Chiari Malformation Type 1: Causes, Symptoms, and Treatment
Medically reviewed by Achuta Uppu, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor treats Chiari Malformation Type 1?
A neurologist (a doctor who treats brain and nerve problems) usually diagnoses Chiari malformation type 1, and a neurosurgeon (a doctor who does brain and spine surgery) treats it when surgery is 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 is Chiari malformation type 1?
Chiari malformation type 1 happens when the cerebellar tonsils (the lower parts of the cerebellum) push down through the foramen magnum (the opening at the base of the skull). The tonsils sit more than 5 millimeters (about one-fifth of an inch) below the opening. It can happen with or without a syrinx (a fluid-filled cyst in the spinal cord).
This is the most common type of Chiari malformation. Some people with it have no symptoms. Doctors sometimes find it on a brain scan done for another reason.
Symptoms
Symptoms vary in when they start and how bad they get. The most common one is a headache near the base of the skull. It often gets worse with coughing, sneezing, or straining. Other symptoms include:
- Neck pain.
- Vertigo (a spinning feeling) and dizziness.
- Ringing in the ears (tinnitus).
- Blurred or double vision.
- Poor balance and coordination.
- Muscle stiffness.
- Numbness, or tingling or burning in the fingers or toes.
- Muscle weakness.
Some people also get a syrinx. As it grows, it can cause loss of muscle mass, numbness to hot and cold, a curve in the spine (scoliosis), or loss of bowel and bladder control.
Causes and who gets it
The exact cause is not known. Chiari malformation type 1 forms before birth, while the skull and brain are growing. In many people, the posterior fossa (the space at the back of the skull) is too small, so the cerebellum gets pushed down.
Sometimes more than one person in a family has it. This suggests that genes play a role in some cases. It can also be part of a larger syndrome, such as Ehlers-Danlos syndrome (a condition that affects the tissue that holds the body together). Doctors usually find this type in teenagers or adults.
How doctors diagnose it
Doctors ask about symptoms and do a physical exam and a neurological exam (checks of balance, touch, reflexes, and movement). The main test is an MRI (magnetic resonance imaging), which uses magnets and radio waves to make pictures of the brain and spinal cord.
The MRI shows how far the tonsils have moved down and whether a syrinx is present. It is usually the preferred test. Sometimes doctors also use a CT scan (a detailed x-ray test) to look at the bones at the base of the skull.
Treatment
People with no symptoms usually do not need treatment. Doctors watch for changes with checkups and imaging tests. For mild headaches or neck pain, physicians may recommend pain medicines or a reduction in heavy lifting and straining.
When symptoms are present, surgery is the main treatment. The most common surgery is posterior fossa decompression (making more room at the base of the skull). The surgeon removes a small piece of bone from the back of the skull. Sometimes the surgeon also opens the dura (the covering of the brain and spinal cord) and sews in a patch to make more space.
Surgery can keep symptoms from getting worse, but some people still have pain or weakness afterward. It can also cause a cerebrospinal fluid leak or an infection. A syrinx usually improves after surgery. People with hydrocephalus (fluid buildup in the brain) may be treated with a shunt (a tube that drains extra fluid).
When to see a doctor
Call your doctor if headaches at the base of the skull, neck pain, or tingling in the fingers start or get worse. Get medical help right away if you lose control of your bowels or bladder. This can be a symptom of a syrinx. If you faint or have trouble breathing, call 911.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. For Chiari malformation type 1, this doctor can do an evaluation, watch mild symptoms over time, and refer you to a neurologist or neurosurgeon when needed.
Common questions
What is the difference between Chiari malformation type 1 and type 2?
In type 1, only the cerebellar tonsils push down below the opening at the base of the skull. In type 2, both the cerebellum and the lower brain stem push down, and it happens with spina bifida (an open spine defect). Type 2 can be found before birth.
Can you have Chiari malformation type 1 without symptoms?
Yes. Some people with type 1 have no symptoms. Doctors sometimes find it on a brain scan done for another reason.
Does Chiari malformation type 1 get worse over time?
Not always. Some people stay symptom free. Others may develop symptoms later in life. Doctors watch for changes with checkups and imaging tests.
What is the surgery for Chiari malformation type 1?
The most common surgery is posterior fossa decompression. The surgeon removes a small piece of bone from the back of the skull to make more room. Sometimes the surgeon also sews a patch into the dura to make more space.
Sources
- National Organization for Rare Disorders (NORD) - Chiari malformation type I
- National Institute of Neurological Disorders and Stroke - Chiari Malformation
- National Organization for Rare Disorders (NORD) - Chiari Malformations
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.
