Neuroangiography: Review of Anatomy, Periprocedural Management, Technique, and Tips

Abstract

Neuroangiography (NA) is a minimally invasive procedure used to diagnose patients with neurovascular diseases. Noninvasive imaging has improved dramatically in recent years and is utilized more frequently; however, further evaluation with NA is still required in certain cases. NA indications include intracranial (cerebral aneurysms, arteriovenous malformations, dural arteriovenous fistula, cerebral vasculitis, cerebral vasospasm, ischemic stroke, nontraumatic subarachnoid hemorrhage, intracerebral hemorrhage, Moyamoya, vein of Galen malformation, intracranial tumors, and pseudotumor cerebri) and extracranial (internal and common carotid artery stenosis, vertebral artery stenosis, carotid artery blowout, vertebral artery blowout, epistaxis, oropharyngeal bleeding, and carotid body tumor) pathologies which can help with diagnosis and potential subsequent endovascular treatment. A thorough understanding of normal and variant cervical/cranial vascular anatomy is required. In addition, periprocedural management, catheter technique, equipment needed, and underlying disease pathology are paramount to successful and safe outcomes. This article will review basic neurovascular anatomy, periprocedural management, NA technique, and tips for safe and successful outcomes.

Indications

The indications for neuroangiography (NA) include intracranial diseases (cerebral aneurysms, arteriovenous malformations, dural arteriovenous fistula, cerebral vasculitis, cerebral vasospasm, ischemic stroke, nontraumatic subarachnoid hemorrhage, intracerebral hemorrhage, Moyamoya, vein of Galen malformation, intracranial tumors, and pseudotumor cerebri) and extracranial diseases (internal and common carotid artery stenosis, vertebral artery stenosis, carotid artery blowout, vertebral artery blowout, epistaxis, oropharyngeal bleeding, carotid body tumor). Advancements in noninvasive vascular imaging have led to decreased NA utilization; however, NA is still required for suspected diseases that may be inconclusive with noninvasive imaging. Examples of disease types that may be inconclusive with noninvasive imaging include nontraumatic subarachnoid hemorrhage, nontraumatic intracerebral hemorrhage, cerebral vasculitis, oropharyngeal bleeding, and dural arteriovenous fistula.

Neurovascular Anatomy

Aortic Arch and the Major Branches

The ascending aorta is approximately 5 cm in length as it ascends behind the sternum. It continues as the transverse aorta given rise to the aortic arch, which lies in the superior mediastinum beginning at the level of the second right sternocostal articulation. The aorta then projects posteriorly and to the left over the left pulmonary hilum. The major branches that originate from the aortic arch are the brachiocephalic artery, left common carotid artery, and left subclavian artery.

The brachiocephalic artery is the most proximal and largest branch. At the level of the sternoclavicular joint, it typically bifurcates into the right common carotid artery and right subclavian artery. The left common carotid artery typically arises just distal to the brachiocephalic artery, ascends anterior to the trachea, then passes posterolaterally. The left subclavian artery typically arises just distal to the left common carotid artery origin and ascends into the neck. It then courses laterally to the medial border of the anterior scalene muscle.

The most common variation of the aortic arch is a bovine arch anatomy consisting of a common origin of the brachiocephalic and left common carotid artery ( Figs. 1 and 2 ) which occurs up to 27% of the time. ¹ Additional common variations include an arch origin of the left vertebral artery which has been reported in 2.4 to 5.8% of cases, ^{2 3} aortic arch origin of the right vertebral artery ( Figs. 1 and 2 ), and aberrant right subclavian artery seen in 0.6% of cases. ¹ Additionally, the aortic arch is classified into three different aortic arch types (I, II, and III). The aortic arch type reflects the vertical distance from the origin of the brachiocephalic artery to the top of the arch in the parasagittal projection. Type I arch anatomy has a vertical distance less than 1 diameter of the left common carotid artery, type II anatomy has a vertical distance between 1 and 2 diameters of the left common carotid artery, and type III anatomy has a vertical distance greater than 2 diameters of the left common carotid artery.

Fig. 1.

Digital subtraction angiography with a 30-degree lateral anterior oblique projection of a patient with bovine aortic arch anatomy, a type II aortic arch, and an aberrant right vertebral artery origin. BC, brachiocephalic artery; LCC, left common carotid artery; LSC, left subclavian artery; LVA, left vertebral artery; RCC, right common carotid artery; RVA, right vertebral artery, RVA origin, right vertebral artery origin.

Fig. 2.

