Brain Magnetic Resonance Imaging Scans of Asymptomatic Patients

Abstract

In a medical era governed by managed health care and scientific advances, physicians have placed increasing emphasis on disease prevention and early diagnosis. The benefits of such a strategy lie both in cost reduction, as it is generally much cheaper to prevent a disease than it is to treat its manifestations, and in treatment efficacy, as most diseases are more amenable to cure or amelioration at earlier time points in their progression. Examples of asymptomatic screening programs that have demonstrated benefits in terms of morbidity and mortality reduction are colorectal cancer with fecal occult stool samples, cervical cancer with Papanicolaou smears, breast cancer with mammography, prostate cancer with digital rectal examinations and prostate-specific antigen serum levels, and coronary artery disease with cholesterol measurements. While these successful programs have created an optimistic environment for the development of additional screening protocols, it is important to realize that early detection programs may have negative consequences, and only in circumstances where such sequelae are outweighed by benefits should such a program be implemented. To this end, Vernooij et al. (N Engl J Med 357:1821–1828, 2007) reviewed the incidental findings on brain magnetic resonance imaging (MRI) scans in 2000 patients. Asymptomatic brain infarcts were present in 145 (7.2%) patients. Among findings other than brain infarcts, aneurysms (1.8%) were the most frequent. All aneurysms except two were located in the anterior circulation, and all except three were less than 7 mm in diameter. Four aneurysms had an intracavernous location. Benign tumors were also frequent (1.6%), with meningiomas being recorded most often (0.9%). A pituitary macroadenoma was present in six patients (0.3%). Vestibular schwannomas had a prevalence of 0.2%. One probable malignant primary brain tumor (low-grade glioma) and one case of multiple cerebral metastases in a patient who, in retrospect, was found to have been treated for lung cancer were discovered. The finding that was most urgent medically was a large, chronic subdural hematoma in an otherwise asymptomatic person, who was found to have had minor head trauma 4 weeks prior. The prevalence of asymptomatic brain infarcts increased with age. The prevalence of meningiomas increased from 0.5% in patients aged 45 to 59 years to 1.6% in patients aged 75 years or older. Aneurysms showed no change in prevalence with age. Although asymptomatic brain MRI scans appear to have benefits, upon closer analysis it becomes clear that these scans should not be recommended for screening healthy populations for reasons of low prevalence, poor predictive value, unequal accessibility, limited effectiveness of intervention, and disproportionate allocation of health care resources. Moving forward, however, brain imaging may have a role in the assessment of cerebrovascular disease, just as recognizing asymptomatic brain infarcts may help identify populations at risk for future ischemic events and allow the initiation of prophylactic life-style modification and medical therapy. Other pathologies may be uncovered, which, in retrospect, were associated with subtle or misinterpreted symptoms such as transient ischemic attacks or partial complex seizures.FIGURE: Magnetic resonance imaging scans revealing asymptomatic cerebrovascular anomaly.The present trend in medicine toward prevention and early diagnosis will continue to have a positive influence on the practice of health care. With the goals of improved cost-effectiveness and reduced morbidity and mortality, the emphasis has been placed on discovering underlying pathology before its overt manifestations. In order for a screening program to be of value to society, however, it must be applied in the proper context. Asymptomatic screening brain MRI scans regardless of age, health, or medical history is an example of an ineffective screening program that results in a high rate of inconsequential findings and an exceedingly low rate of discovering clinically significant abnormalities. Valuable screening programs must address either a highly prevalent disease or apply selectively to high-risk individuals, as well as accurately uncover a treatable disease entity. RICARDO J. KOMOTAR, MD E. SANDER CONNOLLY, JR., MD CLINICAL RESEARCH