Normal measurements of the optic nerve, optic nerve sheath and optic chiasm in the adult population

Abstract

BackgroundImaging assessment of the anterior visual pathway structures, particularly the optic nerves (ON), requires knowledge of normal dimensions. Several studies suggesting techniques and normal ranges have been performed, but most suffer from various methodological flaws. This study is the first to be performed in a South African population.ObjectivesThe aim of this study was to establish normal measurements of the ON, optic nerve sheath (ONS) and optic chiasm (OC) on magnetic resonance imaging (MRI).MethodEighty normal adults between ages of 12 and 65 years were included in this prospective, quantitative, observational, descriptive study to establish normal measurement of the ON, ONS and OC using a T2W 3D MRI sequence. Measurements (width and height) were undertaken by two observers independently.ResultsA total of 80 participants with a mean age of 35 years were studied: 49 females (61.25%) and 31 males (38.75%). There were no statistical differences in the measurements between gender and age correlation. Interobserver agreement was best for larger structures, that is, OC width and intracranial ON width, respectively. The overall mean of OC width was 13.63 mm (range: 11.13 mm–16.92 mm, standard deviation [s.d.] 1.21); intraorbital ON height at 5 mm behind the globe 2.29 mm (range: 1.63 mm–3.33 mm, s.d. 0.43), and intracranial ON width 4.27 mm (range: 2.46 mm–5.19 mm, s.d. 0.53).ConclusionNormal measurements of the anterior visual pathway structures on MRI are best reflected in the larger structures. Interobserver variability was poor for the orbital ON, ONS, intracranial ON height and OC height. We recommend that measurements be obtained for the OC width and intracranial ON width. The overall mean for the OC width is 13.63 mm and intracranial ON width 4.27 mm.

High-resolution MRI assessment of optic nerve sheath diameter in adults: optic nerve sheath variation and a new diagnostic tool for intracranial hypertension

“…Using the ONSD as a technique to monitor ICP requires various additional factors to be considered. Previous studies have found that side of ONSD, sex, and age are not influencing factors in adults (8–11). Vaiman et al.…”

“…MRI and ultrasound have been widely used for the evaluation of ONSD (10,11,18,21,23–25). However, ultrasound-based measurements of ONSD can be adversely affected by examiner inexperience, an incorrect cutting plane, or poor spatial resolution (13).…”

Implementation of deep learning-based auto-segmentation for radiotherapy planning structures: a workflow study at two cancer centers

“…Furthermore, 23 of the 30 cases in this study that utilized the optic chiasm DC had MR images registered to their planning CT scan to help delineate this structure. An MR-based DC model for the optic chiasm and other CNS OARS are currently in development, but some degree of inter-observer variations will likely always be present [ 8 ].…”

“…Furthermore, 23 of the 30 cases in this study that utilized the optic chiasm DC had MR images registered to their planning CT scan to help delineate this structure. An MRbased DC model for the optic chiasm and other CNS OARS are currently in development, but some degree of inter-observer variations will likely always be present [8]. The mandible DC model was not evaluated in our previous validation study, but was included in this study since we hypothesized that the minimal anatomic variability in this structure would lead to high performance.…”

Optical Coherence Tomography Identifies Visual Pathway Involvement Earlier than Visual Function Tests in Children with MRI-Verified Optic Pathway Gliomas

“…Depending on the protocol for underlying pathology, slice thickness was 3–4 mm. The intraorbital part of the optic nerve was defined as normal according to normal values in the literature [ 20 , 21 , 22 ], especially when ectatic and elongated and in the absence of signs of intracranial hypertension, inflammatory or demyelinating disease. Tumor localization and extension according to PLAN score were compared to OCT findings.…”