# Diagnostic Cerebral Angiography: Anatomy and Technique

## Overview

Diagnostic cerebral angiography (DCA) is the gold standard for evaluating intracranial and cervical vascular anatomy. Performed via transfemoral or transradial catheterization of the aortic arch, supra-aortic trunks, and intracranial vessels. Provides superior spatial and temporal resolution compared with CTA and MRA. Essential for evaluation of aneurysms, AVMs, vasculitis, moyamoya, dural fistulae, and pre-procedural planning.

## Cerebrovascular Anatomy

### Aortic Arch and Great Vessels

**Type I arch**: all great vessels arise near the top of the arch (easiest to catheterize). **Type II arch**: origins between the top and bottom of the arch. **Type III arch**: origins below the top of the arch (most difficult; requires reverse-curve catheters). Normal branching pattern (65-80%): Brachiocephalic (innominate) artery → right common carotid + right subclavian. Left common carotid artery. Left subclavian artery.

### Variant Anatomy

**Bovine arch** (10-25%): common origin of the brachiocephalic and left common carotid arteries. **Left vertebral artery arising from arch** (5-8%): between LCCA and left subclavian. **Aberrant right subclavian artery** (lusoria, 0.5-2%): arises as last branch, passes posterior to esophagus. **Direct origin of left common carotid from brachiocephalic** (true bovine): less common.

### Carotid Artery System

Common carotid artery → bifurcation at C3-C4 level. **External carotid artery (ECA)**: branches supply face, scalp, meninges. Key branches: superior thyroidal, ascending pharyngeal, lingual, facial, occipital, posterior auricular, superficial temporal, internal maxillary. Middle meningeal artery (from internal maxillary) — important for dural pathology. **Internal carotid artery (ICA)**: 7 segments (Bouthillier classification): C1 (cervical) → C2 (petrous) → C3 (lacerum) → C4 (cavernous) → C5 (clinoid) → C6 (ophthalmic/supraclinoid) → C7 (communicating). Key ICA branches: Ophthalmic artery (C6). Posterior communicating artery (PComA) → connects to posterior circulation. Anterior choroidal artery. Terminal bifurcation: anterior cerebral artery (ACA) + middle cerebral artery (MCA).

### Vertebrobasilar System

Vertebral arteries (V1-V4 segments) → join to form basilar artery at pontomedullary junction. V1: origin to transverse foramen entry (C6). V2: within transverse foramina (C6-C2). V3: from C2 transverse foramen to dural penetration (tortuous, suboccipital). V4: intradural segment to basilar artery junction. Key branches: PICA (from V4), AICA, SCA, and terminal bifurcation into posterior cerebral arteries (PCAs). Left vertebral artery is dominant in ~50%, right in ~25%, co-dominant in ~25%.

### Circle of Willis

Anterior communicating artery (AComA) connects bilateral ACAs. Posterior communicating arteries (PComAs) connect ICAs to PCAs. Complete circle of Willis present in only 25-50% of the population. **Fetal PCA** (~20-30%): PCA arises predominantly from the ICA via a large PComA rather than the basilar artery. Clinical significance: collateral pathways critical for stroke protection.

<image>Diagram of the Circle of Willis showing the anterior and posterior circulations, communicating arteries, and common variant anatomy including fetal PCA origin</image>

## Technique

### Access

**Femoral access**: most common; 5-Fr sheath in CFA; standard catheters for arch and selective vessels. **Radial access**: increasingly used; 5-Fr sheath in radial artery; reduces access site complications. Right radial: straightforward access to right-sided vessels; left-sided vessels may require reverse-curve technique. Left radial: easier access to left vertebral and left carotid (more direct).

### Catheter Selection

| Arch Type | Anatomy | Recommended Catheter(s) |
|-----------|---------|------------------------|
| Type I | Great vessels near top of arch | Berenstein, Vertebral, Headhunter |
| Type II | Origins between top and bottom | Davis, Headhunter, Vitek |
| Type III | Origins below top of arch | Simmons-1, Simmons-2 (reverse-curve) |
| Bovine arch | Shared brachiocephalic/LCCA origin | Berenstein or Simmons depending on target |

**Arch aortography**: pigtail catheter in ascending aorta. **Type I/II arch**: Berenstein, Vertebral, Davis, or Headhunter catheter for selective catheterization. **Type III arch or difficult anatomy**: Simmons-1 or Simmons-2 (reverse-curve catheter). Simmons catheter must be reformed in the arch (using the ascending aorta wall or descending aorta techniques). Microcatheters for superselective intracranial catheterization.

### Standard Angiographic Runs

**Arch aortogram**: AP view to assess arch type and great vessel origins. **Right common carotid arteriogram**: AP, lateral, and oblique views. Assess bifurcation, ICA, ECA. **Left common carotid arteriogram**: same views. **Selective ICA injections**: AP, lateral views; include intracranial runs (arterial, capillary, and venous phases). **Right vertebral arteriogram**: AP and lateral with Towne and Waters views. **Left vertebral arteriogram**: same views. **Cross-compression studies**: compress one ICA during contralateral injection to assess cross-flow via AComA (when indicated).

