Chiari Malformation: A congenital disorder

Chiari Malformation. The human skull is a bony structure that houses the brain. Along with support, it protects the tissues of the brain and spinal cord from damage. But what if the skull is small or misshapen? In this malformation, a group of structural defects in the skull and cerebellum, the skull loses its protective devices. The abnormal structure injures the brain and causes neurological symptoms. 

Chiari Malformation
Chiari Malformation

What is Chiari Malformation?

Chiari malformation is a congenital disorder in which the skull is misshapen or smaller than normal. The structural defects cause the cerebellum, the part of the brain responsible for muscle movement and coordination, to protrude through a hole at the base of the skull (called the foramen magnum) or another abnormal opening at the back of the skull.

In a healthy body, only the spinal cord passes through the foramen magnum. However, this malformation allows the brain to extend into the foramen magnum and into the spinal canal. As this occurs, the pressure interferes with function controlled by these areas and disrupts the flow of cerebral spinal fluid meant to provide nutrients to the nervous system.

Causes of Chiari Malformation

Chiari malformation is either primary or secondary—with the former being the most common. Primary this malformation is congenital, which means it is present at birth due to genetic mutations or because of an inadequate maternal diet during fetal development. Secondary Chiari malformation presents later in life after injury, disease, or infection drains excessive amounts of cerebral spinal fluid from the spine. The prevalence of Chiari in the general population is an estimated 1 in 1,000 births. Females are more likely to have the condition than males.

Symptoms of Chiari Malformation?

Symptoms of this malformation depend on the individual. Some born with this malformation are asymptomatic until adolescence and adulthood. While symptoms vary by classification, basic symptoms are:  

  • Headache
  • Neck pain that worsens with activity
  • Dizziness and vertigo
  • Muscle weakness
  • Balance problems
  • Numbness and tingling in hands and feet
  • Ringing in ears (tinnitus)  
  • Vision disturbances—double vision (diplopia), light sensitivity (photophobia), involuntary eye movements (nystagmus), blurred vision
  • Difficulty swallowing
  • Changes in bowel or bladder habits
  • Poor hand coordination
  • Hoarseness
  • Sleep apnea
  • Insomnia
  • Nausea and vomiting

Cognitive Effects of Chiari Malformation

Since Chiari affects the nervous system, there are many cognitive symptoms of the disorder. Studies show greater evidence for deficits in executive function than other areas of cognition (Rogers). Those with Chiari might experience problems with memory, difficulty with word retrieval during a conversation, or mood changes. They also exhibit poor concentration with tasks. People with Chiari often develop secondary depression and anxiety.

Chiari Malformation Brain and Spinal Cord Complications

Spinal cord defects and deformities are risk factors for Chiari malformation. Between 30 and 50 percent of Chiari patients have additional spinal cord complications. The specific type of Chiari malformation determines the combination of comorbid conditions.

Spina Bifida

Spina bifida is a birth defect that prevents proper brain and spinal cord development. In utero, the neural tube remains unclosed and upon birth, the backbone does not close completely to protect the spinal cord and its membranes.

Myelomeningocele is a form of spina bifida most common in Chiari malformation. A sac of fluid comes through an opening in the back damaging the nerves. The consequence is a loss of sensation in the person’s lower body, the inability to move their legs or feet, plus urinary or bowel incontinence.


Hydrocephalus is characterized by a buildup of cerebral spinal fluid around the brain and spinal cord. Chiari malformation can block the circulation of spinal fluid. As pressure accumulates in the head, the excessive levels of cerebrospinal fluid cause mental defects and introduces the possibility of further damaging the skull.


Syringomyelia, also referred to as a syrinx, is a cyst at the spinal column. The tubular cyst grows within the central canal of the spinal cord damaging its functions. Pain, weakness, a loss of sensation, and stiffness are signs of syringomyelia occurring in Chiari malformation.

Tethered Cord Syndrome

Tethered cord syndrome is a neurological disorder which hinders the free movement of the spinal cord within the spinal canal. The spinal cord is fixed to the bones in the spine. This abnormal attachment stretches the spinal cord, harming the nerves in the lower body. Tethered cord syndrome causes pain, spasms, and weakness in the back and legs, interferes with bowel and bladder control, and can lead to the inability to walk. It must be treated with surgery when symptoms severely impair function.

Spinal Curvature

Spinal curvature is a frequent diagnosis in individuals with Chiari malformation. A lateral curve or side-to-side curve of the spine is known as scoliosis, whereas a forward bend is called kyphosis.

Chiari Malformation Classifications

There are 4 main types of Chiari malformation. Physicians classify the disorder by level of severity, as well as the specific areas of the brain affected.

Chiari Malformation Type 1

Type 1 Chiari malformation occurs when the cerebellum pushes through the foramen magnum. It is the most common type and symptoms can arise after birth in adolescence or adulthood. Type 1 is usually discovered accidentally by a medical evaluation for another condition.

Chiari Malformation Type 2

Both the cerebellum and a portion of the brain stem (the medulla) protrude into the foramen magnum in type 2 Chiari malformation. Nerve tissue connecting the cerebellum is not formed correctly. Although more severe than the previous type, symptoms appear in childhood. It is associated with myelomeningocele, a form of spina bifida, and hydrocephalus.

