External Carotid Artery: Highway to the Danger Zones

Benjamin Atchie, DO Interventional Neuroradiology Fellow

UT Southwestern Medical Center

Case Examples: Dural AV Fistula

Case Examples: Juvenile Nasopharyngeal Angiofibroma

Case Examples: Facial AVM

Case Examples: Traumatic Hemorrhage

Introduction:

Embolization of the external carotid artery (ECA) territory has become increasingly more frequent: Dural AVF AVMs Tumor embolization Epistaxis Trauma CCF (Type C)

Journal of Vascular and Interventional Radiology, Volume 24, Issue 7, July 2013,

Introduction:

ECA interventions are inherently safer than ICA interventions but are not without complication.

Complications result from: ECA to ICA anastomoses – Ischemic stroke Arterial Supply to Cranial Nerves – Nerve Palsies

External Carotid Artery Embolization: AJNR 2001 22: S12-S13 Aneurysm Endovascular Therapy: AJNR 2001 22: S4-S7

ECA embolization

ECA to ICA Anastomoses: Danger Zones

Embryologic and phylogenetic development closely links the ECAs to the ICAs.

This creates common anastomotic routes to be aware of while doing embolization procedures.

ECA to ICA Anastomoses: Danger Zones

ECA to ICA Anastomoses: Common Pathways

1) The orbital region via the

ophthalmic artery that is the interface between the internal maxillary and internal carotid territories.

2) The petrous-cavernous region via the inferolateral trunk (ILT), the petrous branches of the internal carotid artery (ICA), and the meningohypophyseal trunk to the carotid artery.

3) The upper cervical region via the ascending pharyngeal, the occipital, and the ascending and deep cervical arteries to the vertebral artery.

Orbital & Petrous Anastomoses

Petrous-cavernous Anastomoses

Cervical Region Anastomoses

Neuroangio.org

Cervical Region Anastomoses

ECA to ICA Anastomoses: Common Pathways

Although they may not be visualized on routine catheter angiographies, they are always present.

They may become visible under the following circumstances:

1) With increased intra-arterial pressure (during embolization procedures or superselective injections)

2) In the presence of high-flow shunts as a consequence of the “sump effect,”

3) As collateral routes when occlusions of the major intracranial arteries occur.

Endovascular Strategies to Avoid Inadvertent ICA embolization: Nonvisualized anastomotic arteries ranges from 50 to 80 µm;

therefore, particles that are >150 µm will not penetrate these anastomoses

The visualization of an anastomotic channel is not a contraindication for embolization of the particular artery. Techniques that can be used to prevent embolic material from entering the collaterals: Mechanical blockage of the collateral branch with large particles or coils before

the embolization. Flow-reversal methods using a proximal balloon occlusion, which leads to flow

redirection from the ICA to the ECA territory. Balloon protection of the target ICA artery.

ECA supply to Cranial Nerves: More Trouble

Optic Nerve / Central Retinal Artery

Optic Nerve / Central Retinal Artery

Facial Nerve: The geniculate ganglion

The MMA gives rise to the petrosal branch a few millimeters beyond the foramen spinosum. This branch is the only arterial supply to the seventh nerve ganglion in 25% of cases

Major anastomotic within stylomastoid foramen, between petrosal branch of MMA and the stylomastoid artery, a branch of either occipital or posterior auricular artery

CN VI, IX – XII: The Ascending Pharyngeal

Neuromeningeal trunk is a major branch of the ascending pharyngeal that continues cephalad, but angling gently to the posterior. It has several important branches:

Jugular Branch: Often the largest branch Supplies the IXth - XIth cranial

nerves. Also ascends along the clivus

supplying the cranial nerve VI.

Hypogolssal Branch: Supply to Cranial nerve XII.

CN VI, IX – XII: The Ascending Pharyngeal

Endovascular Strategies to Avoid CN palsies:

Use liquid embolics with caution (Onyx, nBCA)

Penetrate distally into terminal arterioles and capillary beds.

Use Coils or larger particles, at least > 150 µm

Provocative testing

References:

Geibprasert, Pongpech, Armstrong, Krings; Dangerous Extracranial–Intracranial Anastomoses and Supply to the Cranial Nerves: Vessels the Neurointerventionalist Needs to Know; AJNR Am J Neuroradiol 30:1459–68; (2009)

Russell; Functional Angiography of the Head and Neck; AJNR:7,(1986).

Chen, Siddiqui, and Chen; Intracranial Arterial Collateralization: Relevance in Neuro-Endovascular Procedures; Neuroimaging for Clinicians - Combining Research and Practice (2011).

Harrigan, Deveikis ; Handbook of Cerebrovascular Disease and Neurointerventional Technique; (2013).