Computed tomography angiography sagittal image of the same patient as in Fig. 1. BC , brachiocephalic artery; LCC, left common carotid artery; LSC, left subclavian artery; RVA, right vertebral artery.

External Carotid Artery

The external carotid artery (ECA) originates from the common carotid artery at the midcervical level typically at the C4 level. It is typically anterior and medial to the internal carotid artery (ICA) with the internal jugular vein coursing posterolaterally to it. The ECA has eight branches. The eight branches in order from proximal to distal are the superior thyroid artery, ascending pharyngeal artery, lingual artery, facial artery, occipital artery, posterior auricular artery, superficial temporal artery (STA), and internal maxillary artery ( Figs. 3 and 4 ).

Fig. 3.

Lateral digital subtraction angiography of the right external carotid artery depicting a ruptured dural arteriovenous fistula with supply emanating from multiple transosseous branches of the right occipital artery. DAVF, dural arteriovenous fistula; EDV, ectatic draining vein of the DAVF; IMAX, internal maxillary artery; MMA, middle meningeal artery; O, occipital artery; PA, posterior auricular artery; STA, superficial temporal artery.

Fig. 4.

Lateral digital subtraction angiography of the left external carotid artery in a patient with recurrent oropharyngeal bleeding. AP, ascending pharyngeal artery; F, facial artery; L, lingual artery; ST, superior thyroid artery. The AP is the first small branch from the posterior aspect of the ECA. This patient's facial artery exhibits some caliber changes indicative of the known preexisting head and neck cancer and previous radiation treatment.

The superior thyroid artery is typically the first artery that arises from the ECA trunk, but approximately 20% of the time, it arises from the carotid bifurcation. ⁴ The superior thyroid artery supplies the thyroid gland along with the larynx. It has extensive anastomosis from the contralateral superior thyroid artery and inferior thyroid artery, which originates from the thyrocervical trunk, a branch of the subclavian artery.

The ascending pharyngeal artery is typically a small and the first posteriorly projecting ECA branch. It has anteriorly directed pharyngeal branches and posteriorly directed inferior tympanic and muscular branches along with the neuromeningeal branch, which supplies the lower cranial nerves and dura. The neuromeningeal branch must be identified prior to head and neck embolization procedures to prevent nontarget embolization of the lower cranial nerves. ⁵ In addition, anastomotic supply between the ascending pharyngeal artery and the vertebral/ICA circulations poses a potential hazard during embolization with liquid embolic agents. ⁵

The lingual artery is the first anterior ECA branch and provides vascular supply to the tongue and oral cavity. Approximately 10 to 20% of the time it shares a common trunk with the facial artery. ⁶ The facial artery continues to supply the ascending palatine artery, submental artery, labial arteries, buccal branches, masseteric branches, and the lateral nasal artery. The facial artery terminates as the angular artery.

The occipital artery originates from the posterior aspect of the ECA and supplies the posterior scalp and neck, and provides meningeal branch supply to the posterior fossa. It frequently provides supply to dural arteriovenous fistulas via transosseous branches, which can be associated with preexisting head trauma. The occipital artery can have extensive anastomotic supply between segmental branches of the vertebral artery and ascending cervical arteries from the costocervical trunk. This poses another potential hazard during head and neck embolization procedures with liquid embolic agents. ⁵ The posterior auricular artery is a small branch that arises from the posterior aspect of the ECA, typically just superior to the occipital artery origin. It supplies the scalp, pinna, and external auditory canal.

The STA originates from the superior aspect of the ECA. It is the smaller of the two terminal ECA branches and supplies the anterior two-thirds of the scalp, part of the ear, and parotid gland. STA evaluation and caliber is an important consideration prior to surgical STA to middle cerebral artery (MCA) bypass for diseases such as Moyamoya. Anastomotic supply between frontal branches of the STA and ophthalmic artery poses a potential hazard during embolization with liquid embolic agents. ⁵

The internal maxillary artery (IMAX) is the larger of the two terminal ECA branches. It arises in close proximity to the parotid gland and projects into the masticator space. The internal maxillary artery has anastomotic supply with the facial artery and provides collateral blood flow to the ICA. The middle meningeal artery (MMA) is typically the largest branch of the IMAX and courses superiorly to the foramen spinosum where it enters the skull. The MMA is the classic artery implicated in traumatic epidural hematomas. MMA embolization has been utilized with increased frequency in the treatment of recurrent subdural hematomas. ⁷ In addition, the MMA frequently provides supply to dural arteriovenous fistulas and vascular skull base tumors including meningiomas. Other notable branches of the IMAX include the middle pterygoid segment branches (deep temporal arteries, masseteric and buccal arteries) and distal pterygopalatine branches (infraorbital artery, superior alveolar artery, greater palatine artery, and sphenopalatine artery). The sphenopalatine is a specific branch that is frequently a target for embolization in refractory epistaxis cases. ⁸ Distal IMAX and MMA branches provide important anastomotic supply to ophthalmic artery branches, which poses a potential hazard during embolization with liquid embolic agents. ⁵

