Comparative microanatomy and histology of spinal and cerebral veins: Implications for dural arteriovenous fistula clinical presentations

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Cranial dural arteriovenous fistulas (DAVFs) that display cortical venous drainage are at risk of hemorrhage, unlike spinal DAVFs, which seldom bleed. The underlying mechanism for this difference is poorly understood. We hypothesized that cerebral veins are more fragile than spinal veins due to differences in histologic compositions. Thus, spinal and cerebral veins from five formalin-fixed human cadavers were examined through macroscopic and histological analysis, using hematoxylin, eosin and safran (HES), and orcein stains to compare them. Twenty-four cerebral veins and thirteen spinal veins were analyzed. The mean diameter of the cerebral veins was 1.02 ± 0.59 mm, while that of spinal veins was 0.52 ± 0.26 mm (p = 0.003). The mean thickness of cerebral veins was similar to their spinal counterparts (0.09 ± 0.07 mm vs 0.06 ± 0.02 mm; p = 0.12). The mean diameter-to-thickness ratio was 13.76 ± 6.05 mm for cerebral veins and 10.06 ± 7.23 mm for spinal veins (p = 0.023). In most of the analyzed vessels, the venous wall was composed of endothelial cells resting on layers of smooth muscle, separated by elastica lamina. Cerebral and spinal veins exhibit distinct calibers while maintaining comparable wall thicknesses, resulting in a greater diameter-to-thickness ratio for cerebral veins compared to spinal veins. This difference may after their resistance to pressure. Furthermore, variations in the transparietal pressure gradient between cranial and spinal subarachnoid space, along with differences in arterial blood flow through the fistulous veins, might contribute to the observed differences in clinical presentation.