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Functional anatomy of the external carotid artery systems using cross sectional image of rotational digital angiography Poster No.: C-1694 Congress: ECR 2010 Type: Educational Exhibit Topic: Head and Neck Authors: Y. Kondo , H. Kiyosue , Y. Hori , H. Mori , S. Tanoue ; Oita/JP, 1 1 1 2 2 1 2 Yufu/JP Keywords: Neuroradiology, External carotid artery, Anatomy DOI: 10.1594/ecr2010/C-1694 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myESR.org Page 1 of 72 Learning objectives The objective is to illustrate the functional anatomy of the external carotid artery (ECA) system using cross-sectional source images of 3-dimensional (3D) digital angiography. Background Knowledge of the functional anatomy of the ECA is essential for endovascular treatment of head and neck lesions. However, it is often difficult to identify the branches of the ECA in detail because they have complex courses and variations. The anatomical relationships of the branches with the bony structures in the skull base, including the foramen, spinal canal or sulcus, are important for their identification. Rotational digital angiography crosssectional images have high resolution and can clearly depict the course of the branches in relation to the bony structures. In this paper we will demonstrate the 3D functional anatomy of the ECA systems and present cases with head and neck tumors and vascular lesions. Page 2 of 72 Imaging findings OR Procedure details Introduction The external carotid artery (ECA) system, can be classified according to embryology, into the following three groups; the internal maxillary artery system, derived from the embryologic hyostapedial artery (second primitive aortic arch derivative), the thyroid-facial-lingular artery system, derived from the regressed ventral aorta (ventral pharyngeal artery), and the ascending pharyngeal-occipital artery system, formed through caroticobasilar anastomoses (Fig. 1 on page 43). Because embryologic and phylogenetic development closely links the ECA to the intracranial arteries, there are certain common anastomotic routes, which often follow the cranial nerves along the neural foramen. In this paper, we outline the functional anatomy of the main branches of the ECA system and their anatomical relationships to the skull base, using rotational digital angiography cross-sectional source images. Knowledge of potentially adverse anastomotic routes and identification of the cranial nerve supply from the ECA are essential for the clinician to avoid possible major complications such as embolic stroke or cranial nerve palsy. Page 3 of 72 Imaging System and Sample Images (Fig. 2 on page 44)(Fig. 3, click the play button at the sidebar) • • • • • IQ Angiography system: Innova3131 Biplane, GE Healthcare, USA Work station: Advantage workstation VolumeShare2 (AW 4.4), GE Healthcare, USA The 3D datasets were obtained from single rotation with a field of view of 20x20 cm using a floor-mounted C-arm. A total angular range of 200° around patients, with a rotation of 40° per second during administration of the contrast material (Iopamiron 300; Bayer Health Care, France) Injection rates were 21-25 mL at 3.5-4 mL/s, into the common carotid artery and 12-15 mL at 2 mL/s, into the ECA. Content Page 4 of 72 External Carotid Artery System (meningeal branch) (Fig. 4 on page 45) 1. Ascending Pharyngeal - Occipital Artery System 1-1. Ascending Pharyngeal Artery 1. Anterior division (pharyngeal branch) 2. Middle division (inferior tympanic artery) 3. Posterior division (neuromeningeal branch) 1-2. Occipital Artery 1. Stylomastoid artery Page 5 of 72 2. Mastoid branch 2. Internal Maxillary Artery System 2-1. Middle Meningeal Artery 1. Petrosal branch i. cavernous branch ii. petrosal artery Page 6 of 72 2. Anterior division i. lateral branch ii. meningeal branch a. Meningolacrimal artery b. Sphenoidal artery 3. Posterior division i. petrosquamosal branch Page 7 of 72 ii. parieto-occipital branch 2-2. Accessory Meningeal Artery 1. Anterior branch 2. Posterior branch 2-3. Artery of the Foramen Rotundum (Note) Adverse Anastomoses to the Ophthalmic