Internal Carotid Agenesis: Causes, Symptoms, and Treatment
Medically reviewed by Harsha Moole, MD, Internal Medicine. Last reviewed: October 2, 2026.
What kind of doctor treats Internal Carotid Agenesis?
A primary care doctor is often the first doctor involved, and a specialist is usually involved as well. A neurologist treats brain and nerve conditions, while a neurosurgeon or vascular specialist may help when procedures are needed. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What it is
Internal carotid agenesis is a rare condition present from birth in which one or both internal carotid arteries, the main blood vessels to the brain, never formed. The body often makes up for this with other blood vessels, and many people never know they have it.
Symptoms
Most people have no symptoms, and the condition is often found by accident on a brain scan. When symptoms do happen, they can include headaches, seizures, weakness on one side of the body, trouble speaking, or vision problems, usually because the backup blood vessels are working harder than they should.
Causes and who gets it
This condition happens during early pregnancy, when the blood vessels that should become the internal carotid arteries fail to develop. It is very rare and affects males and females, occurring on one side or, less often, on both. Some people with this condition have other health differences; many do not.
How doctors diagnose it
Because there are often no symptoms, doctors usually find this condition by chance during imaging tests, such as a CT scan, an MRI, or an angiogram, which shows blood flow to the brain. These tests show that the artery is missing and how well the backup vessels work.
Treatment
Many people need no treatment. If there are no symptoms, doctors often just watch the condition over time. When symptoms or related blood vessel problems are present, care focuses on those issues, which can include medicines to lower stroke risk or, in some cases, a procedure.
When to see a doctor
Anyone with sudden weakness, trouble speaking, vision loss, or a severe headache should get emergency care right away, as these can be signs of a stroke. A person with internal carotid agenesis should keep regular follow-up visits and mention any new symptoms.
How a direct primary care or concierge doctor fits in
A direct primary care doctor is paid a flat monthly fee rather than billing insurance. A concierge doctor usually charges more and often works alongside insurance. Either one can manage routine care for this condition, including ordering imaging tests, watching for changes, and managing medicines that lower stroke risk.
Common questions
Can I live a normal life with internal carotid agenesis?
Many people do. The body often reroutes blood through other vessels, and the condition causes no symptoms. Outcomes differ from person to person. Regular checkups help your doctor watch for changes.
Is this condition hereditary?
Doctors do not believe it usually runs in families. Most cases happen by chance during development before birth. If you have questions about family risk, a genetic counselor can help you sort through them.
Do I need surgery?
Most people do not need surgery. Procedures are considered only when related blood vessel problems or symptoms call for them. Your doctors would explain the options in detail before any decision.
Why did I only find out now, as an adult?
The condition is present from birth, but it often causes no symptoms. Many people learn about it only when a scan done for another reason shows the missing artery.
Sources
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
