What is Chiari Malformation?

Chiari malformation is a condition where the lower part of the brain does not fit properly inside the skull. A part of the back of the brain, called the cerebellum, slips downwards and moves into the upper part of the spinal canal in the neck, where the spinal cord runs.

This can put pressure on the brain and spinal cord and affect the flow of cerebrospinal fluid, the clear fluid that protects the brain and spinal cord. The most common form is called Chiari malformation type 1, which is the type usually seen in otherwise healthy children and adults.

The types of Chiari malformation describe how much of the back of the brain moves down towards the neck and how severe the associated abnormalities are:

• Type 1: The most common and “mildest” type. Only the lower part of the cerebellum descends slightly towards the neck; it is often found by chance, or it may cause headaches and dizziness.

  
  

• Type 2 (Arnold–Chiari): A more severe type, usually seen in babies with open spina bifida (myelomeningocele). A larger part of the brain moves down towards the neck and hydrocephalus is often present.

Image source: BMJ 2019;365:l1159

• Type 3: Very rare and severe. Parts of the brain protrude outwards through a large defect at the back of the skull (occipital encephalocele).

• Type 4: Extremely rare, with a very small or underdeveloped cerebellum; this classification is now used less often and is mainly of theoretical interest.

  
  

Possible symptoms

Some people with Chiari malformation have no symptoms at all and the finding is discovered by chance on an MRI scan. Others may develop symptoms, which vary from person to person and can be mild or more troublesome.

Common symptoms include:

• Headache, usually at the back of the head, which gets worse with coughing, sneezing, laughing or straining

• Neck pain or stiffness

• Dizziness or a feeling of unsteadiness

• Difficulty with coordination or walking

• Numbness, “pins and needles” or weakness in the arms or legs

• Blurred or double vision, or “shaky” eye movements

• Ringing in the ears (tinnitus) or hearing problems

• Difficulty swallowing, a tendency to choke, or a hoarse voice

  
  

In some people, Chiari malformation is associated with the formation of a fluid‑filled cavity inside the spinal cord, called a syrinx (syringomyelia). Over time this can lead to worsening weakness, stiffness, pain and problems with bladder or bowel control if it is not treated.

Why it happens

In most people, Chiari malformation is present from birth. The back part of the skull (posterior fossa) may be a little smaller or shaped differently, so there is not enough room for the cerebellum and it is pushed downwards.

Less commonly, Chiari malformation can develop later in life, for example after problems with cerebrospinal fluid pressure or flow, or after operations on the spine. It is usually not related to anything the person or their family did or did not do.

Diagnosis

The main test used to diagnose Chiari malformation is an MRI scan of the brain and cervical spine. This shows whether the cerebellum is lower than normal and whether the flow of cerebrospinal fluid is restricted.

The doctor will also take a detailed medical history and carry out a neurological examination, checking strength, sensation, balance, coordination and eye movements. MRI scans of the whole spine are often requested to look for syringomyelia or other related conditions, such as scoliosis.

Management

Not all patients with Chiari malformation need treatment. The choice of management depends on the symptoms, how much they affect daily life, and whether there are complications such as syringomyelia.

Monitoring and conservative measures

If symptoms are mild or absent, monitoring is often recommended. This usually involves regular medical appointments and, when needed, repeat MRI scans to check that the condition remains stable.

Other measures that may help include:

• Painkillers for headache and neck pain, as advised by your doctor

• Physiotherapy and exercises to improve posture and balance

• Advice on adjusting activities and managing fatigue

  
  

Surgical treatment

If symptoms are severe or worsening, or if there is syringomyelia or clear pressure on the brain or spinal cord, surgery may be advised.

The main operation is called posterior fossa decompression. The neurosurgeon removes a small piece of bone at the back of the skull, and sometimes from the top of the cervical spine, to create more space and improve the flow of cerebrospinal fluid.

In some cases the dura mater (the tough outer membrane covering the brain) is opened and enlarged with a graft to provide extra space. Surgery usually stops the condition getting worse and often improves the main symptoms, especially headache and pain, although some long‑standing problems may not fully reverse. As with any major operation, there are possible risks, such as infection, bleeding or cerebrospinal fluid leak, but serious complications are relatively uncommon in specialist centres.

Children

Chiari malformation type 1 can also be found in children, either because they have symptoms (such as headache, neck pain, balance difficulties or learning/developmental problems) or by chance on an MRI scan. In many children it does not cause significant problems and can be managed with regular follow‑up.

If a child has severe or progressive symptoms, syringomyelia or signs of pressure on the brain or spinal cord, a paediatric neurosurgeon may recommend decompression surgery to protect the spinal cord and reduce symptoms. The team will discuss the options with you in detail and explain what to expect before and after surgery.4

Pregnancy and birth

Most women with Chiari malformation type 1 have normal pregnancies and births. Serious complications directly related to Chiari malformation during pregnancy or labour appear to be very rare.

If you have Chiari malformation and are planning a pregnancy or are already pregnant, it is important to inform your neurologist or neurosurgeon, as well as your midwife and obstetrician. They can plan your care together and discuss the safest options for pain relief and mode of delivery; both vaginal birth and caesarean section have been reported as safe options when properly planned.

Outlook and everyday life

For most people with Chiari malformation type 1, the condition is not life‑threatening and many never need surgery. When surgery is required, many patients experience significant improvement in their main symptoms and can return to everyday activities, often with some adjustments.

You should seek urgent medical advice if you develop sudden new or worsening symptoms, such as very severe headache, new weakness, difficulty walking or loss of bladder or bowel control.

For more information, please contact Dr Mazarakis on 6975400064.