title: Superficial subarachnoid cerebrospinal fluid space expansion after surgical drainage of chronic subdural hematoma.
abstract: BACKGROUND
  The present study examined the computed tomography (CT) findings after surgery and overnight drainage for chronic subdural hematoma (CSDH) to clear the significance of inner superficial subarachnoid CSF space and outer subdural hematoma cavity between the brain surface and the inner skull.
  
  
  METHODS
  A total of 73 sides in 60 patients were evaluated. Head CT was performed on the day after surgery and overnight drainage (1st CT), within 3 weeks of surgery (2nd CT), and more than 3 weeks after surgery (3rd CT). Subdural and subarachnoid spaces were identified to focus on density of fluid, shape of air collection, and location of silicone drainage tube, etc. Cases with subdural space larger than the subarachnoid CSF space were classified as Group SD between the brain and the skull. Cases with subarachnoid CSF space larger than the subdural space were classified as Group SA. Cases with extremely thin (<3 mm) spaces between the brain and the skull were classified as Group NS.
  
  
  RESULTS
  Group SA, SD, and NS accounted for 31.9, 55.6 and 12.5% of cases on the 1st CT. No statistical differences were found between Groups SA, SD, and NS in any clinical factors, including recurrence. Group SA were found significantly more on 1st CT than on 2nd and 3rd CT.
  
  
  CONCLUSIONS
  Subarachnoid CSF space sometimes expands between the brain and skull on CT after surgical overnight drainage. Expansion of the arachnoid space may be a passive phenomenon induced by overnight drainage and delayed re-expansion of the brain parenchyma.
authors.affiliation: Fujii Neurosurgical Hospital, Utsunomiya, Tochigi, Japan, nstosaka@gunma-u.ac.jp.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Tosaka
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Tsushima
authors.forename: Saiko
authors.initials: S
authors.lastname: Watanabe
authors.forename: Kazuya
authors.initials: K
authors.lastname: Sakamoto
authors.forename: Masahiko
authors.initials: M
authors.lastname: Yodonawa
authors.forename: Hideo
authors.initials: H
authors.lastname: Kunimine
authors.forename: Haruyasu
authors.initials: H
authors.lastname: Fujita
authors.forename: Takashi
authors.initials: T
authors.lastname: Fujii
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004322:Drainage; D005260:Female; D020200:Hematoma, Subdural, Chronic / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography; D013346:Subarachnoid Space / Q000000981:diagnostic imaging*; D013355:Subdural Space / Q000000981:diagnostic imaging*