title: Cranial arachnoid protrusions and contiguous diploic veins in CSF drainage.
abstract: OBJECTIVE
  Studies have suggested that arachnoid villi or granulations found in the walls of the cranial dural sinuses, olfactory mucosa, and cranial nerve sheaths function as outlets for intracranial CSF. However, their role as CSF outlets has not yet been verified. Here we show that arachnoid protrusions and contiguous diploic veins provide an alternative drainage route for intracranial CSF.
  
  
  METHODS
  Four hundred patients with intact skull, dura mater, and dural sinuses underwent MR imaging to explore arachnoids protruding into the skull and diploic veins. Patients with symptoms of increased intracranial pressure or intracranial hypotension were excluded. For 15 patients undergoing craniotomy, both peripheral and diploic venous blood was collected. Albumin and the CSF-specific biomarkers were measured by enzyme-linked immunosorbent assay.
  
  
  RESULTS
  With MR imaging, arachnoid protrusions into the skull and contiguous diploic veins were consistently identified throughout the cranium with their characteristic appearance depending on the cranial region. In addition, elevated amounts of prostaglandin D synthase and cystatin C were confirmed in diploic veins compared with peripheral venous blood.
  
  
  CONCLUSIONS
  Diploic veins are distributed ubiquitously throughout the cranium. A portion of the intracranial CSF may be drained through arachnoid protrusions and contiguous diploic veins.
authors.affiliation: From the Department of Neurological Surgery (S.T., Y.Y., M.I.), Juntendo University Urayasu Hospital, Chiba, Japan shotaro@juntendo-urayasu.jp.
authors.forename: S
authors.initials: S
authors.lastname: Tsutsumi
authors.affiliation: Department of Neurological Surgery (I.O., M.M., H.A.), Juntendo University School of Medicine, Tokyo, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Ogino
authors.affiliation: Department of Neurological Surgery (I.O., M.M., H.A.), Juntendo University School of Medicine, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Miyajima
authors.affiliation: Division of Radiological Technology (M.N.), Medical Satellite Yaesu Clinic, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: From the Department of Neurological Surgery (S.T., Y.Y., M.I.), Juntendo University Urayasu Hospital, Chiba, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Yasumoto
authors.affiliation: Department of Neurological Surgery (I.O., M.M., H.A.), Juntendo University School of Medicine, Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Arai
authors.affiliation: From the Department of Neurological Surgery (S.T., Y.Y., M.I.), Juntendo University Urayasu Hospital, Chiba, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Ito
mesh_terms: D000328:Adult; D000368:Aged; D001099:Arachnoid / Q000033:anatomy & histology* / Q000502:physiology*; D002555:Cerebrospinal Fluid / Q000502:physiology*; D004388:Dura Mater / Q000098:blood supply; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014680:Veins / Q000033:anatomy & histology* / Q000502:physiology*