Internal Carotid Artery

The ICA typically originates from the common carotid artery at the level of C3–4 or C4–5 and projects posteriorly and laterally to the ECA before coursing medial to the ECA as it ascends toward the skull base. The newest classification (Osborn) divides the ICA into seven segments. In order from proximal to distal, the segments are C1 (cervical), C2 (petrous), C3 (lacerum), C4 (cavernous), C5 (clinoid), C6 (ophthalmic), and C7 (communicating).

C1 (Cervical)

The cervical ICA consists of the carotid bulb and the ascending cervical portion. The carotid bulb forms a focal dilation, which exhibits altered flow dynamics with retrograde fluid eddies making this a vulnerable location for carotid stenosis. The ascending segment projects superiorly within the carotid space. The carotid space encompasses the ICA, internal jugular vein, lymph nodes, postganglionic sympathetic nerves, and multiple lower cranial nerves. The cervical segment terminates as it enters the carotid canal in the petrous temporal bone. Tortuosity of the cervical ICA is relatively common and needs to be carefully considered when performing cerebral angiography in an effort to avoid arterial injury during catheterization.

C2 (Petrous) and C3 (Laceral)

The petrous segment begins after the ICA enters the carotid canal. The carotid canal lies anterior to the jugular foramen. Two branches originate from the petrous segment. The vidian artery is the first branch and passes through the foramen lacerum. It can anastomose with multiple branches of the ECA. The caroticotympanic artery is the second and passes through the stapes to supply the middle ear cavity. Both branches are rarely identified during NA. The laceral segment begins where the carotid canal ends and courses above the foremen lacerum. The laceral segment ends at the petrolingual ligament.

C4 (Cavernous)

The cavernous segment begins at the superior margin of the petrolingual ligament and consists of three segments, which are the posterior genu, horizontal segment, and anterior genu. The cavernous segment exits the cavernous sinus through the dural ring. Two notable branches originate from the cavernous segment. The meningohypophyseal artery originates more proximally from the posterior genu and provides supply to the pituitary gland, tentorium, and clivus. This branch can be seen as a posteromedially projecting blush in the region of the pituitary. It can also be a potential supply to dural arteriovenous fistulas. The inferolateral trunk is the second notable branch and provides blood supply to the third, fourth, and sixth cranial nerves. Tortuosity of the cavernous segment can make intracranial catheterization for the treatment of ischemic strokes, intracranial aneurysms, and other cerebral pathologies challenging.

C5 (Clinoid) and C6 (Ophthalmic)

The clinoid segment is the shortest of all ICA segments and begins at the dural ring just above the anterior genu of the cavernous segment. It ends at the distal dural ring where the ICA enters the subarachnoid space. The ophthalmic segment begins at the distal dural ring and ends proximal to the posterior communicating artery. The largest branch from the ophthalmic segment is the ophthalmic artery, which arises medially to the anterior clinoid process as the ICA exits the cavernous sinus. In 90% of cases, the ophthalmic artery is intradural. The ophthalmic artery has ocular, orbital, and extraorbital branches. The ocular branches are the ciliary arteries and central retinal artery, which supplies the retina and choroid. Although the central retinal artery is rarely visualized, a choroidal blush is frequently seen as a crescent-shaped vascular blush during the late arterial phase. The orbital branches are the lacrimal and muscular branches, which supply the extraocular muscles. Ophthalmic artery catheterization and chemoembolization have been performed more regularly for retinoblastoma treatment. ⁹

The second branch of the ophthalmic segment is the superior hypophyseal artery, which arises from the posteromedial aspect of the ICA. This branch supplies the anterior pituitary lobe, stalk, optic nerve, and chiasm.

C7 (Communicating)

The communicating segment starts just proximal to the posterior communicating artery origin and ends at the ICA bifurcation. The posterior communicating artery is the first branch and arises from the posterior aspect of the intradural ICA. The posterior communicating artery anastomoses with the posterior cerebral artery (PCA). It courses above the oculomotor nerve and has several small anterior thalamoperforating arteries that supply the medial thalamus and walls of the third ventricle. A posterior communicating artery infundibulum is not uncommon and can be seen up to 17% of the time. ¹⁰ In addition, fetal origin (posterior communicating artery has the same diameter as the PCA) of the PCA is relatively common.

