Neuronal Damage after Ischemic Injury in the Middle Cerebral Arterial Territory: Deep Watershed versus Territorial Infarction at MR Perfusion and Spectroscopic Imaging

PURPOSE: To determine the temporal patterns of neuronal injury between infarction subtypes and their possible association with changes in cerebral blood volume (CBV). MATERIALS AND METHODS: Twenty-five patients with ischemic injuries of middle cerebral arterial territories and receiving only conservative treatments were classified into territorial infarction (TI) (n = 16) and watershed infarction (WI) (n = 9) groups and were prospectively evaluated with longitudinal magnetic resonance (MR) examinations. Each patient underwent as many as five MR studies at various stroke stages following stroke symptom onset. Dynamic susceptibility-weighted contrast material-enhanced MR imaging was performed to yield the relative CBV (rCBV). Chemical shift imaging was used to measure the relative levels of N-acetylaspartate (NAA) and lactate of the ischemic brain tissue. Repeated-measures analysis of variance was used to examine the statistical significance in evolutional differences between TI and WI. RESULTS: For patients with TI, rCBV followed a progressively increasing pattern, from initial low values (0.46 +/- 0.28 [SD]) to peak high values (1.23 +/- 0.34) at early chronic stage. Relative NAA level decreased to 0.40 +/- 0.24 during acute stroke and was lost completely 4 days after ictus. Patients with WI showed consistently high rCBV throughout all stages, with residual relative NAA level (0.53 +/- 0.25) even at 1 month after symptom onset. Relative lactate level of patients with TI was significantly higher than that of patients with WI at the acute stage (P <.01). Differences in the temporal changes of both rCBV and brain metabolites between TI and WI were significant (P <.01). CONCLUSION: The different temporal patterns for stroke progression in TI and WI are associated with different evolutions of hemodynamics and neuronal injury.