The ability to detect brain CT abnormalities suggestive of ischemic stroke largely depends upon the time between the onset of symptoms and the CT examination.
Large, cortical strokes are typically not detected on CT for at least 3 hours; Nearly 60% of strokes, however, are detectable on CT within 24 hours from time of infarct, and essentially 100% within 7 days.
Clinical correlation: Be sure that the reported time of symptom onset properly correlates with brain CT findings, as this could affect the decision to treat with tPA in accordance with appropriate time windows. If a patient reports 1 hour of stroke symptoms, for example, and the brain CT shows significant edema and loss of gray/white matter differentiation suggesting infarct, be wary of a time discrepancy.
References
Bryan NR, Levy LM, Whitlow WD,Killian JM, Preziosi TJ, Rosario JA. Diagnosis of acute cerebral infarction: comparison of CT and MRI imaging. AJNR Am J Neuroradiol. 1981;12:611-620.
Mikhael MA. Neuroradiology of cerebral infarction. In: Sarwar M, Batnitzky S, eds. Imaging of Non-traumatic Ischemic and Hemorrhagic Disorders of the Central Nervous System. Boston, Mass: Kluwer Academic Publishers; 1989:193-220.