The second branch of the communicating segment is the anterior choroidal artery, which arises from the posteromedial aspect of the intradural ICA. The proximal (cisternal) segment projects posteromedially below the optic tract and superomedial to the temporal lobe uncus. The distal segment begins at the choroidal fissure and follows the choroid plexus. The anterior choroidal artery supplies many important structures including the posterior limb of the internal capsule, cerebral peduncle, optic tract, choroid plexus, and medial temporal lobe.

Persistent Carotid–Vertebrobasilar Anastomosis

Occasionally the primitive carotid–vertebrobasilar anastomoses persist and are identified during adulthood. These primitive anastomotic connections provide temporary supply from the ICA to the longitudinal neural artery, which is the future vertebrobasilar system. Table 1 details the four types of carotid–vertebrobasilar anastomoses: the persistent trigeminal, otic, hypoglossal, and proatlantal.

Table 1. Persistent carotid–vertebrobasilar anastamoses ¹⁰ .

Persistent trigeminal artery	Most common type with an incidence of 0.5–0.7% Originates from posterior wall of cavernous ICA and joins the distal third of the basilar artery
Persistent otic artery	Extremely rare, only case reports, debatably may not actually exist First to regress Should arise in the petrous segment ICA
Persistent hypoglossal artery	Second most common with an incidence of 0.027–0.29% Originates from posterior wall of cervical ICA between C1 and C3 levels and courses through the hypoglossal canal to form the vertebrobasilar artery
Persistent proatlantal artery	Originates from the common carotid artery bifurcation, ICA (type I), or ECA (type 2) at the C2–4 levels Joins the vertebral artery at the suboccipital region and traverses the foramen magnum

Abbreviations: ECA, external carotid artery; ICA, internal carotid artery.

Anterior Cerebral Artery

The anterior cerebral artery (ACA) is the smallest terminal branch of the ICA. The A1 segment, also called the precommunicating segment, continues to the junction with the anterior communicating artery. The A2 segment extends vertically from the anterior communicating artery to the genu of the corpus callosum. Multiple small medial lenticulostriate arteries arise typically from the A1 segment, as do additional perforating branches to the corpus callosum genu, fornix, and septum pellucidum from the A2. The largest penetrating branch from these segments is the recurrent artery of Heubner, which can originate from the A1 segment, A2 segment, or anterior communicating artery.

The first cortical branch originating from the A2 segment is the orbitofrontal artery, which supplies the inferior frontal lobe. The second is the frontopolar artery, which extends to and supplies the frontal pole. The A2 segment terminates near the corpus callosum genu. It typically bifurcates into the pericallosal artery and callosomarginal artery branches. These arteries along with their branches are classified as A3 segment branches, which then continue to the more distal A4 segment branches. Leptomeningeal collaterals from distal ACA branches to the MCA territory are critical in preserving ischemic penumbra before definitive treatment can be performed with ischemic stroke mechanical thrombectomy.

An important anomalous variant is the azygous ACA. This occurs when the embryonic median artery of the corpus callosum persists. A single ACA arises that supplies both ACA territories. This has been reported with a 0.2 to 4% prevalence. ¹¹ A more common hypoplastic and contralateral dominant ACA A1 segment can be mistaken for this anomaly.

Middle Cerebral Artery

The MCA is the largest terminal branch of the ICA with roughly twice the diameter of the ACA. The first segment is the M1. It has both a pre- and postbifurcation segment prior to turning posterosuperiorly into the sylvian fissure and becoming the M2 segment. The anterior temporal artery typically originates from the M1 segment proximal to the bifurcation and passes directly anteriorly and inferiorly over the temporal lobe. In addition, the lenticulostriate arteries arise from the M1 segment to supply the basal ganglia and other deep structures of the brain including the caudate and internal capsule.

The M1 bifurcates and typically after the origin of the anterior temporal artery, there are two major divisions frequently referred to as the superior and inferior divisions. The MCA continues as the M2 (insular) segment, which includes multiple branch points near the anterior part of the insula. The M2 segment then continues as six to eight major branches that project over the insula while continuing to the circular sulcus. The MCA continues at the top of the circular sulcus as the M3 (opercular) segment and ends at the surface of the lateral cerebral fissure. The M4 (cortical) segment begins at the surface of the sylvian fissure and continues as distal branches supplying the cortical surface of the cerebral hemisphere ( Figs 5 and 6 ).

