Saidha, Shiv

Abstract Background Recently, a posterior pathway for fluid drainage from the retina to the meningeal lymphatics in the optic nerve (ON) sheath was identified in rodents using intravitreal imaging tracers directly injected into the ocular-globe. Fluid and solute clearance along this pathway may be associated with many diseases. However, intravitreal tracers are rarely used in clinical imaging. As intravenous Gadolinium-based-contrast-agent (GBCA) can enter the globe via the blood-ocular-barriers, it may provide an alternative approach to image this pathway. Purpose To establish a clinically feasible intravenous GBCA-based MRI approach for tracking fluid and solute transport along the posterior lymphatic pathway in the ocular glymphatic system. Materials&Methods This prospective study was conducted from March 2021 to September 2022 in healthy participants. Dynamic-susceptibility-contrast-in-the-CSF (cDSC) MRI was performed before, immediately and 4 hours after intravenous-GBCA administration to track GBCA distribution in aqueous humor (AH) and cerebrospinal fluid (CSF) in regions-of-interest (ROIs) in the globe (anterior-cavity, vitreous-body), in the intraorbital and extraorbital ON, and in the intracranial CSF space proximal to the ON (chiasmatic-cistern, interpeduncular-cistern). Kruskal–Wallis tests with post-hoc Dunn’s tests were used for group comparisons. Results Sixteen healthy participants (mean age±SD: 51±21 years, 5 men) were recruited. Intravenous-GBCA enhancement was observed in all ROIs immediately after injection. At 4-hour-post-GBCA, the vitreous body showed a trend of smaller enhancement area (55±11% versus 49±11%, P =.14) and lower GBCA-concentration (0.044±0.014 versus 0.028±0.010 mmol/L, P =.07) compared to immediate-post-GBCA. The intraorbital ON showed more widespread enhancement (39±5% versus 59±6%, P =.01) and significantly higher GBCA-concentration (0.023±0.009 versus 0.059±0.015 mmol/L, P <.001) at 4-hour-post-GBCA. Conclusion Dynamic fluid and solute transportation along the posterior lymphatic pathway in the ocular glymphatic system in healthy participants was measured by tracking intravenous-GBCAs entering the globe via the blood-ocular-barriers using cDSC-MRI. Summary Statement Dynamic fluid and solute transportation along the posterior lymphatic pathway in the ocular glymphatic system in healthy participants was measured by tracking intravenous-Gadolinium-based-contrast-agents entering ocular-globe via blood-ocular-barriers using dynamic-susceptibility-contrast-in-the-CSF (cDSC)-MRI. Key Results In this prospective study of sixteen participants, Gadolinium-based-contrast-agent (GBCA)-induced signal changes were detected in the aqueous-humor and cerebrospinal fluid immediately following intravenous administration using dynamic-susceptibility-contrast-in-the-CSF (cDSC)-MRI. At 4-hour-post-GBCA, the vitreous-body showed a trend of smaller enhancement area (55±11% versus 49±11%, P =.14) and lower GBCA-concentration (0.044±0.014 versus 0.028±0.010 mmol/L, P =.07) compared to immediate-post-GBCA. The intraorbital-optic-nerve showed more widespread enhancement (39±5% versus 59±6%, P =.01) and higher GBCA-concentration (0.023±0.009 versus 0.059±0.015 mmol/L, P <.001) at 4-hour-post-GBCA.

ObjectivePatients with myelin oligodendrocyte glycoprotein antibody (MOG‐IgG)‐associated disease (MOGAD) suffer from severe optic neuritis (ON) leading to retinal neuro‐axonal loss, which can be quantified by optical coherence tomography (OCT). We assessed whether ON‐independent retinal atrophy can be detected in MOGAD.MethodsEighty patients with MOGAD and 139 healthy controls (HCs) were included. OCT data was acquired with (1) Spectralis spectral domain OCT (MOGAD: N = 66 and HCs: N = 103) and (2) Cirrus high‐definition OCT (MOGAD: N = 14 and HCs: N = 36). Macular combined ganglion cell and inner plexiform layer (GCIPL) and peripapillary retinal nerve fiber layer (pRNFL) were quantified.ResultsAt baseline, GCIPL and pRNFL were lower in MOGAD eyes with a history of ON (MOGAD‐ON) compared with MOGAD eyes without a history of ON (MOGAD‐NON) and HCs (p < 0.001). MOGAD‐NON eyes had lower GCIPL volume compared to HCs (p < 0.001) in the Spectralis, but not in the Cirrus cohort. Longitudinally (follow‐up up to 3 years), MOGAD‐ON with ON within the last 6–12 months before baseline exhibited greater pRNFL thinning than MOGAD‐ON with an ON greater than 12 months ago (p < 0.001). The overall MOGAD cohort did not exhibit faster GCIPL thinning compared with the HC cohort.InterpretationOur study suggests the absence of attack‐independent retinal damage in patients with MOGAD. Yet, ongoing neuroaxonal damage or edema resolution seems to occur for up to 12 months after ON, which is longer than what has been reported with other ON forms. These findings support that the pathomechanisms underlying optic nerve involvement and the evolution of OCT retinal changes after ON is distinct in patients with MOGAD. ANN NEUROL 2022;92:476–485