Michael Eller; Peter J Goadsby


Expert Rev Neurother. 2013;13(3):263-273. 

In This Article

MRI of the Brain in the General Population

Looking at people within the general population is indispensable as a guide to the baseline frequency of incidental findings on imaging. One study looked at over 2500 air force recruits with a mean age of 20.5 years,[19] comparable in age of symptom onset of many headache patients.[14] All had a normal neurological examination, and were asymptomatic. A 1.0-T device was used, and magnetic resonance angiography and/or gadolinium contrast were used to help confirm 'suspicious' findings in 8% of scans. A total of 6.5% of the patients had abnormal findings, listed in Table 1. Arachnoid cysts were found in 1.7% of patients, none requiring intervention; vascular abnormalities occurred in 0.51% of patients, including five arteriovenous malformations and three cavernomas – none of these required acute treatment. No cerebral aneurysms were found, which was less than the expected 2%.[20] Intracranial tumors were found in 0.47% of patients, including a low grade glioma, hypophyseal adenoma and lipoma – none required intervention aside from serial scanning. This is similar to extant prevalence estimates.[21] No meningioma was seen, consistent with the age-related incidence of this tumor.[22] Type 1 Chiari malformations were seen in 0.24% of the patients, and one patient was found to have lesions consistent with demyelination. A further 18.45% of the patients had findings that represent normal variations; these 'incidentalomas' included occasional white matter lesions (2.6%), enlarged perivascular spaces (2.6%) and pineal cysts (3.4%).

A meta-analysis of over almost 20,000 asymptomatic people who underwent brain MRI demonstrated a 0.7% prevalence of an intracranial neoplasm (95% CI: 0.47–0.90%). Non-neoplastic lesions, excluding white matter changes, were found in 2% of the patients (95% CI: 1.1–3.1%). The prevalence of neoplastic lesions, silent infarcts and white matter changes all increased with age. Non-neoplastic lesions, excluding white matter changes and infarcts, reached their highest prevalence in the 50–69 year age group.[23]

The conclusion that the incidence of incidental findings on MRI are contingent upon age was supported by the Rotterdam Study, which involved 2000 participants. They had been followed since 1990 (mean age: 63 years; range: 46–97 years), and were investigated with a 1.5-T device: asymptomatic brain infarcts were present in 7.2%, aneurysms were seen in 1.8% and brain tumors in 1.6%, mostly meningiomas (Table 2). An age-related increase in the volume of white matter lesions was noted,[24] a finding that is also more prevalent in some patients with migraine, as outlined below.