Optic nerve sheath diameter on MR imaging: establishment of norms and comparison of pediatric patients with idiopathic intracranial hypertension with healthy controls.

Background and Purpose: IIH is a disorder associated with increased intracranial pressure with no clinical, laboratory, or radiologic evidence of an intracranial space-occupying lesion. The aim of this study was to establish ONSD standards of healthy pediatric subjects and compare the normal measurements with those of patients with IIH.
Materials and Methods: One hundred fifteen MR imaging studies of children 4 months to 17 years of age were blinded and reviewed by a pediatric neuroradiologist. A total of 230 optic nerves were measured. Eighty-six MR imaging examinations were performed in apparently healthy subjects. This control group included subjects who underwent MR imaging for various reasons, and their MR imaging findings were interpreted as normal. Twenty-nine MR imaging examinations were performed in patients with documented IIH. The ONSD was measured 1 cm anterior to the optic foramina on an axial T2 sequence. For statistical analysis, both patients and controls were stratified into 4 age groups (I, 0-3 years; II, 3-6 years; III, 6-12 years; IV, 12-18 years).
Results: The mean ONSD of the control group in all age groups (I, 3.1 mm; II, 3.41 mm; III, 3.55 mm; IV, 3.56 mm) was significantly smaller than the mean ONSD of patients (I, 4.35 mm; II, 4.37 mm; III, 4.25 mm; IV, 4.69 mm). A positive correlation between age and ONSD (r = 0.414, P < .01) was found in the control group.
Conclusions: According to our study, in pediatric patients with IIH, the ONSD is significantly larger than that in healthy controls regardless of age group and sex. This measurement might prove to be an auxiliary tool in the diagnosis of increased intracranial pressure in pediatric patients.