Artery Page 8 of 72 1. Ascending Pharyngeal-Occipital Artery System 1-1. Ascending Pharyngeal Artery The ascending pharyngeal artery is believed to have developed from the primitive hypoglossal artery, one of the carotid-basilar anastomoses (Fig. 5 on page 46). Page 9 of 72 Course The ascending pharyngeal artery usually originates from the posterior or medial surface of the proximal portion of the ECA, and ascends vertically between the internal carotid artery (ICA) and the side of the pharynx, to below the surface of the base of skull, lying on the longus capitis. The artery or its branch may also arise from the ICA after its origin or from the carotid bifurcation. In such cases, its course can follow that of the ICA so that the guidewire or catheter could be inserted unintentionally into it during angiographical procedures (Fig. 6 on page 48). Branches and anastomoses (Fig. 7 on page 48) The ascending pharyngeal artery divides near the cranial base, into three divisions as follows: Page 10 of 72 - anterior division - middle division - posterior division 1. Anterior division (pharyngeal branch) The anteriorly located pharyngeal trunk gives off three branches as follows (Fig. 8 on page 49): - inferior pharyngeal arteries Page 11 of 72 - middle pharyngeal arteries - superior pharyngeal arteries. The latter, also called the eustachian ramus, constitute the most important anastomotic routes, and connect with the vidian artery (artery of the pterygoid canal, Fig. 9 on page 50) from the petrous ICA or the distal internal maxillary artery and the accessory meningeal artery (Fig. 10 on page 51)(Fig. 11 on page 52)(Fig. 12 on page 53). Finally, this artery gives off a carotid branch which follows the ICA entering the carotid canal and anastomoses with the recurrent lacerum branch (branch of the lateral clival artery, which arises from the C5 portion of the carotid siphon) (Fig. 13 on page 54). This recurrent artery of the foramen lacerum also anastomoses with the posterior branch of the inferolateral trunk and the cavernous branch of the middle meningeal artery (MMA). 2. Middle division (inferior tympanic artery) Page 12 of 72 The inferior tympanic artery is a small branch of the ascending pharyngeal artery, which passes through a minute foramen in the petrous portion of the temporal bone in tandem with the tympanic branch of the glossopharyngeal nerve (Jacobson's nerve) to supply the medial wall of the tympanic cavity. It has potential for anastomosis with the other tympanic arteries, such as the superior tympanic artery, which arises from the petrous branch of the MMA, the anterior tympanic artery from the proximal internal maxillary artery (IMA), the stylomastoid artery from the posterior auricular-occipital artery, and the carotico-tympanic artery from the ICA (typically these anastomoses are not visualized on the cerebral angiograms). 3. Posterior division (neuromeningeal branch) The posterior division is the site of origin of neuromeningeal branches, the hypoglossal and jugular branches, and enters the cranial cavity through the corresponding foramens (Fig. 14 on page 55). Both branches give off medial/lateral clival branches immediately after exiting the hypoglossal and jugular foramen, respectively (Fig. 15 on page 55). In addition, they also anastomose with mastoid branches of the occipital artery via the mastoid canal, and the posterior meningeal artery which is from the vertebral artery via the foramen magnum (Fig. 16 on page 56). The jugular branch distal to the jugular foramen supplies the dura facing the inferior part of the cerebellopontine angle. The hypoglossal and jugular branches also supply the adjacent segments of cranial nerves IX through XII. Page 13 of 72 As a remnant of the embryologic hypoglossal artery, the ascending pharyngeal artery keeps its connection with the vertebral artery via two proximal branches. The lowest, usually the most proximal branch of the ascending pharyngeal artery, is the musculospinal branch, which anastomoses laterally with the C3 radicular anastomotic artery of the vertebral artery. The second branch may contribute to the odontoid arterial arch, which has a characteristic U-shaped curve, as seen on the lateral view (Fig. 17 on page 57). 