Hey everyone, it’s Medicine Mondays again. Today is just going to be a short post on “Dural Venous Sinus Variations“.
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Dural Venous Sinus Variations?
Yea.
So, in radiology, we commonly receive studies with clinical concern for dural venous sinus thrombosis. This can be a difficult diagnosis to make. Sometimes it’s a slam dunk and you see abnormal intrinsic T1 signal in the superior sagittal sinus or sigmoid sinus or something. However, other times it can be very subtle. This, in combination with congenital variations in dural venous sinus anatomy can make things difficult.
Unfortunately, the pictures I had saved I can’t seem to find, but I’ve tried to link to representative cases I found online which illustrate my point.
There are lots of articles about dural venous sinus anatomy and how to evaluate for dural venous sinus thrombosis. Here’s one from RSNA 2006 titled Imaging of Cerebral Venous Thrombosis: Current Techniques, Spectrum of Findings, and Diagnostic Pitfalls. I’ve used it many times before. In terms of variations, there’s an article from AJNR titled Cerebral MR Venography: Normal Anatomy and Potential Diagnostic Pitfalls. They’re both pretty good, but combing through them during a busy day may be difficult. For that reason, I’m just going to go over some common variations:
Unfortunately, the pictures I had saved I can’t seem to find, but I’ve tried to link to representative cases I found online which illustrate my point.
Unilateral aplastic (or hypoplastic) transverse sinus
It is very common for one transverse sinus to be dominant.
However, this can sometimes be a dilemma if you are concerned that maybe there is a partial thrombosis of this sinus rather than it simply being hypoplastic. The best thing to do is to correlate with the jugular foramen. The hypoplastic side should have a significantly smaller jugular foramen than the other side. This will you be more certain that this is just a congenital variant.
It’s also important to note that you can see “flow gaps” on the non-dominant side which may mimic thrombosis.
Occipital sinus
This can be enlarged in the presence of an hypoplastic or absent transverse sinus.
Here’s a good representative case from Dr Balaji Anvekar’s Neuroradiology Cases – Occipital Sinus.
Arachnoid granulations
These are rounded filling defects at or within the sinuses which can mimic thrombosis. However, there are common areas where these granulations occur, normally in the transverse and sigmoid sinuses. Additionally, you can usually confirm their presence on a prior noncontrast CT usually with some associated bony remodeling of the calvarium.
Here’s a good AJNR article from 1996 titled Arachnoid Granulations in the Transverse and Sigmoid Sinuses: CT, MR, and MR Angiographic Appearance of a Normal Anatomic Variation.
Absent anterior superior sagittal sinus
also described as “unilateral hypoplasia of the rostral third of the superior sagittal sinus”
This can be 25% or even 50% of the superior sagittal sinus. Additionally, this can look like thrombosis of the anterior margin of the superior sagittal sinus on an MRV. However, this can also be a normal variation. I think it’s helpful to look at the prominent longitudinally oriented cortical veins which would drain the anterior 1/3 of the brain, these should be larger and then drain back into the distal 2/3 of the superior sagittal sinus normally.
Another good representative case from Dr Balaji Anvekar’s Neuroradiology Cases – Hypoplastic Superior Sagittal Sinus.
This isn’t that common of a variation, with some studies suggesting that it is present in 1% of the population. I think it’s important to be aware of this. It’s one of those things where you’re going through cases and you’re 95% sure this is a variation, but want to be 100% sure. Checking for the longitudinally oriented cortical veins makes you confident that this is a congenital variant.
TL;DR
Dural venous sinus thrombosis can be difficult to diagnose.
From my (limited) experience and research, here are my take on the common variations and pitfalls.
-Sensei
Agree? Disagree? Questions, Comments and Suggestions are welcome.
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