Good
evening. I was invited to spend about 15 minutes discussing a
topic that might be of interest to ASAP members, so I chose to speak
about what a typical patient with Chiari I and syringomyelia can expect
after surgery. I am going to talk about this is the context
of 29
consecutive patients that we treated at the National Institutes of
Health. We published our work this January in the Journal of
Neurosurgery—I hope that some or most of you received a pdf-version of
the paper from Patricia by email.
Let me give you some
background. We performed the study to find out how long it
would
take for a syrinx to become smaller after surgery. We
enrolled
patients into the study who had syringes* that were large enough to
distend the spinal cord, with the average diameter of a syrinx being
about 7 mm, which is about 2/3rds of the diameter of a normal spinal
cord.
We chose a reduction of 50% in syrinx diameter as our
primary outcome measure because this amount of reduction in syrinx
diameter would indicate that the syrinx was no longer distending the
spinal cord. We were also interested in what happens over
time
after surgery to major symptoms of syringomyelia such as weakness,
numbness, and dysesthetic (neuropathic) pain.
All patients
gave their informed consent to participate in the research
study.
The research study was approved beforehand by our Institutional Review
Board, which is a committee that evaluates protocols to see if the
research is scientifically sound and that it does not expose patients
to unnecessary risk.
For the research study patients
with Chiari I and syringomyelia came to the Clinical Center of the
National Institutes of Health in Bethesda, Maryland for their
evaluation and treatment. Patients were 16 to 61 years of
age.
Patients underwent MRI scans of the neck before surgery; the diameter
of their syringes was measured using a computer workstation.
We
also recorded a medical history and a neurological
examination.
We
specifically noted the presence and severity of signs and symptoms such
as weakness, atrophy (wasting of muscles), spasticity (tightness of
muscles), ataxia (unsteadiness while walking), pain and unpleasant
sensations in the torso or extremities (dysesthetic pain), and loss of
sensation.
Of
course the MRI scan and a history and neurologic examination are
standard studies for all patients who are being considered for surgical
treatment of the Chiari I malformation and syringomyelia. The
reason that they could be used for research in our study was because of
the way in which these tests were applied:
1. It
was decided before the study began that all patients would have the
same type of MRI study and that all patients would have their
neurological examination recorded in the same manner;
2. The research was designed so that information from the MRI scans and
examinations was entered as each person was examined (prospectively)
rather than from a retrospective analysis of charts on patients who had
completed treatment; and
3. Tests such as the MRI scan,
history, and neurological examination were performed in the same way
after surgery as they were before surgery and were repeated at
specified intervals (1 week, 3-6 months, 1 year, and yearly) after
surgery.
I performed the same surgical procedure,
craniocervical decompression and duroplasty, on all patients in the
study. The average period of follow-up after surgery was 3
years. The number of MRI scans and examinations that were
performed on each patient as part of our study exceeded the number that
would be performed on the basis of clinical care.
We found
that by 6 months after surgery that all but one patient reported
improvement, and that the patient who did not improve reported that he
was stable. In all but 4 patients the syringes became less
than
one-half of their original diameters by 3-6 months after
surgery.
By 2 years after surgery all syringes had become less than one-half of
their original diameters. The length of the syringes also
became
progressively shorter after surgery compared to before surgery.
We
observed that in 12 patients (41%), the syringes did not disappear
completely. There was no difference in outcome in patients
without complete disappearance of their syringes compared to patients
with complete disappearance of their syringes. It was
remarkable
that a minority of patients became free of symptoms after surgery, only
22% at 3 months, 29% at 1 year, and 32% at 2 years after
surgery.
Residual signs and symptoms arose from residual dysfunction of the
spinal cord. The most frequent signs and symptoms that
persisted
after surgical treatment were painful dysesthesias (neuropathic pain)
and loss of sensation, which were found in about one-half of patients.
Our conclusions from the study were that
1. Almost all patients notice some improvement
after surgery,
2. Many patients experience residual symptoms, especially dysesthetic
(neuropathic or chronic) pain and loss of sensation,
3. All syringes will become smaller over time after successful surgery,
although many will not disappear completely, and
4.
Patients that have reduced-size but not complete disappearance of their
syringes had similar clinical outcome compared to patients with
complete disappearance of their syringes.
We do not believe that
a small, collapsed syrinx will cause further injury to the spinal
cord. We do not recommend additional surgery in patients
whose
syringes become smaller but do not resolve completely after surgery,
because symptoms and signs reflect injury to the spinal cord that the
syringes produced before surgery and not ongoing injury to the spinal
cord.
*syringes- plural of syrinx