Fig. 5.

Anteroposterior projection digital subtraction angiography of the left internal carotid artery. A1, ACA A1 segment; A2, ACA A2 segment; C1, cervical ICA; C2, petrous ICA; C4, cavernous ICA; C7, communicating ICA; CA1, contralateral ACA A1 segment supplied via flash filling across the anterior communicating artery(arrow head); M1, MCA M1 segment; M2, MCA M2 segment; M3, MCA M3 segment; M4, MCA M4 segment; single arrow, MCA superior division; double arrows, MCA inferior division; larger arrow, fetal PCA; curved arrow, anterior temporal artery.

Fig. 6.

Lateral digital subtraction angiography of the left internal carotid artery. A2, ACA A2 segment; A3, ACA A3 segment; A4, ACA A4 segment; C1, cervical ICA; C2, petrous ICA; C3, laceral ICA; C4, cavernous ICA; ID, MCA inferior division; OA, ophthalmic artery; M3, MCA M3 segment; M4, MCA M4 segment; black arrow head, posterior communicating artery; small black arrow, anterior choroidal artery; white arrow, MCA bifurcation.

Vertebrobasilar System

The vertebral arteries typically originate from the subclavian artery, although variants occur and are discussed previously in section “Neurovascular Anatomy.” The V1 (extraosseous) segment is the first segment as it courses posterosuperiorly and terminates as it enters the transverse foramen at the C6 level. The V2 segment (foraminal) ascends and traverses the C3–6 transverse foramen and then passes through the C2 transverse foramen laterally before projecting superiorly through the C1 transverse foramen. The vertebral artery continues as the V3 segment in a posteromedial direction around the atlantooccipital articulation. The V3 segment then turns anteriorly and upward toward the dura as it enters the foramen magnum. The vertebral artery continues as the intradural V4 segment and at the pontomedullary junction, the two vertebral arteries converge to form the basilar artery.

The vertebral artery has both muscular branches, which supply deep cervical musculature and spinal branches. In addition, anterior meningeal and posterior meningeal arteries can originate from the V2 segment. The anterior spinal artery is an important smaller branch, which can be seen during NA in certain patients. It typically arises from the distal vertebral artery and can project inferomedially to unite with the contralateral anterior spinal artery.

The largest vertebral artery branch is the posterior inferior cerebellar artery (PICA). It typically arises from the intradural vertebral artery but can have an extradural origin as well occurring 5 to 18% of the time. ¹² The PICA is divided into four segments, which are the anterior medullary segment, lateral medullary segment, posterior medullary (tonsillar loop) segment, and supratonsillar (cortical) segment. The anterior and lateral medullary segments provide supply to the medulla and the more distal segment branches provide supply to the posterior inferior cerebellum. Of note, the vertebral artery can terminate in PICA approximately 0.2% of the time. ¹² In addition, there can be a shared anterior inferior cerebellar artery (AICA)-PICA trunk which is common variant.

The basilar artery is the merging and continuation of the two vertebral arteries near the pontomedullary junction. It continues superiorly and terminates typically as the two PCA branches in the interpeduncular cistern. Numerous perforating branches originate from the basilar artery during its course in the prepontine cistern. These branches include median, paramedian, and lateral pontine perforators.

The AICA is the smallest of the three main cerebellar arteries and originates from the proximal basilar artery. It can arise as a single, duplicate, or triplet branch. It supplies the anterior and lateral portion of the cerebellum and typically provides supply to the labyrinth (internal auditory) artery. ¹³ The superior cerebellar artery (SCA) arises just prior to the basilar artery bifurcation and can exist as a single, duplicate, or triplet branch. The SCA courses below the oculomotor cranial nerve and projects around the cerebral peduncle to form two major distal branches, which supply the superior and lateral cerebellar hemisphere, superior cerebellar peduncle, dentate nucleus, and cerebellar vermis.

Posterior Cerebral Artery

The PCA originates from the basilar artery anterior to the midbrain typically in the interpeduncular cistern. The P1 segment courses through the interpeduncular cistern and continues to its anastomosis with the posterior communicating artery. The P2 (ambient) segment continues from the posterior communicating artery to the posterior aspect of the midbrain as it courses around the cerebral peduncle. As the proximal PCA courses around the midbrain, it supplies many perforating branches to the thalamus, brainstem, and ventricular system including the thalamoperforating branches, thalamogeniculate branches, peduncular perforating branches, and medial/lateral posterior choroidal artery branches. In addition, the proximal and distal P2 segment gives rise to both anterior and posterior temporal artery branches, which anastomose with the anterior temporal artery from the MCA.

