Time course of cerebral infarction in the middle cerebral arterial territory: Deep watershed versus territorial subtypes on diffusion-weighted MR images

PURPOSE: To examine possible differences between the evolution of cerebral watershed infarction (WI) and that of territorial thromboembolic infarction (TI) by using diffusion-weighted (DW) and T2-weighted magnetic resonance ( MR) images and apparent diffusion coefficient (ADC) maps. MATERIALS AND METHODS: Fourteen patients with Tl and nine with Wl underwent MR imaging from the acute to chronic infarction stages. ADC maps were deri ved from DW images. Lesion-to-normal tissue signal intensity ratios on ADC maps (rADC), echo-planar T2-weighted images, and DW images were calculated. Lesion volumes at acute or early subacute infarction stages were measured on-DW, images, and final lesion volumes were estimated on fluid-attenuated inversion-recovery images, RESULTS: Analysis of variance revealed a significant difference in temporal evolution patterns of rADC between Wl and TI (P <.001). rADC pseudonormali zation following Tl began about 10 days after symptom onset, but that follo wing Wl did not occur until about 1 month after symptom onset. The Pearson correlation coefficient between final and initial infarct volumes was 0.989 9 for both infarction subtypes, indicating that the initial ischemic injury volume measured at the acute or early subacute stage predicted the final l esion volume fairly well. CONCLUSION: The evolution time of ADC is faster for TI than for WI. This di fference, which likely originates from the different pathophysiologic and h emodynamic features of the two infarction types, might account for the rela tively large range of ADC values reported for the time course of ischemic s trokes.