Chiari Malformation Type 3

Type 3 Chiari malformation is rare. The entire cerebellum and brain stem herniate through the back of the skull. Membranes surrounding the brain and spinal cord are sometimes included in this structural defect. Severe neurological defects such as seizures and mental delays are likely.

Chiari Malformation Type 4

Type 4 Chiari malformation includes cerebellar hypoplasia—a condition identified by an underdeveloped cerebellum. The cerebellum does not extend into the spinal canal in this type. Instead, the skull and spinal cord are visible because parts of the cerebellum are absent. It is fatal during infancy.

Diagnosing Chiari Malformation

Some severe malformations are visible on an ultrasound before birth. However, most cases are impossible to diagnose while still in-utero.

If a physician suspects Chiari malformation, they first perform a psycho-neurological exam. The exam checks the functions controlled by the cerebellum that may indicate the disorder. They assess memory, cognition, reflexes, sensation, balance, touch, and motor skills. Confirmation of the diagnosis relies on imaging studies:

  • Magnetic resonance imaging (MRI) uses a magnetic field to produce 3-dimensional images of the organs, bones, nerves, and body tissues. MRI is the go-to scan to aid in Chiari malformation diagnosis, as the images are detailed enough to show if the cerebellum is out of position.
  • Cine MRI is an MRI that measures the flow of cerebrospinal fluid. It is a helpful test to check whether the flow of cerebrospinal fluid is disrupted by the structural abnormalities.
  • Computed tomography (CT) produces 2-dimensional images of the bones and blood vessels through x-ray images. It is not as accurate in detecting the defects in the cerebellum and foramen magnum needed to diagnose Chiari, but it can show associated hydrocephalus.

Chiari Malformation Treatment

There is no “one size fits all” rule for treating Chiari malformation. Severity and symptom presentation vary among patients. Those who are asymptomatic are not treated but closely monitored by physicians for disease progression, yet symptomatic patients require effort on behalf of numerous specialists to treat the condition. The doctor tailors the therapies to the patient.


Posterior fossa decompression is a surgical procedure that creates space for the cerebellum. A neurosurgeon starts decompression by removing a section of bone at the base of the skull to uncover the dura—a membrane that covers the brain. Occasionally, this is sufficient to restore the flow of cerebrospinal fluid and decrease symptoms. The next step of decompression is to sew a patch to enlarge the covering. The covering is constructed from artificial material or from the patient’s scalp. It is comparable to adjusting the size of a garment to create more space. Transnasal decompression is similar to posteriorfossa decompression, except the neurosurgeon removes a section of the skull through the nose or mouth at the front of the skull.

Cervical Laminectomy

Cervical laminectomy uses the same approach as decompression. For optimal symptom relief, Chiari malformation treatment combines both procedures. The neurosurgeon removes the upper vertebrae in addition to a piece of the skull. Cervical laminectomy creates space for the cerebellum and the spinal cord.

Cerebrospinal Fluid Diversion or Shunt

A shunt is a surgical device to rapidly resolve increased intracranial pressure. Placing a shunt requires that a surgeon implant a catheter through a small hole in the skull. The catheter is a small tube passed through the brain to divert cerebrospinal fluid elsewhere in the body. The fluid is generally shunted into the abdominal cavity. Cerebrospinal fluid diversion or a shunt is usually successful in patients with hydrocephalus or increased pressure in the head.

Pain Management

Milder cases of Chiari malformation may not warrant surgery. Pain management combines medication and physical therapy with the goal of avoiding an invasive operation. Anti-inflammatories, opioids, or anti-depressants combat pain and headaches. Although engaging in the wrong physical activities exacerbate symptoms, physical therapists guide patients on the right exercises for their bodies to improve strength and pain. Physical therapy is especially important after surgery to preserve range of motion.

Lifestyle Modifications

Massage for Chiari Malformation
Massage for Chiari Malformation

Chiari malformation seems impossible in the midst of frustrating symptoms and invasive procedures, yet patients will be pleased to learn they can still take control of their health. Lifestyle modifications are a beneficial asset to medical therapies.

  • Low impact exercises like walking, yoga, or tai-chi keep the muscles conditioned.
  • Consuming a well balanced diet prevents weight gain that stresses the body.
  • Massage soothes muscle spasms.
  • Acupuncture applies ancient Chinese medicine to decrease pain and muscle tension.
  • Sleeping on an elevated bed lessens the intensity of Chiari-induced headaches.
  • Meditation and relaxation techniques lessens headaches.
  • Attending support groups connects patients with others who live with the condition. Sharing experiences is therapeutic.

What to avoid with Chiari malformation:

  • High-risk activities that strain the neck—roller coasters, trampoline jumping, roller blading, gymnastics, diving, etc.
  • Contact sports—football, soccer, wrestling, etc.
  • Chiropractic manipulation
  • Straining during a bowel movement that aggravates a syrinx
  • Spinal injections


Rogers JM, Savage G, Stoodley MA. A systematic review of cognition in Chiari I malformation. Neuropsychol Rev. 2018;28:176-187.

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