Selecting Patients for Early Stroke Treatment with Penumbra Images

Abstract

Review of results of experimental and clinical studies indicates that the area of physiologically impaired, but potentially salvageable, tissue surrounding the central core of focal cerebral ischemia that develops shortly after onset of vessel occlusion is complex and dynamic with severity and duration thresholds for hypoxic stress and injury that are specific to tissue site, cell type, molecular pathway or gene expression investigated, and efficiency of collateral or residual flow and reperfusion. Identification of this ischemic penumbra in the acute stroke clinical setting is an important goal for stroke researchers and clinicians. Recent advances in neuroimaging allowed a better understanding of this physiopathological process. However, there is not a perfect penumbra imaging technique and each one has its own advantages and disadvantages. Numerous thrombolytic and potentially neuroprotective agents have been studied in stroke patients, with little success, as the only approved therapy is thrombolysis with recombinant tissue plasminogen activator within 3 h of stroke onset in highly selected patients (<10% of all acute stroke patients in some specialized centers). One major obstacle in the development of effective therapies for ischemic stroke has been the lack of versatile imaging techniques. The development of penumbra concept and its detection through modern cerebral image techniques can extend the patients’ selection for thrombolysis. A number of multicenter clinical trials are now under way to test these models and confirm the utility of penumbra imaging for treatment decisions. Present knowledge about visualization of the salvageable penumbra suggests a promising future in which penumbra imaging studies are performed routinely in the acute stroke setting and the data provided by these studies assist in individualizing therapeutic decisions and identifying effective therapies that can be delivered at late time points. So, the main target of management is ‘penumbra’, or salvageable tissue, which is primarily dependent upon the expediency of the whole process, better expressed by the phrase ‘Penumbra (and not Time) is Brain’.

Feasibility of Cerebral Blood Volume Mapping by Flat Panel Detector CT in the Angiography Suite: First Experience in Patients with Acute Middle Cerebral Artery Occlusions

“…This approach offers the possibility of using individual patient-specific physiologic data, rather than artificial time criteria, for decision making. 36,37 There are shortcomings in our study. The number of patients was small, but sufficient to demonstrate that CBV abnormalities can be recognized.…”

“…Calculation of abnormality volumes of Group 1 revealed that the CBV volumes increased from the pretreatment CBV studies to the immediate posttreatment FPCT CBV and the follow-up MSCT stroke lesion volume (37 . Correlation between the volumes observed on the pretreatment PCT CBV studies and those on the immediate posttreatment FPCT CBV studies was poor (r ϭ 0.6, P Ͼ .05).…”

Can angiogenesis be exploited to improve stroke outcome? Mechanisms and therapeutic potential

“…This was confirmed by thrombolytic treatment which reversed critical ischaemia and decreased volume of final infarcts. In patients, the existence of penumbra is now generally accepted and indeed it can be visualized by studies of mismatch on MRI (magnetic resonance imaging) and PET (photon emission tomography) [9]. DWI (diffusion-weighted imaging) in combination with PWI (perfusion-weighted imaging) has become a widely accepted modality for the selection of patients for acute therapy, a mismatch between these procedures suggests viable 'penumbral' tissue.…”

C-Arm Flat Detector CT Parenchymal Blood Volume Thresholds for Identification of Infarcted Parenchyma in the Neurointerventional Suite

“…For example, the C-arm CT softtissue images can reliably exclude intracranial hemorrhage, the angiographic reconstructions can help evaluate proximal vessel occlusion, and the PBV maps provide patient-specific physiologic data that can potentially be used, instead of the more generalized and nonspecific time criteria, in selecting appropriate patients for acute stroke interventions, particularly when a significant delay exists between initial imaging and patient arrival in the angiography suite. 4,20 Similarly, in the patients with aneurysmal SAH who develop delayed clinical deterioration, the PBV maps can be used to determine the hemodynamic significance of vessel narrowing detected on catheter angiography and to identify any ongoing ischemia or established infarcts, thus guiding the angioplasty procedures. For these applications, extended craniocaudal coverage allowing whole-brain PBV measurements would be particularly beneficial-for example, the changes related to vasospasm may be multifocal or global in nature and the acute ischemic stroke may be in a distribution located outside the traditional supratentorial coverage of CTP and may thus be better evaluated with extended craniocaudal coverage of C-arm CT PBV.…”