title: Ultrasound assessment of optic nerve sheath diameter in healthy volunteers.
abstract: BACKGROUND
  Ultrasound assessment of optic nerve sheath diameter (ONSD) has been suggested as a non-invasive measure of intracranial pressure. Numerous small studies suggest its validity; however, discrepancy exists around normal values for ONSD. In this study we sought to define a normal value range for ONSD in a population of healthy adult volunteers.
  
  
  METHODS
  ONSD was measured in healthy adult volunteers and a normal range was defined using descriptive statistics. A regression analysis was used to determine relationship between ONSD measurements and sex, age, height and weight.
  
  
  RESULTS
  One hundred twenty adults were recruited (age 18-65 [mean 29.3]) with 55 male and 65 female subjects. Mean ONSD was 3.68 mm (95% confidence interval [CI], 2.85-4.40). Upon regression analysis, mean ONSD did not vary with age, weight, or height but did vary with sex. Mean ONSD measurements for men were 3.78 mm (95% CI, 3.23-4.48) compared with 3.60 mm (95% CI, 2.83-4.11) for women.
  
  
  CONCLUSIONS
  This study has defined the range of ONSD in a healthy cohort of volunteers. The lack of relationship to age, weight and height is similar to other studies but this is the first study to find a difference depending on sex suggesting the possible need for separate reference ranges for men and women.
authors.affiliation: Department of Surgery, University of Manitoba, Winnipeg, MB, Canada. Electronic address: goeresp@myumanitoba.ca.
authors.forename: Patrick
authors.initials: P
authors.lastname: Goeres
authors.affiliation: Department of Surgery, University of Manitoba, Winnipeg, MB, Canada. Electronic address: umzeiler@cc.umanitoba.ca.
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Zeiler
authors.affiliation: Department of Medical Education, University of Manitoba, Winnipeg, MB, Canada. Electronic address: bertram.j.unger@gmail.com.
authors.forename: Bertram
authors.initials: B
authors.lastname: Unger
authors.affiliation: Department of Internal Medicine, University of South Carolina, Columbia, SC. Electronic address: karakitsosdimitrios@gmail.com.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Karakitsos
authors.affiliation: Department of Surgery, University of Manitoba, Winnipeg, MB, Canada. Electronic address: gillmanlm@yahoo.ca.
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Gillman
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001835:Body Weight; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009900:Optic Nerve / Q000000981:diagnostic imaging*; D012044:Regression Analysis; D012737:Sex Factors; D014463:Ultrasonography; D055815:Young Adult
keywords: Intracranial pressure; Optic nerve sheath diameter; Point of care ultrasound; Ultrasound