title: Abnormal hyperintensity within the subarachnoid space evaluated by fluid-attenuated inversion-recovery MR imaging: a spectrum of central nervous system diseases.
abstract: A variety of central nervous system (CNS) diseases are associated with abnormal hyperintensity within the subarachnoid space (SAS) by fluid-attenuated inversion-recovery (FLAIR) MR imaging. Careful attention to the SAS can provide additional useful information that may not be available with conventional MR sequences. The purpose of this article is to provide a pictorial essay about CNS diseases and FLAIR images with abnormal hyperintensity within the SAS. We present several CNS diseases including subarachnoid hemorrhage, meningitis, leptomeningeal metastases, acute infarction, and severe arterial occlusive diseases such as moya-moya disease. We also review miscellaneous diseases or normal conditions that may exhibit cerebrospinal fluid hyperintensity on FLAIR images. Although the detection of abnormal hyperintensity suggests the underlying CNS diseases and narrows differential diagnoses, FLAIR imaging sometimes presents artifactual hyperintensity within the SAS that can cause the misinterpretation of normal SAS as pathologic conditions; therefore, radiologists should be familiar with such artifactual conditions as well as pathologic conditions shown as hyperintensity by FLAIR images. This knowledge is helpful in establishing the correct diagnosis.
authors.affiliation: Department of Radiology, Mie University School of Medicine, 2-174 Edobashi, Tsu, 514-8507 Mie, Japan. mmaeda@clin.medic.mie-u.ac.jp
authors.forename: Masayuki
authors.initials: M
authors.lastname: Maeda
authors.forename: Akira
authors.initials: A
authors.lastname: Yagishita
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Hajime
authors.initials: H
authors.lastname: Sakuma
authors.forename: Kan
authors.initials: K
authors.lastname: Takeda
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D020520:Brain Infarction / Q000175:diagnosis; D002493:Central Nervous System Diseases / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D018810:Magnetic Resonance Angiography; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008577:Meningeal Neoplasms / Q000175:diagnosis; D008581:Meningitis / Q000175:diagnosis; D008875:Middle Aged; D012680:Sensitivity and Specificity; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis; D013346:Subarachnoid Space / Q000473:pathology