The Alberta Stroke Program Early CT Score (ASPECTS) was introduced to make early ischemic change on non-contrast CT more standardized than a gestalt estimate of how much MCA territory is involved. The original method divided the MCA territory into ten named regions and scored them on a pre-treatment CT.1 It remains widely used for describing early ischemic change, but reader training and full review of the source images still matter.2,8

How the score is built.

Start at 10 and subtract one point for each region showing early ischemic change, including focal swelling or parenchymal hypoattenuation. The score is applied to the MCA territory and organized around two standardized axial levels:2

  • Basal ganglia level (at the level of the thalamus and basal ganglia) — seven regions: caudate, lentiform nucleus, internal capsule, insular ribbon, and the inferior MCA cortical zones M1, M2, M3.
  • Supraganglionic level (just rostral, above the basal ganglia) — three regions: the superior MCA cortical zones M4, M5, M6.

M1–M3 are the anterior, lateral, and posterior cortical segments at the ganglionic level; M4–M6 are the corresponding segments immediately above it. A score of 10 has no scored early ischemic regions; 0 means all ten regions are involved. ASPECTS should be recorded with the affected side and the regions scored down, not only the total.

Bedside pearl

Each region is one point regardless of size — the tiny caudate counts the same as the large M5 cortical zone. ASPECTS counts how many regions are involved, not how much of any one region. Review an appropriate narrow stroke window alongside standard brain windows to improve the visibility of subtle gray–white loss.

What the score describes.

In the original derivation cohort of patients treated with intravenous alteplase within 3 hours, a lower baseline ASPECTS was associated with worse 3-month functional outcome and a higher risk of symptomatic intracerebral hemorrhage.1 At the cohort level, lower scores reflect early ischemic change across more MCA regions. ASPECTS is not a direct measurement of infarct volume, penumbra, or tissue viability, and it should not be used alone to predict treatment benefit or bleeding risk for an individual patient.

Why there is no treatment verdict here.

Older endovascular pathways often emphasized ASPECTS ≥6. Large-core randomized trials including SELECT2, ANGEL-ASPECT, RESCUE-Japan LIMIT, and TENSION subsequently demonstrated benefit from thrombectomy in selected patients with larger established infarcts, including trial populations with ASPECTS 3–5.3–6 The January 2026 AHA/ASA acute ischemic stroke guideline therefore reflects expanded endovascular treatment for some patients with larger ischemic cores.9

That evidence does not turn one ASPECTS number into a universal yes/no rule. Treatment selection depends on the occlusion, time, clinical deficit, prestroke function, the complete imaging profile, and the applicable protocol. This page calculates and explains the imaging score; it does not issue an automated reperfusion recommendation.

Where readers go wrong.

ASPECTS is only as good as the regions and source slices actually inspected. The caudate and insula can be subtle, especially when attention is drawn to more conspicuous cortical change. Deliberately inspect the insular ribbon, deep nuclei, internal capsule, and every cortical region. Reader agreement varies with experience; a schematic can orient the eye, but it cannot replace image-review training.8

Pitfall

Do not treat either a teaching map or an automated score as ground truth. Automated systems can perform comparably with expert reads in some datasets, but agreement is not perfect and source-image review remains necessary.10

Practical use at the bedside.

Use ASPECTS as one imaging description within a broader assessment that may include time from last-known-well, the NIHSS clinical deficit, vessel occlusion site on CTA, collateral status, and advanced imaging when applicable. Document the side, total, and the regions scored down so the next reader can reconcile the interpretation. This page is for clinician education and does not substitute for individualized clinical judgment or an institutional reperfusion protocol.