Mismatch between lactate and the apparent diffusion coefficient of water in progressive focal ischemia

In this study, we examined mismatch in the area indicated by the normal apparent diffusion coefficient (ADC) of water and increased lactate in the early stage of focal cerebral ischemia. Five rats were subjected to permanent middle cerebral artery (MCA) occlusion. Diffusion‐weighted echo planar imaging (DWEPI) and proton echo planar spectroscopic imaging (EPSI) were performed from 20 to 170 min after MCA occlusion, and lactate and N‐acetyl asparate images were obtained by EPSI. Postmortem histological analysis was also performed. The areas of increased lactate and normal ADC were observed in the surrounding border zone of ischemia at approximately 20 min after MCA occlusion. This initial lactate in the border zone was significantly higher than that in the normal area, but lower than that in the ischemic core, which showed a reduction of ADC. However, this area was progressively involved in the ischemic core at 170 min without any treatment. The lactate–ADC mismatch in the initial period of ischemia may offer unique diagnostic information for ischemic tissue at high risk, followed by progressive involvement in the ischemic core without treatment. Considering that the accumulation of initial lactate in this area was not excessive, our findings may suggest that the lactate–ADC mismatch in the early period of ischemia indicates potentially salvageable tissue at high risk, requiring aggressive treatment. Copyright © 2001 John Wiley & Sons,Ltd. Abbreviations used: ADC apparent diffusion coefficient DWEPI diffusion‐weighted echo planar imaging EPSI echo planar spectroscopic imaging MCA middle cerebral artery NAA N‐acetyl aspartate PWI perfusion‐weighted image.