Focal parenchymal lesions in transient ischemic attacks: correlation of computed tomography and magnetic resonance imaging.

Abstract

SUMMARY Twenty-two patients with the clinical diagnosis of transient ischemic attacks were prospectively evaluated by computed tomography (CT) and proton magnetic resonance imaging (MRI). Nineteen patients also underwent cerebral angiography. The MRI studies were performed with a prototype superconductive magnet using a 0.6 Tesla or a 1.5 Tesla magnetic field. Two pulse sequence techniques were used resulting in Tl and T2 weighted images. All studies were interpreted descriptively by a single neuroradiologist La a blinded fashion, with special attention to focal parenchymal abnormalities. Patients with previously documented clinical strokes or reversible ischemic neurologic deficits lasting more than 24 hours were excluded. The CT scans revealed focal areas of abnormalities in 7 of 22 patients (32%), while the MRI scans showed focal changes in 17 patients (77%). All the CT lesions were clearly visualized on MRI. The MRI changes were better seen on T2 weighted images as areas of increased signal intensity. There was a marked preponderance of deep hemispheric lesions on both CT and MRI studies. Focal parenchymal abnormalities were not limited to the symptomatic vascular territory. We conclude that MRI reveals focal parenchymal changes in the majority of patients with transient ischemic attacks and is more sensitive than late generation CT scans. However, specificity appears to be poor, and may limit clinical usefulness. While the significance of the MRI "lesions" remains speculative, they may represent markers of chronic cerebrovascular disease in these patients. Stroke Vol 17, No 3, 1986 TRANSIENT ISCHEMIC ATTACKS (TIA's) are episodes of focal neurologic dysfunction referable to a specific arterial distribution, and resolving within 24 hours. The classical clinical concept initially implied a truly reversible process without permanent parenchymal damage. More recently, it has been recognized that some patients presenting with TIA's have actually sustained cerebral infarction with timely resolution of signs and symptoms. '* Some authors argue for a separate classification of TLA patients with parenchymal lesions, and suggest a different therapeutic approach to these patients. 4 The advent of late generation computed tomographic (CT) scanning and magnetic resonance imaging (MRI) has added a new dimension to the problem. These more sensitive imaging techniques are identifying an increasing number of focal parenchymal abnormalities in TIA patients and are raising questions about the frequency, nature, and clinical significance of these lesions. In this study, we prospectively examine the CT and MRI findings in 22 TIA patients, and correlate these findings with the clinical presentation and angiographic findings. Patients and MethodsTwenty-two patients with the clinical diagnosis of TIA's were prospectively evaluated by proton MRI and CT scanning as part of their initial evaluation at the Cleveland Clinic Hospital. These represented a group of consecutive cases evaluated by the cerebrovascular surgery and neurology...

Incidental subcortical lesions identified on magnetic resonance imaging in the elderly. I. Correlation with age and cerebrovascular risk factors.

“…1 The nature of those additional incidental MRI lesions was uncertain, and the authors cautioned against their "overinterpretation. "…”

“…Furthermore, MRI has proven to be highly sensitive to subtle changes in brain parenchyma which accompany a wide variety of neurologic disorders. 1 Such sensitivity has already found practical application in the screening of patients for multiple sclerosis. 1214 Conversely, the lack of specificity of MRI has limited its clinical usefulness in the presence of unexpected or incidental lesions.…”

What is the best imaging strategy for acute stroke?

“…In the two studies (82 patients) that included patients with TIA, MR was markedly better at demonstrating ischaemic lesions in one study (21% on CT compared with 68% on MR 203 ), but less obviously better in the other (MR demonstrated lesions not seen on CT in 14%, but CT demonstrated lesions not seen on MR in 9% 228 ).…”

“…As previously, the patient groups under investigation differed (some studies including more than one patient group): TIA (two studies, 41 patients), 203,228 lacunar stroke (five studies, 166 patients), 203,230,232,233,235 cerebellar stroke (one study 14 patients); 229 lateral medullary syndrome (one study, six patients) 231 and unselected stroke (four studies, 356 patients). 204,206,207,234 Again, studies were uniformly small.…”

“…204,206,207,234 Again, studies were uniformly small. Nine studies (75% of studies) collected data prospectively, 203,204,206,207,228,230,[233][234][235] while six studies (50%) blinded readers of scans either to clinical history 203,207,228,234,235 or to other imaging. 204 In only one study (0.8%) was the order in which CT or MR was performed varied (although not randomised); 207 two studies performed both scans on the same day but did not document the order in which they were done; 228,232 in five studies, CT was always performed before MR. 203,204,206,234,235 The extent of the difference in times varied: in one study where all patients were scanned within 24 hours, CT was performed a mean of 4 hours earlier, 234 in another study of imaging within the first 3 weeks of stroke, CT was performed a median of 4 days earlier, 203 and in three studies the order of scanning was not defined.…”