This is an area of particular interest for Neurosurgical Consultants
with our experience encompassing over 200 successfully treated patients
with this condition.
We now have experience with over 200 of these procedures with follow up
ranging to 30 years. The operation that has been effective in our
patients over these many years involves a Suboccipital Craniectomy
(surgical opening of the bony compartment of the back of the head) to
decompress the cerebellar tonsils with laminectomy of C1 and/or C2
(removal of the roof of the first two cervical vertebrae) to
decompress the cervical spinal cord.
This is a congenital anomaly of the cerebellum and brainstem. Although
four types have been described, types I and II are more common. Type
I is identified by excessive protrusion of cerebellar tonsils (the
cerebellum is the balance and coordination center of the brain)
through the foramen magnum (the passage way between the skull and
the spinal canal through which the spinal cord travels to join the
brainstem), down to the C1 or C2 level of the cervical spine. With
the herniation of the Cerebellum, the brain stem and upper spinal
cord can be compressed resulting in some potential serious damage.
This condition may or may not be associated with syringomyelia
(dilated areas within the center of the spinal cord) and as a
consequence may also be associated with spinal cord mediated
NOTE: Type II (the most common type of Arnold-Chiari malformation)
is usually identified at birth since it is always associated with
myelomeningocele (exteriorization of spinal contents near the base
of the spine).
Arnold-Chiari type I malformation patients are usually identified
as a consequence of symptoms beginning in the late teenage years or
early in adulthood. Our patients have ranged from age 12 to 50 years.
The most common symptoms are headache or neck pain (made worse by
coughing, sneezing, or extension of the head and neck.) Other symptoms
may include problems with balance, or visual motor problems which
the patient notices as "distorted vision". For those patients who
may also harbor the associated structural problem of syringomyelia,
altered sensation or weakness of the arms and/or legs may add to
their difficulties that bring them to our attention.
The diagnosis of Arnold-Chiari malformation (and syringomyelia) is best
made by MRI scan of the brain and/or cervical spine.
The only effective treatment for Arnold-Chiari malformation is
surgery. The operation that has been effective in our patients
over these many years involves a Suboccipital Craniectomy
(surgical opening of the bony compartment of the back of the head)
to decompress the cerebellar tonsils with laminectomy of C1 and/or
C2 (removal of the roof of the first two cervical vertebrae) to
decompress the cervical spinal cord. The dura mater (a tough
leather-like covering of the brain and spinal cord) is also
opened. It is important to microsurgically cut bands of adherent
tissue inside the dura mater that attach to the spinal cord and
brain stem. In addition, we invariably open the space between
and separate the herniated cerebellar tonsil so as to re-establish
more "normal" cerebrospinal fluid pathways. This is particularly
important for patients with the additional problem of
syringomyelia. (We strongly disagree with the concept of
"amputating" or removing the cerebellar tonsils, a procedure
practiced by some neurosurgeons.)
In order to maintain adequate decompression of the brain, brain
stem and spinal cord in this region, it is imperative to sew
in a decompressive graft as part of the closure of the dura
mater. There are a number of materials that can be effectively
used for this without adding any additional incisions or
prolonging surgery by taking tissue grafts from the patient.
These patients are monitored post-operatively in the Intensive
care unit and are discharged from hospital within a couple of days.
Recovery to full function usually requires a couple of months since
tissues must heal. Generally it takes three months for scar tissue
to be firm and six months to be solid. While activities such as
walking usually begins within one-two days of operation, some
strenuous sports activities should be avoided until healing has
The results of this operation have been most encouraging with the
vast majority of patients having resolved their pre-operative
symptoms including the incapacitating pre-operative headaches and
neck pain. Most of our patients with disabling pre-operative eye
movement disorders have either resolved their movement disorder
or recovered to the point of not being aware of the problem.
Patients with syringomyelia are in a different category. Most of
our patients have stabilized their pre-operative deficits with
many enjoying some improvement. Part of the ultimate outcome for
these patients is determined by the extent of their pre-operative
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This page last edited on 2/20