1-2. Occipital Artery The occipital artery is a remnant of the embryologic carotid-vertebrobasilar anastomosis, namely, type I and type II proatlantal intersegmental arteries (Fig. 18 on page 57). Full persistence of these segmental arteries is extremely rare; however, the occipital artery, as their remnant, still retains its connection from the external carotid system to the vertebral artery. Page 14 of 72 Course The occipital artery generally originates from the posterior surface of the ECA, usually above the ascending pharyngeal artery, at the level of the angle of the mandible. However, there are numerous and frequent variations; it may arise from the vertebral, internal carotid, or ascending cervical artery. It then ascends posteriorly, and passes deep to the posterior of the digastric muscle in the occipital groove of the temporal bone. Branches and anastomoses The occipital artery is divided into three portions as follows: - first portion: ascending cervical - second portion: cervico-occipital or horizontal Page 15 of 72 - third portion: ascending occipital The meningeal branches most frequently originate from the second or third arterial portions (Fig. 19 on page 58). The first portion gives rise to muscular branches, the auricular branch, and occasionally to the ascending pharyngeal artery. The posterior anastomotic radicular branches, which are major collaterals from the vertebral artery to the external carotid system, arise from the horizontal portion of the occipital arteries at both the C1 and C2 level. Neural/meningeal branches of the occipital artery Page 16 of 72 i. The stylomastoid artery, which may arise from either the posterior auricular or the occipital artery, passes through the stylomastoid foramen to the tympanic cavity and then supplies the mastoid portion of the facial nerve (Fig. 20 on page 59). The artery anastomoses via the superior tympanic artery with the petrosal branch of the MMA, which supplies the petrosal segment of the facial nerve. Supply of the geniculate ganglion of the facial nerve is through the facial arcade, which, in most of the cases, consists of the petrous branch of the MMA and the stylomastoid branch. Occlusion of the stylomastoid artery during either embolization or surgery may result in a facial nerve deficit. The stylomastoid artery, when present, marks the position of the distal part of the facial canal on angiograms. ii. The mastoid branch, also called the artery of the mastoid foramen, originates from the horizontal portion of occipital artery. It enters the cranial cavity by passing through the mastoid foramen (Fig. 21 on page 60). The mastoid branch emerges intracranially at the posterior border of the upper end of the sigmoid sinus and divides into three groups of branches: Page 17 of 72 - descending - ascending - posteromedial The descending branches are directed toward the jugular foramen and anastomose with the jugular branch of the ascending pharyngeal artery (Fig. 16 on page 56). The ascending branches, which are directed to the dura covering the superior part of the posterior surface of the temporal bone that faces the cerebellopontine angle, anastomose with the subarcuate branch of the anteroinferior cerebellar artery. Page 18 of 72 The posteromedial branches anastomose with the petrosquamous branch of the MMA and constitute the main supply to the lateral part of the dura matter covering the cerebellar fossae, which border the hypoglossal branch of the ascending pharyngeal artery and/or the posterior meningeal branch of the vertebral artery. The small transosseous emissary arteries can supply the posterior dura matter via emissary canals (Fig. 22 on page ). The occipital artery thus constitutes a virtual anastomotic crossroads. The nature of its connection with the vertebral artery must be carefully detailed at the outset of any intraarterial therapy and during the course of the procedure. 