Книги по МРТ КТ на английском языке / Neurovascular anatomy in interventional neuroradiology Krings et al 2015

5 and 7. In brief, the meningohypophyseal trunk gives rise to the artery of the free margin of the tentorium that runs posterosuperiorly; the dorsal meningeal artery that courses inferiorly to Dorello’s canal, where it anastomoses with clival branches of the ascending pharyngeal artery; and the basal tentorial artery, which runs posterolaterally along the superior aspect of the petrous bone ( Fig. 31.5).

The ILT will supply the cavernous sinus and the middle cranial fossa, including the dura surrounding the foramen ovale and rotundum. It is connected to the ophthalmic artery via its recurrent branch. The arterial system of this region can be regarded as a para-cavernous network that connects the MMA

system with the accessory meningeal artery, the ICA, the ophthalmic artery, the marginal tentorial artery, and the ascending pharyngeal artery. Hypervascularized tumors in this region will therefore derive their supply from all of these potential sources, whereas arteriovenous shunting lesions will enlarge these preexisting channels to contribute to the shunt ( Fig. 31.6).

The ophthalmic artery has two major subdivisions: the medial and the lateral groups (see Case 8). The lateral group can supply the dura via the recurrent meningeal artery, which anastomoses with the MMA. The medial group has a more significant dural supply: Via perforating branches through the cribriform plate, the anterior and posterior ethmoidal arteries supply the

anterior cranial fossa. In addition, the distal anterior ethmoidal artery gives rise to the artery of the falx cerebri (anterior falcine artery) through the foramen cecum. This artery supplies the falx and anastomoses distally and cranially with the MMA ( Fig. 31.7).

The following intradural arteries can participate in the supply to the dura: Both the intradural vertebral artery (more commonly, however, from its extradural compartment) and the intradural posterior ICA can give rise to the artery of the falx cerebelli and the posterior meningeal artery to supply the dura of the posterior fossa. The superior cerebellar artery can give rise to a tentorial branch. This so-called medial dural tentorial artery is classically only visible in dural tentorial arteriovenous fistulas and will arise from the rostral trunk of the superior cerebellar artery in its lateral pontomesencephalic segment in the ambient cistern directly under the free margin of the tentorium. The posterior cerebral artery can give rise to small dural

branches from both its distal cortical and its choroidal vessels. These have been coined the arteries of Davido and Schechter and are classically only seen in the setting of tumors or vascular malformations, as they are too small to be visualized on routine angiographies.

31.3 Clinical Impact

Endovascular presurgical treatments aim to decrease vascularity (less blood loss), induce necrosis (as a softer tumor will enable easier cleavage), and enable complete removal of certain deep-seated skull base tumors. Depending on the goal, di erent embolization materials/techniques and di erent times between embolization and surgery can be chosen. To lessen blood loss, one has to aim for deep feeders, and a ligation-type embolization may be su cient if surgery is performed within the first 48 hours; however, if time between embolization and surgery is

longer, dural anastomoses will reconstitute the ligated vessels. If one aims to induce tumoral necrosis, very small particles have to be used (45–150 μm). As necrotic tumors tend to expand slightly within the first day after embolization, one should wait for at least 72 hours and up to 1 week to have the best intraoperative results and to capitalize on the soft necrotic tumor. This technique is not indicated if one works close to “dangerous vessels,” as the particles may penetrate through the anastomoses or occlude the vasa nervorum. In these cases, larger particles (300–500 μm) are safer, but revascularization will appear faster.

31.4 Additional Information and

Cases

See Fig. 31.8, Fig. 31.9, Fig. 31.10, Fig. 31.11, andFig. 31.12.

Fig. 31.10 A 52-year-old woman presented with progressive facial hypesthesias, ataxia, and headaches. MRI with sagittal contrast-enhanced T1-weighted images (a,b) revealed a meningioma of the clivus. Tumors of the clivus will be supplied both from the neuromeningeal trunk of the ascending pharyngeal artery via the clival branches (f) and from the dorsal meningeal artery of the meningohypophyseal trunk of the ICA (c,d,e). This anastomosis has to be kept in mind when embolizing tumors in this region.

Pearls and Pitfalls

●Intraventricular meningiomas are supplied by the choroidal arteries; therefore, distal catheterization and embolization are mandatory to avoid inadvertent embolization toward healthy territories.

●One must di erentiate true dural supply arising from pial arteries (i.e., the medial dural tentorial artery of the superior cerebellar artery and the artery of Davido and Schechter of the posterior cerebral artery) from induced distal pial supply to dural arteriovenous fistulas: although the latter can lead to catastrophic hemorrhage if the dural arteriovenous fistula is occluded, the former will not.

