title: Transorbital optic nerve sheath ultrasonography in normal children.
abstract: OBJECTIVE
  Early diagnosis of acute intracranial hypertension is essential to enable prompt, optimal treatment. The optic nerve sheath diameter (ONSD) is increased in raised ICP and there has been recent interest in the use of ultrasound to diagnose and indirectly monitor raised ICP by ONSD measurement. The advantages of the technique include its non-invasiveness, wide availability, portability, low cost and the absence of ionizing radiation. This prospective study was designed to establish the range of normal values for ONSD in infants and children up to 15 years of age.
  
  
  METHODS
  One hundred and two children attending the hospital for other reasons were recruited to the study. Three measurements of the ONSD were taken for each eye, 3 mm behind the optic nerve head using a 7 MHz sector probe.
  
  
  RESULTS
  The range for ONSD was 2.1-4.3 mm, mean 3.08 (SD 0.36). There were no significant differences on ONSD measurement between boys and girls (P = 0.59) or between right and left eyes (P=0.66). When the data were grouped and analysed, a correlation between increasing age and increasing ONSD was seen (r2=0.48), with the greatest increase occurring in the first 2 months of life.
  
  
  CONCLUSIONS
  Using the technique described here, our results suggest that an ONSD of greater than 4 mm in infants less than 1 year, and 45 mm or greater in older children, should be regarded as abnormal.
authors.affiliation: Department of Radiology, Royal Hospital for Sick Children, Yorkhill, Glasgow, UK.
authors.forename: J
authors.initials: J
authors.lastname: Ballantyne
authors.forename: A S
authors.initials: AS
authors.lastname: Hollman
authors.forename: R
authors.initials: R
authors.lastname: Hamilton
authors.forename: M S
authors.initials: MS
authors.lastname: Bradnam
authors.forename: R
authors.initials: R
authors.lastname: Carachi
authors.forename: D G
authors.initials: DG
authors.lastname: Young
authors.forename: G N
authors.initials: GN
authors.lastname: Dutton
mesh_terms: D000293:Adolescent; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D019586:Intracranial Hypertension / Q000000981:diagnostic imaging*; D008297:Male; D009186:Myelin Sheath / Q000000981:diagnostic imaging*; D009900:Optic Nerve / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D012016:Reference Values; D012680:Sensitivity and Specificity; D014463:Ultrasonography