2. Internal Maxillary Artery System Embryology (Fig. 23 on page 61) Page 19 of 72 The phylogenesis of the maxillary artery is complicated; by the fifth gestational week, the stapedial artery arises from the hyoid artery (second aortic arch derivative) originating at the proximal ICA and extends intracranially forming the obturator foramen of the stapes. The stapedial artery gives rise to both an upper division and a lower division. The upper division eventually becomes the MMA and the lower division exits through the foramen spinosum to become the inferior alveolar and infraorbital arteries. An anastomosis develops between the lower division and the ventral pharyngeal artery (the future ECA). The ECA becomes progressively more differentiated as it forms definitive thyroidal, lingual, occipital and internal maxillary branches. Then the IMA links up with the maxillomandibular division while the proximal stapedial artery regresses. The derivations of the end of the stapedial artery form the superior tympanic artery arising from the MMA and the anterior tympanic artery from the IMA, while the derivative of the embryologic hyoid artery is the carotico-tympanic artery branching from the petrous portion of ICA. Thus, the proximal site of the IMA and MMA has a branch toward the tympanic cavity, suggesting their potential anastomoses via the carotico-tympanic artery with the ICA or with the stylomastoid artery from the posterior auricular artery or occipital artery. Course The IMA is the deep terminal branch of the ECA and is much larger than the superficial temporal artery. It arises in the parotid gland at the neck of the mandible and extends to the apex of the pterygopalatine fossa. Page 20 of 72 Branches 1. First segment (mandibular segment) - deep auricular artery - anterior tympanic artery - inferior alveolar artery - MMA - accessory meningeal artery Page 21 of 72 2. Second segment (pterygoid segment) - anterior deep temporal artery - posterior deep temporal artery - buccal artery - masticator artery 3. Third segment (pterygopalatine segment) - inferior orbital artery - descending palatine artery Page 22 of 72 - vidian artery - artery of foramen rotundum Of the branches listed above, we address the following three most important branches in terms of endovascular treatment. 2-1. Middle Meningeal Artery Since the MMA is the most frequent target of transarterial embolization of the ECA, knowledge of its functional anatomy is essential. Page 23 of 72 Course (Fig. 24 on page 61) The MMA normally arises from the first segment of the IMA, just before the tortuosity which defines the beginning of the second segment. It enters the cranium through the foramen spinosum. The MMA gives off a short branch adjacent to the foramen spinosum. It divides into the petrosal artery laterally and a cavernous branch to the trigeminal ganglion medially. The main stem of the MMA courses laterally, along the greater sphenoid wing, where it branches into its anterior and posterior divisions. Angiographically, in the anterior view, the MMA is easily recognized by a sharp turn along the floor of the middle fossa after passing through the foramen spinosum. Branches and anastomoses Page 24 of 72 1. Petrosal branch i. cavernous branch ii. petrosal artery 2. Anterior division i. lateral branch ii. medial branch a. meningolacrimal artery Page 25 of 72 b. sphenoidal artery (recurrent meningeal artery) 3. Posterior division i. petrosquamosal branch ii. parieto-occipital branch The petrosal branch runs along the greater petrosal nerve and penetrates the temporal bone by passing through the facial hiatus, supplying the facial nerve and walls of the tympanic cavity. The arterial supply of the geniculate ganglion of the facial nerve is through the facial arcade, which, in most of the cases, consists of the petrous branch of the MMA and the stylomastoid branch of the posterior auricular artery. In addition, the petrous branch gives rise to superior tympanic artery, which anastomoses with the stylomastoid artery. Page 26 of 72 Attention must be given to the possibility that the petrous branch may supply the cerebellopontine angle and anastomose with the subarcuate artery from the anterior inferior cerebellar artery. The anterior division is distributed to the