Further Reading

[1]Banerjee AD, Ezer H, Nanda A. The artery of Bernasconi and Cassinari: a morphometric study for superselective catheterization. AJNR Am J Neuroradiol 2011; 32: 1751–1755

[2]Cavalcanti DD, Reis CV, Hanel R et al. The ascending pharyngeal artery and its relevance for neurosurgical and endovascular procedures. Neurosurgery 2009; 65 Suppl: 114–120, discussion 120

[3]Martins C, Yasuda A, Campero A, Ulm AJ, Tanriover N, Rhoton A, Jr. Microsurgical anatomy of the dural arteries. Neurosurgery 2005; 56 Suppl: 211–251

[4]Merland JJ, Bories J, Djindjian R. The blood supply of the falx cerebri, the falx cerebelli and the tentorium cerebelli. J Neuroradiol 1977; 4: 175–202

[5]Merland JJ, Théron J, Lasjaunias P, Moret J. Meningeal blood supply of the convexity. J Neuroradiol 1977; 4: 129–174

[6]Morris P. Practical Neuroangiography. Philadelphia: Wolters Kluwer Health; 2007

[7]Shukla V, Hayman LA, Ly C, Fuller G, Taber KH. Adult cranial dura I: intrinsic vessels. J Comput Assist Tomogr 2002; 26: 1069–1074

[8]Théron J, Lasjaunias P, Moret J, Merland JJ. Vascularization of the posterior fossa dura mater. J Neuroradiol 1977; 4: 203–224

32.1 Case Description

32.1.1 Clinical Presentation

A 76-year-old man presented with progressive dementia for 1 year and recent new onset of seizures.

32.1.2 Radiologic Studies

See Fig. 32.1, Fig. 32.2, and Fig. 32.3.

32.1.3 Diagnosis

Malignant-type superior sagittal sinus (SSS) dural arteriovenous fistula (dAVF) with occlusion of the posterior SSS and rerouting of the shunt into transmedullary veins.

32.2 Embryology and Anatomy

In a 4-week embryo (4 mm), three meningeal venous plexuses (anterior, middle, and posterior) can be identified draining into the primitive head vein. By the 14-mm embryo stage, the primordium of the SSS, the sagittal plexus can be appreciated, formed from the midline coalescence of the anterior and middle venous plexuses. The numerous epidural plexuses, by

confluence of their lumen, will evolve to become what is in adult life seen as the SSS. The development of the brain and skull base leads to the adult configuration of the SSS by the 50mm stage (9-week fetus), in which the SSS joins with the straight sinus to drain into the torcular herophili. During this development, asymmetrical growth of the SSS predisposes it to drain freely into one side more than another, usually to the right transverse sinus; the straight sinus typically prefers the left transverse sinus.

Several variations of the SSS may be encountered. The most extreme form includes absence of the posterior SSS and drainage of the anterior portion of the brain through an anteriordominant sinus pericranii via a midline vein at the forehead. If no posterior outlet for the SSS exists, occlusion of this vein must be avoided to prevent cerebral venous infarctions. Posteriorly, there may be a high division of the SSS, with two separate channels going to each transverse sinus.

This so-called duplication of the SSS is likely related to incomplete midline fusion of the plexuses that form the SSS. In its incomplete form, if the dural sinuses retain some of their embryologic plexiform pattern, septations within the SSS may be seen (more frequently in the posterior aspect; Fig. 32.4).

Cavernous spaces located within the walls of the dural sinuses, including the SSS, have been reported. On occasion, these spaces may also bulge into the lumen of the dural sinus. Small

Fig. 32.1 Unenhanced axial CT (a,b) demonstrates an area of white matter hypodensity at the high left frontoparietal region. Contrastenhanced axial (c) and coronal CT (d) reveal abnormal vessels along the cortical sulci and periventricular white matter in bilateral cerebral hemispheres. These findings are suggestive of venous hypertension with venous infarction, likely related to an underlying dAVF and/or venous thrombosis.

arteries from the middle meningeal branches are also observed to terminate within these cavernous spaces; these may play a role in the formation of dAVFs and are presumably also related to the dural sinus malformations seen in childhood.

The SSS serves as a major drainage route for the superior convexity veins and the vein of Trolard. Most of the cortical veins

draining into the SSS are usually 1 mm or less in size. In the anterior frontal region, they enter the SSS perpendicularly, but the angle becomes progressively more acute posteriorly. In the occipital region, they may even curve anteriorly before draining into the SSS and may sometimes be confused with developmental venous anomalies. In some cases, the SSS may be absent in the

Fig. 32.4 Venous 3D phase contrast MRA (a) and contrast-enhanced CT venography (b) in the same patient demonstrate thrombus within the right channel of the SSS close to the torcular. It is best seen on CT and is not as well appreciated on magnetic resonance because of the compartmentalization of the sinuses.

