Metabolic counterpart of decreased apparent diffusion coefficient during hyperacute ischemic stroke: a brain proton magnetic resonance spectroscopic imaging study.
OBJECTIVE
Recent studies have shown that the brain ischemic area defined by the map of decreased apparent diffusion coefficient (ADC) obtained by diffusion-weighted imaging (DWI) during the first hours of ischemic stroke includes a significant part of ischemic penumbra. We hypothesize that the misjudgment of the final infarct size by ADC mapping may be related to a restricted ability of DWI to capture variations in the intensity of cellular suffering. In an attempt to characterize metabolically the hypoperfused brain parenchyma, we studied the relationship between ADC values and brain metabolic parameters measured by proton MR spectroscopic imaging (SI).


METHODS
Six patients with hyperacute ischemic stroke were explored within the first 7 hours after onset with the use of a MR protocol including T2*-weighted MRI, DWI, SI, perfusion-weighted imaging, and MR angiography.


RESULTS
This study demonstrates, for the first time, a wide gradient of ischemia-related metabolic anomalies within the abnormal area delineated by DWI during hyperacute ischemic stroke. In the narrow range of decreased mean ADC values (0.60 to 0.40 x 10(-9) m2 x s(-1)), a 33% decrease in mean ADC is associated with a 122% increase in lactate/N-acetyl aspartate ratio. Mean ADC values never fall below 0.40 x 10(-9) m2 x s(-1) within the severely affected ischemic tissue, while SI still detects a large metabolic heterogeneity inside areas showing similar decreased mean ADC values close to this threshold.


CONCLUSIONS
Our results indicate that the region of very low mean ADC values observed during hyperacute ischemic stroke contains areas of various tissue damage intensity characterized by SI in relation to different stages of cellular metabolic injury. This observation may explain why ADC mapping does not reliably predict final infarct size.
Nicoli
F
F
Centre de Résonance Magnétique Biologique et Médicale, UMR CNRS No. 6612, Faculté de Médecine de Marseille, France.
Lefur
Y
Y
Denis
B
B
Ranjeva
J P
JP
Confort-Gouny
S
S
Cozzone
P J
PJ
D000208:Acute Disease; D000328:Adult; D000368:Aged; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D001921:Brain / Q000098:blood supply / Q000378:metabolism*; D002545:Brain Ischemia / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D002560:Cerebrovascular Circulation; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging; D018450:Disease Progression; D005260:Female; D005682:Gadolinium; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D018810:Magnetic Resonance Angiography; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011522:Protons; D020521:Stroke / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D013997:Time Factors
D011522:Protons; D001224:Aspartic Acid; D019344:Lactic Acid; C000179:N-acetylaspartate; D005682:Gadolinium