Asymptomatic MRI Abnormalities: A European Study

The HUNT study is a continuing multipart survey of health in a Norwegian county. Part of the study included brain MRI scan of the normal population, done on a population of 50 to 66 year old men and women in that European region. The study demonstrated a large percentage of asymptomatic MRI anomalies, generally minor ones: 32% of the MRI scans were abnormal. Of these, the findings were felt to be of some clinical revelance in about half the abnormal scans (15.1% of individuals), but, although almost 10% of the abnormalities were found to be intracranial tumors, mostly incidental meningiomas, only 1.4% of the study participants eventually had surgery or radiotherapy.

Thus, in persons aged 50 to 66, MRI's are abnormal 1/3 of the time, but less than 2% of MRI's will show a brain tumor requiring treatment. I also note that about 2% of the scans showed incidental circle of Willis aneurysms, none of which required catheter or surgical intervention.




Incidental Intracranial Findings and Their Clinical Impact; The HUNT MRI Study in a General Population of 1006 Participants between 50-66 Years

Authors: Asta Kristine Håberg , Tommy Arild Hammer , Kjell Arne Kvistad , Jana Rydland , Tomm B. Müller, Live Eikenes , Mari Gårseth , Lars Jacob Stovner

Published: March 7, 2016DOI: 10.1371/journal.pone.0151080


Evaluate types and prevalence of all, incidental, and clinically relevant incidental intracranial findings, i.e. those referred to primary physician or clinical specialist, in a cohort between 50 and 66 years from the Nord-Trøndelag Health (HUNT) study. Types of follow-up, outcome of repeated neuroimaging and neurosurgical treatment were assessed.

Material and Methods

1006 participants (530 women) underwent MRI of the head at 1.5T consisting of T1 weighted sagittal IR-FSPGR volume, axial T2 weighted, gradient echo T2* weighted and FLAIR sequences plus time of flight cerebral angiography covering the circle of Willis. The nature of a finding and if it was incidental were determined from previous radiological examinations, patient records, phone interview, and/or additional neuroimaging. Handling and outcome of the clinically relevant incidental findings were prospectively recorded. True and false positives were estimated from the repeated neuroimaging.


Prevalence of any intracranial finding was 32.7%. Incidental intracranial findings were present in 27.1% and clinically relevant findings in 15.1% of the participants in the HUNT MRI cohort. 185 individuals (18.4%) were contacted by phone about their findings. 40 participants (6.2%) underwent ≥ 1 additional neuroimaging session to establish etiology. Most false positives were linked to an initial diagnosis of suspected glioma, and overall positive predictive value of initial MRI was 0.90 across different diagnoses. 90.8% of the clinically relevant incidental findings were developmental and acquired cerebrovascular pathologies, the remaining 9.2% were intracranial tumors, of which extra-axial tumors predominated. In total, 3.9% of the participants were referred to a clinical specialist, and 11.7% to their primary physician. 1.4% underwent neurosurgery/radiotherapy, and 1 (0.1%) experienced a procedure related postoperative deficit.


In a general population between 50 and 66 years most intracranial findings on MRI were incidental, and >15% of the cohort was referred to clinical-follow up. Hence good routines for handling of findings need to be in place to ensure timely and appropriate handling.



The above study's statistical outcome data can be usefully compared to other studies performed more typically in that population for health screening reasons, such as colonoscopy for cancer screening. So, let's compare that with the situation with colonoscopy in this population, as shown in the study following the MRI study. That study showed, in a similarly aged population of Austrians aged an average of 61 years, that the incidental finding of ordinary adenomas was 19.7%, with advanced stage adenomas in 6.3% and actual colorectal carcinomas found in 1.1%.



Sex-Specific Prevalence of Adenomas, Advanced Adenomas, and Colorectal Cancer in Individuals Undergoing Screening Colonoscopy

Monika Ferlitsch, MD; Karoline Reinhart, MD; Sibylle Pramhas, MD; Caspar Wiener, MD; Orsolya Gal, MD; Christina Bannert, MD; Michaela Hassler; Karin Kozbial; Daniela Dunkler, PhD; Michael Trauner, MD; Werner Weiss, MD

JAMA. 2011;306(12):1352-1358. doi:10.1001/jama.2011.1362. Text Size: A A A


Although some studies have shown that men are at greater age-specific risk for advanced colorectal neoplasia than women, the age for referring patients to screening colonoscopy is independent of sex and usually recommended to be 50 years.


To determine and compare the prevalence and number needed to screen (NNS) for adenomas, advanced adenomas (AAs), and colorectal carcinomas (CRCs) for different age groups in men and women.