orbital region (Fig. 25 on page ), to the floor of the anterior fossa, and to the meninges of the frontal convexity. The supraorbital artery passes forward through the lateral part of the superior orbital fissure or through the canal of Hyrtl (cranio-orbital foramen) to anastomose with the lacrimal artery, and the branches are called the recurrent meningeal artery and the meningolacrimal artery. Although they supply extraocular tissues such as lacrimal glands, these branches are well-known for their anastomosis with the lacrimal artery of the ophthalmic artery as extracranial-intracranial collateral routes. The distal maxillary artery anastomoses with the inferior branch of the lacrimal artery of the ophthalmic artery through the anterior deep temporal artery and through the infraorbital artery. The posterior division gives rise to a petrosquamosal branch at the junction of the cranial base and convexity. This branch supplies the insertion of the tentorium along the petrous ridge and groove of the transverse sinus, the dura of the torcula and the junction of the sigmoid, transverse and superior petrosal sinuses, and extends to the dura of the posterior fossa. The petrosquamosal artery has anastomoses with the lateral clival Page 27 of 72 artery of the ICA, the mastoid branch of the occipital artery or the jugular branch of the ascending pharyngeal artery (Fig. 26 on page ). The distal part of the petrosquamosal branch anastomoses with the branches of the occipital artery, which pass through the mastoid foramen or other emissary canals, at the level of the junction of the sigmoid, transverse and superior petrosal sinuses, and with the meningeal branches of the ascending pharyngeal and vertebral arteries. The MMA may also anastomose with a branch of the basilar artery and dural branch of the posterior cerebral artery (Davidof artery). The parieto-occipital branch of the MMA supplies the posterior dura. 2-2. Accessory Meningeal Artery The accessory meningeal artery mainly supplies the membranous portion of the Eustachian tube and external acoustic meatus and the lateral pharyngeal wall. It has been suggested that it be called the pterygomeningeal artery, because the extracranial structures receive the predominance of its flow, whereas the intracranial branch receives only 10%. Page 28 of 72 Course The accessory meningeal artery may arise from either the maxillary or middle meningeal artery. In 60-78% of cases, the accessory meningeal artery enters the cranium through the foramen ovale. In the remaining 22%, it passes through the sphenoidal emissary foramen (foramen of Vesalius) (Fig. 27 on page 64). Branches and anastomoses The artery passes forward to the lateral pterygoid plate and divides into two branches: 1. Anterior branch 2. Posterior branch Page 29 of 72 The anterior branch runs along the Eustachian tube to its pharyngeal end and supplies the mucosa and muscles (Fig. 28 on page 65). It anastomoses with the vidian artery and the superior pharyngeal branch of the ascending pharyngeal artery. The posterior branch is meningeal and passes through the foramen ovale, running anterior to the mandibular nerve. It supplies the lateral wall of the cavernous sinus, the region of the Gasserian ganglion and adjacent middle fossa dura, where it anastomoses with the meningeal branches from the ophthalmic artery and MMA and the carotid siphon (inferolateral trunk). The intracranial portion of the accessory meningeal artery has a reciprocal relationship with the inferolateral trunk of the intracavernous carotid in the supply of the mandibular nerve and the dura adjacent to the cavernous sinus. It has prominent anastomoses with the posterolateral branch of the inferolateral trunk (Fig. 29 on page 66). Page 30 of 72 2-3. Artery of the Foramen Rotundum The artery of the foramen rotundum arises from the termination of the IMA and runs alongside the maxillary nerve, passing through the foramen rotundum (Fig. 30 on page 67)(Fig. 31 on page 67). As mentioned earlier, it connects with the branches of the inferolateral trunk of the intracavernous ICA. Thus, it forms an important anastomotic pathway between