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Incidental Findings on Brain MRI

Asymptomatic brain infarcts were the most common findings, followed by aneurysms and benign tumors.

Incidental findings of varying clinical significance are encountered frequently on magnetic resonance imaging. In this population-based cohort study from the Netherlands, 2000 people aged 45 or older underwent routine brain MRI.

Common findings were asymptomatic brain infarcts (7.2%), cerebral aneurysms (1.8%), and benign tumors (1.6%), which included mainly meningiomas, vestibular schwannomas, and pituitary adenomas. Less common were arachnoid cysts (1.1%) and type I Chiari malformations (0.9%). One person each had a possible glioma, multiple cerebral metastases, and a chronic subdural hematoma. Only two patients — both with hearing loss — reportedly had symptoms related to MRI findings. Surgery was performed in two patients: the person with the subdural hematoma and a person with a 12-mm aneurysm (most incidentally discovered aneurysms were smaller than 7 mm). More than 95% of patients had white matter lesions, presumably indicating subclinical vascular disease; the volume of such lesions increased with age.

Comment: This descriptive study shows us the spectrum of incidental findings on MRI of the brain. Rarely, findings will demand immediate intervention. In contrast, many harmless findings can be ignored, but may create anxiety when patients learn about them. Certain lesions such as aneurysms and meningiomas require intervention only in selected cases; because the explosive use of MRI will uncover such lesions with increasing frequency, we need better data on their natural history and optimal follow-up strategies.

— Allan S. Brett, MD

Published in Journal Watch General Medicine October 31, 2007

Citation(s):

Vernooij MW et al. Incidental findings on brain MRI in the general population. N Engl J Med 2007 Nov 1; 357:1821.

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