Blue Circle=tumor blush. The superficial sylivan vein is prominent within the circle and extends over the temporal lobe towards the superior petrosal sinus (dark blue arrow). Labbe=black. No trolard is seen, various superior cortical veins drain into the SSS. Basal vein=light blue, dominant posterior drainage. Very nice demonstration of the deep venous system tributaries. Anterior Septal vein=bright green, capturing territory of hypoplastic anterior cerebral vein. The inferior sagittal sinus is absent. Thalamostriate vein with large longitudinal caudate vein=yellow. Direct lateral vein=pink. Posterior caudate/splenial veins=brown.
A prominent Pericalossal Vein empties into a large inferior sagittal sinus. Also note hypoplasia of the superior sagittal sinus proximal to a large superior frontal convexity tributary.
Dark blue=percalossal vein. Light blue=inferior sagittal sinus. Pink=frontal convexity vein. Orange=anterior septal vein. Yellow=thalamostriate vein. Red=Internal cerebral vein.
Occipital sinus (blue arrows on the sagittal and MRI axial projections), draining into the marginal sinus (dark blue arrows on the AP projections.) The occipital sinus is more commonly seen in children.
Cavernous sinus. Cavernous sinus is a metaphysical entity. It is a collection of anatomically and functionally separate venous compartment which, altogether, constitute the single venous space we have come to regard as a distinct anatomical structure. It is critical for the neurointerventionalist to understand this, because his or her treatments will be, of necessity, targeting these varied and complex compartments. This is a distinctly different view than the classical question of whether or not the sinus as a whole is involved in a disease process.
The classical view holds:
1) Basal vein of Rosenthal — typically flows toward CC, but easily reverses flow in cases of fistula, etc.
2) Ophthlamic vein — again typically flow is into the sinus, but can easily reverse itself
3) Sphenoparietal sinus — also reverses easily. Drains sylvian venous network into the sinus.
1) Superior Petrosal Sinus
2) Inferior Petrosal Sinus
3) Foramen Rotundum, Foramen Ovale, and other skull base foramina to the pterygoid venous plexus
4) Contralateral Cavernous sinus thru transcavernous channels
5) Clival venous plexus down to foramen magnum region and from there into jugular veins or marginal sinus
A neat way of projecting arterial phase as a mask for venous phase to demonstrate carotid artery relationship to the cavernous sinus. Many tributaries and egress routes of the cavernous sinus are visible.
Cavernous Sinus=orange. Tributaries: Sphenoparietal sinus=brown. Outflow: Superior petrosal sinus=dark blue; Clival venous plexus=purple; Foramen Ovale=green; Foramen Rotundum=red; Pterygoid venous plexus = light blue and yellow. Notice shadow of skull base just below the sphenoparietal sinus.
Cavernous Sinus (dark blue). The sylvian network and sphenoparietal sinus (orange) is well seen draining into the cavernous sinus with a well-developed inferior petrosal sinus (light blue). Notice superimpositing of the basal vein (purple) and the anterior choroidal artery (red)
Another demonstration of a small cavernous sinus (purple) receiving sphenoparietal sinus (dark blue) inflow and draining into the superior petrosal sinus (light blue). Notice the relationship of the sphenoparietal sinus to the sphenoid ridge on the unsubtracted views. The basal vein (yellow) is superimposed on the anterior choroidal artery (green)
Ophthalmic Vein Cavernous Sinus anatomy via a carotid cavernous fistulogram.
Left ICA injection demonstrating enlarged superior (purple) and inferior (light blue) ophthalmic veins draining a carotid-cavernous sinus (dark blue) fistula. The fistula was approached via an orbitotomy cutdown gaining access into the superior ophthalmic vein (lateral center and AP right images) and closed by coiling. The microcatheter is labeled in red.
The size of this sinus, like any other, is determined by the sum total of the tributaries it gathers, much like a river is exactly as large as the total volume of streams which feed it. The principal feeders of the sphenoparietal sinus, which runs along the sphenoid ridge, as in the above figure, are the superficial Sylvian veins; their relative prominence dictates the size of the sphenoparietal sinus. Classically, as shown above, this sinus empties into the anterolateral aspect of the cavernous sinus. However, this need not always be the case, a fact best appreciated angiographically rather than through destructive anatomical dissections which do not provide information on flow and violate hemodynamically separate venous compartments. For example, in this patient with a sizable CN V shwannoma, consisting of intracavernous (yellow) and prepontine, intradural (white) components artificially separated by the posterior cavernous sinus wall dura, the cavernous sinus compartment is completely filled with tumor. This fact cannot be appreciated on an MRI study, where both tumor and sinus are expected to enhance, however it is well seen angiographically. The sphenoparietal sinus (pink) receives superficial (purple) and deep (orange) Sylvian veins. Notice that the sphenoparietal sinus is situated lateral to the mass, and therefore outside of the lateral wall of the cavernous sinus which contains, among other cranial nerves, the CNV portion involved by the tumor.
