Real time laser-Doppler perfusion imaging of cortical spreading depression in rat neocortex

Laser-Doppler perfusion imaging (LDPI) is a new technique which provides recordings of blood flow in rapid sequence. In this study we applied LDPI to the brain for the first time to demonstrate propagating waves of cortical spreading depression (CSD) elicited by a needle stab in the frontal cortex of barbiturate-anesthetized rats. Under resting conditions, LDPI recordings of the superficial cortex showed a heterogeneous pattern, partly due to the high flow rate in pial arteries compared with cortical tissue. Within 1 min after elicitation of the CSD a zone of increased signal intensity (96 +/- 5%) up to 6 mm across appeared in the exposed cortex. The rate of propagation away from the site of elicitation for 16 such waves was 2.8 +/- 0.1 mm min-1. The increased signal intensity was partly due to dilatation of pial arterioles and veins, partly to increased blood flow in the microvascular bed. The data are consistent with previous studies of CSD using other techniques for measurement of cortical blood flow. LDPI gives real time images of cerebral blood flow, and may be applied to demonstrate CSD or CSD-like phenomena during neurosurgical operations in man.