Transcriptions from an ASAP teleconference presented by Dr. John Heiss, National Institutes of Health, Bethesda, Maryland.
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 Neurosurgeryâ€”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:
- 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;
- 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;
- 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.
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
- Almost all patients notice some improvement after surgery
- Many patients experience residual symptoms, especially dysesthetic (neuropathic or chronic) pain and loss of sensation
- All syringes will become smaller over time after successful surgery, although many will not disappear completely
- 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.