Study population
This retrospective observational study was conducted in the period from January 2017 to November 2019. It included 753 adult patients (389 {51.7%} males and 364 {48.3%} females), with a mean age of {± SD} 49.8 years {± 18.68}, age range (18–96 years). They were referred to radiology department for MRI scanning of the orbits, paranasal sinuses (PNS), or petrous temporal bones. Patients were referred with a variety of symptoms including nasal obstruction, sinus headache, proptosis, local orbital swellings, and hearing problems. Initial scans included axial FLAIR and axial T2WI of the whole brain. Upon spotting an incidental brain lesion during the initial review, the scan was extended following the standard brain MRI protocol described below. Inclusion criteria were the following: adult patients who were neurologically healthy with no clinical evidence of neurologic deficit. Exclusion criteria were the following: patients with incidental brain finding that might be related to patient’s chief complaint and scans significantly compromised by motion artifacts. Out of the 830 scans initially reviewed, 753 patients were finally included in the study. The study was approved by the local Research Ethics Committee on 24 November 2019, reference number of approval: 191119-RAD-12. All patients included in this study gave written informed consent to participate in this research.
Examination protocol
MRI scans were performed using a 1.5-Tesla unit (TOSHIBA, Excelart Vantage). Patients were scanned in the supine position using a 16-channel head coil. Before MR examination, patients were asked to remove any metallic objects around the head. Five hundred thirty-five patients received intravenous contrast agents according to the main indication of the scan.
The basic MRI scan protocol of the brain included
T1WI (TR = 464 m/s, TE = 12 m/s, FOV = 24 cm, NS = 20, matrix = 192 × 352 pixels), T2WI (TR = 4300 m/s, TE = 105 m/s, matrix = 256 × 448 pixels), and FLAIR (TR = 7200 m/s, TE = 100 m/s, TI = 2000 m/s, matrix = 192 × 352 pixels) were obtained in the axial plane using 5-mm contiguous scans. Sagittal T1WI (TR = 540 m/s, TE = 17 m/s, FOV = 25.6 cm, matrix = 192 × 320 pixels, ST = 4.6 mm), coronal T2WI (TR = 4280 m/s, TE = 105 m/s, FOV = 24 cm, matrix = 192 × 448 pixels, ST = 6 mm), and DWI (b = 1000, TR = 6800 m/s, TE = 120 m/s, FOV = 26 × 26 cm, matrix = 128 pixels, ST = 5.3 mm) were also obtained.
Assessment of incidental findings
Images were transferred by computer network to workstation (Aze Virtual Place FujinRaijin 310) on which images were carefully examined. A trained radiologist (with more than 10 years of experience in neuroradiology) examined the scans and recorded the presence of incidental findings. Patients having multiple similar findings were counted as one finding (e.g., multiple meningiomas), while patients having two different findings were counted separately.
Seven patients required referral to specialists (neurologist, oncologist) (5 patients with subdural collections “2 of which underwent surgical evacuation,” 1 patient with suspicious low-grade glioma (DENT), and 1 patient with suspicious metastatic deposits). Diagnosis of neoplastic lesions was based on the imaging findings and no histopathologic confirmation was obtained.
Nineteen patients with meningiomas, 6 patients with aneurysms, 9 patients with pituitary macroadenomas, and 11 patients with arachnoid cysts were also referred to specialists (neurologist, internist) for further assessment and long-term follow-up.
The rest of the patients were informed about their unexpected abnormalities and reassured.
Anatomic variants of no clinical significance like cavum septum pellucidum and lateral ventricles asymmetry, as well as empty sella turcica and dilated Virchow-Robin spaces (VRS) were not included in the study. The current study did not include white matter hyper-intensities or lacunar infarcts either, being prevalent in the old age group and considered by most authors to be a part of the normal aging process of the brain.
Statistical analysis
Results were analyzed using an IBM compatible personal computer with SPSS statistical package version 23 (SPSS Inc. Released 2015. IBM SPSS Statistics for Windows, version 23.0, Armnok, NY: IBM Corp).
Data was expressed in number (No), percentage (%), mean (x̅), and standard deviation (SD). Z test was used to compare two proportions in two groups. Two-sided P value of < 0.05 was considered statistically significant.