as analysis of the linear regression revealed a p-value < 0.0001 comparing CBF values obtained by NIRS and CT perfusion.

“We believe that our data, although small in number, may validate the use of NIRS as an important noninvasive real-time bedside application for NIRS in critically ill brain-injured patients who are too unstable to transport to a CT scanner for the CT perfusion-derived method,” wrote the authors. NIRS would also eliminate the risks inherent with CT perfusion that stem from radiation exposure and the administration of contrast medium.

One downside of the NIRS method is that it has a more limited field for measuring blood oxygen and flow, which might not make it beneficial to all patients, according to the researchers.

“Some inherent technical limitations of NIRS need to be addressed. Cerebral blood flow measurements are of a regional nature, in contrast to CT perfusion and xenon-enhanced CT, which allow a more global assessment of brain perfusion,” wrote the authors.

If the device is successfully tested in upcoming studies and miniaturized, the NIRS might also be useful in military settings to assess and monitor blood functioning due to brain injuries, according to Freeman.