A Chiari malformation is a congenital (present at birth) defect in the area of the back of the head where the brain and spinal cord connect. The condition is also called Arnold Chiari malformation. In general the condition is an abnormality where the base of the brain, the cerebellar tonsils, protrude through the base of the skull and crowd the space that usually houses the brainstem and spinal cord. Symptoms are a result of compression of the important stuctures that travel thrrough this area and are crowded by the misplaced tonsils.
There are Four Types of Chiari Malformations
Type I – commonly goes unnoticed until problems arise in the adolescent or adult years of life. In this condition, the base of the skull and the upper spinal area are not formed properly.
Type II – this is the most common type of Chiari malformation. In this condition, part of the back of the brain shifts downward through the bottom of the skull area.
Type II Chiari malformations are typically seen in infants who are born with spina bifida, a neurological condition that causes a portion of the spinal cord and the surrounding structures to develop outside, instead of inside, the body. Type II Chiari malformations can also be associated with a condition known as hydrocephalus. Hydrocephalus is a condition in which there is an overproduction or lack of absorption of the cerebral spinal fluid (CSF) that is found inside the ventricles (fluid-filled areas) inside of the brain. The increased fluid causes the pressure inside of the head to increase and the skull bones to expand to a larger than normal appearance.
Type III – the back of the brain protrudes out of an opening in the back of the skull area. (very rare)
Type IV – the back of the brain fails to develop normally. (very rare)
Chiari Malformation Causes
Although the exact cause of Chiari malformation is unknown, it is thought that a problem during fetal development may cause the abnormal brain formation. The simple form of Chiari malformation is typically congenital and likely results from the part of the skull housing the cerebellum being too small.
In some cases an increase in pressure in the brain above the cerebellum can cause downward pressure on the cerebellum and forcing the tonsils through the base of the skull. This can be seen in association with hydrocephalus (excess fluid on the brain), hematoma or blood on the brain, stroke, infection, or other disorders that cause increased pressure in the brain.
Chiari Malformation Symptoms
Many Chiari malformations do not cause any symptoms or problems and will often go unnoticed. Sometimes a Chiari can be discovered when an MRI is obtained for some other diagnosis. The following are the most common Chiari malformation symptoms. However, each child may experience different symptoms. In infants and older children born with this Chiari malformation, symptoms may include:
- breathing problems, sleep apnea, snoring
- decreased strength in the arms or hands
- developmental delays
- poor feeding and swallowing
- stiffness or pain in the neck or back of the head area
- weak cry
- walking problems or leg weakness
Chiari malformation symptoms may resemble other conditions or medical problems. Always consult your child’s physician for a diagnosis.
Diagnosis & Treatment
MRI of the brain and spinal cord is going to be the best study to identify a Chiari malformation. If a Chiari malformation occurs with other congenital defects, the diagnosis may be made at birth. Other times, the diagnosis is made after the onset of specific signs and symptoms and after diagnostic testing.
Evaluation to determine the diagnosis will include obtaining your child’s medical and developmental history. Developmental milestones and growth are important in establishing if there are any delays related to a Chiari malformation or other neurologic disorders.
It is also important to identify other issues that can be associated with Chiari malformation. These include:
- Hydrocephalus – a build up of fluid inside the brain
- Syringomyelia – a build up of fluid inside the spinal cord
- Tethered Cord – thickening of a small band at the base of the spinal cord that can lead to bowel or bladder problems or leg weakness if not addressed
Diagnosing a Chiari Malformation
Diagnostic tests are necessary to confirm the diagnosis of a Chiari malformation and evaluate for other associated problems:
Magnetic Resonance Imaging (MRI) – a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body. Often, MRI’s of the brain and entire spine are required to evaluate for other abnormalities.
Sleep Study – a diagnostic study to evaluate how your child sleeps and breathes while sleeping. This sometimes helps identify if there are subtle symptoms of a Chiari malformation.
Spinal X-Rays – a diagnostic test to look at the development of the bones of the spine and evaluate for abnormal curvature of the spine (scoliosis).
Chiari Malformation Treatment
Specific Chiari malformation treatment will be determined by the Chiari team and is based on:
- your child’s age, overall health and medical history
- the severity of the malformation
- the type of condition
- expectations for the course of the condition
- your opinion or preference
Medical management consists of periodic physical examinations and diagnostic testing to monitor the growth and development of the brain, spinal cord, skull, and backbones. Parents are instructed to watch for any changes that may indicate the malformation is becoming symptomatic such as occipital headaches, snoring, problems walking, or weakness in the hands or arms.
Some types of Chiari malformations may require Chiari surgery to relieve increased pressure inside the head or neck area, or to help drain excess cerebral spinal fluid from the brain. The general approach in surgery is to expand the part of the skull and spine where the tonsils are compressing the spinal cord. The dura or covering of the brain is also typically expanded by adding a “patch” of either graft material or tissue from the scalp near the incision. Additionally the tonsils can be “shrunk” to increae the space around the brainstem and open up the normal fluid pathways. The main goal of surgery is to relieve the compression and restore the normal flow of spinal fluid which is obstructed by the tonsils.
After surgery the child is typically observed overnight in the Pediatric ICU and then moved to a regular room the next day. Typically patients are in the hospital for 3-4 days. For further information see “What to expect if you or your child is having surgery- Chiari Malformation.”
Lifelong Considerations for a Child with a Chiari Malformation
The full extent of the problems associated with a Chiari malformation are usually not completely understood immediately at birth, but may be revealed as the child grows and develops. Children born with a Chiari malformation require periodic examinations and diagnostic testing by your child’s doctor to monitor the development of the head as the child grows. The medical team works hard with your family to provide education and guidance to improve the health and well-being of your child.
The Chiari Team
The Chiari Team is composed of various pediatric specialties. Prior to your evaluation you will be asked to complete a Chiari questionaire to help us determine what studies and physicians will be needed to streamline your child’s care.
The team is composed of:
- Dr. Renatta Osterdock- Pediatric Neurosurgery
- Dr. Ramon Cuevas – Pediatric Neurology and Sleep Medicine
- Dr. Jaren Riley – Pediatric Orthopedics
- Dr. Suzanne Rosenberg – Pediatric Rehabilitation Medicine
Sometimes additional evaluation by neuropsychology, ENT, pulmonology, urology, or general surgery may be required to complete the evaluation.