Transorbital optic nerve sheath ultrasonography in normal children

AIM: Early diagnosis of acute intracranial hypertension is essential to ena ble prompt, optimal treatment. The optic nerve sheath diameter (ONSD) is in creased in raised ICP and there has been recent interest in the use of ultr asound to diagnose and indirectly monitor raised ICP by ONSD measurement,Th e advantages of the technique include its non-invasiveness, wide availabili ty, portability, low cost and the absence of ionizing radiation. This prosp ective study was designed to establish the range of normal values for ONSD in infants and children up to 15 years of age. PATIENTS AND METHODS: One hundred and two children attending the hospital f or other reasons were recruited to the study. Three measurements of the ONS D were taken for each eye, 3 mm behind the optic nerve head using a 7 MHz s ector 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 groupe d and analysed, a correlation between increasing age and increasing ONSD wa s seen (r(2) = 0.48), with the greatest increase occurring in the first 2 m onths of life. CONCLUSION: Using the technique described here, our results suggest that an ONSD of greater than 4 mm in infants less than I year, and 45 mm or greate r in older children, should be regarded as abnormal. Ballantyne, J. et al. (1999) Clinical Radiology 54, 740-742. (C) 1999 The Royal College of Radiol ogists.