Nonenhanced Computed Tomography Evaluation Of Ischemic Stroke Patients Presenting After 4.5 Hours From Onset Of Symptoms Using Aspects, Posterior Circulation-Aspects And X-Ray Attenuation Ratio: The “Tissue Window”

Background: Stroke is a major cause of disability and mortality world-wide. Ischemic stroke is reversible when patients present early. With the current treatment guideline in Nigeria, most ischemic stroke patients present after the 4.5 hours treatment “time window” and are ineligible for intravenous thrombolysis (IVT). However, studies with computed tomography and magnetic resonance imaging have shown variability in the duration of tissue viability, with some remaining viable up to 24 hours and beyond. These advanced imaging are not readily available in the sub-Saharan Africa but the X-ray attenuation ratio of hypoattenuating lesions on the easily accessible nonenhanced computed tomography (NECT), have recently shown to be a valuable alternative. In late presentation, IVT and endovascular thrombectomy (EVT) have proven to have reasonable degree of success in recanalization. Hence, the need for the study. Materials and method: This was a retrospective cross-sectional study of ischemic stroke patients who presented between 4.5 and 24 hours for NECT. The extent of the ischemia was determined using the Alberta stroke programme early CT score (ASPECTS), while the Hounsfield unit ratio of the hypodense lesions was used to determine tissue viability. Results: Fifty-five patients met the inclusion criteria and had a mean age of 58.8 years. Four (7.27%) patients clearly had ASPECTS and Hounsfield unit ratio (HUr) scores suggestive of salvageable penumbral tissue, while another four (7.27%) had the probability of being reversible. Conclusion: Some patients were still eligible for treatment after the current guideline’s 4.5 hours treatment “time window” using the ASPECTS and HUr scores on NECT.