Background and Purpose This study was performed to document the progression of ischemic brain damage after middle cerebral artery occlusion in the rat using magnetic resonance imaging and histopathologic methods.Methods Cerebral ischemia was induced through permanent tandem occlusion of ipsilateral middle cerebral and common carotid arteries. The evolution of magnetic resonance imaging and histopathologic parameter changes was studied, both short term (1.5 to 8 hours) and long term (24 to 168 hours), in five specific brain regions within the middle cerebral artery territory.Results Significant changes in proton nuclear magnetic resonance spin-lattice and spin-spin relaxation times and the "apparent" diffusion coefficient of water could be detected within hours after the onset of permanent focal cerebral ischemia, whereas significant alterations in proton spin-density ratios were not apparent until approximately 48 hours. Histological changes were evident within 12 hours, with a significant loss of neurons seen in the most severely damaged regions at

We measured brain energy phosphate metabolism and intracellular pH (pHi) in a cross-sectional study of migraine patients by in vivo phosphorus 31 NMR spectroscopy. During a migraine attack the ratio ATP/total phosphate signal (mole % ATP) was preserved, but there was a decrease in mole % phosphocreatine (PCr) and an increase in mole % inorganic phosphate (Pi) resulting in a decrease of the PCr/Pi ratio, an index of brain phosphorylation potential. This was found in classic but not common migraine. Mole % Pi was also increased in combined brain regions between attacks. There was no alteration in brain pHi during or between attacks. Energy phosphate metabolism but not pHi appears disordered during a migraine attack.

We studied the effect of focal cerebral ischemia on the "state" of brain water using proton nuclear magnetic resonance imaging. Focal cerebral ischemia was induced in five halothaneanesthetized rats via tandem occlusion of the left common carotid artery and the left middle cerebral artery. The proton transverse relaxation time, the proton density, and the water diffusion coefficient were measured at various times from the same region of brain tissue from 1.5 to 168 hours after occlusion. Early measurements indicated significant changes in the transverse relaxation time (p=0.004) and water diffusion coefficient (/>=0.002) of ischemic brain tissue compared with a homologous region from the contralateral hemisphere. However, the transverse relaxation time, proton density, and water diffusion coefficient in ischemic brain tissue showed different temporal evolutions over the study period. Diffusion coefficient weighting was superior to relaxation time and proton density weighting for the visualization of early cerebral ischemia. Our data suggest that nuclear magnetic resonance imaging is sensitive in detecting changes in proton-associated parameters during early cerebral ischemia and confirm significant changes (p^O.Ol) in the temporal evolution of transverse relaxation times, proton densities, and diffusion coefficients following middle cerebral artery occlusion. (Stroke 1991^2:802-808) N uclear magnetic resonance (NMR) offers the ability to assess noninvasively several physical parameters that are directly related to the amount and "state" of water in brain tissue. The spin-spin relaxation time (T 2 ) is exquisitely sensitive to the relatively slow motions (i.e., rotation of proteins) of the system. Proton density (p) images reveal the spatial distribution of the number of NMR-visible nuclei in the tissue. More recently, NMR has been used to generate images the contrast of which is based on the diffusion coefficient of water (D w ). '-4 We document the temporal evolution of changes in T 2 , p, and D w following occlusion of the middle cerebral artery (MCA) in rats. These measurements provide new information regarding the relative time course of changes in these parameters in experimental ischemia Received August 20, 1990; accepted February 8, 1991. based on the physical properties of water. Characterization of the time course of these NMR-measurable parameters, for both normal and ischemic brain tissue, may provide new insight into the mechanisms responsible for ischemic brain damage and cerebral edema.Comparison of the various types of images may be clinically useful when the physical basis of these changes is more thoroughly understood. Materials and MethodsFive fasted adult male Fisher rats weighing 175-250 g were anesthetized with an inhaled mixture of 69% N 2 O, 30% Oj, and 1.0-1.5% halothane. The rats were allowed to breathe spontaneously throughout all surgical and NMR procedures. Focal cerebral ischemia was induced using tandem occlusion of the left common carotid artery and the left MCA, similar to t...

Brain magnesium was measured in migraine patients and control subjects using in vivo 31-Phosphorus Nuclear Magnetic Resonance Spectroscopy. pMg and pH were calculated from the chemical shifts between Pi, PCr and ATP signals. Magnesium levels were low during a migraine attack without changes in pH. We hypothesize that low brain magnesium is an important factor in the mechanism of the migraine attack.