The PCA continues as the P3 segment, which extends from the quadrigeminal plate to the calcarine fissure. The P3 segment projects medially within the perimesencephalic cistern before terminating as the distal P4 segment branches. The medial division of the P4 segment branches divides into the parietooccipital and calcarine arteries. The lateral division of the P4 segment continues as the lateral occipital artery ( Fig. 7 ).

Fig. 7.

Anteroposterior digital subtraction angiography of the left vertebral artery with reflux into the contralateral vertebral artery. BA, basilar artery; CPT, contralateral posterior temporal artery; CVA, contralateral vertebral artery; P1, PCA P1 segment; P2, PCA P2 segment; P3, PCA P3 segment; P4, PCA P4 segment; V2, vertebral artery V2 segment; V3, vertebral artery V3 segment; V4, vertebral artery V4 segment; arrow, contralateral PICA; arrow tip, left AICA/PICA complex; small arrow, left SCA.

Clinical Evaluation and Preprocedural Management

Preprocedural evaluation, history, and physical examination are critical prior to NA. Communication with the referring physician is highly recommended prior to the procedure to fully understand the underlying problem that needs to be answered. The physician should perform a focused history and neurologic exam documenting known neurologic deficits in clinic or prior to the procedure. Detailed informed consent should be discussed including specific risks of the procedure (pain, infection, bleeding, acute renal insufficiency, systemic/cervical/intracranial dissection, stroke, and groin hematoma).

Relative contraindications to NA include renal insufficiency, coagulopathy, and contrast allergy. At our institution, we use 32 mg of methylprednisolone 12 hours before and 2 hours before the procedure. If chronic or acute renal insufficiency is present, we prehydrate with normal saline and use minimally needed amounts of iodinated contrast. ¹⁴

The neurologic exam should include mental status, orientation, memory, language, cranial nerve evaluation, sensation, motor, and gait testing. An adverse event in the course of NA is rare; however, calls to evaluate the patient postprocedure are frequent. Having a detailed and documented neurologic exam will provide reassurance if known neurologic deficits exist. Serologic evaluation before the procedure should include a complete blood cell count, serum creatinine, and protime/international normalized ratio, as dictated by the patient's clinical situation. Anticoagulants should be held when possible. At the authors' institution, oral anticoagulants are held and low-molecular-weight heparin is given in substitute 4 days before and 2 days after the procedure. Patients should eat nothing by mouth 6 hours prior to the procedure and the morning insulin dose should be given in half its full dose.

Diagnostic Neuroangiography Technique

Sedation and Positioning

At the authors' institution, a combination of fentanyl and midazolam is used in minimum doses needed to achieve comfortable conscious sedation. Presedation evaluation does include American Society of Anesthesia and airway assessment. The patient is positioned on the table supine with a headrest. To reduce motion artifact, the patient is instructed to hold still and in certain cases to hold their breath. Uncooperative patients may require higher doses of sedation and a head strap to reduce motion artifact.

Access

At the authors' institution, the common femoral artery (CFA) is the typical access site for NA. However, transradial and transbrachial accesses are occasionally used and have been more frequently utilized in patients with tortuous aortic arch anatomy. ¹⁵ Under ultrasound guidance, the periarterial tissue is infiltrated with lidocaine and the right CFA is accessed with a micropuncture set. After introduction of the micropuncture set dilator, a J-wire (curved atraumatic tip) is inserted and a 5-Fr sheath (Cordis, Hialeah, Fl) is inserted. This is connected to a continuous heparinized saline infusion.

Catheterization, C-Arm Positioning, and Power Injector Settings

Many catheters and wires are available for NA. Important criteria to consider prior to selecting a catheter are vascular anatomy, patient's age, and preexisting arterial disease. At the authors' institution, we occasionally obtain cervical arch aortography when there is a known aortic arch disease or an anomaly that warrants evaluation. In addition, cervical arch aortography may be needed when catheterization is challenging. At the authors' institution, a 5-Fr pigtail catheter (Cook Medical, Bloomington, IN) is used. The pigtail catheter is a multiside-holed flush 90-cm catheter, which provides enough length to reach the ascending aorta proximal to the brachiocephalic artery. Once the pigtail catheter is appropriately positioned, the catheter is connected to the power injector while carefully inspecting the catheter system for any air. Cervical aortography is performed with a standard injection rate of 20 mL/s for a total of 40 mL. A 30-degree lateral anterior oblique projection helps elongate the transverse aorta and separate the origins of the great vessels ( Fig. 1 ). If aortography is performed at the beginning of the procedure, the pigtail catheter is subsequently withdrawn into the descending aorta and exchanged for the NA catheter over a J wire.

