Aspects Score Calculator

Calculate the Alberta Stroke Program Early CT Score for acute ischemic stroke assessment. Enter values for instant results with step-by-step formulas.

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Formula

ASPECTS = 10 - (number of affected MCA territory regions)

Starting from a perfect score of 10, one point is subtracted for each of the 10 defined MCA territory regions showing early ischemic change on CT. Regions include 4 deep structures (C, L, I, IC) and 6 cortical zones (M1-M6).

Worked Examples

Example 1: High ASPECTS Score - Thrombectomy Candidate

Problem: A 67-year-old presents 2 hours after sudden left-sided weakness. Non-contrast CT shows subtle hypodensity in the right insular cortex and loss of gray-white differentiation in the right lentiform nucleus. All other MCA regions appear normal.

Solution: Regions affected: Insular cortex (I) and Lentiform nucleus (L)\nRegions normal: Caudate, Internal capsule, M1-M6 (8 regions)\nASPECTS = 10 - 2 = 8\nInterpretation: Small ischemic core, favorable for intervention\nCTA showed right M1 occlusion with good collaterals

Result: ASPECTS 8/10 - Favorable for mechanical thrombectomy with high likelihood of good functional outcome

Example 2: Low ASPECTS Score - Large Infarct Core

Problem: A 72-year-old presents 5 hours after aphasia onset. CT shows extensive hypodensity involving the left caudate, lentiform, insula, internal capsule, M1, M2, and M3 regions. M4-M6 show subtle swelling.

Solution: Regions affected: C, L, I, IC, M1, M2, M3, M4, M5, M6 (all 10)\nASPECTS = 10 - 10 = 0 (or near 0 if some regions spared)\nWith 7 clearly affected: ASPECTS = 10 - 7 = 3\nInterpretation: Large established infarct core\nHigh hemorrhagic transformation risk with reperfusion

Result: ASPECTS 3/10 - Unfavorable for intervention; high risk of hemorrhagic transformation

Frequently Asked Questions

What is the ASPECTS score and how is it calculated?

ASPECTS (Alberta Stroke Program Early CT Score) is a 10-point quantitative scoring system used to evaluate the extent of early ischemic changes on non-contrast CT in patients with acute middle cerebral artery (MCA) territory stroke. The MCA territory is divided into 10 regions: 4 deep structures (caudate nucleus, lentiform nucleus, insular cortex, and internal capsule) and 6 cortical regions (M1 through M6). A normal scan receives a score of 10, and one point is subtracted for each region showing early ischemic change such as loss of gray-white matter differentiation, tissue swelling, or hypodensity. Lower scores indicate larger areas of established infarction.

How does the ASPECTS score guide thrombectomy decisions?

The ASPECTS score has become a critical selection criterion for mechanical thrombectomy in acute ischemic stroke. Multiple landmark clinical trials including MR CLEAN, ESCAPE, EXTEND-IA, SWIFT PRIME, and REVASCAT established that patients with ASPECTS scores of 6 or higher benefit significantly from endovascular thrombectomy when performed within 6 hours of symptom onset. More recent trials like DAWN and DEFUSE 3 extended the treatment window to 24 hours for selected patients using advanced perfusion imaging. Generally, an ASPECTS of 7-10 indicates a favorable treatment profile, while scores below 6 suggest extensive infarction where the risk of intervention may outweigh the benefit.

What are the 10 regions evaluated in ASPECTS scoring?

The ASPECTS score evaluates 10 specific regions within the MCA territory at two standardized CT axial levels. At the basal ganglia level, four structures are assessed: the caudate nucleus (C), lentiform nucleus (L), insular ribbon or cortex (I), and internal capsule (IC). At the supraganglionic level, six cortical MCA regions are evaluated: M1 (anterior MCA cortex corresponding to the frontal operculum), M2 (MCA cortex lateral to the insular ribbon), M3 (posterior MCA cortex corresponding to the temporal cortex), M4 (anterior MCA territory superior to M1), M5 (lateral MCA territory superior to M2), and M6 (posterior MCA territory superior to M3). Each region showing ischemic change loses one point from the starting score of 10.

How reliable is ASPECTS scoring between different clinicians?

Inter-observer reliability for ASPECTS scoring has been studied extensively, with results showing moderate to good agreement among trained interpreters. Studies report kappa values ranging from 0.40 to 0.72, depending on the experience level of the readers and the timing of the CT scan relative to symptom onset. Neuroradiologists tend to show higher agreement than emergency physicians or general neurologists. The deep structures (caudate, lentiform, internal capsule) typically show better inter-rater agreement than the cortical M regions. Several factors can improve reliability including standardized training, use of narrow window settings, comparison with the contralateral hemisphere, and awareness of common pitfalls. Automated ASPECTS scoring using artificial intelligence is being developed to reduce this variability.

What is the role of CT angiography in conjunction with ASPECTS?

CT angiography (CTA) complements the ASPECTS score by providing crucial information about the site and extent of arterial occlusion. While ASPECTS evaluates the brain parenchyma for ischemic damage, CTA identifies the location of the thrombus (ICA terminus, M1 segment, M2 segment, tandem lesions) and assesses the collateral circulation. Good collateral flow can sustain penumbral tissue despite proximal occlusion, meaning a patient with a high ASPECTS and good collaterals has the best chance of benefiting from thrombectomy. CTA source images can also serve as a surrogate for cerebral blood volume, potentially improving the detection of ischemic core compared to non-contrast CT alone. The combination of ASPECTS plus CTA findings provides the most comprehensive pre-intervention assessment.

How does ASPECTS differ from CT perfusion for stroke assessment?

ASPECTS and CT perfusion (CTP) provide complementary but different information about acute ischemic stroke. ASPECTS evaluates structural changes on non-contrast CT that represent established or near-established infarction, while CTP uses contrast bolus tracking to measure cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and time-to-maximum (Tmax) to differentiate the ischemic core from the surrounding penumbra. CTP can identify salvageable tissue (mismatch between core and penumbra) that may benefit from reperfusion, even when ASPECTS appears relatively normal. However, ASPECTS is faster to obtain, more widely available, does not require contrast, and has less technical variability. Current guidelines recommend either approach for patient selection in extended time windows.