*2.4.1 Non-contrast computed tomography (NCCT) brain*

Ideally, within 25 minutes after presenting at the hospital, a non-contrast CT (NCCT) brain with an axial section thickness no more than 5 mm may detect the

<sup>1</sup> The MRS is a scale that measures disability from stroke that is scored from 0 to 5 with a higher score indicating higher disability. A score of 0 means no disability, 1 means mild symptoms, 2 means inability to carry out previous activities, 3 means requiring help but able to walk, 4 means inability to walk without assistance, and 5 means, bedridden.

following: acute hemorrhage which is an absolute contraindication to IV tPA, early ischemic changes, chronic infarcts, and dense artery sign [7, 22]. NCCT has a sensitivity and specificity exceeding 95–98% for the detection of intracranial hemorrhage [23]. Hypoattenuation (dark on NCCT) of gray matter, in forms of the insular ribbon sign defined by loss of gray-white distinction, obscured outline and partial disappearance of the lentiform nucleus, and loss of gray-white matter differentiation, tend to be subtle when patients present early [24, 25]. The hyperdense artery sign (**Figure 1**) can be seen within 90 minutes of an MCA stroke and is usually caused by thromboembolic material in the lumen of the MCA [24] but can also commonly seen in the anterior cerebral artery (ACA), posterior cerebral artery (PCA), and basilar artery [26].
