Editorial

Incidental Findings on Brain Magnetic Resonance Imaging: Who is in Charge?

We call the detection of cranial anatomic abnormalities “incidental”, if it is unexpected and unrelated to the purpose of the scan and current clinical symptoms. Among these abnormalities are findings that are completely harmless like a certain eye color (A, no referral required), others that may become clinically relevant under specific conditions (B, routine referral required), and others that may bear a risk for the patient’s health (C, urgent referral recommended). Category A incidental findings are, e.g., visible single perivascular spaces, falcial calcification, developmental venous anomalies, choroid plexus cysts, enlarged cisterna magna, and a slight increase in signal of the posterior limb of the internal capsule on T2-weighted spin echo sequences. Category B incidental findings become clinically relevant in the presence of specific symptoms, but are otherwise harmless like sinusoidal soft tissue swelling, white matter lesions, arachnoid cysts with and without partial aplasia of brain tissue, pineal gland cysts, brain volume loss, prominent brain arteries, and the asymmetry of cerebral hemispheres or ventricles. Category C incidental findings are asymptomatic brain infarcts, arteriovenous malformations, cavernous hemangiomas, aneurysms, tumors, e.g., meningiomas, schwannomas, and pituitary adenomas, which could remain undetected and clinically silent for years.

Incidental findings could be a real challenge for the examiner and require all his or her experience. The examiner has to differentiate between anatomic variants and brain pathology. If brain pathology is detected, the examiner should decide whether this finding is really incidental and not related to less obvious symptoms, e.g., slight cognitive impairment, and whether or not the pathology may represent a disease that could harm the patient later on. It has to be considered whether so far asymptomatic brain disease can or should be treated. In the research domain, MR images are not diagnostic and researchers often not trained in evaluating the MRI of brain anatomy and pathology. Incidental findings are frequent, however, and detected in up to 37% of asymptomatic volunteers with MRI [1]. A considerable proportion may require urgent referral, in particular in younger research subjects [2–4]. Incidental findings unexpected for the researchers are then either ignored or misinterpreted. The consequences for the patient or the research volunteer might be a missed diagnosis of a treatable disease or unnecessary further examinations and even treatment attempts accompanied by the unjustified fear to suffer from brain disease. This happens, if all these images are not evaluated with neuroradiologic care and experience. Moreover, the question whether incidental findings might influence brain research results cannot be answered by a researcher inexperienced in diagnostic MRI.

I cannot follow Heinemann et al. who regard the involvement of neuroradiologist desirable, but beyond the scope of brain research with MRI [5]. By contrast, the National Institutes of Health, Bethesda, MD, USA, requires clinical neuroradiologic diagnostics in addition to brain research imaging [6]. According to a survey by Illes et al., neuroradiologist involvement is a requirement by the institutional review board (IRB) for 22% (11/49) of laboratories reporting on this question [7]. Where neuroradiologist involvement is not required by the IRB, neuroradiologists nonetheless evaluate 13% of the scans all the time and 69% of scans with suspicious findings.

It is timely that German neuroradiologists consider their role and responsibility in brain research with MRI. Furthermore, incidental findings are only one aspect among various ethical and juridical problems in fMRI research. The article by Daniela Seixas & Margarida Ayres Basto in this issue of Clinical Neuroradiology gives an excellent overview [8]. The recent article by Schleim et al. clearly outlines the juridical questions [9]. Theirs reading is highly recommended.

Neuroradiologists, let us take a lead in these issues. Who else can do it?

References

1. Illes J, Desmond JE, Huang LF, et al. Ethical and practical considerations in managing incidental findings in functional magnetic resonance imaging. Brain Cogn 2002;50:358–65.
2. Katzman GL, Dagher AP, Patronas NJ. Incidental findings on brain magnetic resonance imaging fro 1000 asymptomatic volunteers. JAMA 1999;282:36–9.
3. Illes J, Rosen AC, Huang L, et al. Ethical consideration of incidental findings on adult brain MRI in research. Neurology 2004;62:888–90.
4. Weber F, Knopf H. Incidental findings in magnetic resonance imaging of the brains of healthy young men. J Neurol Sci 2006;240:81–4.
5. Heinemann T, Hope C, Listl S, et al. Zufallsbefunde bei bildgebenden Verfahren in der Hirnforschung. Dtsch Ärztebl 2007;104:1684–9.
6. Check E. Brain-scan ethics come under the spotlight. Nature 2005; 433:185.
7. Illes J, Kirschen MP, Karetsky K, et al. Discovery and disclosure of incidental findings in neuroimaging research. J Magn Reson Imaging 2004;20:743–7.
8. Seixas D, Ayres Basto M. Ethics in fMRI studies: a review of the EMBASE and MEDLINE literature. Clin Neuroradiol 2008;18:79–87.
9. Schleim S, Spranger T, Urbach H, et al. Zufallsfunde in der bildgebenden Hirnforschung. Empirische, rechtliche und ethische Aspekte. Nervenheilkunde 2007;26:1041–5.

Rüdiger von Kummer, Dresden