Preoperative angiogram of the same patient demonstrates complete occlusion of the cavernous sinus, as shown by lack of contrast opacification in the venous phase of the angiogram, and widening of the cavernous sinus space (blue double arrow). The arterial phase image mask shows the location of the ICA. The sphenoparietal sinus drains independently into the pterygopalatine venous plexus (dark blue arrow) below the skull base.
Stereo pair of the lateral projection, better demonstrating the deep sylvian contribution (orange)
Similar disposition is seen in a different patient, with no cavernous sinus pathology, where at least a portion of the sphenoparietal sinus (pink) receiving prominent Sylvian veins (purple) drains into the pterygopalatine plexus (dark blue) via a channel (light blue) separate from the cavernous sinus proper (green).
Finally, the compartmentalization of the cavernous sinus is shown here by another pathologic entity, the cavernous sinus dural arteriovenous fistula. Injections of the right and left carotid arteries demonstrate a fistula at the posterior aspect of the left cavernous sinus medial compartment (pink), supplied by various branches of the left and right MHT. The venous drainage of this compartment is directed into the engorged superior ophthalmic vein (red). At the same time, the patient’s normal hemispheric venous drainage, via dominant deep sylvian veins, proceeds via the sylvian veins and sphenoparietal sinus (light blue) into an anatomically distinct lateral compartment of the cavernous sinus (purple), which empties via the foramen ovale (yellow) into the pterygopalatine venous plexus.
The same arrangement is shown in the lateral projections of early (left) arteriovenous shunting and brain venous phase (right) lateral compartment drainage. Neither compartment communicates with the other, as evidenced by their mutually separate drainage routes. Understanding this anatomy allows the operator to consider transvenous coiling of the fistulous medial compartment without compromise of the sylvian venous outflow.
Transverse Sinus Asymmetry
The transverse sinus is more often asymmetric than not — usually the right one is bigger, some say because pulsations of the right atrium are propagated cranially in a valveless system to impart a larger capacitance to the ipsilateral jugular system and intracranial sinuses. The above images illustrate an additional layer of complexity — a prominent vein of Labbe (dark blue) empties into the distal right transverse sinus, significantly enlarging its caliber and that of the right sigmoid sinus (pink), whereas the more proximal right transverse sinus is hypoplastic. In this person the left transverse sinus is dominant (yellow). Unless this anatomy is understood, the appearance (particularly on MRI and MRV) may be misconstrued as transverse sinus thrombosis. Notice presence of bilateral emissary veins at the sigmo-jugular junction (white).
Multiple routes of egress from cavernous sinus demonstrated in a case of CC fistula.
Red=ECA (catheter seen on lateral); Orange=foramen rotundum branch; Yellow=MMA; green=cavernous sinus; dark blue=ophthalmic vein; light blue=facial angular vein; purple=basal vein; bright green=straight sinus; black=sigmoid sinus; brown=jugular bulb; pink=superior petrosal sinus; white=inferior petrosal sinus; double yellow=sphenoparietal sinus; double light blue=reflux into brain veins via basal vein (likely pontomesencephalic and lateral mesencephalic veins)
Falcine Sinus — developmental variation of persistence of a falcine channel (which can be anywhere along the falx, but most commonly seen in the parietal region). These venous channels within the falx cerebri are transiently present during emrbyogenesis before formation of definitive sinuses, and usually regress.
Persistence of falxine sinus is associated with developmental arterioevnous shunts, best exemplified by the Vein of Galen malformation. In the true VOG malformation, the shunt involves tributaries of what would otherwise become the vein of Galen (internal cerebral, basal vein). When this kind of high-flow shunting involves the primitive venous system, the true vein of Galen and the straight sinus are absent. Instead, the more developmentally primitive falxine sinus persists. This is the the very simple way to recognise a true, congenital Galen malformation — the Galen itself (and straight sinus) are missing! It is therefore true that the name VOG malformation is an unfortunate misnomer. If, on the other hand, you see an AVM or some other shunt in the region (such as quadrigeminal plate AVMs or periatrial ones) but the Galen and straight sinus is present, this means that the lesion was not hemodynamically active in the embryonic phase. The same goes for dural shunts of the trigonal area. Look for the Falxine sinus to tell you whether the lesion was hemodynamically active in utero or not. This has important treatment implications, as one must be especially careful not to occlude the true vein of Galen with Onyx, glue or other embolic (if you think it is the true Galen!), as many other small but vital veins drain there also.
