MRI measurements of the normal pediatric optic nerve pathway. (February 2018) - Maresky, Hillel S.
Highlights: No age-appropriate reference value or range of normal values for optic nerve diameter exists in the literature. Measuring the optic pathway can be a critical diagnostic tool to predict neurologic pathology. One-hundred and thirty-seven orbital optic nerve (OON), prechiasmic optic nerve (PON) and optic tracts (OT) were measured. The OON/OT ratio maintained a steady mean value 1 (IQR = 0.93–1.1) regardless of age (p = .7). There is a positive correlation between age and mean diameter measurements of optic pathways. Abstract: The purpose of this work is to establish a reference scale of optic nerve pathway measurements in pediatric patients according to age using MRI. Optic nerve pathway measurements were retrospectively analyzed using an orbits equivalent sequence on brain MRI scans of 137 pediatric patients (72 male, 65 female, average age = 7.7 years, standard deviation = 5.3). The examinations were performed on a 1.5-T or 3-T Siemens MR system using routine imaging protocols. Measurements include diameters of the orbital optic nerves (OON), prechiasmatic optic nerves (PON), optic tracts (OT), and optic chiasm (OC). Measurements were performed manually by 2 neuroradiologists, using post-processing software. Patients were stratified into five age groups for measurement analyses: (I) 0–1.49 years, (II) 1.5–2.99 years, (III) 3–5.99 years, (IV) 6–11.99 years, and (V) 12–18 years. The observed value range of OON mean diameter was 2.7 mm (Interquartile range (IQR) = 2.4–2.9), PON was 3.2 mm (IQR = 3.05–3.5), OT 2.6 mm (IQR = 2–2.9). A strong positive correlation was established between age and mean diameter of OON (r = 0.73, p < .001), PON (r = 0.59, p < .001), and OT (r = 0.72, p < .001). A significant difference in mean OON diameters was found between age groups I–II (d = 0.3, p = .01), II–III (d = 0.5, p < .001), III–IV (d = 0.5, p < .001) followed by a plateau between IV-V (d = 0.l0, p = .19). OON/OT ratio maintained a steady mean value 1 (IQR = 0.93–1.1) regardless of age (p = .7). The diameter of optic pathways was found to increase as a function of age with consistent positive correlation between nerve and tract for all ages.