As mentioned earlier, aortic arch anatomy along with the patient's age will help in identifying the appropriate catheter for NA. Type I and Type II aortic arch configurations are more easily catheterized with angled catheters, while reverse curve catheters are frequently needed for Type III aortic arches. For young patients with Type I and Type II arch anatomy, a 5-Fr glide catheter (Terumo Interventional Systems, Somerset, NJ) is typically used at the authors' institution. The authors believe the catheter tip is less traumatic and poses a lower risk of vascular injury when selecting vessels as opposed to catheters with more acutely angled tips. If the great vessel origin has too sharp of a curve, then a 5-Fr Davis catheter (Cook Medical) is used. For challenging Type III aortic arch configurations, a 5-Fr Simmons-2 catheter (Cook Medical) should be considered for great vessel selection. In instances where a Type II or III arch occurs in conjunction with a tortuous bovine arch configuration, a 5-Fr VTK catheter (Cook Medical) is extremely helpful. In certain instances, a 5-Fr H1 catheter (Cook Medical) is necessary especially for tortuous brachiocephalic to subclavian artery navigation when trying to select the right vertebral artery.

At times catheterization of the distal cervical arteries may not be possible via the CFA route. If the distal portion of the cervical artery of interest is impossible to select due to tortuosity, a radial approach or in rare cases (i.e., ischemic stroke) direct carotid puncture may be necessary. An additional alternative during NA is to utilize one of the aforementioned catheters and position it in the proximal portion of the great vessel. A Progreat 2.8-Fr microcatheter (Terumo Interventional Systems) can be inserted with a 0.014-in Synchro 2 microwire (Stryker, Kalamazoo, MI) through the NA catheter to select the more distal portion of the cervical artery of interest. The Progreat microcatheter can then be directly connected to the power injector for a power injection as it is rated to 1,000 psi.

Once the NA is selected, the catheter is advanced over a J wire (if not already positioned) into the descending aorta at the level of the umbilicus. The NA catheter is meticulously flushed with heparinized saline, which helps minimize the risk of air and thrombotic emboli propagation into the cerebral vasculature. Next, the catheter is connected to a Tuohy adapter, which is then connected to a three-way stopcock. The three-way stopcock and catheter are connected to a continuous heparin infusion (6,000 units of heparin per 1 L of NS) which is run at a drip rate of approximately 1 to 2 per second throughout the duration of the procedure. Attached to the other end of the three-way stopcock is a duct tube, which is connected to the power injector via another three-way stopcock. A contrast syringe or heparinized saline syringe can be connected to the other side port of the three-way stopcock to allow for test injections during the procedure and to complete the system flushing prior to NA. After the catheter system has been inspected and all air has been removed, NA is performed.

Under fluoroscopic guidance, a 0.035-in glide wire (Terumo Interventional Systems) is advanced through the NA catheter positioned in the descending aorta. The glide wire is advanced over the aortic arch and into the ascending aorta. The NA catheter is advanced over the glide wire and positioned distal to the origin of the target vessel. The catheter is pulled back gently into the origin of the great vessel. At this point, the wire is readvanced carefully paying special attention to anatomic landmarks and utilizing tactile feedback to select the target vessel of interest. In certain instances due to atherosclerotic or tortuous cervical anatomy, a 0.035-in tapered glide wire (Terumo Interventional Systems) may be necessary. Once the wire is positioned in the desired location of the target vessel, the NA catheter is advanced over the wire. The wire is slowly removed to prevent any inadvertent vacuum effect if the NA catheter is obturating a small artery or if the tip is against the wall of the target vessel.

If a Simmons-2 or VTK catheter is required, the catheter must be formed prior to advancement over the aortic arch. The Simmons-2 can be formed by selecting the contralateral common iliac artery, positioning a stiff wire up to its primary angle, and gently pushing the Simmons-2 catheter up the descending aorta. This will form the catheter into its reverse curve shape. A similar technique can be performed in the left subclavian artery. The VTK catheter can typically be advanced over the aortic arch without a wire in it. Once advanced over the arch the VTK typically forms. Next, the primary angle of the catheter is retracted into the target artery. The glide wire can be advanced thereafter; however, rapid advancement of a stiff glide wire can cause the catheter to prolapse into the proximal aortic arch.

