Incidental findings on brain magnetic resonance imaging: systematic review and meta-analysis

doi:10.1136/bmj.b3016

Published 17 August 2009, doi:10.1136/bmj.b3016
Cite this as: BMJ 2009;339:b3016

Research

Incidental findings on brain magnetic resonance imaging: systematic review and meta-analysis

Zoe Morris, senior clinical fellow in neuroradiology¹, William N Whiteley, CSO clinical academic fellow¹, W T Longstreth, Jr, professor of neurology and epidemiology², Frank Weber, consultant neurologist³, Yi-Chung Lee, attending physician⁴, Yoshito Tsushima, associate professor of diagnostic radiology⁵, Hannah Alphs, medical student⁶, Susanne C Ladd, consultant radiologist⁷, Charles Warlow, emeritus professor of medical neurology¹, Joanna M Wardlaw, professor of applied neuroimaging¹^,8, Rustam Al-Shahi Salman, MRC clinician scientist and honorary consultant neurologist¹

¹ Division of Clinical Neurosciences, Western General Hospital, Edinburgh EH4 2XU, ² Departments of Neurology and Epidemiology, Harborview Medical Center, Seattle, WA, USA, ³ German Air Force Institute of Aviation Medicine, Department of Neurology, Fuerstenfeldbruck, Germany, ⁴ Department of Neurology, Taipei Veterans General Hospital, Taiwan, ⁵ Department of Diagnostic Radiology and Nuclear Medicine, Gunma University Hospital, Japan, ⁶ Department of Radiology and Radiological Sciences, Johns Hopkins Hospital, Baltimore, MD, USA, ⁷ Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Germany, ⁸ SFC Brain Imaging Research Centre, University of Edinburgh

Correspondence to: R Al-Shahi Salman Rustam.Al-Shahi{at}ed.ac.uk

Objective To quantify the prevalence of incidental findingson magnetic resonance imaging (MRI) of the brain.

Design Systematic review and meta-analysis of observationalstudies.

Data sources Ovid Medline (1950 to May 2008), Embase (1980 toMay 2008), and bibliographies of relevant articles.

Review methods Two reviewers sought and assessed studies ofpeople without neurological symptoms who underwent MRI of thebrain with or without intravenous contrast for research purposesor for occupational, clinical, or commercial screening.

Main outcome measures Overall disease specific and age specificprevalence of incidental brain findings, calculated by meta-analysisof pooled proportions using DerSimonian-Laird weights in a randomeffects model.

Results In 16 studies, 135 of 19 559 people had neoplastic incidentalbrain findings (prevalence 0.70%, 95% confidence interval 0.47%to 0.98%), and prevalence increased with age ( ${chi}$ ² for linear trend,P=0.003). In 15 studies, 375 of 15 559 people had non-neoplasticincidental brain findings (prevalence 2.0%, 1.1% to 3.1%, excludingwhite matter hyperintensities, silent infarcts, and microbleeds).The number of asymptomatic people needed to scan to detect anyincidental brain finding was 37. The prevalence of incidentalbrain findings was higher in studies using high resolution MRIsequences than in those using standard resolution sequences(4.3% v 1.7%, P<0.001). The prevalence of neoplastic incidentalbrain findings increased with age.

Conclusions Incidental findings on brain MRI are common, prevalenceincreases with age, and detection is more likely using highresolution MRI sequences than standard resolution sequences.These findings deserve to be mentioned when obtaining informedconsent for brain MRI in research and clinical practice butare not sufficient to justify screening healthy asymptomaticpeople.

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: http://creativecommons.org/licenses/by-nc/2.0/ and http://creativecommons.org/licenses/by-nc/2.0/legalcode.

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