Background

Chiari malformation is a neurologic disorder in which there is an abnormal shape or position of part of the brain near the base of the skull. The most common type is the Chiari I malformation, which we will focus on here.

Chiari I occurs when a part of the cerebellum called the tonsils (not the tonsils in your throat) descends beneath the bottom of the skull through an opening called the foramen magnum. When the cerebellar tonsils sit below the foramen magnum and occupy part of the upper spinal canal, they can squeeze or compress the back of the brainstem, causing symptoms.

Chiari I is considered a congenital or developmental disorder, meaning that a person is born with it, though there are some examples of it developing later in life. Many patients do not experience symptoms until young adulthood or even later. Chiari I is estimated to affect roughly 1 in 1000 people.

Symptoms

Many patients with Chiari I never develop symptoms. For those who do, the most common symptoms are headaches at the back of the head and upper neck pain. In particular, the headache and neck pain tend to be brought on or worsened by activities such as coughing, sneezing, laughing, straining, or exercising. Other symptoms may include nausea and vomiting, sleep apnea, difficulty swallowing, balance problems, tinnitus (ringing in the ears), and double vision.

Some Chiari malformations can cause a buildup of fluid within the spinal cord, called a syrinx. Patients with a syrinx usually complain of arm symptoms, ranging from burning to numbness and tingling to weakness. Treating the Chiari malformation (see below) usually improves or resolves the syrinx.

Diagnosis

Chari I can be diagnosed after a careful medical history, physical examination, and review of a scan of your brain (usually an MRI).

Treatment

The primary treatment for Chiari I is surgery, often referred to as a Chiari decompression. Importantly, not all Chiari malformations need surgery! Surgery is generally reserved for malformations causing severe headaches that cannot be managed with medications, for patients with more alarming signs of brainstem compression (difficulty swallowing, choking, sleep apnea, double vision, etc.), and for those with a syrinx in the cervical spinal cord.

The goal of a Chiari decompression is to open up space around the cerebellar tonsils so that they are no longer pushing against the brainstem. This is achieved by shaving away bone at the base of the skull to widen the foramen magnum. Often, part of the arch of the first cervical vertebrae (C1) is also removed. The amount of bone removal depends on how low the tonsils descend. Your surgeon may also open and expand the covering around the brain called the dura.

After Surgery

Most patients stay in the hospital one or two nights, depending on how they feel. The muscles in the back of the neck near the base of the skull tend to be sore or stiff for a few weeks after the operation. Relief from Chiari headaches tends to occur quickly, though it can sometimes be hard to tell in the beginning due to pain from the incision. Syrinx symptoms tend to take longer to improve. It's important to discuss with me in the office which of your symptoms are most bothersome to you and whether they are likely to respond to surgery.

If you live near Denver and have a Chiari malformation, please consider meeting me in consultation to learn about treatment options. Below are additional images showing scans from before and after Chiari surgery.