Incidental Findings on Brain MRI in the General Population
Abstract & Commentary
By Mary Elina Ferris, MD, Clinical Associate Professor, University of Southern California; Dr. Ferris reports no financial relationship to this field of study.
Synopsis: Asymptomatic brain MRI findings of infarct, cerebral aneurysms and benign tumors were fairly common in the general population. The clinical significance of these findings is unknown.
Source: Vernooij M, et al. N Engl J Med. 2007;357:1821-1828.
A prospective, ongoing, population-based study of age-related brain changes investigating inhabitants of a suburb of Rotterdam in the Netherlands started in the year 2000, with 8,000 participants aged 46-98 years receiving MRI brain scans every 2-3 years. A standardized non-contrast brain MRI was performed on 2,027 eligible participants, and any incidental findings were reviewed by two neuroradiologists without knowledge of any clinical history.
Asymptomatic brain infarcts were present in 7.2% (145 persons); aneurysms in 1.8%; and benign tumors in 1.6% (most often meningiomas). Most aneurysms were less than 7mm in diameter, and meningiomas ranged from 5 to 60mm diameter. The next most common findings were arachnoid cysts in 1.1% (22 persons) and Type I Chiari malformation in 0.9% (18 persons). Pituitary macroadenomas were present in 0.3% (6 persons) and vestibular schwannomas in 0.2% (4 persons). One asymptomatic large chronic subdural hematoma was found in a person with minor head trauma 4 weeks prior to the scan.
The presence of asymptomatic brain infarcts increased with age: 4% up to age 60, 7% from 60-74 years, and 18% over age 75. However, aneurysms had no age-related increase in incidence.
Commentary
Age-related changes such as asymptomatic brain infarcts and aneurysms have been reported in the general elderly population, but this study demonstrates these incidental findings in much higher prevalence than previously appreciated. For example, a previous study found 0.11% of persons over age 65 years had aneurysms,1 whereas this current study found 1.8%. An autopsy study found 2% prevalence of aneurysms in adults without risk factors,2 which more closely matches the new study.
Meningiomas were also found, and are thought to progress very slowly, leading to estimates of only 50% being discovered at autopsy; 3% of persons over age 60 have these tumors found at autopsy, usually less than 1cm diameter. What this all emphasizes is that we really do not know the natural clinical course of these asymptomatic findings. With the current increased resolution of MRI scanning, more information from ongoing studies will help us advise patients on what these results mean, but until then we are left with unexpected findings without knowing their actual significance.
References
1. Yue NC, et al. Radiology. 1997;202:41-46.
2. Rinkel GJ, et al. Stroke. 1998;29:251-256.
Asymptomatic brain MRI findings of infarct, cerebral aneurysms and benign tumors were fairly common in the general population. The clinical significance of these findings is unknown.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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