Here the story gets a bit more complicated. The
feeling fibers coming in from the spinal nerves enter the spinal cord on its back surface. They connect to
the spinothalamic fibers that then travel to the front and opposite side of the spinal cord before they enter
the spinothalamic highway up to the brain. Thus, the fibers bringing information in about pain and
temperature of the right side of the body cross to the left side of the body cross to the right side of the cord.
They cross is near the center of the spinal cord. Syringomyelia often starts at the center of the spinal
cord. Thus fibers carrying information about pain and
temperature are among the first affected in patients with
syringomyelia. As the syrinx enlarges, it can affect other tracts and result in weakness and
problems walking. Often, one side is more affected than the other. The mix of symptoms depends on
which type of fibers and nerve cells are affected.
Discovery of the Syringomyelia & Chiari Malformations
1827, Charles Prosper Ollivier dAngers, published an article about disorders of the spinal cord. In a few spine
specimens he found a cavity inside the spinal cord. Since the cavity had not been described before and had no name,
he created the name syringomyelia by combining the Greek word syrinx meaning pipe, tube or channel, and the
Greek word myelus, meaning marrow. Sixty-four years later, in 1891, Hans von Chiari, Professor of Morbid Anatomy at Charles University in Prague,
published a report describing three cases with malformations of the lower part of the cerebellum and brain stem. Each
of the three cases was different thus Chiari described three types of malformation: the type I, II, and III. Later, these
malformations would be named the Chiari malformations in his honor.
The Chiari malformation Type I (CMI) consists of displacement (herniation) of the cerebellar tonsils into the upper
cervical spinal canal. In some cases the lower brain stem also hangs down into the spinal canal. In the Type II
malformation (almost always associated with spina bifida), the lower brain stem, cerebellar vermis, and tonsils hang
down below the foramen magnum. In the very rare Type III malformation the tissues of the posterior fossa are
displaced into a soft sac (meningocele) at the back of the head and upper neck.
Dr. Chiari continued his studies and four years later published another report. In this one he described an additional 24
cases and made another important discovery. He found that some of the patients with the Chiari I and II malformations
also had a cavity within the spinal cord - syringomyelia - the type of cavity that had been described by
Charles Ollivier.
In the article, Dr. Chiari also reported a new type of malformation, Type IV,
which consisted of underdevelopment of the cerebellum known as cerebellar
hypoplasia. However, today we believe that the Type IV malformation is different
from the other three and most specialists no longer include it within the Chiari classification.
Dr. Chiaris studies, performed over one hundred years ago, still serve as the foundation of our modern understanding
of these malformations.
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