Reply:
======

* A.S. Larson
* W. Brinjikji

We read with interest the letter by Balak regarding our study. We appreciate the interest in our study. We agree that perhaps the right terminology is not to say that the occipital sinus regresses, because it is likely always persistent, but that it no longer plays a dominant role in the dural venous sinus drainage pathway. There have been numerous examples in the literature of embryonic sinuses (of which we consider the occipital sinus to be one) recanalizing or playing a dominant role in cerebral venous drainage due to the presence of arteriovenous shunting lesions or venous sinus thrombosis.1⇓-3 In this regard, the author is correct; in all likelihood, the occipital sinus is present but just does not have enough flow to be opacified on the MRV study.

## References

1.  1.Varma D, Reddy B, Rao R. Recanalization and obliteration of falcine sinus in cerebral venous sinus thrombosis. Neurology 2008;70:79–80 doi:10.1212/01.wnl.0000277449.59456.cf pmid:18166710
    
    [FREE Full Text](http://www.ajnr.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiRlVMTCI7czoxMToiam91cm5hbENvZGUiO3M6OToibmV1cm9sb2d5IjtzOjU6InJlc2lkIjtzOjc6IjcwLzEvNzkiO3M6NDoiYXRvbSI7czoxOToiL2FqbnIvNDIvNC9FMjguYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9) 

2.  2.Kawauchi T, Ikeda H, Miyakoshi A, et al. Occipital sinus dural arteriovenous fistula presenting with cerebellar hemorrhage. World Neurosurg 2019;131:116–19 doi:10.1016/j.wneu.2019.07.231 pmid:31398518
    
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3.  3.Tanaka J, Fujita A, Maeyama M, et al. Cognard type V dural arteriovenous fistula involving the occipital sinus. J Stroke Cerebrovasc Dis 2017;26:e62–63 doi:10.1016/j.jstrokecerebrovasdis.2017.01.004 pmid:28161148
    
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