Dural arteriovenous fistulae (DAVF) is a rare but potentially devastating vascular disorder of the central nervous system, with ocular manifestations such as papilledema and visual decline being major causes of long-term disability in affected patients 1-3. The pathophysiological link between DAVF-related venous hypertension, elevated intracranial pressure, and optic nerve injury has long been recognized, yet the lack of objective, non-invasive imaging biomarkers to quantify optic nerve involvement and predict visual outcomes has hindered timely risk stratification and personalized treatment 1, 3. This gap underscores the clinical urgency of identifying reliable imaging tools to guide management and preserve vision in DAVF patients. In this issue of Journal of Magnetic Resonance Imaging, Kumar et al. investigated the value of sagittal 3D FLAIR MRI-derived optic nerve signal intensity ratios (SIR) in DAVF patients 4. The single-center retrospective study enrolled 54 DAVF patients (27 with papilledema, 27 without) and 27 matched healthy controls, analyzing 162 optic nerves with a focus on segmental signal alterations and their correlation with papilledema, visual decline, and post-embolization outcomes. The primary results are profoundly significant: optic nerve SIR, particularly in the intracanalicular segment, differs significantly across groups, with the highest values observed in patients with visual deterioration; an SIR cutoff of 1.7 predicts papilledema with visual loss with 79.2% sensitivity and 63.3% specificity; and 3D FLAIR imaging demonstrates excellent interobserver reproducibility (Cohen's κ = 0.84, ICC = 0.81). Additionally, post-embolization follow-up showed that 23.1% of visually impaired patients improved, while 61.5% stabilized, highlighting the potential of SIR to track treatment response. This study makes several contributions to DAVF management. First, it validates 3D FLAIR MRI as an alternative tool for detecting optic nerve involvement in DAVF, extending the application of this sequence, traditionally used for demyelinating and inflammatory neuropathies, to vascular causes of optic nerve injury 5, 6. The identification of the intracanalicular segment as the most sensitive site for signal changes aligns with biomechanical models of papilledema, where the rigid optic canal forms a pressure bottleneck, making this segment the earliest and most reliable indicator of nerve compromise. Second, the quantification of SIR using the ipsilateral temporalis muscle as a reference provides an objective, reproducible metric that complements subjective fundus evaluation and angiographic grading, addressing the limitations of current clinical assessments. Third, the study establishes a clinically actionable SIR threshold, offering a practical screening tool to identify patients at high risk of visual deterioration who may benefit from early intervention, such as endovascular embolization or adjunctive CSF diversion. Despite these strengths, several limitations should be acknowledged to the findings. The retrospective, single-center design introduces inherent selection bias and limits generalizability, emphasizing the need for prospective, multi-center validation to confirm the SIR cutoff and its clinical utility across diverse populations. The manual placement of regions of interest may introduce operator-dependent variability, and automated segmentation techniques, such as deep learning-based tools, could enhance reproducibility in future studies. Additionally, the lack of uniform optical coherence tomography (OCT) data prevents integration of retinal nerve fiber layer thickness, a well-established structural marker of optic nerve injury, which would strengthen the correlation between imaging findings and functional visual outcomes. Finally, the relatively modest follow-up duration (mean 1.7 years) limits insights into long-term visual prognosis and the durability of treatment-related changes in SIR. Future research should build on these findings to address these gaps and expand the clinical application of 3D FLAIR-derived SIR. Prospective studies with standardized imaging protocols, concurrent OCT assessments, and longer follow-up are needed to validate the predictive value of SIR for delayed visual decline and recurrence. Investigations into alternative reference tissues and the integration of SIR with angiographic features may further refine risk stratification algorithms 7. Additionally, exploring the utility of 3D FLAIR in other venous outflow disorders associated with papilledema, such as cerebral venous sinus thrombosis and idiopathic intracranial hypertension, could establish SIR as a generic biomarker of pressure-related optic neuropathy, transcending disease-specific etiologies. In conclusion, this study demonstrates that sagittal 3D FLAIR MRI-derived intracanalicular SIR serves as a valuable, non-invasive imaging biomarker for assessing optic nerve involvement in DAVF. It correlates significantly with papilledema and visual decline while also effectively tracking treatment response. By addressing the current lack of objective imaging tools for DAVF-related visual impairment, this approach has the potential to reshape clinical practice, from early risk stratification to personalized treatment planning and long-term monitoring.
Luguang Chen (Wed,) studied this question.