SUMMARY The pathological correlates of subcortical lesions noted on magnetic resonance imaging (MRI) in the elderly are not known. Postmortem in vitro proton MRI was performed on the brains of seven consecutive elderly patients dying of nonneurologic causes. Scans were done in the fresh and fixed states with the specimen immersed in saline and formaldehyde respectively. A 1.5 Tesla superconductive system was used with a multiple spin-echo protocol generating T 2 weighted images. Subcortical MRI lesions were localized in three dimensions and identified at brain cutting. In addition, pathological correlations were obtained from an eighth patient who underwent MRI eleven days before death. Histological examinations were performed in a blinded fashion, including control areas from the same brains. Subcortical MRI lesions were found to be associated with arteriosclerosis, dilated perivascular spaces, and vascular ectasia (p < 0.05). These histological changes were characteristic of "e~tat crible"" which, like subcortical MRI lesions, is associated with age and hypertension. Shrinkage (or atrophy) of the brain parenchyma around ectatic blood vessels would result in an extensive network of tunnels filled with extracellular water. The proton MRI signal from such areas of the brain would be increased. Gliosis and small areas of infarction occasionally coexisted with "£tat crible'," but these were not present in all areas with MRI lesions and could not be distinguished by MRI signal alone. While these appear as foci of increased signal intensity on MRI, 1 -13 it is unlikely that extensive subcortical white and gray matter infarction can occur without severe symptomatology. A chronic alteration in brain parenchyma, other than frank infarction, is therefore most likely to be responsible for the multiple, patchy, and sometimes confluent incidental lesions noted on MRI. The literature is limited regarding the pathological correlates of these lesions.Pathological correlations of incidental premortem radiological findings are difficult to perform. The pathological process often progresses to more advanced and symptomatic stages before death. Furthermore, it may be complicated by terminal events prior to postmortem examination. To circumvent these difficulties, postmortem MRI was performed in vitro on the brains of seven consecutive elderly patients dying of nonneurologic causes and autopsied at this institution. An additional elderly patient had an MRI study eleven days before dying of acute renal failure. Incidental MRI lesions were identified in these eight cases and were localized precisely at brain cutting. Gross and histologic correlations were performed, including a blinded analysis of control areas from the same brains (areas not harboring MRI lesions). Patients and MethodsThe patients represented consecutive cases over 60 years of age, who died of nonneurologic causes, and who underwent postmortem examination at the Barrow Neurological Institute. Cases with known demyelinating disease, known structural brain pathology, ...

SUMMARY Patchy subcortical foci of increased signal intensity are frequently identified on magnetic resonance imaging (MRI) in the elderly. The incidence and clinical correlates of these lesions remain unknown. In this report, 240 consecutive MRI scans performed over a 6-month period were reviewed (excluding patients with recent brain trauma or known demyelinating disease). Subcortical incidental lesions (ILs) were identified, which could not be accounted for by the patient's current clinical diagnosis, neurological status, or CT scan. The ILs were graded according to size, multiplicity, and location. The incidence and severity of ILs increased with advancing age (p < 0.0005). Among patients over 50 years of age, the incidence and severity of ILs were correlated with a previous history of ischemic cerebrovascular disease (p < 0.05) and with hypertension (p < 0.05). Multivariable regression analysis identified age, prior brain ischemia, and hypertension as the major predictors of ILs in the elderly. Diabetes, coronary artery diseases, and sex did not play a significant role. With the exception of cerebrovascular disease, there was no association between ILs and any particular clinical entity, including dementia. It is concluded that subcortical parenchyma! lesions are frequent incidental findings on MRI in the elderly, and may represent an index of chronic cerebrovascular diseases in such patients. Stroke Vol 17, No 6, 1986MAGNETIC RESONANCE IMAGING (MRI) of the brain has become a recognized and increasingly popular diagnostic modality. Unprecedented spacial resolution, flexibility in imaging, and the lack of ionizing radiation have all contributed to its widespread use. Furthermore, MRI has proven to be highly sensitive to subtle changes in brain parenchyma which accompany a wide variety of neurologic disorders. ' '«• l7 They are usually subcortical and multiple, and exhibit increased signal intensity on T 2 weighted images. Lesions of this nature have been described in conjunction with known cerebrovascular disease, but are difficult to correlate with previous symptoms.1 3 1 7 Similar lesions have been reported in association with dementia 4 ' 7 ' " and in asymtomatic elderly patients.3 ' 17 While there has been much speculation about the nature of such lesions, little is known about their clinical significance, prevalence in various age groups, or pathologic correlates.In this report, a definition and a grading scheme for incidental MRI lesions are proposed, and their incidence and clinical associations are examined in 240 consecutive patients undergoing MRI at our institution. Multivariable regression analysis is used to determine the impact of age and cerebrovascular risk factors on the incidence and severity of these lesions. In an accompanying report, the pathological correlates of these lesions are investigated, and an etiologic hypothesis is presented to account for their clinical and pathological associations.2

