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

Further Reading

[1]Auguste KI, Ware ML, Lawton MT. Nonsaccular aneurysms of the azygos anterior cerebral artery. Neurosurg Focus 2004; 17: E12

[2]Baptista AG. Studies on the arteries of the brain. II. The anterior cerebral artery: some anatomic features and their clinical implications. Neurology 1963; 13: 825–835

[3]Baykal S, Ceylan S, Dinç H, Soylev E, Usul H, Akturk F. Aneurysm of an azygos anterior cerebral artery: report of two cases and review of the literature. Neurosurg Rev 1996; 19: 57–59

[4]Huh JS, Park SK, Shin JJ, Kim TH. Saccular aneurysm of the azygos anterior cerebral artery: three case reports. J Korean Neurosurg Soc 2007; 42: 342– 345

[5]Kanemoto Y, Tanaka Y, Nonaka M, Hironaka Y. Giant aneurysm of the azygos anterior cerebral artery—case report. Neurol Med Chir (Tokyo) 2000; 40: 472–475

[6]Lasjaunias P, Berenstein A, ter Brugge KG Surgical Neuroangiography. Vol. 1. 2nd ed. Berlin: Springer; 2006

13.1 Case Description

13.1.1 Clinical Presentation

A 53-year-old man had a sudden onset of headaches and left-sided hemiparesis and was brought to the emergency department.

13.1.2 Radiologic Studies

See Fig. 13.1, Fig. 13.2, and Fig. 13.3.

13.1.3 Diagnosis

Ruptured arteriovenous malformation (AVM) fed by the inferior parietal branch of the distal anterior cerebral artery (ACA).

13.2 Embryology and Anatomy

Similar to the anatomy of the cortical branches of the middle cerebral artery (MCA), which are discussed in Case 16, there is

considerable variation in the cortical branches of the ACA. Their nomenclature is primarily based on the cortical territory they supply. The distal ACA supplies the medial aspect of the frontal and parietal lobes and extends to a variable degree over the convexity in equilibrium with the distal MCA branches. Given its interhemispheric central supply, occlusion of the ACA is commonly associated with contralateral lower extremity weakness. After the anterior communicating artery, the A2 courses under the lamina terminalis and the genu of the corpus callosum to ascend in the interhemispheric fissure. The vessel continues as the pericallosal artery in the epicallosal cistern and gives rise to multiple branches that are named according to their vascular supply. Posteriorly, the pericallosal artery will be in hemodynamic balance with the pericallosal branch of the posterior cerebral artery at the level of the splenium. Via this anastomosis, the ACA can take part in the supply to the medial posterior choroidal arteries. The cortical branches of the ACA are, in order of appearance, the orbitofrontal, frontopolar, internal frontal (anterior, middle, and posterior), paracentral, superior parietal, and inferior parietal arteries. The largest branch of the A2 is the callosomarginal artery, which lies superior to the peri-

Fig. 13.1 Unenhanced CT (a) demonstrates a right apical frontoparietal hemorrhage. CTA (coronal reformats: b,c,d; 3D reconstruction: e) revealed, as the source for the hemorrhage, an AVM fed by the distal ACA (inferior parietal branch) with a focal intranidal outpouching (arrow) that was held responsible for the bleed. Drainage of this monocompartimental AVM was directed into a median parietal vein. Case is continued in Fig. 13.2.

callosal artery and from which some of the aforementioned branches may originate ( Fig. 13.4). In addition to these cortical branches, the pericallosal artery also supplies the corpus callosum via short radially oriented callosal arteries that traverse the corpus callosum to supply the septum and the fornix.

13.3 Clinical Impact, Additional

Information and Cases

See Fig. 13.5, Fig. 13.6, and Fig. 13.7.

Pearls and Pitfalls

●Cortical branches of the ACA are named depending on the cortical territory they supply and are highly variable in their origin from the distal ACA.

●The ACA communicates, via its distal pericallosal branch, with both cortical and choroidal branches of the posterior cerebral artery, and is in hemodynamic balance with the MCA over the convexity.

