Evaluation of cerebral infarction by computed tomography with special emphasis on microinfarction

Microinfarcts in an older population-representative brain donor cohort (MRC CFAS): Prevalence, relation to dementia and mobility, and implications for the evaluation of cerebral Small Vessel Disease

Introduction

Microinfarcts, small ischaemic foci common in ageing brain, are associated with dementia and gait dysfunction. We determined their relationship with dementia, mobility and cerebrovascular disease in an older population‐representative brain donor cohort. These data on microinfarcts were evaluated in relation to pathological assessments of clinically significant cerebral small vessel disease (SVD).

Methods

Microinfarcts were assessed in the MRC Cognitive Function and Ageing Study (n = 331). Nine brain areas were staged according to the number of areas affected.

Results

36% of brains showed at least 1 microinfarct. Higher cortical microinfarct stage was associated with dementia at death (OR 1.41, 95% CI 1.02; 1.96, P = 0.038), whilst cortical and subcortical microinfarct stages were associated with impaired mobility (OR 1.36, 95% CI 1.05–1.74; P 0.018) and falls (OR 1.96, 95% CI 1.11–3.43; P = 0.02). Adding data on microinfarcts to a definition of SVD, based on white matter lesions (WMLs), lacunes and significant arteriosclerosis, were assessed by comparing area under ROC curve (AUC) with and without microinfarcts. SVD was significantly related to dementia status with or without inclusion of microinfarcts. Modelling potential pathological definitions of SVD to predict dementia or impaired mobility indicated optimal prediction using combined assessment of WMLs, lacunes and microinfarcts.

Conclusion

Cortical (dementia) and subcortical microinfarcts (impaired mobility) are related to diverse clinical outcomes. Optimal pathological assessment of significant SVD in brain ageing is achieved based on WMLs, lacunes and microinfarcts and may not require subjective assessment of the extent and severity of arteriosclerosis.

Pediatric brain computed tomography

Computed tomography today provides good anatomic depiction of the brain and its gross disease processes that have as a manifestation alteration of brain density, disturbance in blood-brain barrier, or mass effect. As such, computed tomography often provides valuable diagnostic information in the appropriate clinical setting. This article reviews many of the more common pediatric central nervous system disease states that have been demonstrated more easily as a result of computed tomography.

CT in hemispheric ischaemic attacks

The authors report the three principal characteristics of hemispheric ischaemic attacks on CT scan and their development over time: hypodensity, mass effect and contrast enhancement. Their pathophysiological mechanism and prognostic importance are discussed. The topography of the territories of the large arteries vascularising the brain and their main branches is described on the basis of twelve sections cut parallel to the cantho-meatal line. Finally, selected special aspects are described (misleading aspects, haemorrhagic infarcts, border zone infarcts).

Emission and transmission tomography of the brain in cerebrovascular disease

Transmission and emission computed tomography (T-CT and E-CT, respectively) scans of the brain in 149 patients with cerebrovascular disease were compared to establish the diagnostic accuracy of the two methods. The T-CT scan yielded an overall rate of true-positive results of 80.75% in major infarcts, 80% in intracerebral hematomas, and 75.9% in subarachnoid hemorrhage. In contrast, the percentages of true-positive results yielded by the E-CT scan were 92.3, 55, and 34.5%, respectively, in each type of cerebrovascular disease. The false-negative results obtained with the T-CT scan were higher in infarcts but lower in hematomas and subarachnoid hemorrhage; the reverse was true for the diagnoses obtained with the E-CT scan. The false-positive diagnoses produced by the T-CT scan were high for hemorrhagic strokes compared to those of the E-CT scan. The diagnostic sensitivity of each scan was not affected by the location of the lesion. Thus, the E-CT scan is more sensitive for thromboembolic disease and less so for hemorrhagic types of stroke. The reverse is true for the T-CT scan.