the arteries of the cavernous region and the termination of the IMA in the pterygopalatine fossa. (Note) Adverse anastomoses of the ophthalmic artery Page 31 of 72 The ophthalmic artery usually arises from the intradural ICA (Fig. 32 on page 68), and an extradural origin has also been identified. An ophthalmic artery originating from the MMA has been recognized as a rare anomaly. The ECA system forms a rich vascular network around the orbit with potential for an anastomotic pathway with the ophthalmic artery (summarized in Table 1 on page 69). The most important risk for embolization within this region is occlusion of the central retinal artery (CRA), which results in visual impairment and blindness of the patient. In addition, embolic stroke could occur through retrograde filling of the ICA (Fig. 33 on page 68). Page 32 of 72 Page 33 of 72 Page 34 of 72 Page 35 of 72 Page 36 of 72 Page 37 of 72 Page 38 of 72 Page 39 of 72 Page 40 of 72 Page 41 of 72 Page 42 of 72 Images for this section: Page 43 of 72 Fig. 1: Diagram to show the origin of the main cranial arteries (left) crown-rump(C.R.) length 7- to 12-mm stage of development. SOB: supraorbital branch, IOB: infraorbital branch, MB: mandibula branch, VPA: Ventral pharyngeal artery, PMA: primitive mandibular artery (right) C.R. length 20- to 24-mm stage. Sup.TA: superior tympanic artery, Ant TA: anterior tympanic artery, CTA: caroticotympanic artery, MMA: middle meningeal artery, IMA: internal maxillary artery Fig. 2: 2D Digital angiography(DA) (left) and thin-section maximum intensity projection(MIP) (right) obtained from the external carotid 3D rotational digital angiography (lateral view) using a C-arm mounted flat- panel detector(FPD) in a patient with cavernous sinus dural arteriovenous fistula. Although the both images could show the fistulous point (arrow), its anatomic details are still unclear. Page 44 of 72 Fig. 3: A slideshow movie with the serial source images of the right common carotid 3D rotational digital angiography using a C-arm mounted FPD in a patient with right cervical internal carotid artery stenosis. ECA; external carotid artery, ICA; internal carotid artery, FA; facial artery, LA; lingual artery, APA; ascending pharyngeal artery, PhB; pharyngeal branch (of the APA), OA; occipital artery, PAA; posterior auricular artery, NMB; neuromeningeal branch (of the APA), HGB: hypoglossal branch (of the APA), JB; jugular branch (of the APA), AMA: accessory meningeal artery, IMA: internal maxillary artery, MMA: middle meningeal artery Page 45 of 72 Fig. 4: Diagram to show the distribution and reciprocal anastomotic pattern of the meningeal arteries at the skull base. AFR: artery of foramen rotundum, AMA: anterior meningeal artery, HGB: hypoglossal branch (ascending pharyngeal artery), IMA: internal maxillary artery, ILT: inferolateral trunk, JB: jugular branch (ascending pharyngeal artery), LCA: lateral clival artery, MCV medial clival artery, MB: mastoid branch (occipital artery), MMA: middle meningeal artery, PB: petrosal branch, PMA: postenior meningeal artery (vertebral artery), PSB: petrosquamous branch, RFL: recurrent artery of foramen lacerum Page 46 of 72 Page 47 of 72 Fig. 5: A case with the persistent primitive hypoglossal artery (arrows) arising from the left ICA, which is demonstrated on MRA. Fig. 6: An ascending pharyngeal artery branching from the lower portion of the ECA. Left common carotid angiogram of the patient with anterior condylar vein dural AVF shows the ascending pharyngeal artery trunk branching from the extremely lower portion of ECA, whose course is similar to that of ICA on both the frontal(A) and the lateral(B) view (green arrow heads). It is dilated as a feeding artery of the dural AVF. Page 48 of 72 Fig. 7: Diagram of the anastomotic routes via the vidian artery(VA) between the superior pharyngeal branch(SPB) of the ascending pharyngeal artery(APA), the accessory meningeal artery(AMA) and the distal internal maxillary artery. AFR: artery of the foramen rotundum, AMA: accessory meningeal artery, APA: ascending pharyngeal artery, CB: carotid branch, IOA: infraorbital artery, MMA: middle