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With the advent of high-resolution, state-of-the-art MRI, the prevalence of subclinical, asymptomatic brain abnormalities is growing, according to findings reported in the New England Journal of Medicine. With the advent of high-resolution, state-of-the-art MRI, the prevalence of subclinical, asymptomatic brain abnormalities is growing, according to findings reported in the New England Journal of Medicine for November 1.

"This study was performed in the asymptomatic general population aged 45 years and older," Dr. Aad van der Lugt told Reuters Health. "The Rotterdam Scan Study is embedded in an ongoing population-based cohort study (the Rotterdam Study).

The participants were scanned between 2005 and 2007, "with the primary aim of investigating structural and functional brain changes that occur with aging and to investigate their determinants and consequences."

The study cohort was 2000 persons aged 46 to 97 years. Asymptomatic brain infarcts were the most common abnormalities (n = 145, 7.2 per cent), according to the research team, based at Erasmus MC University Medical Center. Other lesions included cerebral aneurysms (n = 35, 1.8 per cent) and benign primary tumors (n = 31, 1.6 per cent).

"The tumors were classified as benign based on typical radiological characteristics, such as the location, shape and signal intensity on MRI," Dr. van der Lugt said. Tumors deemed to be benign included meningiomas, vestibular schwannomas, intracranial lipomas, pituitary adenomas, and one trigeminal schwannoma.

However, "indication for surgery or other medical treatment of incidental brain findings can never be based on imaging alone," the investigator warned. "Persons who exhibited potentially clinically relevant findings on MRI were referred to medical specialists."

One subject had a possibly malignant low-grade glioma, and one case of cerebral metastases occurred in a person undergoing treatment for lung cancer. Two subjects were referred for surgery to treat a "large, chronic subdural hematoma" and a 12-mm aneurysm of the medial cerebral artery.

"Some incidental findings warrant follow-up imaging," Dr. van der Lugt said. "Most benign tumors have a slow rate of growth and can be monitored using follow-up imaging. Follow-up is normally done after one year, using MRI."

He suggested that their observations are most pertinent to research studies. As such, he proposed that "the informed consent of the research study should include information on the possibility of detecting incidental brain findings and participants should be able to opt out on being informed of the existence of such brain abnormalities."

He emphasized that "imaging studies should comprise a protocol for the reading of brain scans by professionals and for the management of such incidental brain findings.