Further Reading

[1]Gomes FB, Dujovny M, Umansky F et al. Microanatomy of the anterior cerebral artery. Surg Neurol 1986; 26: 129–141

[2]Morris P. Practical Neuroangiography. 3rd ed. Philadelphia: Lippincott Williams & Wilkins; 2013

[3]Perlmutter D, Rhoton AL, Jr. Microsurgical anatomy of the distal anterior cerebral artery. J Neurosurg 1978; 49: 204–228

[4]Türe U, Yaşargil MG, Krisht AF. The arteries of the corpus callosum: a microsurgical anatomic study. Neurosurgery 1996; 39: 1075–1084, discussion 1084–1085

14.1 Case Description

14.1.1 Clinical Presentation

A 65-year-old patient with a long-standing history of high blood pressure presented with a stroke in the watershed territory between the lenticulostriate perforators and the penetrating leptomeningeal arteries. Outside magnetic resonance angiography described a filiforme middle cerebral artery (MCA) stenosis, and the patient was scheduled for intracranial percutaneous transluminal angioplasty and stenting

14.1.2 Radiologic Studies

See Fig. 14.1, Fig. 14.2.

14.1.3 Diagnosis

Occlusion of the M1 main trunk in the setting of a fenestrated MCA.

14.2 Embryology

The anterior cerebral artery (ACA) is the first and phylogenetically oldest telencephalic vessel and can be considered the

terminal branch of the internal carotid artery (ICA). During the first weeks of fetal life, when the embryo is 7 to 12 mm long, lateral striate arteries arise from its wall and provide blood supply for embryonic structures of the telencephalic vesicle that will eventually become the MCA territory. Around the ninth week, after the maturation of the vertebrobasilar system, the MCA develops from the fusion of several ACA perforators of the lateral striate group. This developmental pattern matches that of the recurrent artery of Heubner (RAH). Because both the MCA and the RAH therefore share the same phylogenetic origin, their territories and anatomical variations are related to each other.

Both vessels give rise to perforating centripetal corticostriatal branches supplying, among other territories, the medial putamen, the caudate, and part of the anterior limb of the internal capsule, as is further discussed in Case 15.

Anatomical variations of the MCA have to be recognized when planning interventions to avoid damage or occlusion of perforating vessels that arise from the MCA and to assess their contribution to the perfusion of the deep MCA territory.

These variations are encountered less frequently than variants of other intracranial arteries and include the fenestrated MCA and the presence of a duplicated or accessory MCA (AMCA). Both types of variations are related to a persistence of

transient embryological vessels with a variant pattern of pruning the definitive vessel tree.

14.2.1 Fenestration

A fenestrated MCA arises as a single vessel from the ICA and feeds the MCA territory, but it diverges and reconverges along its course. It is a rare finding, with an incidence of less than 0.5% in angiographic series but as high as 1% in some anatomical series. This variant is usually located in the M1 segment and is often unilateral. A fenestration should not be confused with

an early branching of the MCA, with a dissection with a patent pseudolumen, or with a superimposed vessel. The mechanism leading to MCA fenestration remains unclear. In their series of five MCA fenestrations, Gailloud et al. reported an early temporopolar branch arising from the inferior limb of the fenestrated MCA in all cases, suggesting this vessel could play a role in the absent fusion of the early perforating arteries. Perforating branches arise from the upper limb. Although this is a clinically silent anomaly, it is an area of hemodynamic stress and, thus, a site for aneurysmal development, similar to an unfused basilar artery ( Fig. 14.3). See also Case 20.

14.2.2 Duplicated MCA and AMCA

These two anomalies have usually been described separately, but they probably simply represent the two extremes of the spectrum of anomalies in the coalescence of the ACA embryonic perforating arteries toward the MCA. These branches can feed variable territories. Usually, one vessel supplies the perforators and the other one is purely cortical. There are, however, cases in which both MCAs supply perforators.

Several classifications have been proposed: Teal di erentiates the AMCA from the duplicated MCA by the artery from which they arise. The duplicated MCA has its origin in the ICA, whereas the AMCA arises from the ACA. Manelfe classified the AMCA into three types. Type 1 is an anomalous vessel that arises from

the internal carotid artery at a point proximal to its bifurcation (the duplicated MCA in Teal’s classification), type 2 originates from the proximal portion of the ACA, and type 3 originates from the distal portion of the A1 segment of the ACA near the anterior communicating artery.

