CHICAGO—Chiari I malformation with syringomyelia can be optimally managed with surgery — posterior fossa decompression — followed by arachnoid opening with or without duraplasty, according to findings from a retrospective study reported here at the annual meeting of the American Association of Neurological Surgeons by investigators from the University of Virginia.
Chiari I malformations, which are congenital, occur where the brain and the spinal cord join. Portions of the cerebellum or brainstem lie lower than usual and frequently the cerebellar tonsils protrude into the spinal cord causing pressure in the brain, causing headaches, double vision, difficulty walking, dizziness, and weakness in the arms.
Posterior fossa decompression removes sub-optimal bone from the back of the posterior fossa; the dura may be opened and a graft inserted.
In the current study, investigators performed posterior fossa decompression, opened the arachnoid with further dissection into the foramen of majendie, and either closed the dura or performed a dural graft.
Study participants included 74 adults surgically treated for Chiari I malformation with syringomyelia between 1995 and 2007; arachnoid opening was performed in 54 and a dural graft was done in 28 patients.
A significantly higher rate of syrinx improvement was seen in the patients with arachnoid opening (53) compared to 15 patients in whom the arachnoid was left largely intact (p=0.001).
There was no significant difference in syrinx improvement between those who received a dural graft and those who did not. However, among the 24 patients who achieved a complete syrinx resolution, the dural graft was associated with a significantly higher rate of complete syrinx resolution compared to patients who did not have a dural graph (15 vs. 10, p=0.012).
Reporting on the study, Rupa Gopalan, a third-year medical student at the University of Virginia in Charlottesville, said that neither treatment contributed significantly to the rate of major complications. She noted that this is important given that one of the major objections to arachnoid opening is the risk of complications.
Based on the results, the investigators, led by senior author John A. Jane, MD, PhD, professor of neurological surgery and director of the Neurosurgical Training Program at the University of Virginia, “advocate arachnoid opening with or without dural graft” for optimal treatment of Chiari I malformation with syringomyelia in adult patients.
Commenting on the study, Ulrich Batzdorf, MD, a neurosurgeon at the David Geffen School of Medicine at the University of California-Los Angeles, pointed out that the age of the patients was not clearly defined — study participants ranged in age from 13 to 74 years — so it was not clear whether better results might have been achieved in a particular age group.
Gopalan responded, however, that the study did not examine age as an independent variable in syrinx outcome. “Our goal was to develop a recommendation, which applies broadly to Chiari I with syringomyelia cases, regardless of variations in presentation,” she said.
As to whether opening the arachnoid is the optimal approach, Dr. Batzdorf thinks caution is necessary. “Many surgeons are very successful in treating patients with the arachnoid intact and I have done so myself when I felt there was an unusual risk to opening the arachnoid,” he said.
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• Gopalan R, et al. Outcome analysis in surgery for adult Chiari I malformation with syringomyelia, with or without arachnoid opening and dural graft. Annual meeting of the American Association of Neurological Surgeons. April 29, 2008. Abstract 704.