Chiari Malformation

CHIARI (prodounced key-AR-ee) MALFORMATION, previously called an Arnold-Chiari malformation, occurs in one (1) out out of every 1000 births. Certain types of chiari malformations may not have any other associated spine or brain abnormality while others may have neuroanatomy deformities such as myelomeningocele, hydrocephalus, syringomyelia, tethered cord syndrome, or a curvature of the spine. A chiari malformation is a condition where a portion of the brain, the tonsillar region of the cerebellum, becomes wedged into a hole in the base of the skull and is referred to as a tonsillar herniation. Normally, the cerebellum lies above this hole in the base of the skull which is called the foraman magnum. The brain is connected to the spine via the brain stem which is the only anatomic structure that travels through the foramen magnum and once it passes through, becomes the spinal cord. The spinal cord is immediately protected within  the spinal canal that is formed by the vertebral bones of the spinal column. If a chiari malformation causes severe symptoms, a neurosurgeon needs to correct the herniationof the brain herniation by decompressing the pressure on the brain and restoring the brain back into the skull. At Centers for Neurosurgery, Spine, and Orthopedics, the New Jersey team includes world-renowned neurosurgeons, pain management doctors, and physical therapists that have years of experience successfully treating  adolescents and adults with Chiari malformations.

Types & Causes

There are three types of Chiari malformations depending on which part of the brain is pushed into the spinal canal and whether there are abnormalities of the brain or spine. Symptoms are believed to be due to the abnormalities affecting the flow of the cerebrospinal fluid (CSF) in the brain and spinal canal as well as pressure on the brain and brain stem.

  • Type I is associated with the brain and the base of the skull growth. Thus, it is usually diagnosed in late childhood or adulthood as a portion of the brain herniates through the base of the skull. Referred to as Chiari I.
  • Type II has a greater amount of the brain herniating through the base of the skull and frequently is accompanied by a myelomeningocele which is also a birth defect of the spine. Most commonly, a Type II is diagnosed by ultrasound of the infant while still in the mother’s uterus, shortly after birth, or during early infancy. Referred to as Chiari II.
  • Type III is the most severe cerebellum herniation of the three types of chiari malformations. Type III can be life-threatening. It should be detected by ultrasound during pregnancy or at birth. It is associated with a higher mortality rate than the other types of chiari malformations because there are more severe neurological abnormalities.

Several factors may contribute to a Type II or Type III congenital chiari malformation. Genetic mutations may cause the fetus to develop abnormally. The lack of proper vitamins such as folic acid during pregnancy may interfere with fetal development and neural tube formation.  Infection or fever during the pregnancy may also interfere with the development of the fetus along with exposure to toxic chemicals, illegal drugs, or alcohol consumption. Other associated congenital conditions are spinal bifida, Ehlers-Danlos, and an abnormal union of the vertebrae within the neck referred to as Klippel-Feil Syndrome.


Depending on the type of chiari malformation, the symptoms a patient experiences may differ. In Type I, symptoms may manifest as a headached,frequent loss of balance, lack of hand coordination, neck pain, dizziness, difficulty swallowing, and might be associated with choking, gagging, or vomiting.  Patients might also experience speech problems or horseness and may also experience sleep-related breathing disorders. These symptoms may be due to the elevated intracranial pressure, cranial neuropathies, brainstem compression, myelopathy orcerebellar dysfunction caused by the brain’s herniation. Type II is usually found at birth or prenatally. Symptoms may manifest as dysphagia, weakness in the arms, stridor, apneic episodes, and aspiration. Type III is associated with a high mortality rate usually due to respiratory failure during infancy. Those that survive may suffer from severe mental retardation, seizures, loss of muscle tone, spasticity, and nerve palsies.


Since there are no biomarkers in bloodwork, cerebrospinal fluid, or tissue biopsies, neuroimaging is the only diagnostic tool which will reveal the craniocervical structural abnormality. Magnetic resonance imaging (MRI) is the best imaging study for the evaluation of the brain and spine anatomy and how it relates to the bone structures. Different angles and views of the brain and spinal cord in the cervical regionare taken to detect any craniocervical abnormalities which might exist causing a negative affect  on the brainstem, cranial nerves, brain, and specifically the cerebellar tonsillar portion of the brain.


The medical management of a chiari malformation depends on the nature of the malformation and the degree of associated neurological impairments. Patients with chiari malformation Type I who do not have syringomyelia and are asymptomatic may be managed conservatively with observation by MRI and clinical management. A small craniectomy and surgical decompression for chiari malformation Type I may be needed if the patient is symptomatic. These symptoms may include severe neck pain, an occipital headache, myelopathy a.k.a. muscle strength weakness, loss of balance and coordination, facial or cranial palsies, syringomyelia. 

Surgical intervention that involves a proportionally larger craniectomy and decompression is needed for Types II and III including closure of the open neural tube defects shortly after birth, a ventriculostomy for the treatment of any existing hydrocephalus (a fluid-filled collection of CSF within the brain) and decompression of the wedged structures. In Type II and Type II, there may also be an encephalocele that needs to be corrected.  Medical issues involve managing neurogenic bowel and bladder, neonatal feeding difficulties, respiratory failures, and apnea will also need to be treated.


Patients after surgery for chiari malformation Type I typically have a prognosis that depends on the extent of pre-operative neurological deficits. The patients with only a few deficits whose symptoms are primarily pain can expect an excellent outcome. Patients with a long history of neurological symptoms, severe weakness, and a loss of muscle mass, improve more slowly. Surgery usually results in a significant improvement of symptom. Type II and Type III should be treated early in infancy by a Pediatric Neurosurgeon. The progress is more guarded.

Centers for Neurosurgery, Spine, & Orthopedics Can Help

The dedicated neurosurgical team at Centers for Neurosurgery, Spine, and Orthopedics (CNSO) routinely diagnoses and treats chiari malformations in patients over the age of 14. Our treatment greatly improves patients lives. The comprehensive approach includes recognized board-certified neurosurgeons, physiatrists, rehabilitation specialists, and certified physical therapists as needed, providing patients with comprehensive coordinated care and treatment.

CNSO offers multiple convenient locations spanning from Passaic County to Morris County and nearby towns including Clifton, Jersey City, and Parsippany, NJ. Northern NJ patients can learn more about a chiari malformation and any necessary spinal decompression surgery or conservative care by contacting the doctors at CNSO today.


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In order to provide an accurate diagnosis with the most effective treatment option for “back problems” and brain tumors, CNSO is led by neurosurgeons and orthopedic spine surgeons. Under the care of our award-winning neurosurgeons and orthopedic spine surgeons, Northern NJ patients can have the confidence that their medical condition will be handled with consideration for their comfort and long-term well-being as well as technical excellence.

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