meningeal artery, NMT: neuromeningeal trunk, OA: occipital artery, SPB: superior pharyngeal branch, VA: vidian artery Page 49 of 72 Fig. 8: Selective ascending pharyngeal angiogram of a patient with anterior condylar vein dural AVF immediately after transvenous embolization in lateral view ( * indicates coil mass). Page 50 of 72 Fig. 9: The vidian artery(arrows) passing through the vidian canal (pterygoid canal) anteriorly into the pterygopalatine fossa(*) is clearly delineated on the cross-sectional source image of the 3D-DA. Page 51 of 72 Fig. 10: The anastomotic routes between the superior pharyngeal branch(SPB) of the ascending pharyngeal artery and the vidian artery(arrows) are demonstrated on the reconstructed sagittal source image of the 3D-DA. Page 52 of 72 Fig. 11: The superior pharyngeal branch(arrows) of the ascending pharyngeal artery connecting with the vidian artery arised from petrous portion of the ICA(arrow head) and the pterygovaginal artery (pharyngeal branch of the internal maxillary artery, black arrows) are demonstrated on the reconstructed sagittal source image of the 3D-DA. Page 53 of 72 Fig. 12: The anastomotic routes via the vidian artery(arrows) through the vidian canal (pterygoid canal) are demonstrated on the reconstructed sagittal source image of the 3D-DA. Page 54 of 72 Fig. 13: The recurrent artery of the foramen lacerum(arrow head), which is a branch of the lateral clival artery, is demonstrated on axial (A) and reconstructed sagittal (B) source image of the 3D-DA. It has potential anastomotic routes with the carotid branch of the ascending pharyngeal artery, the posterior branch of the inferolateral trunk and the cavernous branch of the middle meningeal artery(MMA). Fig. 14: The neuromeningeal trunk(*) divides into the hypoglossal branch(HB) and the jugular branch(JB), entering the cranial cavity through corresponding foramen. Page 55 of 72 Fig. 15: A patient with the cervical ICA stenosis. The anastomosis between the jugular branch(JB) and the medial/lateral clival artery(MCA/LCA) is seen on the source image of the 3D-DA. Page 56 of 72 Fig. 16: The same case as Fig. 15. The anastomosis between the hypoglossal branch(HB) and the mastoid branch(arrow heads) of the occipital artery(OA) is seen. Fig. 17: Odontoid arterial arch (A) A patient with right ICA stenosis. The odontoid arterial arch(arrowheads) is clearly shown on the source image of the 3D-DA. (B) Right occipital angiogram of the patient with ipsilateral cerebellar hypervascular tumor shows the anastomosis from the neuromeningeal branch of the ascending pharyngeal artery to the vertebral artery via the odontoid arterial arch(arrows). It has a characteristic Ushaped curve, as seen on the lateral view(right). Page 57 of 72 Fig. 18: A case with the type# proatlantal intersegmental artery(arrows) arising from the left ICA, which is demonstrated on MRA. Page 58 of 72 Fig. 19: Occipital angiogram of a patient with sigmoid sinus dural AVF shows dilated mastoid branch(MB) via the mastoid canal and meningeal branches of the occipital artery, including the posterior anastomotic radicular branch(arrows). The neuromeningeal trunk(NMT) of the ascending pharyngeal artery also supplies the dural AVF. Page 59 of 72 Fig. 20: The stylomastoid artery(arrows) arised from the posterior auricular artery(PAA) passing through the stylomastoid foramen (*) to the tympanic cavity is depicted on the source images of the 3D-DA. SP: styloid process, OA: occipital artery Fig. 21: The mastoid branch(arrow heads) of the occipital artery(OA) passing through the mastoid foramen is demonstrated on axial (A) and reconstructed oblique sagittal (B) source image of the 3D-DA. Fig. 22: A patient with left transverse-sigmoid sinus dural AVF. The source images of the 3D-DA demonstrate the anastomoses between the mastoid branch (red arrowhead) of the occipital artery and the petrosquamousal artery (green arrows) of the middle meningeal artery. The small transosseous emissary arteries also enter the cranium via emissary canals to supply lateral/posterior part of dura matter. Page 60 of 72 Fig. 23: Diagram to show the embryologic development