Sulcal hyperintensity on fluid-attenuated inversion recovery MR images in patients without apparent cerebrospinal fluid abnormality

OBJECTIVE. Failure to suppress cerebrospinal fluid (CSF) signal intensity ( sulcal hyperintensity) on fluid-attenuated inversion recovery (FLAIR) image s has been reported in patients with abnormal CSF such as those with mening itis and subarachnoid hemorrhage. Our study investigates the clinical histo ry and MR findings associated with sulcal hyperintensity on FLAIR images in patients without apparent CSF abnormality. SUBJECTS AND METHODS. Three hundred consecutive MR imaging examinations wer e prospectively screened for patients with sulcal hyperintensity on FLAIR i mages. Nine patients with clinical, CT, or laboratory evidence suggesting a bnormal CSF were excluded. The distribution of sulcal hyperintensity on FLA IR images and associated abnormal enhance ment were evaluated, The presence of the "dirty CSF" sign (mild increase in CSF signal on unenhanced T1-weig hted images or mild decrease on T2-weighted images) in the corresponding hy perintense sulcus was also assessed. RESULTS. Twenty-six (8.9%) of the 291 patients had sulcal hyperintensity (1 6 focal. 10 diffuse) associated with 18 masses (6.1%) and eight vascular ab normalities (2.7%). Sulcal hy perintensity was frequently associated with t he dirty CSF sign (69.2%) and abnormal contrast enhancement (overall, 96.2% ; 88.5%, leptomeningeal; 53.8%, vascular enhancement). CONCLUSION. Our study shows that sulcal hyperintensity on FLAIR imaging can occur in patients without apparent CSF abnormality. Its frequent associati on with mass effect, vascular disease, abnormal vascular enhancement, and d irty CSF sign suggests that an increase in blood pool, a small amount of pr otein leakage, and the "flow-entering" phenomenon of the congested blood ma y contribute to sulcal hyperintensity on FLAIR images.