In addition to difficult aortic arch anatomy, extreme tortuosity including 360-degree turns of the cervical vasculature can make NA challenging. In these cases, a tapered glide wire or 0.035-in stiff glide wire (Terumo Interventional Systems) can be very useful. Once the wire is a certain distance past the region of tortuosity, the artery typically straightens allowing the catheter to be advanced to the target location. In some cases, this may predispose the artery to occlusion, vasospasm, or dissection; therefore, special attention during the test injection following catheterization is extremely important. If this occurs, the catheter should be removed. Vasospasm occasionally resolves on its own. In certain cases at the authors' institution, intra-arterial verapamil can be administered for catheter-induced vasospasm in small doses of 5 to 10 mg while carefully monitoring the patient's blood pressure and heart rate for deleterious hemodynamic changes. At the discretion of the interventionalist, NA may need to be aborted if a vascular injury or obturation of the artery occurs.

At the authors' institution, we prefer direct catheterization of the ICA and ECA (if needed) for many of the intracranial diseases mentioned earlier as opposed to only common carotid artery injections. If the patient is older or has a history of cervical artery atheromatous disease, a hand injection roadmap can be performed in the common carotid artery prior to catheterizing the ICA or ECA. If a hand injection is performed, the contrast syringe should be held with the plunger facing up after removing all air bubbles from the syringe. If a common carotid artery will suffice for diagnostic evaluation, a power injection of 6 mL/s for a total of 12 mL is performed. For common carotid arteriography, we use standard anteroposterior (AP) and lateral projections. A common landmark when positioning for a standard AP view is to align the petrous ridges in the midorbit region.

If selection of the ICA or ECA is needed, the wire is gently advanced into the artery of interest and the catheter is subsequently advanced over the wire using the same technique described earlier. Special attention should be noted during selection of the ECA to avoid vasospasm. Intra-arterial verapamil can be administered in small doses for catheter-induced spasm if needed. A hand injection using a contrast syringe is performed to ensure no vascular injury, vasospasm, or obturation of the artery has occurred. In addition, this helps the interventionalist determine optimal injection rates based on the vessel caliber. For ICA injections, the authors typically use an injection rate of 4.5 mL/s for a total of 9 mL. For ECA injections, the authors use an injection rate of 2 mL/s for a total of 8 mL. For ICA and ECA injections, standard AP and standard lateral projections are utilized. Multiple oblique views are obtained to evaluate the ICA summit, MCA, and ACA branches further.

The left vertebral artery is preferred over the right vertebral artery when only one vertebral artery is needed for NA because it is typically the dominant vertebral artery. If right vertebral artery pathology is not suspected or if adequate reflux supplies the right PICA from the left vertebral artery injection, left vertebral injection will suffice. Catheterization of the vertebral artery can be especially dangerous because the vertebral artery is prone to dissection and vasospasm. Delayed washout after contrast injection raises the concern for obturation of the artery, vasospasm, dissection, or possible thromboembolic phenomenon from catheterization. Once again, it is prudent to slowly remove the catheter to identify the problem and determine if further action needs to be taken (i.e., verapamil infusion, thrombectomy). For the vertebral artery injection, the authors typically use an injection rate of 4 mL/s for a total of 8 mL. An AP Townes view (align the petrous ridges with the top of the orbit) is utilized along with standard lateral projection. Multiple oblique views are obtained once again to evaluate the PICA, basilar artery branches, and PCA branches.

Postprocedural Management and Complications

After NA is complete, closure can be obtained with either manual compression or percutaneous closure. At our institution, we typically hold pressure for approximately 20 minutes with a 5-Fr system. The authors use a ProGlide (Abbott, Chicago, IL) if the CFA meets closure criteria (sufficient diameter, puncture above the CFA bifurcation, no or minimal atheromatous disease). We routinely examine the patient after NA to ensure no neurologic changes have occurred. If a neurologic change occurs, CT or MRI may be warranted. Standard institution neurologic and groin checks are performed while the patient recovers in the postprocedure area prior to discharge.

Complications can occur during NA. Older patient, increased procedure time, number of catheter exchanges, and amount of contrast are associated with increased rates of complications. ¹⁶ Stroke is the main neurologic complication that can occur with reported permanent neurologic deficit rates of 0 to 2.5%. ¹⁶ Other complications include renal failure, systemic arterial occlusions, dissections, and groin hematomas.

Conclusion

NA is an essential diagnostic tool to evaluate certain neurovascular disease. An understanding of neurovascular anatomy, NA technique, and image interpretation is paramount to performing safe and successful evaluation. Periprocedural care is of fundamental importance as well to ensure patient safety and appropriate complication management if needed.