The findings at magnetic resonance (MR) imaging in a group of 36 pathologically verified supratentorial gliomas were analyzed and compared with the biopsy diagnoses (a) to determine whether MR imaging could be used to classify astrocytic-series tumors into a three-tiered system of low-grade astrocytoma, anaplastic astrocytoma, and glioblastoma multiforme; and (b) to evaluate MR imaging features that may aid in this classification. The MR characteristics evaluated were crossing of the midline, edema, tumor signal heterogeneity, hemorrhage, border definition, cyst formation or necrosis, and mass effect. The statistically significant MR characteristics (positive predictors) were mass effect (P = .0000) and cyst formation or necrosis (P = .0512). The MR accuracy rate approached that of neuropathologic diagnosis, which is subject to sampling errors. MR imaging may serve as an adjunct in case management when the clinical course and MR findings appear to be at odds with the neuropathologic diagnosis.

To assess the clinical efficacy of two-dimensional time-of-flight magnetic resonance (MR) angiography in the evaluation of carotid artery stenosis, a group of patients was evaluated in which 73 vessels were studied with both MR and conventional angiography. Four experienced neuroradiologists each scored both the MR and conventional angiograms in a blinded manner by using a standardized scoring scheme. Comparison of the scores revealed a high degree of correlation. In particular, MR angiography served to discriminate reliably between mildly narrowed and severely narrowed or occluded vessels. Furthermore, severe stenoses were accurately discriminated from occlusions in all cases. MR angiography is a robust and accurate modality for the characterization of carotid artery stenosis. It is useful in conjunction with routine MR imaging of the brain in the evaluation of the patient with suspected carotid arterial disease.

With the advent of magnetic resonance imaging (MRI) of the brain, a large number of incidental lesions (ILs) are being identified. The prevalence and clinical significance of these ILs are not known. The MRI and clinical records of 86 consecutive patients who underwent technically satisfactory brain imaging at a large urban referral center were reviewed. Patients with definite or probably demyelinating disease were excluded. Incidental lesions were defined as parenchymal areas of increased signal intensity on T2-weighted imaging, which could not be directly explained by the patient's current clinical diagnosis, neurological status, or computed tomographic (CT) scan. The ILs were noted and graded according to size, multiplicity, and location and were correlated with age, clinical presentation, CT scan findings, and risk factors for cerebrovascular disease. One or more IL were identified in 22% of patients under 40 years of age, in 57% of patients 41 to 60 years of age, and in 90% of patients over 60 years of age. Large patches of confluent ILs were not encountered in any patient less than 40 years of age; they were present in 10% of patients 41 to 60 years of age, and in 30% of patients over 60 years of age. The incidence of severity of ILs correlated significantly with age (P less than 0.0005) and with risk factors for cerebrovascular disease (P less than 0.02). Patients with most severe ILs also had areas of vague periventricular leukomalacia on the CT scan. The clinical significance of incidental MRI lesions in various age groups is discussed in detail.(ABSTRACT TRUNCATED AT 250 WORDS)