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

BMJ 2009; 339 doi: (Published 17 August 2009) Cite this as: BMJ 2009;339:b3016
  1. Zoe Morris, senior clinical fellow in neuroradiology1,
  2. William N Whiteley, CSO clinical academic fellow1,
  3. W T Longstreth Jr, professor of neurology and epidemiology2,
  4. Frank Weber, consultant neurologist3,
  5. Yi-Chung Lee, attending physician4,
  6. Yoshito Tsushima, associate professor of diagnostic radiology5,
  7. Hannah Alphs, medical student6,
  8. Susanne C Ladd, consultant radiologist7,
  9. Charles Warlow, emeritus professor of medical neurology1,
  10. Joanna M Wardlaw, professor of applied neuroimaging18,
  11. Rustam Al-Shahi Salman, MRC clinician scientist and honorary consultant neurologist1
  1. 1Division of Clinical Neurosciences, Western General Hospital, Edinburgh EH4 2XU
  2. 2Departments of Neurology and Epidemiology, Harborview Medical Center, Seattle, WA, USA
  3. 3German Air Force Institute of Aviation Medicine, Department of Neurology, Fuerstenfeldbruck, Germany
  4. 4Department of Neurology, Taipei Veterans General Hospital, Taiwan
  5. 5Department of Diagnostic Radiology and Nuclear Medicine, Gunma University Hospital, Japan
  6. 6Department of Radiology and Radiological Sciences, Johns Hopkins Hospital, Baltimore, MD, USA
  7. 7Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Germany
  8. 8SFC Brain Imaging Research Centre, University of Edinburgh
  1. Correspondence to: R Al-Shahi Salman Rustam.Al-Shahi{at}
  • Accepted 27 May 2009


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

Design Systematic review and meta-analysis of observational studies.

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

Review methods Two reviewers sought and assessed studies of people without neurological symptoms who underwent MRI of the brain with or without intravenous contrast for research purposes or for occupational, clinical, or commercial screening.

Main outcome measures Overall disease specific and age specific prevalence of incidental brain findings, calculated by meta-analysis of pooled proportions using DerSimonian-Laird weights in a random effects model.

Results In 16 studies, 135 of 19 559 people had neoplastic incidental brain findings (prevalence 0.70%, 95% confidence interval 0.47% to 0.98%), and prevalence increased with age (χ2 for linear trend, P=0.003). In 15 studies, 375 of 15 559 people had non-neoplastic incidental brain findings (prevalence 2.0%, 1.1% to 3.1%, excluding white matter hyperintensities, silent infarcts, and microbleeds). The number of asymptomatic people needed to scan to detect any incidental brain finding was 37. The prevalence of incidental brain findings was higher in studies using high resolution MRI sequences than in those using standard resolution sequences (4.3% v 1.7%, P<0.001). The prevalence of neoplastic incidental brain findings increased with age.

Conclusions Incidental findings on brain MRI are common, prevalence increases with age, and detection is more likely using high resolution MRI sequences than standard resolution sequences. These findings deserve to be mentioned when obtaining informed consent for brain MRI in research and clinical practice but are not sufficient to justify screening healthy asymptomatic people.


  • We thank the Edinburgh Stroke Research Group for its comments.

  • Contributors: RA-SS, WW, CPW, JMW, and ZM conceived and designed the study. ZM, WW, and RA-SS collected and analysed the data. WTL, FW, Y-CL, YT, HA, and SCL extracted and contributed additional grouped summary data from studies included in this review. RA-SS, ZM, and WW wrote the paper. All authors had full access to the data in the study, can take responsibility for the integrity of the data and the accuracy of the data analysis, and edited and approved the final version. RA-SS is the guarantor.

  • Funding: The Chief Scientist Office of the Scottish Government supports WW with a Clinical Academic Training Fellowship, and ZM with a research and development infrastructure award for radiology to Lothian Universities Hospitals NHS Trust Research and Development Office. The UK Medical Research Council supports RA-SS with a clinician scientist fellowship. JMW is partly supported by the Scottish Funding Council and Chief Scientist Office through the SINAPSE (Scottish Imaging Network. A Platform for Scientific Excellence) Collaboration ( The Cardiovascular Health Study is funded by the National Heart, Lung, and Blood Institute. The researchers are independent of the funders, and the study sponsors had no role in the study design; the collection, analysis, and interpretation of data; the writing of the report; and the decision to submit the article for publication.

  • Competing interests: None declared.

  • Ethical approval: Not required.

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