Chiari malformation: symptoms, causes and treatment

The NHS says many people with a Chiari I malformation will not have any symptoms. When symptoms do develop, the most characteristic is a headache felt at the back of the head, which may be brought on or made worse by coughing, straining, sneezing or bending over.

The NHS also lists a wider range of problems that can occur. They tend to come from pressure on the brainstem and spinal cord, or from obstructed flow of the fluid that surrounds them. Not everyone will have all of them, and many of these symptoms have other, more common causes, which is why a scan and specialist assessment matter.

• Headaches at the back of the head, often triggered by coughing, straining, sneezing or bending over.

• Neck pain.

• Dizziness and balance problems.

• Muscle weakness.

• Numbness or tingling in the arms or legs.

• Blurred vision, double vision and sensitivity to light.

• Swallowing problems.

• Hearing loss and tinnitus.

• Feeling and being sick.

• Difficulty sleeping (insomnia) and clinical depression.

A Chiari malformation is a structural problem at the base of the skull. The NHS explains that in someone with Chiari I, the lowest part of the back of the brain extends into the spinal canal. This can put pressure on the brainstem and spinal cord, and obstruct the flow of fluid.

The NHS page focuses on the Chiari I type. The Brain Charity lists the related names Chiari I, II, III and IV and describes the condition simply as one where part of the brain pushes down into the spine. Because the condition is usually present from birth, it is sometimes found in childhood and sometimes only in adulthood.

The NHS says the severity varies from person to person. Chiari I malformations are not considered life-threatening, many people have no symptoms, and some have painful headaches, movement problems and other unpleasant symptoms.

The main concern it highlights is syringomyelia, where a fluid-filled cavity called a syrinx develops in the spinal cord. This can damage the spinal cord if it is not treated promptly. If you develop syringomyelia, the NHS says you may also have problems using your hands, difficulty walking, pain, and problems with bladder or bowel control.

The NHS adds that surgery can usually stop the symptoms getting worse and can sometimes improve them, although some problems may remain. It suggests talking to your doctor about what the condition means for you and what treatment you may need.

The NHS says treatment depends on whether you have any symptoms and how severe they are. You might not need any treatment if you do not have symptoms. Painkillers can help with headaches and neck pain.

If headaches are severe, or there are problems caused by pressure on the spinal cord (such as movement difficulties), surgery may be recommended. The main operation is decompression surgery. Under general anaesthetic, a cut is made at the back of the head and the surgeon removes a small piece of bone from the base of the skull, and possibly a small piece from the top of the spine. This reduces the pressure on the brain and lets the fluid in and around the brain and spinal cord flow normally.

The aim of surgery is to stop existing symptoms getting worse. The NHS says some people also notice improvement, particularly in headaches, but surgery sometimes results in no improvement or symptoms getting worse, and there is a small risk of serious complications such as paralysis or a stroke. It suggests discussing the options, benefits and risks with your surgeon.

The NHS says the exact cause of Chiari I malformations is unknown. It tends to be present from birth, but is normally only found in adulthood when symptoms develop or when an MRI scan is done. Many cases are thought to be the result of part of the skull not being large enough for the brain.

Chiari I malformations can also develop in people with a tethered spinal cord, a build-up of fluid on the brain (hydrocephalus) and some types of brain tumour. They can sometimes run in families, possibly through a gene that affects skull development, but the NHS says the risk of passing one on to your child is very small.

Two conditions appear repeatedly alongside Chiari malformation. A syrinx in the spinal cord is the more common concern, and the NHS names it as the main reason prompt treatment matters.

Hydrocephalus is a build-up of fluid in the brain. The NHS says it puts pressure on the brain and, if left untreated, can be fatal. Its symptoms in children and adults include headache that can be worse on waking, being sick, blurred or double vision, difficulty walking and confusion. For hydrocephalus in general, including how shunts and ETV work, see the dedicated guide.

The NHS advice for people already diagnosed with a Chiari malformation is to contact your doctor if you develop any new symptoms or your symptoms worsen.

If you have not been diagnosed, see a GP about symptoms such as headaches at the back of the head that are triggered by coughing or straining, new balance problems, or numbness and tingling. For hydrocephalus-type symptoms, the NHS says to call a GP or use NHS 111 if you think you or your child may have them.

In the NHS, a GP can arrange a scan and refer you to a neurologist or neurosurgeon. Decompression surgery is carried out by a specialist neurosurgical team. Private neurology and neurosurgery services also exist, and the tests and operations are broadly the same; ask who will manage your follow-up scans and what happens if symptoms change.

The NHS says your clinical team may pass information about you to the National Congenital Anomaly and Rare Disease Registration Service, which helps scientists look for better ways to prevent and treat the condition, and that you can opt out at any time. The Brain Charity lists the Ann Conroy Trust and the Brain & Spine Foundation among UK sources of information and support.