title: The aqueduct of Sylvius: applied 3-T magnetic resonance imaging anatomy and morphometry with neuroendoscopic relevance.
abstract: BACKGROUND
  The aqueduct of Sylvius (AqSylv) is a structure of increasing importance in neuroendoscopic procedures. However, there is currently no clear and adequate description of the normal anatomy of the AqSylv.
  
  
  OBJECTIVE
  To study in detail hitherto unavailable normal magnetic resonance imaging morphometry and anatomic variants of the AqSylv.
  
  
  METHODS
  We retrospectively studied normal midsagittal T1-weighted 3-T magnetic resonance images in 100 patients. We measured widths of the AqSylv pars anterior, ampulla, and pars posterior; its narrowest point; and its length. We recorded angulation of the AqSylv relative to the third ventricle as multiple deviations of the long axis of the AqSylv from the Talairach bicommissural line. We statistically determined age- and sex-related changes in AqSylv morphometry using the Pearson correlation coefficient. We measured angulation of the AqSylv relative to the fourth ventricle and correlated this to the cervicomedullary angle (a surrogate for head position).
  
  
  RESULTS
  Patients were 13 to 83 years of age (45% male, 55% female). Mean morphometrics were as follows: pars anterior width, 1.1 mm; ampulla width, 1.2 mm; pars posterior width, 1.4 mm; length, 14.1 mm; narrowest point, 0.9 mm; and angulation in relation to the third and fourth ventricles, 26° and 18°, respectively. Age correlated positively with width and negatively with length of the AqSylv. There was no correlation between AqSylv alignment relative to the foramen magnum and the cervicomedullary angle.
  
  
  CONCLUSIONS
  Normative dimensions of the AqSylv in vivo are at variance with published cadaveric morphometrics. The AqSylv widens and shortens with cerebral involution. Awareness of these normal morphometrics is highly useful when stent placement is an option during aqueductoplasty. Reported data are valuable in guiding neuroendoscopic management of hydrocephalus and aqueductal stenosis.
authors.affiliation: *Section of Neuroradiology; and ‡Department of Neurosurgery, Addenbrooke's Hospital, Cambridge, United Kingdom; §Department of Radiology, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Matys
authors.forename: Avril
authors.initials: A
authors.lastname: Horsburgh
authors.forename: Ramez W
authors.initials: RW
authors.lastname: Kirollos
authors.forename: Tarik F
authors.initials: TF
authors.lastname: Massoud
mesh_terms: D000236:Adenoma / Q000601:surgery; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002535:Cerebral Aqueduct / Q000473:pathology* / Q000601:surgery; D015331:Cohort Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D044583:Neuroendoscopy / Q000379:methods*; D010911:Pituitary Neoplasms / Q000601:surgery; D012189:Retrospective Studies; D012727:Sex Characteristics; D055815:Young Adult