title: Brain herniations into arachnoid granulations: about 68 cases in 38 patients and review of the literature.
abstract: BACKGROUND
  Brain herniations (BH) into arachnoid granulations (AG) in dural venous sinuses and calvarium have rarely been reported in the literature.
  
  
  METHODS
  MRIs of 38 patients with BH into AG (BHAG) were retrospectively analyzed. Locations of BHAG, gyrus/lobe of the herniated brain, parenchymal abnormalities of the BH, and clinical and radiological conditions with raised intracranial pressure were recorded.
  
  
  RESULTS
  Sixty-eight BHAG were found, by order of frequency, in the occipital squama (OS), transverse sinus (TS), lateral lacuna of the superior sagittal sinus (LLSSS), and straight sinus (SS), with cerebellar tissue being the most frequently involved in BHAG (94.5 % of OS, 55 % of TS, 100 % SS BHAG). Multiple BHAG were found in 58 % of the patients (up to five per patient). Parenchymal signal and structural changes (SSCG) were observed in 46 % of BHAG (100 % were cerebellar). Three patients had pseudotumor cerebri (PTCS); one patient had only MRI signs of PTCS. Twenty-one percent of patients had intracranial conditions susceptible of increasing cerebrospinal fluid (CSF) pressure other than PTCS.
  
  
  CONCLUSIONS
  BHAG occurred in the OS, TS, LLSSS, and the SS. SSCG of the herniated cerebellum were frequent and possibly result from tethering/strangulation in the AG. No symptoms could be clearly attributed to BHAG, though in three cases of PTCS, TS BHAG could have contributed to sustaining the raised CSF pressure. Various factors are probably involved in the development of BHAG including normal pia-arachnoid bridges between the brain surface and the AG, hydrodynamic constrains on the brain and AG, and, in some cases, increased intracranial pressure.
authors.affiliation: Unité de neuroradiologie, Service d'imagerie diagnostique et interventionnelle, Hôpital de Sion, CHVR, Avenue du Grand-Champsec 80, 1950, Sion, Switzerland.
authors.forename: Sonaz
authors.initials: S
authors.lastname: Malekzadehlashkariani
authors.affiliation: Zentrum für Neuroradiologie, Klinik Hirslanden, Zurich, Switzerland.|Institutes für Diagnostische und Interventionelle Radiologie und Neuroradiologie, Universitätsklinikum Essen, Essen, Germany.
authors.forename: Isabel
authors.initials: I
authors.lastname: Wanke
authors.affiliation: Zentrum für Neuroradiologie, Klinik Hirslanden, Zurich, Switzerland.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Rüfenacht
authors.affiliation: Unité de neuroradiologie, Service d'imagerie diagnostique et interventionnelle, Hôpital de Sion, CHVR, Avenue du Grand-Champsec 80, 1950, Sion, Switzerland. diego.san-millan-ruiz@hopitalvs.ch.|Zentrum für Neuroradiologie, Klinik Hirslanden, Zurich, Switzerland. diego.san-millan-ruiz@hopitalvs.ch.
authors.forename: Diego
authors.initials: D
authors.lastname: San Millán
mesh_terms: D001099:Arachnoid / Q000000981:diagnostic imaging / Q000473:pathology*; D002531:Cerebellum / Q000000981:diagnostic imaging / Q000473:pathology*; D002550:Cerebral Veins / Q000000981:diagnostic imaging* / Q000473:pathology*; D004677:Encephalocele / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Acquired meningo-encephalocele; Arachnoid granulations; Brain herniation; Parenchymal abnormalities