Towards a Deeper Understanding of Cerebrospinal Fluid Transport in the Optic Nerve Subarachnoid Space: A Computational Approach.

Cerebrospinal fluid (CSF) dynamics within the optic nerve subarachnoid space (ONSAS) are increasingly recognised as potential factors contributing to the pathogenesis of optic neuropathies, including normal-tension glaucoma (NTG) and idiopathic intracranial hypertension (IIH). In this study, high-resolution T2-weighted magnetic resonance imaging (MRI) data were manually segmented and processed for greyscale analysis and pixel-intensity mapping, enabling anatomically accurate three-dimensional reconstructions of the ONSAS. These reconstructions were imported into OpenFOAM software for computational fluid dynamics (CFD) simulations, incorporating physiologically realistic inlet pressure waveforms, boundary conditions, tissue porosity, and lymphatic drainage characteristics in the near optic nerve head portion of ONSAS, called the distal portion. Solver selection in OpenFOAM was optimised for the narrow geometry and unique boundary features of the ONSAS, yielding high-resolution maps of CSF flow dynamics. Multiple drainage scenarios were simulated to represent healthy, NTG, and IIH conditions. Area-averaged CSF velocities were quantified for each condition and compared with the scarce and available values reported in phase-contrast MRI (PC-MRI) studies. The results provide novel, physiologically relevant insights into CSF transport behaviour in the ONSAS under different physiological and pathophysiological conditions, with potential implications for the diagnosis, management, and treatment of optic neuropathies.