What is the Alberta Stroke Programme Early Computed Tomography Score (ASPECTS)?

What is the Alberta Stroke Program Early CT Score (ASPECTS)?

ASPECTS is a 10-point quantitative topographic CT scoring system that systematically evaluates early ischemic changes in the middle cerebral artery (MCA) territory to predict functional outcomes and guide treatment decisions in acute ischemic stroke patients. 1

Scoring Methodology

• The score starts at 10 points, with 1 point subtracted for each region showing early ischemic changes in the MCA territory on non-contrast CT 2
• The MCA territory is divided into 10 standardized regions: 4 cortical regions (M1-M6 representing frontal, insular, temporal, and parietal cortex) and 6 subcortical regions (caudate, lentiform nucleus, internal capsule, insula, M1, M2, M3, M4, M5, M6) 3
• Higher ASPECTS values (closer to 10) indicate less ischemic involvement and better prognosis, while lower scores indicate more extensive early infarction 2

Clinical Utility and Prognostic Value

• ASPECTS was originally developed to identify patients unlikely to recover fully despite thrombolytic therapy 1
• The score predicts functional outcome and symptomatic intracranial hemorrhage risk after IV thrombolysis, with a linear relationship between ASPECTS and outcome rather than a strict threshold 4
• ASPECTS ≥6 was used as an inclusion criterion in multiple landmark endovascular thrombectomy trials (ESCAPE, SWIFT PRIME, REVASCAT), establishing Level A evidence for this threshold 1
• Patients with ASPECTS <6 have uncertain benefit from endovascular therapy, as most positive trials excluded this population 1

Application Beyond Non-Contrast CT

• ASPECTS can be applied to CT angiography source images, CT perfusion, and diffusion-weighted MRI (DWI) 1, 2
• Cerebral blood volume ASPECTS on CT perfusion outperforms non-contrast CT ASPECTS in predicting outcome 4
• For posterior circulation strokes, a modified pc-ASPECTS (posterior circulation ASPECTS) assigns 10 points differently: 2 points for pons, 2 for midbrain, 1 point each for bilateral thalami, bilateral cerebellum, and bilateral PCA territories 1

Performance and Reliability

• Substantial agreement between real-time ASPECTS and expert scoring can be achieved by experienced readers (weighted κ 0.69,95% CI 0.59-0.79), though correlations are not perfect 1
• Physician accuracy in detecting ischemia involving >1/3 MCA territory is approximately 70-80%, with variable reliability and reproducibility 1, 5
• Automated e-ASPECTS software demonstrates non-inferior performance to neuroradiologists, with sensitivity of 44-46% and specificity of 91-94% 6, 7

Critical Limitations and Pitfalls

• ASPECTS is limited to the anterior circulation (MCA territory only) and cannot assess posterior circulation strokes without the modified pc-ASPECTS version 1
• The template is unequally weighted, and correlation with actual lesion volume depends heavily on lesion location 4
• Early CT signs may not be visible in the first hours after stroke onset, with CT showing abnormalities in less than 50% of patients initially 1, 5
• Do not delay thrombolytic therapy to obtain more detailed ASPECTS assessment if the patient is otherwise eligible based on initial non-contrast CT 8, 5
• ASPECTS assessment should not be the sole determinant of treatment eligibility—clinical assessment, time from onset, and other factors remain paramount 1

Time-Specific Considerations

• For patients within 6 hours of last known well, ASPECTS <6 was typically an exclusion criterion in thrombectomy trials 1
• For extended window patients (6-24 hours), trials combined ASPECTS criteria with core volume measurements (e.g., DAWN excluded core >50 mL, DEFUSE 3 excluded core >70 mL) 1
• Complete CT examination within 25 minutes of emergency department arrival for rtPA candidates, with interpretation within an additional 20 minutes 1, 5