In this child with a left parasagittal posterior splenial/atrial AVM, stereo MIP image of post-contrast MRI following successful treatment (volumetric T1 post is better than TOF MRV for veins) shows the falxine sinus (blue), with tributaries of inferior sagittal sinus (green), internal cerebral vein (purple) coming into the false vein of Galen (pink). Notice absence of the straight sinus, with superior cerebellar veins (yellow) instead draining directly into the torcular. Also seen is a “sheet” of venous blood along the tentorial leaf (white arrows), another vestige of primitive drainage.
The pre-embo vertebral injection images of the AVM nidus (black) draining into the false Galen (pink) and the Falxine sinus (blue). The AVM is supplied via the posterior lateral choroidal arteries (red).
Same AVM from the ICA injection, with a large primary atrial vein (dark blue).
Following embolization, resection, recurrence (as frequently the case with childhood AVMs) and gamma-knife, things look good. Stereo, of course.
In this following case of falxine sinus with no associated shunt, the facine sinus connects the parietal portion of the sagittal sinus iwth the straight sinus. The sagittal sinus distal to the falcine sinus is hypoplastic and in fact is draining “retrograde” towards the falcine sinus which empties into the straight sinus. There is no torcula. A very prominent inferior sagittal sinus is present, which is also somewhat unusual.
Falcine sinus=light blue; Superior sagittal sinus=dark blue; Straight sinus=purple; Inferior sagittal sinus=pink; Internal cerebral vein=yellow.
These are usually present in the posterior occipital region — being emissary (meaning going from intracranial sinus thru some sort of unnamed hole in the bone into the soft tissues) from the mastoid or occipital regions. They are often seen on MRI and angio and should not, by themselves, promt concern for some kind of fistula unless other evidence of fistula is present. There are however emissary veins present in various other places such as along the superior sagittal sinus. The example below illustrates such a situation — the emissary vein near the vertex runs in the subgaleal space on the left towards the pterygoid plexus. It is usually seen later than even the late venous phase of the brain, as these veins take time to fill.
Emissary vein marked in dark blue, opacifying in a very late venous phase of the brain.
Another example of an emissary vein from the anterior third of the Superior Sagittal Sinus (black arrow). The single vein (white) traverses the skull, marked by its fainter appearane due to skull density. Once part of the scalp, it splits into the ipsilateral (light blue) and contralateral (purple) channels which ultimately empty into the ipsilateral (dark blue) and contralateral (pink) pterygopalatine fossae venous plexuses. The emissary vein can be appreciated without the stereo capability by its course anterior to the sagittal sinus. Since the sagittal sinus is a midline structure, anything anterior to it on a standard lateral projection has to be either intra-osseous or trans-osseous.
Emissary veins should NOT be confused with diploic veins, which are simply veins in the diploic space of the skull (between inner and outer tables). The diploic veins drain the marrow of the skull, not the brain. By definition, seeing a vein go through the skull on an internal carotid artery injection (thereby making sure that skull-supplying arteries such as the meningeal family are not injected, implies that the vein is an emissary, not diploic, vein.
Sagittal Sinus Thrombosis — collaterals. All of the above anatomic knowledge can become very useful in evaluation of venous thrombosis. Numerous collateral pathways develop in this setting attempting to compensate for the loss. The most dramatic cases usually involve the largest channel — the superior sagittal sinus. In this case, a man presented with what initially was thought to be vasculitis-related brain hemorrhage. Subsequent workup led to an angiogram, where sagittal sinus thrombosis with extensive trans-cerebral and trans-osseous emissary vein collateral channels was seen. In retrospect, these findings were present on the patient’s earlier contrast MRI. “Venovibe” or other contrast-enhanced MR venograms can very sensitive, particularly when interpreted with the appropriate index of suspicion. Noncontrast 2-D time of flight MRV I consider to be next to useless as a problem-solving technique. Any thin-slice postcontrast T1 study is vastly superior.
2-D TOF (top left). Sagittal post-contrast MRI (top middle and right). Late (bottom right) and super-late (bottom left) venous phase images of a catheter angiogram. MRI demonstrates a parietal hemorrhage (green, additional sequences confirm hemorrhagic nature). Notice that while the anterior frontal and occipital lobes of the bottom right angiogram are in venous phase, the posterior frontal and parietal lobe drainage is delayed (green arrows). No SSS is visible. Numerous trans-cerebral veins (dark blue) , normally invisible, have enlarged to provide alternative dranage of cortex into the internal cerebral vein (purple). The Trolard (brown), previously draining towards the thrombosed sagittal sinus (because it is larger in caliber near the top) now drains inferiorly into a parietooccipital vein and into the sigmoid sinus. The sylvian network (light blue) is prominent, maximizing its cortical territory. Notice also transosseosus emissary veins (red) draining the brain into scalp veins (orange) on the delayed venous phase bottom left.