Satoshi Tsutsumi1, Hideo Ono2, Hisato Ishii3. 1. Department of Neurological Surgery, Juntendo University Urayasu Hospital, 2-1-1 Tomioka, Urayasu, Chiba, 279-0021, Japan. shotaro@juntendo-urayasu.jp. 2. Division of Radiological Technology, Medical Satellite Yaesu Clinic, Tokyo, Japan. 3. Department of Neurological Surgery, Juntendo University Urayasu Hospital, 2-1-1 Tomioka, Urayasu, Chiba, 279-0021, Japan.
Abstract
PURPOSE: The present study aimed to explore the glymphatic pathway in the intraorbital optic nerve (ON) using magnetic resonance imaging (MRI). METHODS: Following conventional MRI examination, a total of 89 outpatients underwent T2-weighted imaging in thin-sliced coronal and sagittal sections. Moreover, three injected cadaver heads were dissected. RESULTS: In the cadaver specimens, differences in appearance between the central and peripheral parts of the ON were not observed. On the axial T2-weighted MRI performed in the initial examination, the central part of the intraorbital ONs was delineated as a well-demarcated, linear hyperintense area in 19% of patients. On the thin-sliced serial coronal images, the hyperintense areas were identified on both sides in 91% of patients. They were delineated as continuous hyperintense areas in the ONs with an inconsistent appearance even in the same nerve. In 12.4% of patients, the areas were divided into the upper and lower parts by a horizontal septum, while others showed variable morphologies, lacking a septum. On thin-sliced sagittal images, hyperintense areas were identified in 46% of patients. CONCLUSION: Hyperintense areas in the intraorbital ON detected on T2-weighted sequences may involve a glymphatic pathway with perivascular spaces of the ON and central retinal artery. These may be collapsed and difficult to identify on surgical and cadaver specimens.
PURPOSE: The present study aimed to explore the glymphatic pathway in the intraorbital optic nerve (ON) using magnetic resonance imaging (MRI). METHODS: Following conventional MRI examination, a total of 89 outpatients underwent T2-weighted imaging in thin-sliced coronal and sagittal sections. Moreover, three injected cadaver heads were dissected. RESULTS: In the cadaver specimens, differences in appearance between the central and peripheral parts of the ON were not observed. On the axial T2-weighted MRI performed in the initial examination, the central part of the intraorbital ONs was delineated as a well-demarcated, linear hyperintense area in 19% of patients. On the thin-sliced serial coronal images, the hyperintense areas were identified on both sides in 91% of patients. They were delineated as continuous hyperintense areas in the ONs with an inconsistent appearance even in the same nerve. In 12.4% of patients, the areas were divided into the upper and lower parts by a horizontal septum, while others showed variable morphologies, lacking a septum. On thin-sliced sagittal images, hyperintense areas were identified in 46% of patients. CONCLUSION: Hyperintense areas in the intraorbital ON detected on T2-weighted sequences may involve a glymphatic pathway with perivascular spaces of the ON and central retinal artery. These may be collapsed and difficult to identify on surgical and cadaver specimens.