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CT Neck Angiography & Venography: Complete Arterial and Venous Anatomy

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OVERVIEW IMAGE: Aortic Arch to Intracranial Vessels

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PART 1: CT NECK ANGIOGRAPHY (ARTERIAL ANATOMY)

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1. AORTIC ARCH

• Bovine arch: left CCA arises from the brachiocephalic trunk (~13-15%) - most common variant
• Aberrant right subclavian artery (arteria lusoria): retroesophageal course (~0.5-2%)
• Left vertebral artery arising directly from arch (~2-5%)

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2. COMMON CAROTID ARTERIES (CCA)

• Normal wall thickness: 1-2 mm, smooth internal and external contour
• Atheroma: calcified or soft plaque causing luminal irregularity
• Dissection: intimal flap, double lumen, or mural hematoma (crescentic hypodensity in wall on non-contrast; false lumen often slightly smaller caliber)

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3. CAROTID BIFURCATION

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4. INTERNAL CAROTID ARTERY (ICA)

ICA Segment Diagram (DSA, labeled):

ICA Segment Illustration (color-coded):

ICA Segments - Detail:

DSA/Angiographic image showing ICA segments with branches and bone landmarks:

What to Assess on CTA:

• Stenosis: NASCET method (compare residual lumen to ICA above bulb). Hemodynamically significant at >50%, surgical threshold at >70%
• Occlusion: Absent enhancement; compare to contralateral side
• Dissection: Mural hematoma (crescent sign), intimal flap, pseudolumen, pearl-and-string pattern; may extend from C1 into petrous segment
• Pseudoaneurysm: Focal saccular outpouching, often at prior dissection site or trauma
• Fibromuscular dysplasia (FMD): String-of-beads appearance, most common in C1-C2; young women; bilateral in 60%; non-atherosclerotic

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5. EXTERNAL CAROTID ARTERY (ECA)

ECA Branches (mnemonic: Some Angry Ladies Fight Over PMS):

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6. VERTEBRAL ARTERIES (VA)

• V1: Look for origin stenosis; the right VA arises from the subclavian distal to the thyrocervical trunk
• V2: Seen within the transverse foramina - compare caliber bilaterally (left VA dominant in ~50%)
• V3: The "exit loop" at C2 is visible just posterior to the C1-C2 joint
• V4: Visible entering the foramen magnum, converging toward the basilar artery

• Left VA arises directly from aortic arch (~2-5%)
• VA hypoplasia (diameter <2 mm): usually right side; important before posterior fossa surgery
• Fenestration of VA (uncommon; associated with aneurysm)

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7. SUBCLAVIAN ARTERIES

• Right subclavian: Arises from the brachiocephalic trunk, behind the right sternoclavicular joint
• Left subclavian: Arises directly from the aortic arch (third branch)
• Both pass posterior to the anterior scalene muscle

1. Vertebral artery (first branch)
2. Internal thoracic (mammary) artery
3. Thyrocervical trunk (gives inferior thyroid, suprascapular, transverse cervical arteries)
4. Costocervical trunk (gives supreme intercostal, deep cervical)

• Subclavian steal syndrome: >70% stenosis of proximal subclavian (pre-vertebral origin) causes retrograde flow in ipsilateral VA (best shown on CTA + Doppler or DSA)
• Aneurysm: Fusiform dilation, often post-stenotic or in thoracic outlet syndrome
• Aberrant right subclavian (arteria lusoria): Arises as fourth aortic arch branch, courses behind the esophagus; can cause dysphagia lusoria

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PART 2: CT NECK VENOGRAPHY (VENOUS ANATOMY)

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VENOUS ANATOMY DIAGRAM (Lateral View):

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SUPERFICIAL VEINS

External Jugular Vein (EJV)

• Formed by the posterior auricular vein and the posterior division of the retromandibular vein behind the ear
• Descends obliquely across the sternocleidomastoid muscle (SCM), superficial to it
• Pierces the deep cervical fascia and drains into the subclavian vein
• Receives: posterior external jugular, transverse cervical, suprascapular veins
• On CTA/CTV: Visible as a thin vessel crossing SCM; larger and more prominent when the patient performs Valsalva

Anterior Jugular Vein (AJV)

• Arises near the chin (mental region), descends near the midline
• Connects to the opposite side via the jugular venous arch (suprasternal)
• Drains into the external jugular vein or directly into the subclavian vein
• Highly variable; may be paired or a single midline vessel

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DEEP VEINS

Internal Jugular Vein (IJV)

CT image showing IJV - sigmoid sinus relationship:

Axial CT showing jugular foramen anatomy:

Major Tributaries of the IJV:

Vertebral Vein

• Begins in the suboccipital triangle, descends through the transverse foramina of C1-C6 alongside the vertebral artery
• Drains into the brachiocephalic vein (not the IJV)
• The vertebral venous plexus is a rich paravertebral network; a pathway for metastatic spread (Batson's plexus)

Deep Cervical Vein

• Runs in the posterior neck alongside the deep cervical artery
• Drains the posterior neck muscles
• Drains into the vertebral or brachiocephalic vein

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CENTRAL VEINS

Brachiocephalic Veins (Innominate Veins)

• Formed by the union of the IJV + subclavian vein at the venous angle (Pirogoff angle), behind the sternoclavicular joint
• Right brachiocephalic vein: Short (~2.5 cm), nearly vertical
• Left brachiocephalic vein: Longer (~6 cm), horizontal course across the superior mediastinum, anterior to the aortic arch branches
• Both join to form the SVC

Superior Vena Cava (SVC)

• Formed behind the right first costal cartilage
• Receives the azygos vein posteriorly before entering the right atrium
• On CTA: Look for opacification defects suggesting SVC thrombosis; extrinsic compression (mass, lymph nodes); SVC syndrome

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DURAL VENOUS OUTFLOW

Superior sagittal sinus + Inferior sagittal sinus
            ↓
     Straight sinus (via great vein of Galen)
            ↓
      Confluence of sinuses (Torcular Herophili)
            ↓
    Transverse sinuses (bilateral, within tentorium)
            ↓
      Sigmoid sinuses (S-shaped, posterior fossa)
            ↓
       Jugular bulb (at jugular foramen)
            ↓
    Internal jugular vein (cervical course)
            ↓
    Brachiocephalic vein → SVC → Right atrium

Dural sinus diagram (axial view from above):

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VENOUS PATHOLOGY - WHAT TO ASSESS

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CONGENITAL VASCULAR VARIANTS (Summary)

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CTA READING APPROACH (Search Pattern)

1. Non-vascular structures first: Thyroid, lymph nodes, soft tissues, lungs, brain, bones
2. Neck arteries (anterior, right to left):
   • Right CCA → bifurcation → ICA (to skull base) → ECA
   • Left CCA → bifurcation → ICA → ECA
3. Neck arteries (posterior):
   • Right VA: subclavian origin → V1 → V2 → V3 → skull base
   • Left VA: same pattern
4. Head arteries (if included): ICA siphon → MCA → ACA → posterior circulation → basilar → PCA
5. Venous phase / CTV (if obtained): Sigmoid sinuses → jugular bulbs → IJVs → brachiocephalic veins → SVC

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