of the ECA system with regression of the Hyo-Stapedial artery. (left) crown-rump(C.R.) length 7- to 12-mm stage of development. SOB: supraorbital branch, IOB: infraorbital branch, MB: mandibula branch, VPA: Ventral pharyngeal artery (right) C.R. length 20- to 24-mm stage. Sup.TA: superior tympanic artery, Ant TA: anterior tympanic artery, CTA: caroticotympanic artery, MMA: middle meningeal artery, IMA: internal maxillary artery Page 61 of 72 Fig. 24: The MMA enters the cranium through the foramen spinosum(red arrow head), and then divides into petrosal branch, anterior division and posterior division. The covernous branch is clearly demonstrated(green arow heads) on the source image of the 3D-DA in a patient with right cervical ICA stenosis. Page 62 of 72 Fig. 25: The anterior division of MMA distributing to the orbital region is seen on the source images of the 3D-DA. The recurrent meningeal artery is noted(*). Page 63 of 72 Fig. 26: 3D-DA source image (the same parient as Fig. 22.) demonstrates the petrosquamousal branch(green arrows) anastomosing with the mastoid branch of the occipital artery and the jugular branch of the ascending pharyngeal artery(red arrowheads). Page 64 of 72 Fig. 27: An accessory meningeal artery (AMA) entering the cranium through the sphenoidal emissary foramen (foramen of Vesalius) is demonstrated on the source image of the 3D-DA. Page 65 of 72 Fig. 28: The anterior branch of the accessory meningeal artery (AMA) running along the Eustachian tube is shown on the source image of the 3D-DA. Page 66 of 72 Fig. 29: A patient with left cavernous sinus dural AVF supplied from the cavernous branch of the MMA and the artery of the foramen rotundum. The posterior branch of the accessory meningeal artery (AMA) passing through the foramen ovale(arrowhead) has anastomose with the inferolateral trunk to supply the lesion. Fig. 30: The artery of the foramen rotundum(green arrows) are depicted on the source images of the 3D-DA in a patient with right cervical ICA stenosis. It anastomoses with the inferolateral trunk of the intracavernous ICA. Page 67 of 72 Fig. 31: A patient with left cavernous sinus dural AVF ( the same as Fig. 29). The foramen rotundum and th vidian canal (pterygoid canal) and the corresponding arteries are easily identified on reconstructed coronal source image of the 3D-DA. Fig. 32: Diagram(A) and MIP images on axial(B) and sagittal(C) view of the ophthalmic artery from the source image of the 3D-DA. Page 68 of 72 Fig. 33: A patient with right cervical ICA stenosis. Right common carotid angiogram shows anastomosis between the MMA and the ophthalmic artery through the lacrimal system with retrograde filling to the ICA(arrows). Page 69 of 72 Fig. 34: Table 1: Summary of the branches of the ophthalmic artery and their anastomoses to the ECA. Page 70 of 72 Conclusion The cross-sectional source images of 3D digital angiography(3D-DA) provide a high spatial resolution, thus allowing a reliable visualization of the meningeal branches of the external carotid artery systems in relation to fine osseous structures along the skull base. Knowledge of the potential anastomotic routes between the extracranial and intracranial arteries is essential for the neurointerventionalists. Personal Information Yayoi Kondo Department of Radiology, Nagatomi Neurosurgical Hospital, 2-1-20, Nishi-Omichi, Oita-city, Japan. mail to: [email protected] References 1. Hacein-Bey L, Daniels DL, Ulmer JL, et al. The Ascending Pharyngeal Artery: Branches, Anastomoses, and Clinical Significance. AJNR Am J Neuroradiol 23:1246-1256, 2002. 2. Kakeda S, Korogi Y, Miyaguni Y, et al. A Cone-Beam Volume CT Using a 3D Angiography System with a Flat Panel Detector of Direct Conversion Type: Usefulness for Superselective Intra-arterial Chemotherapy for Head and Neck Tumors. AJNR Am J Neuroradiol 28:1783- 88, 2007 Page 71 of 72 3. Geibprasert S, Pongpech S, Armstrong D, et al. Dangerous Extracranial-Intracranial Anastomoses and Supply to the Cranial Nerves: Vessels the Neurointerventionalist Needs to Know. AJNR Am J Neuroradiol 30:1459-68, 2009. 4. 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