Neurologic Diseases: Chiari Malformation

What is this condition?

Chiari malformation, also called as Arnold-Chiari malformation is a congenital malformation of the brain (patient is born with this condition).

Types of chiari-malformation

There are four types typically described, although some of them are very rare.

Type 1:

In this type the cerebellar tonsils (the lowermost poles of the cerebellum) descend downward (herniated) towards the cervical spinal canal (neck area). This is the most frequent type and a neurologist and neurosurgeons not uncommonly come across this condition in the clinical practice.

Type 2:

This is type 1 with additional malformations like spinal myelomeningocele, hydrocephalus etc. According to some authorities Arnold-Chiari malformation is the name only for type 2, however others use it for all four types.

Type 3:

Here the patient has occipital encephalocele (herniation of occipital lobe through the skull bone defect).

Type 4:

These patients have cerebellar developmental problems.

Type1 is the commonest and least dangerous type. Rest of them all produces major neurological dysfunction.

How does patient present?

The manifestations depend upon the type of chiari malformation and may include the following.

• Headache
• Neck pain
• Nystagmus (abnormalities of eye movements)
• Dizziness
• Vertigo (spinning sensation)
• Arm & leg weakness, numbness etc
• Bowel and/or bladder symptoms
• Swelling on the lower back
• Swelling on the back of the head
• Gait difficulties etc.


An MRI of the cranio spinal junction is the single most important investigation to confirm the diagnosis. Even Brain MRI or MRI of cervical spine shows the downward displacement of the cerebellar tonsils. Almost all type 1 can be picked up by these tests.

With type 2 radiological studies of the lower spine is also necessary.

Type 3 & 4 can be diagnosed with MRI brain scan.


Type 1 is treated conservatively as long as possible. When symptoms and/or the cerebellar-tonsil herniation progresses then surgery to widen the upper cervical spinal canal is done.

Type 2 may require surgical intervention at the lower spine as well (myelomeningocele etc). If patient has hydrocephalus then that has to be addressed too (ventriulo peritoneal shunt etc).

Chiari Malformation to Neurology Articles