Kevin S. Attenhofer, MD
Dankbaar JW, Horsch AD, van den Hoven AF, Kappelle LJ, van der Schaaf IC, van Seeters T, et al. Prediction of Clinical Outcome After Acute Ischemic Stroke: The Value of Repeated Noncontrast Computed Tomography, Computed Tomographic Angiography, and Computed Tomographic Perfusion. Stroke. 2017
A significant aspect of stroke care is the long-term ramifications with respect to a patient’s ability to manage their activities of daily living. Part of the physician’s role is to help the patient navigate this challenge to maintain as much independence as possible. Understanding likely outcomes helps set the stage for realistic expectations and goals. Today, the most commonly used metric to score outcomes is the modified Rankin scale (mRS) performed well after the index event (often 90 days).
In stroke research, follow-up imaging markers such as computed tomographic angiography (CTA) recanalization and computed tomographic perfusion (CTP) reperfusion are sometimes used as proxy measurements for clinical outcomes. In this study, Dankbaar et al. used multimodality commuted tomography to predict mRS at 90 days.
The authors looked at patients from the DUST study (Dutch Acute Stroke Study) who had an intracranial anterior circulation large vessel occlusion with a focal perfusion deficit, as well as multimodality follow-up imaging 3 days after index event. They dichotomized the mRS into good outcome (0-2) and poor outcome (3-6). They created models to calculate odds ratios for poor outcome. Model 1 assessed baseline patient and imaging characteristics (NIHSS, age, time from symptom onset to scan, whether or not patient received thrombolysis, presence of a proximal occlusion, poor collateral filling, extracranial ICA stenosis >70%, ASPECTS on MTT and CBV maps). The area under the curve of the receiver operating characteristic curve was 0.81.
They then looked at 3 models which each incorporated follow-up imaging in their prediction in addition to the aforementioned baseline characteristics. Model 2 assessed for infarct volume on non-contrast computed tomography (NCCT) head. Model 3 included CTA reperfusion and model 4 included CTP reperfusion.
In each case, follow-up imaging improved outcome predictions when compared with model 1 alone, with areas under the curve for NCCT 0.85 (p = 0.02), CTA 0.86 (p = 0.01), and CTP 0.86 (p = 0.01). Neither assessment of recanalization on follow-up CTA nor reperfusion on follow-up CTP outperformed measurement of infarct volume on NCCT (OR 1.19 per 10 cc) for clinical outcome prediction.
The authors considered the time frame (3 days) to be a limitation in their study. Previous studies have shown CTP reperfusion to be a better predictor of outcome in the 24–48-hour window following index event; however, evaluation of reperfusion is not standardized. By day 3, the area of core infarct is well established. At that point, there is no significant benefit for CTA or CTP over NCCT for determining prognosis, and the risks of contrast administration should be carefully considered.