Diffusion weighted imaging and magnetic resonance spectroscopy in a low flow ischaemia model due to endothelin induced vasospasm

The aim of this MR study was to determine if vasospasm induced by applicati on of endothelin-l (ET-I) in the rat brain would model the abnormalities at tributed to vasospasm described in patients with subarachnoid haemorrhage ( SAH) with reversible neurological deficits. Following application of ET-I i n concentrations of 10(-4) M or 10(-6) M to the middle cerebral artery, the re was an immediate drop in pH, an increase in the inorganic phosphate (Pi) to phosphocreatine (PCr) ratio and elevated lactate. There was gradual rec overy to control in the 10(-6) M group, but in the 10(-4) M group there was a loss of approximately 10% in the absolute signal intensities of PCr and adenosine triphosphate (ATP). In a second similarly treated group of animal s, the area. of the hemisphere with a low apparent diffusion coefficient (A DC) was 27 +/- 6% at 30 min and remained at about 20-21% at 90 min and beyo nd. Together these data suggest that the regions with persistently low ADC were metabolically compromised, with incomplete recovery of PCr and ATP, an d represent irreversibly damaged tissue. This raises the possibility that M R spectroscopy and imaging could be a sensitive indicator of tissue viabili ty. This is a potentially useful model of low how as seen in clinical vasos pasm following SAH. Copyright (C) 2000 John Wiley & Sons, Ltd.