Diagnosis and Management of Acute Ischemic Stroke

*Anwer Zohaib Siddiqi, Angela Young and Ankur Wadhwa*

## **Abstract**

This chapter will review updates in the various imaging modalities used to diagnose acute ischemic stroke (AIS), how these are used to select patients for intervention, and the different interventions used for management of AIS. The backbone of the AIS diagnostic algorithm remains the computed tomography scan (CT) given its speed of use and sensitivity. CT-angiography (CTA) is crucial in diagnosing large-vessel occlusions (LVOs) and multiphase CTA and CT-perfusion (CTP) can demonstrate the number of collaterals in the area and remaining salvageable tissue. MRI can be used to select patients presenting in an unknown time window for thrombolysis. The primary goal of AIS management is to rescue the ischemic penumbra and the approach to treating AIS has gone from a timebased to tissue-based approach. While tPA is still the agent of choice for thrombolysis in patients with AIS, tenecteplase (TNK) may be just as effective and more efficient to use. Endovascular thrombectomy (EVT) has shown considerable efficacy for alleviating LVOs and using CTP, patients can be selected for hours after symptom-onset if viable tissue remains. It remains unclear if an "EVT-alone" strategy is superior to "tPA + EVT" strategy but this may be dependent on clot, patient, and geographical characteristics.

**Keywords:** stroke, ischemia, neuroimaging, thrombolysis, thrombectomy

#### **1. Introduction**

Globally, stroke remains the second leading cause of death and the third leading cause of death and disability (as expressed by disability-adjusted life-years lost— DALYs) [1]. 88% of all acute strokes are ischemic strokes, caused by reduced blood flow and of the remaining, 10% are intracerebral hemorrhages, due to rupture of cerebral arteries and 2% subarachnoid hemorrhages, due to trauma or rupture of aneurysm [2]. This chapter will focus on acute ischemic strokes (AIS). Among AIS, 22% are cardioembolic (thrombus originally formed in the heart), 23% due to large artery atherosclerosis, 22% due to small vessel occlusion or lacunar infarct (2–20 mm in size and occur deep in the brain), and 29% are other causes [3, 4].

The typical presentation of AIS is abrupt focal neurological deficit that is due to a lack of blood flow [5, 6]. As neurological dysfunctions caused by focal brain, retinal or spinal cord ischemia may be reversible if presented early and treated promptly, acute stroke care at the hospital setting should begin with prompt history taking, neurological exam, emergent neuroimaging and pertinent investigations to establish a plan of management [7].

The TOAST (Trial of Org 10,172 in Acute Stroke Treatment), classification categorizes ischemic stroke etiologies into five major subtypes [8]: large artery sclerosis, cardioembolism, small artery occlusion, stroke of other determined cause, and stroke of undetermined cause. Newer classification criteria such as the Causative Classification System further stratifies high and low risk cardiac sources of embolism. In this system, the 'stroke of undetermined cause' category is divided into unknown, incomplete evaluation, unclassified stroke with more than one etiology, and cryptogenic embolism, where there is evidence of embolism in otherwise normal looking artery or subsequent complete recanalization [9].

Other disorders may masquerade as ischemic strokes (**Table 1**). Between 15 and 25% stroke suspects presented to the emergency room are stroke mimics [2, 5]. Patients who have seizures often present with post-ictal hemiparesis, also known as Todd's Paresis. This is a transient weakness that usually resolves within 24 hours [10]. Migraine auras may present as motor weakness, aphasia, sensory disturbances, and visual auras, that potentially resemble stroke symptoms. Focal neurological deficits are frequently the sequalae of severe hypoglycemia, necessitating blood glucose measurements. Tumors can cause seizures, may directly compress surrounding vessels, and can be easily ruled out with MR brain. Other stroke mimics include hyponatremia, conversion disorder, and positional vertigo [11]. The key to ruling out the mimics is through heightened clinical suspicion and tailored investigations.
