Cranial Noncontrast Computed Tomography in Acute Cerebrovascular Stroke, with Special Reference to Circadian Variation in Stroke

Neuroimaging is fundamental to stroke diagnosis and management. Non-contrast computed tomography (NCCT) has been the primary imaging modality utilized for this purpose for almost four decades. Although NCCT does permit identification of intracranial hemorrhage and parenchymal ischemic changes, insights into blood vessel patency and cerebral perfusion are limited. Advances in CT technology now permit identification of acute and chronic arterial lesions, as well as cerebral blood flow deficits.

To study noncontrast computed tomography findings in acute cerebrovascular stroke and to investigate the possibility that stroke has a circadian variation.

The study was conducted at the Department of Radiology, Muzaffarnagar Medical College & Hospital, Muzaffarnagar on 50 cases of acute stroke (25 cases of ischemic stroke and 25 cases of hemorrhagic stroke) aged 18–80 years, admitted in the emergency, medicine ward and intensive care unit during the period of September 2012 to September 2014. Time of onset of stroke and associated risk factors like age, sex, hypertension, smoking, diabetes mellitus and dyslipidemia were studied. The patients were thoroughly examined clinically and underwent hematological & biochemical investigations and cranial noncontrast computed tomography. All patients were followed up for a month after the onset of stroke.

Early ischemic changes (EIC) in brain parenchyma seen on non-contrast CT (NCCT) include focal swelling (sulcal effacement) and hypoattenuation. The sensitivity of NCCT for ischemia is time-dependent; in the first 3 h, it is less than 50% and increases to 80–90% at 6 h. For the diagnosis of lacunar infarcts within the first 6 h, the sensitivity is less than 50%. There was a circadian pattern in the onset of stroke, with a significantly higher risk of ischemic stroke in the morning while hemorrhagic stroke was found predominantly in late afternoon to early evening.

Despite its shortcomings, NCCT imaging is still the most widely used modality for selection of patients for reperfusion therapy. It has the advantages of wide availability, short acquisition time and a high sensitivity for identification of intracranial hemorrhage. NCCT demonstrates areas of irreversible infarction, but in most cases provides little insight into the presence or extent of penumbral tissue. Fortunately, more advanced CT-based imaging techniques can be used to gain additional pathophysiological information.