Illustration of a dural arteriovenous fistula at the foramen magnum causing a subarachnoid hemorrhage

Uncommon Cause, Serious Threat: What You Need to Know About Foramen Magnum Dural Arteriovenous Fistulas

Reese Marlowe in Health & Wellness November 2025 • 4 min read.

"Discover how a rare type of arteriovenous fistula can lead to life-threatening brain bleeds and why early diagnosis is crucial."

When it comes to health scares, the element of surprise can be the most frightening. Imagine experiencing a sudden, severe headache unlike anything you've felt before, accompanied by stiff neck and sensitivity to light. While many might dismiss it as a migraine, these could be signs of a subarachnoid hemorrhage (SAH), a type of stroke where bleeding occurs in the space surrounding the brain.

While aneurysms are often the primary suspect in cases of SAH, there are other, less common culprits to be aware of. One such rare condition is a dural arteriovenous fistula (D-AVF) located at the foramen magnum, the opening at the base of the skull where the spinal cord connects to the brain. This unusual type of D-AVF can cause SAH when a connected venous varix ruptures, leading to serious health consequences.

This article aims to shed light on this infrequent but critical condition, exploring its causes, symptoms, diagnostic challenges, and treatment options. By increasing awareness of foramen magnum D-AVFs and their potential to cause SAH, we hope to empower individuals to seek timely medical attention and improve outcomes.

Dural Arteriovenous Fistula (D-AVF): Understanding the Basics

Illustration of a dural arteriovenous fistula at the foramen magnum causing a subarachnoid hemorrhage

A dural arteriovenous fistula (D-AVF) is an abnormal connection between arteries and veins in the dura mater, the tough membrane that surrounds the brain and spinal cord. Unlike normal blood flow, where arteries smoothly transition to veins through a network of capillaries, a D-AVF creates a direct, high-pressure shortcut. This can lead to various neurological problems, depending on the location and size of the fistula.

D-AVFs at the foramen magnum are particularly rare, making up a small fraction of all D-AVFs. Their location near the base of the brain and critical structures like the brainstem and spinal cord contributes to their potential for serious complications.

Here's a breakdown of what makes these D-AVFs dangerous:

Venous Hypertension: The abnormal connection causes increased pressure in the veins, leading to venous hypertension.
Venous Varix Formation: Over time, venous hypertension can cause veins to weaken and bulge, forming a venous varix.
Rupture and Hemorrhage: The thin walls of a venous varix are prone to rupture, causing a subarachnoid hemorrhage (SAH).

One of the challenges in diagnosing D-AVFs at the foramen magnum is their low incidence. Additionally, when the fistula is fed exclusively by the ascending pharyngeal artery (APA), a branch of the external carotid artery, it can be easily missed during standard angiographic evaluations that don't specifically focus on this vessel.

Takeaway

While dural arteriovenous fistulas at the foramen magnum are uncommon, it’s important to be aware of them. Be proactive about your health. If you experience symptoms like sudden severe headaches, especially with neck stiffness, seek immediate medical attention. Early diagnosis and treatment, often through embolization techniques, can significantly improve outcomes and prevent potentially devastating consequences.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.7461/jcen.2018.20.2.120, Alternate LINK

Title: A Rare Case Of Subarachnoid Hemorrhage Caused By Ruptured Venous Varix Due To Dural Arteriovenous Fistula At The Foramen Magnum Fed Solely By The Ascending Pharyngeal Artery

Subject: Industrial and Manufacturing Engineering

Journal: Journal of Cerebrovascular and Endovascular Neurosurgery

Publisher: Korean Society of Cerebrovascular Surgeons/Korean Society of Endovascular Surgery

Authors: Hyunjun Kim, Yoon-Soo Lee, Ho-Jun Kang, Min-Seok Lee, Sang-Jun Suh, Jeong-Ho Lee, Dong-Gee Kang

Published: 2018-01-01

Everything You Need To Know

What is a Dural Arteriovenous Fistula (D-AVF) and how does it relate to the foramen magnum?

A Dural Arteriovenous Fistula (D-AVF) is an abnormal connection between arteries and veins within the dura mater, the protective membrane around the brain and spinal cord. When a D-AVF occurs at the foramen magnum, the opening at the base of the skull where the spinal cord meets the brain, it's a particularly rare and dangerous type. The location of the foramen magnum D-AVF close to critical structures increases the risk of severe complications, making early detection essential.

What are the potential dangers associated with a foramen magnum D-AVF that lead to serious health issues like subarachnoid hemorrhage?

The primary danger of a foramen magnum D-AVF stems from the abnormal blood flow it creates. This leads to venous hypertension, where there's increased pressure in the veins. Over time, this can cause a venous varix, a weakened and bulging vein. This venous varix is prone to rupture, which can cause a subarachnoid hemorrhage (SAH). A SAH is a type of stroke where bleeding occurs in the space surrounding the brain, leading to potentially life-threatening consequences.

Why are foramen magnum D-AVFs often difficult to diagnose, and what are the diagnostic challenges?

Diagnosing a foramen magnum D-AVF can be challenging due to its low incidence. Making it even more complicated is when the D-AVF is fed exclusively by the ascending pharyngeal artery (APA). Standard angiographic evaluations might miss the APA, the branch of the external carotid artery. This can lead to delayed or missed diagnoses, highlighting the need for specialized imaging and a high index of suspicion when patients present with relevant symptoms.

What symptoms might indicate a foramen magnum D-AVF, and what should someone do if they experience these symptoms?

Symptoms of a foramen magnum D-AVF that could suggest a serious condition include sudden, severe headaches, often unlike any previously experienced, along with neck stiffness and sensitivity to light. These symptoms can mimic those of a migraine but could indicate a subarachnoid hemorrhage (SAH). Anyone experiencing these symptoms should seek immediate medical attention. Early diagnosis and treatment, often through embolization techniques, can significantly improve outcomes and prevent devastating consequences.

How are foramen magnum D-AVFs typically treated, and what is the significance of early intervention?

Foramen magnum D-AVFs are often treated using embolization techniques. Early intervention is crucial because the longer the D-AVF remains untreated, the greater the risk of venous hypertension, venous varix formation, and subsequent rupture leading to a subarachnoid hemorrhage (SAH). Prompt diagnosis and treatment with embolization can prevent these devastating consequences by stopping the abnormal blood flow and preventing rupture of the venous varix, thereby significantly improving patient outcomes.