Interventional Radiology · Neurointervention · Original 1985 classification
Barrow Classification of Carotid–Cavernous Fistulas
An anatomical–angiographic classification of carotid–cavernous fistulas according to whether the fistula is direct or dural and whether its arterial supply arises from the internal carotid artery, external carotid artery or both.
Purpose
To classify carotid–cavernous fistulas according to the anatomical arterial connection demonstrated on angiography.
| Type | Arterial connection to cavernous sinus | Category |
|---|---|---|
| A | Direct connection from the intracavernous internal carotid artery | Direct, high-flow fistula |
| B | Meningeal branches of the internal carotid artery | Indirect dural fistula |
| C | Meningeal branches of the external carotid artery | Indirect dural fistula |
| D | Meningeal branches of both the internal and external carotid arteries | Indirect dural fistula |
How to use it
- Type A is a direct shunt between the intracavernous internal carotid artery and the cavernous sinus.
- Types B–D are indirect dural fistulas supplied by meningeal arterial branches.
- Type B has internal carotid supply, type C has external carotid supply and type D has supply from both carotid systems.
- Digital subtraction angiography remains the reference standard for classification and for defining the feeders, fistulous site and venous drainage.
Common mistake
Do not classify the fistula solely by flow rate or aetiology. Although type A fistulas are commonly high-flow and traumatic, the Barrow type is determined by the anatomical arterial connection.
Exam pearl
Remember the arterial sequence: A = direct ICA, B = ICA branches, C = ECA branches and D = dual ICA plus ECA branches.
Viva questions
- What does the Barrow classification describe?
- It is an anatomical–angiographic classification of carotid–cavernous fistulas based on whether the shunt is direct or dural and on the carotid arterial system supplying it.
- Enumerate the four Barrow types.
- Type A is a direct ICA-to-cavernous sinus fistula. Type B is supplied by ICA meningeal branches, type C by ECA meningeal branches and type D by meningeal branches of both the ICA and ECA.
- Which Barrow type represents a direct carotid–cavernous fistula?
- Type A, consisting of a direct connection between the intracavernous internal carotid artery and the cavernous sinus.
- How do Barrow types B and C differ?
- Both are indirect dural fistulas. Type B is supplied by meningeal branches of the internal carotid artery, whereas type C is supplied by meningeal branches of the external carotid artery.
- What is a Barrow type D fistula?
- It is an indirect dural carotid–cavernous fistula supplied by meningeal branches of both the internal and external carotid arteries.
- What is the reference-standard investigation for classifying a carotid–cavernous fistula?
- Digital subtraction angiography, because it defines the arterial feeders, fistulous connection and venous drainage required for treatment planning.
- What is a common pitfall when applying the Barrow classification?
- Assigning the type purely from flow rate or presumed traumatic aetiology. The definitive Barrow type depends on the anatomical arterial connection.