Stroke is The Second Most Common Cause of Morbidity Worldwide

Introduction

Stroke is a term describe the sudden onset of a constant neurological deficit caused by partial or complete obstruction (ischemic stroke) or rupture of a cerebral blood vessel (haemorrhage). (1)

Stroke is the second most common cause of morbidity worldwide and is the primary cause of acquired disability, Ischemic stroke, which constitutes the vast majority of cases (~ 85%), risk factors for ischemic stroke include age, gender, family history, smoking, hypertension and diabetes. The middle cerebral artery (MCA) territory is the most commonly affected territory in a cerebral infarction, due to the size of the territory and the direct flow from internal carotid artery into the middle cerebral artery, providing the easiest path for thromboembolism. (2)

Hemorrhagic transformation is a complication of cerebral ischemic infarction and can significantly worsen prognosis. The proportion of hemorrhagic transformation of ischemic strokes have been variably reported, but generally over half of all cerebral infarcts at some phase develop some hemorrhagic component, while the majority (89%) are petechial hemorrhages, and a minority (11%) hematomas. (3)

Although hemorrhagic transformation can occur spontaneously, it is more commonly encountered in patients who receive anticoagulant treatment and even more frequent in those undergoing thrombolytic therapy, the overall rate of spontaneous hemorrhagic transformation (with hematoma) has been reported to be as high as ~5%, the frequency of symptomatic hemorrhagic transformation is however much lower between 0.6 and 3% in untreated patients and up to 6% of patients treated with intravenous Tissue plasminogen activator (tPA).(4)

Imaging of acute ischemic stroke

Non-contrast computed tomography (NCCT): NCCT of the brain remains the mainstay of imaging in the setting of an acute stroke. It is fast, inexpensive and readily available. Its main restriction, however, is the inadequate sensitivity in the acute setting. Detection depends

on the territory, the experience of the interpreting radiologist and of course the time of the scan from the onset of symptoms. Whether tissue is supplied by end arteries (e.g. lenticulostriate arteries) or has collateral supply (much of the cerebral cortex) will influence how quickly cytotoxic oedema develops.(5) Detection of MCA territory infarct has been shown to be approximately 60-70% in the first 6 hours,(6) although changes in the deep grey matter nuclei (especially lentiform nucleus) can be visible within 1 hour of occlusion in up to 60% of patients. Within the first few hours, a number of signs are visible depending on the site of occlusion and the presence of collateral flow. Early features include:

Loss of grey-white matter differentiation, and hypoattenuation of deep nuclei.Cortical hypodensity with associated parenchymal swelling with resultant gyral effacement.(5)

Petechial hemorrhages, as the name suggests, usually appear as tiny punctate regions of haemorrhage, often not able to be individually resolved, but rather resulting in increased attenuation of the area on CT. In the case of secondary hematomas hemorrhage is often patchy, scattered throughout the infarcted tissue, and usually represents only a small part of the abnormal tissue.(4)