*2.4.2 The Alberta stroke program early CT score (ASPECTS), a treatment and prognosis tool*

NCCT allows computing the ASPECTS, which assesses early ischemic changes *in the anterior circulation* using 10 anatomically defined regions: 1 point for subcortical structures such as the caudate, lentiform, internal capsule, insular ribbon, and 6 for cortical MCA territories designated M1 to M6 [27, 28]. Therefore, an ASPECTS of 10 indicates no ischemic change in the above territories but does not eliminate infarcts in posterior circulation territories, and an ASPECTS of 0 is tantamount to very large infarcts that involves all the above anterior circulation territories. ASPECTS has a sensitivity of 78% and specificity of 96% for predicting functional outcome [27]. As the score predicts functional independence after thrombolysis, one generally requires a cut off score of 6 or more, age older than 18, an NIHSS score of 6 or more, and a

#### **Figure 1.**

*Non-contrast CT scan demonstrating hyperdense left middle cerebral artery sign (arrow). It is evident that the vessel shows up as brighter or hyperdense, compared to the contralateral vessel. A clot in the artery is more dense as it contains more red blood cells and therefore, more iron.*

reasonable pre-stroke functional baseline to be eligible for thrombectomy, as will be discussed later [29]. There are however drawbacks to the ASPECTS. First, it is not helpful for strokes in the posterior circulation. Second, there is significant variation in interrater reliability. Finally, ASPECTS can be affected by the quality of the NCCT as well as bone and metal artifacts [24].