Lasjaunias et al. postulated that there is a proximal type AMCA (that comprises Manelfe’s type 1 and type 2) and a distal type (Manelfe type 3). In the proximal type, the AMCA (i.e., the more cranial vessel) feeds the medial and lateral striate territories, whereas the MCA (proximal) is purely cortical ( Fig. 14.4). In the distal-type AMCA, there is in fact an enlarged RAH arising from the ACA or close to the AComA ( Fig. 14.5). In these cases, the MCA will not always be purely cortical but may also give rise to lateral perforators.

Fig. 14.6 A 55-year-old man with recurrent metastatic squamous cell carcinoma of the neck with left carotid blow out. Right ICA angiogram in AP view under balloon occlusion test of the left ICA demonstrates an incidental finding of a proximal type of right MCA duplication. Note that the more caudal branch is mainly supplying the cortex, whereas the lenticulostriate arteries (arrows) arise from the cranial branch.

In all of these scenarios, the true RAH may still be present, which will add complexity to the evaluation of the supply of the perforators and may even lead to the clinical picture of a “triplicated” MCA.

14.3 Clinical Impact

In cases with variant MCA trunk anatomy, it is important to identify which artery gives rise to the perforators and which one is purely cortical, or if they both feed the deep and superficial territories. It is quite evident that the planning of an endovascular procedure involving the ICA, ACA, or MCA (i.e., stenting and/or percutaneous transluminal angioplasty to treat an intracranial stenosis, as in our case) should include a thorough assessment of the presence of anatomical variants and their territories, as well as assessment of supply to the perforators, which (as we have seen) can arise from any of the aforementioned vessels with great variability. Without a complete evaluation of these structures, there is a risk that the intervention may interrupt the functional balance or cause occlusion of the perforating arteries.

An association between the duplicated MCA or the AMCA and cerebral aneurysms has been well documented.

Fig. 14.7 Left ICA angiogram in AP view demonstrates similar findings to those in Fig. 14.4 of a proximal duplicated MCA, with the lenticulostriate arteries originating from the cranial branch.

Pearls and Pitfalls

●In cases of AMCAs, the perforators arise typically from the cranial segment, especially if the AMCA arises proximally from the ICA.

●A fenestrated M1 segment has to be di erentiated from a dissection, a stenosis, or an intraluminal thrombus.

14.4 Additional Information and

Cases

See Fig. 14.6, Fig. 14.7, and Fig. 14.8.

[3]Gailloud P, Albayram S, Fasel JH, Beauchamp NJ, Murphy KJ. Angiographic and embryologic considerations in five cases of middle cerebral artery fenestration. AJNR Am J Neuroradiol 2002; 23: 585–587

[4]Kang HS, Han MH, Kwon BJ, Kwon OK, Kim SH, Chang KH. Evaluation of the lenticulostriate arteries with rotational angiography and 3D reconstruction. AJNR Am J Neuroradiol 2005; 26: 306–312

[5]Komiyama M, Nakajima H, Nishikawa M, Yasui T. Middle cerebral artery variations: duplicated and accessory arteries. AJNR Am J Neuroradiol 1998; 19: 45–49

[6]LaBorde DV, Mason AM, Riley J, Dion JE, Barrow DL. Aneurysm of a duplicate middle cerebral artery. World Neurosurg 2012; 77: e1–e4

[7]Lasjaunias P, Berenstein A, ter Brugge KG. Surgical Neuroangiography. Vol. 1. 2nd ed. Berlin: Springer; 2006

[8]Manelfe C, David J, Caussanel JP. L’artère cérébrale moyenne accessoire. Colloque d’anatomie radiologique de la tête, Montpellier. 1972

[9]Lasjaunias P, Berenstein A, ter Brugge KG. Surgical Neuroangiography. Vol 3: Clinical and Interventional Aspects in Children. 2nd ed. Berlin: Springer; 2006