Chiari Malformations

Chiari type I malformations (CMI) occur in the region where the brain and the spinal cord join. In this disorder, the portions of the brain called the cerebellum and/or brainstem lie lower than usual. Often, a portion of the cerebellum called the cerebellar tonsils protrudes out of the base of the skull into the spinal canal. This protrusion causes pressure in the brain, contributing to the symptoms people experience. The cause of CMI is not known. Some CMI cases are believed to be present at birth. There are many symptoms associated with CMI. These symptoms may include headaches, especially at the base of the skull, dizziness, double vision, weakness in the arms, and/or difficulty walking. When symptoms are present, they are often vague or nonspecific. As a result, the diagnosis of CMI is often delayed until more severe symptoms present themselves or after current symptoms persist for some time.

Since the advent of MRI, the incidence of the Chiari I malformation has risen dramatically. MRI is safe and painless, and currently the most reliable means available for diagnosing Chiari malformations. Chiari malformations are also known as herniation of the cerebellar tonsils, cerebellar ectopia, hindbrain herniation, and Arnold-Chiari malformations. 

  1. What are the symptoms of Chiari I malformation?
    Many people with the Chiari I Malformation experience no symptoms. When symptoms are present, they usually do not appear until adolescence or early adulthood, but can occasionally be seen in young children. The majority of patients complain of severe head and neck pain. Headaches are often accentuated by coughing, sneezing, or straining. Patients may complain of dizziness, vertigo, disequilibrium, muscle weakness, or balance problems. Often, fine motor skills and hand coordination will be affected.

    Vision problems can also occur. Some patients experience blurred or double vision, difficulty in tracking objects, or a hypersensitivity to bright lights. Physical examination may reveal nystagmus (involuntary eye movements). Other symptoms include tinnitus (buzzing or ringing in the ear), hearing loss, or vocal cord paralysis. Patients may have difficulty swallowing, frequent gagging and choking, and in some cases, sleep apnea may be present.

    The Chiari I malformations may also be associated with other disorders such as hydrocephalus (build up of fluid in the ventricles of the brain), or Syringomyelia. Syringomyelia is a disorder in which cerebrospinal fluid enters the spinal cord, forming a cavity known as a syrinx. It is recommended that patients diagnosed with a Chiari malformation have the entire spine imaged to rule out the presence of a syrinx, since it may be a consideration in treatment and prognosis.
  2. What is the treatment for Chiari I malformation?
    Surgical procedures to enlarge the posterior fossa are considered a treatment option for patients with the Chiari I malformation. Techniques are quite diversified amongst neurosurgeons, and patient responses vary greatly. A successful surgery will alleviate pressure on the neural elements, and may result in an improvement of symptoms.

    The decision to treat a Chiari malformation surgically requires careful consultation between patient and physician. Factors to be considered are the patient's current neurological condition and progression of symptoms over a period of time.
  3. Is Chiari I malformation a hereditary condition?
    Research into the risk of inheritance for the Chiari I malformation is still in its early stages. In some families, more than one member has been documented to have the Chiari I malformation. Familial recurrences are suggestive of a possible genetic component of the condition, but unfortunately, there is no conclusive answer to the question of inheritance at this time. It is currently recommended that only those relatives experiencing symptoms commonly associated with the Chiari I malformation need undergo investigational procedures.


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  1. What is syringomyelia?
    Syringomyelia, often referred to as SM, is a chronic disorder involving the spinal cord. For reasons that are only now being understood, cerebrospinal fluid enters the spinal cord, forming a cavity known as a syrinx. (Doctors sometimes use other words such as cyst, hydromyelia, or syringohydromyelia). This syrinx often expands and elongates over time, destroying the center of the spinal cord. As the nerve fibers inside the spinal cord are damaged, a wide variety of symptoms can occur, depending upon the size and location of the syrinx.

    There are two major types of SM. In most cases, it is related to a congenital malformation involving the hindbrain (cerebellum) called a Chiari I malformation (CMI), named after the physician who first described it. This malformation occurs during fetal development, and is characterized by downward displacement of the lower part of the brain (cerebellar tonsils) beneath the foramen magnum, into the cervical spinal canal. This displacement blocks the normal flow of cerebrospinal fluid. When normal flow is obstructed, a syrinx can then form in the spinal cord. However, not all patients with Chiari malformations will develop a syrinx.

    SM can also occur as a complication of trauma, meningitis, tumor, arachnoiditis, or a tethered spinal cord. In these cases, the syrinx forms in the section of the spinal cord damaged by these conditions. As more people are surviving spinal cord injuries, more cases of post-traumatic SM are being diagnosed as the syrinx can form years after the trauma.
  2. What are the symptoms of syringomyelia?
    The symptoms of SM are numerous, and a person may have various combinations of different symptoms. Symptoms tend to develop slowly, although sudden onset may occur with coughing and straining. Some common symptoms include: loss of sensitivity, especially to hot and cold; muscle weakness and spasticity; motor impairment; loss of bowel and bladder control; as well as osteoporosis and scoliosis. The majority of patients suffer from headaches and chronic pain.

    Although Syringomyelia was first described over 400 years ago, very little research was performed, and as a result, little was known about the disorder. Only recently, with the advent of MRI and the dramatic rise in diagnosed cases, have significant advancements been made. In the past, SM was considered a disorder that always resulted in slow, progressive degeneration. Researchers now believe it is possible that some patients may never progress.
  3. What is the treatment for syringomyelia?
    The first step after diagnosis is finding a neurosurgeon who is experienced in the treatment of SM. Selecting a Penn State specialist is highly recommended. Surgery is the only viable treatment for SM, but not all patients will advance to the stage where surgery is needed. Evaluation of the condition is often difficult because SM can remain stationary for long periods of time, and in some cases, progress rapidly.

    Treatment is aimed at correcting the condition that allowed the syrinx to form, if possible. In cases involving a Chiari malformation, the main goal of surgery is to provide more space for the cerebellum at the base of the skull and upper cervical spine. This often results in a flattening or disappearance of the syrinx as the normal flow of cerebrospinal fluid is restored. In some cases, it may be necessary to insert a shunt into the cavity, rerouting the cerebrospinal fluid from the spinal cord. A successful surgery will stabilize the condition and perhaps gain a modest improvement in symptoms, but over time, surgery is not always successful, and multiple surgeries may be necessary.

    Since the natural history of SM is poorly understood, a conservative approach may be recommended. When surgery is not yet advised, patients should be carefully monitored by a neurologist or neurosurgeon. Periodic MRI's and physical evaluations should be scheduled at the recommendation of a qualified physician.

    Syringomyelia is a condition characterized by a syrinx (fluid-filled cyst) in the spinal cord. In some instances, syringomyelia is caused by an injury. However, there are also some cases that are congenital (present at birth). Often, patients with CMI are also diagnosed with syringomyelia.