Imaging of acute stroke: CT and/or MRI.

Acute ischemic stroke is now clearly recognized as a medical emergency. As such diagnosis has to be done quickly and in a precise way during the therapeutic window. Both computed tomography and magnetic resonance imaging are tools that can adequately demonstrate ischemia really very early on. MRI using diffusion techniques has a much higher sensitivity for acute lesions but its implementation has not been unproblematic due to initial resistance and some technical problems. Thus, very often CT is still preferred with MR used for situations where the answer given is not sufficient as well as for follow-up of lesions. However, the parallel development of new therapeutic strategies have rendered the precision of the tools more and more sophisticated and their combined use can help to improve patient outcomes in ways never imagined previously. No matter which technique is used, be it alone or in combination, the idea is to speed up and optimize management in order to provide early revascularization and reperfusion.

Combined use of pulsed arterial spin-labeling and susceptibility-weighted imaging in stroke at 3T.

BACKGROUND AND PURPOSE: In acute stroke it is no longer sufficient to detect simply ischemia, but also to try to evaluate reperfusion/recanalization status and predict eventual hemorrhagic transformation. Arterial spin labeling (ASL) perfusion may have advantages over contrast-enhanced perfusion-weighted imaging (cePWI), and susceptibility weighted imaging (SWI) has an intrinsic sensitivity to paramagnetic effects in addition to its ability to detect small areas of bleeding and hemorrhage. We want to determine here if their combined use in acute stroke and stroke follow-up at 3T could bring new insight into the diagnosis and prognosis of stroke leading to eventual improved patient management. METHODS: We prospectively examined 41 patients admitted for acute stroke (NIHSS >1). Early imaging was performed between 1 h and 2 weeks. The imaging protocol included ASL, cePWI, SWI, T2 and diffusion tensor imaging (DTI), in addition to standard stroke protocol. RESULTS: We saw four kinds of imaging patterns based on ASL and SWI: patients with either hypoperfusion and hyperperfusion on ASL with or without changes on SWI. Hyperperfusion was observed on ASL in 12/41 cases, with hyperperfusion status that was not evident on conventional cePWI images. Signs of hemorrhage or blood-brain barrier breakdown were visible on SWI in 15/41 cases, not always resulting in poor outcome (2/15 were scored mRS = 0-6). Early SWI changes, together with hypoperfusion, were associated with the occurrence of hemorrhage. Hyperperfusion on ASL, even when associated with hemorrhage detected on SWI, resulted in good outcome. Hyperperfusion predicted a better outcome than hypoperfusion (p = 0.0148). CONCLUSIONS: ASL is able to detect acute-stage hyperperfusion corresponding to luxury perfusion previously reported by PET studies. The presence of hyperperfusion on ASL-type perfusion seems indicative of reperfusion/collateral flow that is protective of hemorrhagic transformation and a marker of favorable tissue outcome. The combination of hypoperfusion and changes on SWI seems on the other hand to predict hemorrhage and/or poor outcome.

Stroke severity and residual flow determined by transcranial colour-coded ultrasound (TCCD) predict recanalization and clinical outcome during thrombolysis.

OBJECTIVE: To determine clinical, neuroradiological or ultrasonographic parameters associated with early recanalization and clinical outcome in patients treated with intravenous (IVT) or combined intravenous-intra-arterial (IVT-IAT) thrombolysis. METHODS: From 2004 to 2007, all consecutive ischemic stroke patients admitted within a 3-hour window and who underwent thrombolytic therapy were reviewed. Degree of occlusion and recanalization during IVT was assessed by transcranial color-coded ultrasound (TCCD) using Thrombolysis In Brain Ischemia (TIBI) classification. According to our protocol, in case of recanalization (modification of TIBI grade > or = 1) after 30 min of IVT, the procedure was maintained over 1h. When TIBI grade failed to improve after 30 min, IVT was discontinued and IAT performed using the remaining tPA dose. The study endpoints were early recanalization defined as achievement of TIBI > or = 3 grade at 30 min (for this endpoint all patients presenting a TIBI grade 3 at admission were excluded from the model) and clinical outcome at 3 months assessed by the modified Rankin scale. RESULTS: Seventy-one patients underwent either IVT (n=41) or IVT-IAT (n=30). Among all the variables, NIHSS and TIBI grades assessed at baseline were the only independent factors associated with early recanalization and clinical outcome. Furthermore, the combination of these two parameters was superior in predicting early recanalization and outcome to either one of them taken separately. An inverse correlation between NIHSS, TIBI grades and early recanalization was found: the lower the TIBI grade, the lower the probability to recanalize for any given NIHSS. CONCLUSION: Baseline NIHSS and TIBI grades were the only independent factors associated with early recanalization and clinical outcome. The combination of these two parameters was superior to each single variable in predicting the study endpoints and could therefore be used to improve the selection of patients for IVT or more aggressive therapies.