What Is Chiari Malformation?


Chiari malformation is a cerebellum structural defect in which part of the lower skull is too small, forcing the cerebellum to be pushed down into the spinal column. The cerebellum is the part of the brain that controls movement, muscle control, equilibrium and balance. Chiari malformation is a rare condition; however, increased use of imaging tests has led to more frequent diagnoses.

Primary and secondary Chiari malformation

Primary Chiari malformation occurs during fetal development. Inadequate intake of vitamins and minerals during pregnancy causes pressure on the fetus' cerebellum which, in turn, blocks the flow of cerebrospinal fluid (the fluid that surrounds and protects the brain and spinal cord). Secondary Chiari malformation can occur later in life due to trauma, disease or infection.

Types of Chiari malformation

Chiari malformation is categorized into four types: Type I, Type II, Type III and Type IV.

  • Type I is found in children and is the most common type of Chiari malformation. In Type I, part of the cerebellum extends into an opening at the base of the skull.
  • Type II is the classic form of Chiari malformation and found in children born with spina bifida. Spina bifida is a condition in which the spinal cord doesn't completely form and properly close, resulting in damage to the spinal cord and nerves.
  • Type III is very rare and involves protrusion of the cerebellum and brain stem into the spinal cord.
  • Type IV is also very rare and consists of an underdeveloped cerebellum. It is sometimes associated with exposed parts of the skull and spinal cord.

Symptoms of Chiari malformation

Oftentimes, individuals with Chiari malformation do not experience symptoms. However, depending on the type and severity, Chiari malformation can cause a number of health issues. Individuals with Chiari malformation may experience the following:

  • Weakening of the muscles, slow heart rhythm, abnormal breathing
  • Balance issues, dizziness, difficulty with fine motor skills
  • Headaches (especially after coughing, sneezing or straining)
  • Neck pain
  • Numbness of the hands and/or feet
  • Difficulty hearing, tinnitus (ringing in the ear)
  • Vision problems, rapid downward eye movements
  • Sleep interruption, sleep apnea
  • Depression
  • Curvature of the spine
  • Difficulty swallowing, vomiting, hoarse speech

Risk factors for Chiari malformation

Chiari malformation appears more often in females than in males, and Type II is more common among specific ethnicities, including individuals of Celtic descent. Although research is still ongoing, Chiari malformation may include a hereditary component.

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