The Chiari (kee-ar-ee) malformations are congenital abnormalities of
the posterior fossa (base of brain where the spinal column joins the skull).
This usually causes a protrusion of the cerebellum through the bottom
of the skull (foramen magnum) into the spinal canal. This results in a
poor circulation of cerebrospinal fluid from the brain to the spinal cord.
HISTORY: Professor Hans Chiari was a German pathologist
who first described these abnormalities of the brain at the junction of
the skull with the spine in 1890. Another doctor, Arnold, later added
to the type II description, hence the name “Arnold-Chiari Malformation.”
Of the four classifications of Chiari, only two types of the malformation
have practical importance, commonly referred to as Chiari type I and Chiari
type II.
DESCRIPTION: The *Chiari I malformations are
a result of the smallest herniation of an otherwise normal hindbrain.
The tonsils would normally be round but often become elongated as they
protrude down the spinal canal. Diagnosis can be difficult because not
all patients will have the classical sign of deeply herniated tonsils.
The Chiari II is usually found in children with spina bifida or myelomeningocele.
Not only is part of the cerebellum unusually low and lying below the bottom
of the skull, but the brain stem can be malformed in several ways. This
malformation is part of a much greater malformation of the nervous system.
This type of Chiari malformation is correctly referred to as “Arnold-Chiari”
malformation.
SYMPTOMS: Usually symptoms of Chiari malformations
do not appear until early adutlhood but can occasionally be seen in young
children. Some common symptoms include headaches, neck pain, dizziness,
vision problems, balance problems and muscle weakness. Other symptoms
include difficulty swallowing, frequent gagging and choking and, in some
cases sleep apnea may be present.
TREATMENT: Surgery to enlarge the opening of
the posterior fossa of the skull is often recommended for patients. 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.
*Chiari I is the type of malformation being discovered in people diagnosed
with fibromyalgia and CFIDS.
This is an illustration (midline view) showing the anatomical structures
involved in the production and flow of cerebrospinal fluid through the
ventricular system, brain and spinal cord, and finally absorption into
the bloodstream. You'll also see the difference between a "normal"
cerebellum and the cerebellum of an ACM patient with the cerebellar tonsils
protruding through the foramen magnum.
World Arnold Chiari
Malformation Association (WACMA)
National Fibromyalgia Research Association
PO Box 500, Salem, OR 97308
