Incidental Findings Common with Brain MRI

ROTTERDAM, Netherlands, Oct. 31 -- Incidental brain findings on MRI may be common once people hit middle age, although it is unclear what clinicians should do about such findings, researchers said.
MRI showed asymptomatic strokes in 7.2% of the general population in Rotterdam, according to a population-based study published in the Nov. 1 issue of the New England Journal of Medicine.
The prevalence of incidentally discovered cerebral aneurysms was 1.8% and for benign tumors it was 1.6%, reported Aad van der Lugt, M.D., of Erasmus MC University Medical Center here, and colleagues.
Overall, the results suggest that one in every 7.3 asymptomatic persons scanned will have an incidental finding, commented Adrian A. Jarquin-Valdivia, M.D., R.D.M.S., of Vanderbilt University in Nashville, Tenn., a spokesperson for the American Academy of Neurology, in an interview with MedPage Today.
Although these lesions are associated with an increased risk of adverse neurological events, "the clinical relevance and natural course of these unexpected asymptomatic findings are largely unknown," the researchers wrote.
Dr. van der Lugt's group analyzed incidental MRI findings in the Rotterdam Scan Study, which was designed to investigate age-related brain changes. It was embedded within the larger prospective, population-based Rotterdam Study.
The analysis included 2,000 participants ages 45 to 96 (mean 63.3), of whom 52.4% were women. The patients were continuously monitored for incident clinical stroke through a linked database with general practitioners and hospitals.
Overall, there were 272 incidental findings reported. The most common type was asymptomatic stroke (145 cases, 7.2%). Lacunar infarcts were more common than cortical infarcts (5.6% versus 2%).
Aneurysms were next most frequent at 1.8%. All but two of the 35 aneurysms were located in the anterior circulation, and only three were larger than 7 mm in diameter.
Benign tumors were a close runner-up with a rate of 1.6%. Meningiomas were most common (0.9%) and ranged in size from five to 60 mm in diameter.
MRI detected one possibly malignant primary brain tumor -- a low-grade glioma -- and one case of multiple cerebral metastases in a patient who had previously been treated for lung cancer.
The most urgent finding was a large, chronic subdural hematoma in a patient who was discovered to have had minor head trauma a month prior to the scan, the researchers said.
Other findings included:
Seven cases of cavernous angioma (0.4% prevalence)
22 cases of arachnoid cyst (1.1% prevalence)
18 type I Chiari malformations (0.9% prevalence)
Nine cases of major-vessel stenosis (0.5% prevalence)
One dermoid cyst of the lateral orbital rim (less than 0.1% prevalence)
One case of fibrous dysplasia (less than 0.1% prevalence)
White-matter lesions were found in all but 5.4% of participants ages 45 to 59 and all but 2% of those 75 and older. The prevalence of asymptomatic aneurysms and meningiomas increased with age as well.
Subclinical vascular pathologic changes have been linked to increased risk of stroke and cognitive decline, but preventive therapies have not been evaluated in randomized trials, they noted.
"Then the question becomes, is it worth knowing early?" Dr. Jarquin-Valdivia said.
For typically slow-growing, asymptomatic meningiomas, "the current practice of many clinicians is to perform MRI yearly for at least two to three years to ascertain that rapid tumor growth does not occur," Dr. van der Lugt and colleagues noted.
For otherwise healthy, asymptomatic adults, as in the study, the resulting medical costs and psychological burden suggest this practice may need to be reviewed, they said.
Risk of rupture for the small aneurysms found in the study is low and "preventive surgery or treatment of risk factors may thus not be indicated in the general population," the researchers added.
However, the story may be different for patients with subclinical strokes, Dr. Jarquin-Valdivia said.
Although it is not well known whether treating subclinical strokes would prevent future strokes, the findings from the Perindopril Protection Against Recurrent Stroke Study (PROGRESS) showed that treating patients with symptomatic cerebrovascular disease with a combination of an ACE inhibitor and indapamide (Lozol) could prevent recurrent strokes (number-needed-to-treat 11).
If this were true for the asymptomatic patients in the Rotterdam study as well, "we could potentially have prevented 13 new symptomatic strokes over the course of one year," Dr. Jarquin-Valdivia concluded. "That may be worthwhile."
The study was supported by the Erasmus MC University Medical Center and Erasmus University Rotterdam; the Netherlands Organization for Scientific Research; the Netherlands Organization for Health Research and Development; the Research Institute for Diseases in the Elderly; the Ministry of Education, Culture, and Science; the Ministry of Health, Welfare, and Sports; the European Commission; the Municipality of Rotterdam; and by grants from the Netherlands Organization for Scientific Research.
The researchers reported no potential conflict of interest. Dr. Jarquin-Valdivia reported no conflicts of interest.Primary source: New England Journal of MedicineSource reference: Vernooij MW, et al "Incidental Findings on Brain MRI in the General Population" N Engl J Med 2007; 357: 1821-8.