Design, Setting, and Patients

Cohort study of 44 350 participants in a national screening colonoscopy program over a 4-year period (2007 to 2010) in Austria.

Main Outcome Measures

Prevalence and NNS of adenomas, AAs, and CRCs in different age groups for men and women.


The median ages were 60.7 years (interquartile range [IQR], 54.5-67.5 years) for women and 60.6 years (IQR, 54.3-67.6 years) for men, and the sex ratio was nearly identical (51.0% [22 598] vs 49.0% [21 572]). Adenomas were found in 19.7% of individuals screened (95% CI, 19.3%-20.1%; n = 8743), AAs in 6.3% (95% CI, 6.1%-6.5%; n = 2781), and CRCs in 1.1% (95% CI, 1.0%-1.2%; n = 491); NNS were 5.1 (95% CI, 5.0-5.2), 15.9 (95% CI, 15.4-16.5), and 90.9 (95% CI, 83.3-100.0), respectively. Male sex was significantly associated with a higher prevalence of adenomas (24.9% [95% CI, 24.3%-25.4%] vs 14.8% [95% CI, 14.3%-15.2%]; P < .001; unadjusted odds ratio [OR], 1.9 [95% CI, 1.8-2.0]), AAs (8.0% [95% CI, 7.6%-8.3%] vs 4.7% [95% CI, 4.4%-4.9%]; P < .001; unadjusted OR, 1.8 [95% CI, 1.6-1.9]), and CRCs (1.5% [95% CI, 1.3%-1.7%] vs 0.7% [95% CI, 0.6%-0.9%]; P < .001; unadjusted OR, 2.1 [95% CI, 1.7-2.5]). The prevalence of AAs in 50- to 54-year-old individuals was 5.0% (95% CI, 4.4%-5.6%) in men but 2.9% (95% CI, 2.5%-3.4%) in women (adjusted P = .001); the NNS in men was 20 (95% CI, 17.8-22.6) vs 34 in women (95% CI, 29.1-40; adjusted P = .001). There was no statistical significance between the prevalence and NNS of AAs in men aged 45 to 49 years compared with women aged 55 to 59 years (3.8% [95% CI, 2.3%-6.1%] vs 3.9% [95% CI, 3.3%-4.5%] and 26.1 [95% CI, 16.5-44.4] vs 26 [95% CI, 22.5-30.2]; P = .99).


Among a cohort of Austrian individuals undergoing screening colonoscopy, the prevalence and NNS of AAs were comparable between men aged 45 to 49 years and women aged 55 to 59 years.

As in many countries, including the United States, the recommended age in Austria for screening colonoscopy for colorectal cancer (CRC) in average-risk patients is 50 years for both men and women1- 4 because of the increase in the prevalence of CRC in the sixth decade of life. The goal of screening colonoscopy is to find and remove adenomas and particularly advanced adenomas (AAs). Although transition rates from AA to CRC are similar for women and men, the prevalences of AA and CRC are higher in men than in women (8% vs 4.3% for AA, 1.4% vs 0.6% for CRC, respectively),5- 8 which may result from a larger number of adenomas present in men in their 40s.7 Based on the results of a national screening program in Poland, Regula et al5 have suggested that the age for starting screening colonoscopy should be sex specific, because the number needed to screen (NNS) to detect an AA among men aged 40 to 49 years was similar to that of women aged 50 to 59 years. A study by Brenner et al6 revealed that the same incidence of CRC and CRC mortality occurred in women 4 to 8 years later than in men, but the patients included in this study were 55 years or older. Nevertheless, a modification of the screening recommendations because of sex has not been implemented because the optimal age for screening has remained insufficiently explored.

In 2007, a national project entitled Quality Management for Colon Cancer Prevention was initiated to define and control standards for quality and documentation of screening colonoscopies in Austria. The objective of our study was to investigate the most appropriate age for initial screening colonoscopy for both male and female patient groups to achieve a higher detection rate of adenoma, AA, and CRC, which could result in a lower CRC mortality rate.



In summary, brain MRI abnormalities are common in older human age groups, but they need intervention only rarely. The incidence of clinically significant brain tumor is similar to that of carcinoma found by colonoscopy, but, unlike colonoscopy where adenomas and advanced adenomas can often be removed during the procedure which detects them, MRI does not show promise as a tool for preventative health.

Unlike colonoscopy, MRI as a pure screening tool seems to have little reason for implementation as a public health measure to detect tumor or aneurysm. Despite this, MRI's sensitivity when chosen to examine a previously known or suspected structural abnormality, such as with clinically symptomatic stroke or MS, remains excellent.

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