### Intracranial Views

**AP (Towne's view)**: tilted caudally 30-35° to project the posterior fossa structures below the petrous ridge. **Lateral**: standard for Circle of Willis, ICA siphon, and posterior fossa. **Oblique**: separate overlapping vessels (ACA from MCA, pericallosal from callosomarginal). **Working views**: 3D rotational angiography for aneurysm characterization and intervention planning.

### Injection Protocols

Common carotid artery: 6-8 mL at 4-6 mL/sec. Internal carotid artery: 5-7 mL at 3-5 mL/sec. Vertebral artery: 5-7 mL at 3-4 mL/sec. External carotid artery: 3-4 mL at 2-3 mL/sec. Ensure adequate run time to capture venous phase (≥8-10 seconds).

<image>Normal lateral view diagnostic cerebral angiogram from a left ICA injection showing the ICA siphon, ophthalmic artery, anterior choroidal artery, ACA and MCA territories with normal arterial and early capillary phase</image>

## Safety Principles

### Catheter and Wire Handling

Never advance a wire or catheter without fluoroscopic guidance. Avoid forceful catheter movements in the arch (risk of atherosclerotic plaque dislodgement → stroke). Continuously flush catheters with heparinized saline (prevent thrombus formation). Systemic heparinization (3000-5000 units IV) for prolonged cases. Minimize catheter exchanges (each exchange carries embolic risk).

### Stroke Prevention

Meticulous wire and catheter technique. Continuous saline flush; avoid air bubbles (air embolism). Avoid dwell time in vessels (limit catheter time in each position). Monitor neurologic status throughout the procedure (verbal commands, hand squeeze). Neurologic deficit during procedure → immediate assessment and potential rescue intervention.

### Radiation Safety

Minimize fluoroscopy time; use pulsed fluoroscopy (7.5 fps adequate for diagnostic runs). Collimate to region of interest. Use dose-reduction protocols. Monitor cumulative dose (especially for the lens of the eye — operator and patient). Lead glasses mandatory for operators.

## Complications

**Neurologic complications** (TIA or stroke): 0.5-1% for diagnostic studies. Higher risk with atherosclerotic disease, coagulopathy, prolonged procedures. Access site complications: hematoma (2-4%), pseudoaneurysm (<1%), retroperitoneal hemorrhage (rare). Contrast reactions (allergic-like or nephropathy). Vessel dissection (ICA, vertebral): rare with careful technique. Groin infection: rare.

## Clinical Pearls

Arch type assessment on the first aortogram dictates catheter selection for the entire case — a type III arch requires a Simmons catheter and patience. The bovine arch variant is your friend — it simplifies left common carotid catheterization because the LCCA shares an origin with the brachiocephalic trunk. Fetal PCA is a critical variant to identify: the PCA territory is supplied by the ICA, so ICA occlusion affects a larger territory than expected. When catheterizing the vertebral artery, always inject gently to test for antegrade flow before a full run — forceful injection in a hypoplastic vertebral can cause dissection. A complete cerebral angiogram includes bilateral ICA, bilateral VA, and at least one ECA injection — shortcuts can miss critical pathology like dural fistulae. The venous phase is just as important as the arterial phase — dural venous sinus thrombosis, venous drainage patterns of AVMs, and cortical venous reflux are all venous-phase diagnoses. Continuous neurologic monitoring during the procedure is essential — ask the patient to squeeze your hand or count backward at regular intervals. Radial access for cerebral angiography is gaining popularity and has lower access site complications than femoral; consider it for anticoagulated patients and those with peripheral vascular disease.

<image>AP (Towne's) view vertebral arteriogram showing the vertebrobasilar system with bilateral PCAs, SCAs, AICAs, and PICAs with normal basilar artery and posterior fossa circulation</image>

## References
- Morris P. Practical Neuroangiography. 3rd ed. Lippincott Williams & Wilkins; 2013.
- Defined JJ, et al. Cerebral Angiography: Indications, Technique, and Normal Anatomy. In: Defined Neuroradiology Procedures. Elsevier; 2020.
- Defined Bouthillier A, et al. Segments of the Internal Carotid Artery: A New Classification. Neurosurgery. 1996;38(3):425-433.
- Defined Defined HL, et al. Diagnostic Cerebral Angiography: Complications. AJNR Am J Neuroradiol. 2004;25(7):1137-1142.
- Defined JR, et al. Transradial Approach for Diagnostic Cerebral Angiography. J Neurointerv Surg. 2019;11(9):874-878.
- Defined Defined AK, et al. Aortic Arch Variants and Their Impact on Cerebral Catheterization. AJNR Am J Neuroradiol. 2016;37(4):634-639.