Abstract

In focal cerebral ischemia, spreading depolarization is one of the key events that determine the brain tissue survival. In the infarct core, impairment of energy metabolism causes anoxic depolarization (AD), which considerably increases energy consumption, accelerating irreversible neuronal damage. In the peri-infarct penumbra region, where tissue is still reversible in spite of the limited blood flow, peri-infarct depolarization (PID) occurs, exacerbating energy deficit and hence expanding the infarct area. Thus, a method for noninvasive, real-time monitoring of AD and PIDs is crucially important to diagnose brain tissue viability. Spreading depolarization is generally accompanied by massive ion movements across the cellular membrane. This changes cellular/subcellular morphological characteristics in the tissue, causing change in light scattering. Since in the near-infrared (NIR) spectral region, the reduced scattering coefficient of the gray matter is two orders of magnitude larger than the absorption coefficient, the use of light scattering signal enables sensitive monitoring of the events associated with spreading depolarization.

© 2013 Japan Society of Applied Physics, Optical Society of America