Fig. 32.5 Left ICA injection in AP and lateral view in the venous phase demonstrates hypoplasia of the left transverse sinus with distal reconstruction of the sigmoid sinus, mainly via the vein of Labbé. The right transverse sinus demonstrates significant narrowing in its distal third. Although hypoplasia of one of the transverse sinuses is relatively common, the additional finding of stenosis of the contralateral site is typical for idiopathic intracranial hypertension or pseudotumor cerebri.

Fig. 32.8 Right ICA angiogram in AP (a) and lateral (b) views in the late venous phase demonstrate the presence of bilateral deep developmental venous anomalies and a falcine sinus (arrow) in a patient with a dAVF of a persistent petrosquamosal sinus. Variation of the right posterior cerebral artery territory (thin double arrows) and developmental venous anomalies within the posterior fossa (arrowheads) are also noted on the left VA angiogram in AP view in the arterial (c) and late venous (d) phases.

frontal region, anterior to the coronal suture. When this happens, the superior frontal veins typically take over the territory and converge more posteriorly to form the SSS.

The transverse-sigmoid sinus starts to appear by the 18-mm embryo stage as an anastomosing channel between the middle

Fig. 32.7 Left VA angiogram in lateral view (a) demonstrates a dAVF at an isolated transverse sinus with significant cortical venous reflux. A catheter was placed into the diseased transverse sinus surgically (b). Contrast injection through the microcatheter (c) confirms the correct location. Postcoiling left VA angiogram in oblique view (d) reveals complete obliteration of the dAVF.

and posterior venous plexuses, passing dorsal to the otic capsule and just lateral to the endolymphatic sac. The anterior and middle venous plexuses later merge to become only the anterior dural plexus, and its drainage route forms the transverse sinus. By the 50-mm stage, the distal end, from the entry point of the superior petrosal sinus down to the jugular fossa or the sigmoid portion of the sinus, consists of a large channel and is already similar to that in the adult, whereas the proximal portion or the transverse sinus is less well defined, with a large capillary network composed of several smaller channels. As the blood flow from the SSS and straight sinus become more established, the smaller venous plexuses coalesce, leaving only a larger channel. After the 50-mm stage, the transverse-sigmoid sinus gradually bends backward until it becomes perpendicular to the internal jugular vein in the adult.

In an adult, the transverse sinus receives blood from the inferior cerebellar hemispheric veins and veins from the inferior and lateral surfaces of the temporal and occipital lobes, including the vein of Labbé. As mentioned previously, the superior petrosal vein also enters the transverse sinus at its terminal end. On occasion, the transverse sinus may connect with nuchal and scalp veins via the mastoid emissary vein. The sigmoid sinus starts where the transverse sinus leaves the tentorial margin and drains into the jugular bulb inferiorly. It receives blood from the pons and medulla and may connect with the vertebral plexuses and suboccipital muscular and scalp veins via the mastoid and anterior and posterior condyloid emissary veins. Hypoplasia or aplasia of the transverse sinuses may be encountered in up to 20% of the population, with the left more commonly a ected than the right side. The size of the jugular foramen usually correlates with the size of the transverse sinus and may be helpful in di erentiating aplasia from thrombosis ( Fig. 32.5).

32.3 Clinical Impact

In the case of dAVFs with isolated pouches, either at the SSS or transverse sinus, the involved segment is no longer used for venous drainage of the brain and therefore can be sacrificed with-

Fig. 32.9 Left ICA angiogram in AP (a) and lateral (b) views in venous phase demonstrating the absence of the anterior aspect of the SSS, taken over by a large left frontal vein (arrows), entering the SSS posterior to the coronal suture, which is a normal variation and should not be mistaken for thrombosis.

out any complications. There are several approaches to reach the isolated segment. The reopening technique has been reported as a safe and e ective method to gain access to isolated venous pouches and the cavernous sinus. The major alternatives to this approach are a transarterial approach or open surgery with direct puncture of the involved sinus.

In cases in which the dural sinus is still patent, sacrificing the involved segment may not be possible because of drainage of the superior convexity cortical veins and vein of Trolard into the SSS and vein of Labbé and inferior cerebellar hemispheric veins into the transverse sinus. Accidental occlusion of these veins may lead to venous infarction and hemorrhage, and therefore, transvenous embolization may be contraindicated. A venous approach may still be possible if there is compartmentalization of the sinus, with the fistula being present only in one distinct venous channel of the dural sinus. In the SSS, an oblique anteroposterior (AP) view on conventional angiogram, together with subtraction of the shunt feeder and internal carotid artery injections, is the best way to identify the presence of this compartment. The normal and abnormal/involved compartments will be opacified separately during selective injections into the internal and external carotid angiograms ( Fig. 32.6).