Abstract: Objective · To explore the frequency, nondetection rate, and clinical importance of incidental extracerebral findings (IECFs)on brain nonenhanced magnetic resonance imaging(MRI).  Methods · The MRI data of  7 930 cases with suspected intracerebral lesionin were retrospectively analyzed. IECFs were categorized as E1 (clinically unimportant, e.g., sinus mucosal thickening), E2 (likely unimportant, e.g.,pharyngeal mucosal symmetrical thickening), and E3 (potentially important, e.g., pharyngeal mucosal asymmetrical thickening). The nondetection rate was determined by comparing the results of the structured approach with the initial MRI reports. The medical records were examined for patients with E3 IECFs to assess clinical importance and outcome of these lesions.  Results · A total of 5 992 IECFs were found in 4 213 patients (53.13%, 4 213/7 930). IECFs with E1 was 82.2% (4 924/5 992), E2 was 16.6% (995/5 992) and E3 1.2% (73/5 992). Overall IECFs and E1 findings were occurred more commonly in male patients (P=0.000, P=0.024). And the statistically significant difference was also found among different age groups (P=0.000). The nondetection rate was 56.9% (3 409/5 992) for overall IECFs and 32.9% (24/73) for E3 IECFs. Of the 73 patients with E3 IECFs, 34 (46.6%) received final diagnosis and appropriate treatment during the study period.  Conclusion · IECFs are prevalent in clinical patients on brain MRI with a nondetection rate of 32.9% for potentially important (E3) findings. The reporting of IECFs according to clinical importance is helpful for patients’ management.

Key words:  incidental findings, cerebral, magnetic resonance imaging, incidence