title: Measurement of optic nerve sheath diameter by ultrasound: a means of detecting acute raised intracranial pressure in hydrocephalus.
abstract: OBJECTIVE
  To evaluate the utility of measuring the optic nerve sheath diameter in children with shunted hydrocephalus, suspected of having raised intracranial pressure.
  
  
  METHODS
  23 children with shunted hydrocephalus were examined, six had well controlled ICP, 17 however manifested symptoms suggestive of intracranial hypertension. A clinical history was taken from all patients and their parents or carers. The shunt valve was examined clinically, and signs of raised intracranial pressure were sought. Ultrasound examination was performed in both eyes to measure the optic nerve sheath diameters 3 mm behind the globe. These measurements were compared with control data obtained from 102 children who attended the radiology department for unrelated renal ultrasound examination.
  
  
  RESULTS
  Control data suggested that the upper limit of normal for optic nerve sheath diameter is 4.5 mm (measured 3 mm behind the globe) in patients over 1 year of age, and 4.0 mm in children less than 1 year of age. Those patients with functioning ventriculoperitoneal shunts had a mean optic nerve sheath diameter of 2.9 (SD 0.5) mm; those with raised intracranial pressure had a mean optic nerve sheath diameter of 5.6 (0.6) mm (p<0.0001). These results confirm that optic nerve sheath diameters in excess of the control data are strongly suggestive of raised intracranial pressure.
  
  
  CONCLUSIONS
  The evaluation of the optic nerve sheath diameter is a simple non-invasive procedure, which is a potentially useful tool in the assessment and monitoring of children with hydrocephalus suspected of having raised intracranial pressure.
authors.affiliation: Department of Ophthalmology, The Royal Hospital for Sick Children, Yorkhill, Glasgow G3 8SJ, UK. Bill_Newman@eyeweb.org.uk
authors.forename: W D
authors.initials: WD
authors.lastname: Newman
authors.forename: A S
authors.initials: AS
authors.lastname: Hollman
authors.forename: G N
authors.initials: GN
authors.lastname: Dutton
authors.forename: R
authors.initials: R
authors.lastname: Carachi
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D006801:Humans; D006849:Hydrocephalus / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D007223:Infant; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D007427:Intracranial Pressure; D009900:Optic Nerve / Q000000981:diagnostic imaging* / Q000473:pathology; D014463:Ultrasonography