CT findings in hemorrhagic cerebral infarct

Hemorrhagic cerebral infarcts can be detected by computer tomography (CT) as a high density lesion in the margins or inside a low density infarcted area. However the CT features are not always characteristic and the specific diagnosis is sometimes impossible. We describe the CT findings in initial and follow-up examinations of three arterial and one venous hemorrhagic infarcts and discuss the diagnostic problems.

Contrast enhancement of cerebral infarcts. Incidence and clinical value in different states of cerebral infarction

Information obtained from CT scan after contrast administration was evaluated in 59 consecutive stroke patients. CT scans before and after contrast administration were performed 3 days and 2 1/2 weeks after stroke. A plain CT scan was repeated 6 months later. Contrast enhancement was practically not seen on the first examination, but was seen in 46% on the second examination. There was a close relationship between the occurrence of contrast enhancement and the socalled "fogging effect". Contrast scanning gave additional information only when this effect was present. Plain CT scans 3 days after stroke were superior to contrast scans taken at any time for detecting and visualizing cerebral infarcts.

Sensitivity of computer assisted radionuclide angiography in transient ischemic attack and prolonged reversible ischemic neurological deficit. Comparison with findings in radiographic angiography and transmission computerized axial tomography

Computer assisted radionuclide angiography (CARNA) with 99mTc-DTPA was employed to study 143 patients with transient ischemic attacks (TIA) and 79 patients with prolonged reversible ischemic neurologic deficit (PRIND). The results of CARNA were compared with findings from radiographic angiography (RGA) in 173 patients and with findings in transmission computerized axial tomography (T-CAT) in 154 patients. In patients with TIA, CARNA showed a hemispherical perfusion deficit in 74.8%, and with PRIND 87.3%. This deficit, determined as the relative difference between the involved and the non-involved hemisphere, was significantly (p less than 0.0025) greater in PRIND (minus 23%) than in TIA (minus 17%). Sensitivity of CARNA was independent of the interval from ictus to examination for more than 4 months. RGA in TIA revealed true positives in 82.0%, in PRIND it was 89.5%. T-CAT was positive in TIA in only 16.8% but in PRIND it was 64.4%. Combined sensitivities in TIA (92.4%) and in PRIND (94.0%) were highest with the combination of CARNA and RGA. However, in PRIND the combination of non-invasive methods (CARNA and T-CAT) revealed 93.2% positive findings. Combinations of these evaluation methods may be used to detect cerebrovascular disease in patients with such dysfunction.

Reversible contrast-enhanced lesions of basal ganglia and brain stem on computed tomography

Two cases of reversible CT contrast-enhanced lesions simulating brain neoplasms are described. Following steroid therapy and shunting procedure normalization of the clinical signs and of the CT scans occurred. The role of a vasculomyelinopathy as a possible pathogenetic factor of these lesions is stressed.

Intravascular contrast injection in ischaemic lesions. II. Effect on prognosis

In a consecutive series of patients with cerebral infarcts, the degree of recovery was better in those who were not administered contrast medium (sodium iothalamate). The various factors known to influence recovery were examined but did not appear to account fully for the difference. It is postulated that extravasation of the contrast medium may adversely affect potentially viable neural tissue.

Contrast enhancement in ischaemic lesions. I. Relationship to prognosis

The contribution of post-enhancement CT scans to the diagnosis of acute cerebral infarction was studied in a consecutive series of infarcts. The timing, density and pattern of enhancement were also analysed for any possible prognostic information, and the incidence of factors of known prognostic significance was estimated on plain and contrast enhanced scans. Enhancement patterns of infarcts were variable and in those cases in which the plain CT diagnosis was equivocal the post-enhancement CT was not infrequently ambiguous also, and occasionally misleading. The outcome of infarcts that enhanced was significantly poorer than in those not showing enhancement, although no relationship between the timing, density or pattern of enhancement and prognosis could be shown. Consideration of the distribution of other factors known to adversely affect prognosis in the two groups does not adequately account for the difference between them suggesting that the contrast medium itself could be the cause of the poorer outcome. There are few positive indications for post-contrast scanning of suspected infarcts and the possible adverse effects of contrast medium should be considered prior to administration.