Chiari malformation is a condition in which brain tissue extends into your spinal canal.
Chiari malformation is a structural defect in the base of the skull and cerebellum (the part of the brain that controls balance). The most common types of Chiari malformations are:
This is the most commonly observed type. It usually becomes symptomatic in adulthood. It may be an incidental diagnosis. In this type, the lower part of the cerebellum, but not the brain stem, extends into an opening at the skull base (foramen magnum). Typically, only the spinal cord passes through this opening.
This is usually only seen in children born with spina bifida. Spina bifida is the incomplete development of the spinal cord and/or its protective covering. This type is also known as “classic” Chiari malformation or Arnold-Chiari malformation. In this type both the cerebellum and the brain stem extend into the foramen magnum.
The symptoms of type I Chiari malformation include:
Less often, people with Chiari malformation may experience:
In Chiari malformation type II, a more significant amount of tissue extends into the spinal canal than Chiari malformation type I. The signs and symptoms can include a form of spina bifida called myelomeningocele that nearly always accompanies Chiari malformation type II. In myelomeningocele, the backbone and the spinal canal haven’t closed properly before birth.
Signs and symptoms may include:
Chiari malformation type II is usually noted with ultrasound during pregnancy. It may also be diagnosed after birth or in early infancy.
There’s some evidence that Chiari malformation runs in some families. However, research into a possible hereditary component is still in its early phase.
Your doctor will review your medical history and symptoms. They will conduct a physical examination to diagnose your condition. Your doctor will also order imaging tests to diagnose your condition and determine its cause. Tests may include:
The treatment for Chiari malformations and syringomyelia depends on the exact type of malformation and its progression in anatomy changes or symptoms.
Chiari I asymptomatic malformations should be left alone. This involves the majority of Chiari malformations. There is no indication for “prophylactic” surgery on these.
If the malformation is defined as symptomatic or is causing a syrinx, treatment is usually recommended.
Chiari II malformations are treated if the patient is symptomatic, and physicians have determined that there are no complications from hydrocephalus. In some patients, consideration of a tethered cord is also explored. In many infants who become symptomatic from a Chiari II malformation, the symptom onset and progression are severe and rapid, requiring an urgent or emergency approach.
Surgical treatment of these malformations depends on the type of malformation. The goal of surgery is to relieve the symptoms or stop the progression of the syrinx or symptoms. There are many different types of surgery based on the degree of compression or other anomalies.
Chiari I malformations: Patients who are symptomatic from this condition are surgically treated. The surgeon will decompress the overlying bones and release the dura (a thick membrane covering the brain and spinal cord). A cervical laminectomy may also be required to achieve decompression of the full extent of the herniation.
After Chiari malformation surgery, fatigue and weakness, and headaches are common. It is important to watch for signs of infection during this time. This can include redness, inflammation, fever, or fluid accumulating or leaking around the incision. It’s important to call your doctor if you have worsening headaches, severe neck pain when you bend your head forward, increased drowsiness, or weakness in the arms or legs.
You’ll also see your doctors for follow-up visits to monitor your recovery and remove stitches and staples in the days after surgery. If you take medications for other health conditions, your doctors may modify your doses while you recover.