The cerebellum controls a person's sense of balance. When the indented, bony space located at the rear of a person's skull is smaller than average, their cerebellum and brain stem may be pushed downward. Pressure results on the person's cerebellum and may block the flow of their cerebrospinal fluid, a liquid that both surrounds and protects their brain and spinal cord. People affected by Chiari malformation can experience symptoms ranging from muscle weakness, dizziness, vision problems, and numbness to headaches and problems with coordination and balance.
Chiari malformation (CMs) is a condition affecting the brain. It consists of a downward displacement of the cerebellar tonsils through the foramen magnum (the opening at the base of the skull), sometimes causing non-communicating hydrocephalus as a result of obstruction of cerebrospinal fluid (CSF) outflow. When part of the cerebellum is located below the foramen magnum, it is called a Chiari malformation.
Women are three times more likely than men to have a congenital Chiari malformation.
In the past, it was estimated that the condition occurs in about one in every 1,000 births. However, the increased use of diagnostic imaging has shown that CM may be much more common. Complicating this estimation is the fact that some children who are born with the condition may not show symptoms until adolescence or adulthood, if at all. CMs occur more often in women than in men and Type II malformations are more prevalent in certain groups, including people of Celtic descent.
There are various different forms of Chiari malformations, with the most common type being the Chiari I malformation (CM), the main one approached in this article.
Although the names are used less frequently, Chiari I malformation might also be referred to as, 'Arnold Chiari malformation,' 'tonsillar herniation,' or, 'tonsillar ecotopia.' Many people who experience a Chiari malformation have it congenitally, meaning the condition is present from the time of the person's birth.
Type II Chiari malformation is often accompanied by a form of spina bifida known as, 'myelomeningocele-a,' that happens when a person's spinal canal and backbone do not close prior to the person's birth, causing their spinal cord to protrude through an opening in their back. The disability may cause either partial or complete paralysis below the spinal opening.
Type III Chiari malformation is the most serious form of CM, one that causes severe neurological defects.
An average person's anatomy finds their cerebellar tonsils located just above the foramen magnum. People with Chiari malformations have tonsils that herniate into their spinal canal. The degree of variation to which the affected person's tonsils extend can be tremendous. Additional conditions that are sometimes associated with Chiari malformation include syringomyelia, hydrocephalus, and curvature of the person's spine.
The most common symptom experienced by persons with Chiari malformation is a headache. The headache usually starts at the back of the person's head and neck, then radiates upward. The pain is many times worsened, or may be started by, sneezing, coughing, or straining. These activities are referred to as, 'valsalva maneuvers.'
Nystagmus, or involuntary eye movements, and other visual problems such as blurred or double vision are symptoms people with Chiari malformations can experience. They may experience vertigo, difficulties with balancing, and dizziness. Some people with Chiari might have cranial nerve compression, something that may result in apnea, swallowing difficulties, gagging, temporary loss of consciousness, or facial numbness.
People with Chiari malformation can also experience muscle weakness, notably in their upper extremities. They may have coordination problems, as well as gait abnormalities. An imaging study of the person may reveal a collection of fluid inside of their spinal cord, also known as a, 'syrinx.' Some people with Chiari malformation also have hydrocephalus, a buildup of fluid in the ventricles of their brain.
Symptoms can include:
Chiari malformation varies greatly where the symptoms are concerned. Many people who have type I do not experience any symptoms and are not even aware they have the condition. A number of people with the more severe forms of Chiari malformation pursue surgery and experience a reduction in their symptoms, or have a prolonged period of relative stability - although paralysis is commonly permanent.
If the symptoms a person is having related to Chiari malformation are mild and not progressive, a doctor might recommend conservative management. Supportive care that includes pain and headache management, a reduction in activities, and physical therapy might help in dealing with the person's symptoms. Medications can help with certain symptoms such as pain. Where functional disturbances are concerned, surgery is the only form of treatment available. Surgery is also the form of treatment used to halt the progression of damage to the person's central nervous system. More than one surgery may be required to treat some forms of Chiari malformation.
Upon receiving a diagnosis, the first step is a consultation with a neurosurgeon who has experience in treating and managing Chiari malformation. Finding and consulting with a neurosurgeon with this kind of experience might require travel, and consultation with more than one specialist may be required.
An operation called a, 'posterior fossa decompression,' may be recommended. A surgeon creates more room in the back of the person's head by removing small pieces of the person's skull bones, reducing compression of the person's brain stem and allowing their tonsils to move back into their natural position. The particular surgical techniques vary among surgeons and there is no consensus on the best variation of the surgical procedure at this time.
Medical researchers have investigated the genetic implications of Chiari malformation, both with and without syringomyelia. A genetic prevalence has been identified in some families. Researchers are continuing to search for the particular gene or genes that are responsible for producing the Chiari malformation. MRI scanning is recommended for family members who have signs and symptoms of the disorder.