Naval Hospital Camp Pendleton, CA (Dr. Ford); Naval Medical Center San Diego, CA (Dr. Hegde); Naval Hospital Bremerton, Washington (Dr. Dore) brian.ford@usuhs.edu
The authors reported no potential conflict of interest relevant to this article.
The views expressed herein are those of the authors and do not reflect the official policy of the US Department of the Navy, US Department of Defense, or US government.
A criticism of the NIHSS is its bias toward left-hemispheric ischemic pathology.17 NIHSS includes 11 questions on a scale of 0 to 42; typically, a score < 4 is associated with a higher chance of a positive clinical outcome.18 There is no minimum or maximum NIHSS score that precludes treatment with thrombolysis or EVT.
Other commonly used scores in acute stroke include disability assessments. The modified Rankin scale, which is used most often, features a score of 0 (symptom-free) to 6 (death). A modified Rankin scale score of 0 or 1 is considered an indication of a favorable outcome after stroke.19 Note that these functional scores are not always part of an acute assessment but can be done early in the clinical course to gauge the response to treatment, and are collected for stroke-center certification.
Imaging modalities
Imaging is recommended within 20 minutes of arrival in the ED in a stroke patient who might be a candidate for thrombolysis or thrombectomy.3 There, imaging modalities commonly performed are noncontrast-enhanced head computed tomography (NCHCT); computed tomography (CT) angiography, with or without perfusion; and diffusion-weighted magnetic resonance imaging (MRI).20,21 In addition, more highly specialized imaging modalities are available for the evaluation of the stroke patient in specific, often limited, circumstances. All these modalities are described below and compared in the TABLE,20,21 using the ACR Appropriateness Criteria (of the American College of Radiology),21 which are guidelines for appropriate imaging of stroke, based on a clinical complaint. Separate recommendations and appraisals are offered by the most recent American Heart Association/American Stroke Association (AHA/ASA) guideline.3
NCHCT. This study should be performed within 20 minutes after arrival at the ED because it provides rapid assessment of intracerebral hemorrhage, can effectively corroborate the diagnosis of some stroke mimickers, and identifies some candidates for EVT or thrombolysis3,21,22 (typically, the decision to proceed with EVT is based on adjunct imaging studies discussed in a bit). Evaluation for intracerebral hemorrhage is required prior to administering thrombolysis. Ischemic changes can be seen with variable specificity and sensitivity on NCHCT, depending on how much time has passed since the original insult. In all historical trials, CT was the only imaging modality used in the diagnosis of acute ischemic stroke (AIS) that suggested benefit from IV thrombolysis.23-25
Acute, subacute, and chronic changes can be seen on NCHCT, although the modality has limited sensitivity for identifying AIS (ie, approximately 75% within 6 hours after the original insult):
Acute findings on NCHCT include intracellular edema, which causes loss of the gray matter–white matter interface and effacement of the cortical sulci. This occurs as a result of increased cellular uptake of water in response to ischemia and cell death, resulting in a decreased density of tissue (hypoattenuation) in affected areas.
Subacute changes appear in the 2- to 5-day window, including vasogenic edema with greater mass effect, hypoattenuation, and well-defined margins.3,20,21
Chronic vascular findings on NCHCT include loss of brain tissue and hypoattenuation.
