Novel microendoscopic treatment for spinal dural arteriovenous fistulas

Barry D. Birch, M.D., and his neurosurgical colleagues at Mayo Clinic in Arizona now perform a new, minimally invasive surgical approach for certain types of spinal dural arteriovenous fistulas (SDAVFs).

Although rare, SDAVFs make up the majority of vascular malformations in the spine. An SDAVF is an abnormal connection (fistula) between one or more radicular arteries and a draining medullary vein at the junction of the proximal nerve root sleeve and the dura of the spine. SDAVFs can lead to pain and myelopathy.

As the medical center with the largest SDAVF practice in the United States, Mayo Clinic has a long tradition and a depth of experience with the disorder. John L. D. Atkinson, M.D., a neurosurgeon at Mayo Clinic in Rochester, Minnesota, notes that patients often arrive in a deteriorating condition because their symptoms have been misinterpreted. SDAVFs often go underrecognized because the symptoms can be subtle and nonlocalizing and can be mistakenly attributed to coexisting abnormalities, such as lumbar stenosis, disk herniation, or vertebral anterolisthesis, that appear in imaging studies.

Treatment in which the fistula is disconnected can abruptly stop the deteriorating process and, if not too severely damaged, the spinal cord will regain function. Drs. Atkinson and Birch hope increased awareness in the medical community about the symptoms of SDAVFs will generate earlier referrals to centers with expertise in managing this disorder, leading to a better chance of recovery.

Surgical obliteration of SDAVFs

Last year, Mayo Clinic published the largest retrospective study ever conducted on the outcomes of patients with surgically treated SDAVFs (Saladino et al. Neurosurgery. 2010;67[5]:1350-8). On the basis of the series of 154 consecutive patients, the authors concluded that surgical obliteration of SDAVFs is safe and effective, with a good prognosis for motor function recovery.

The mainstay of treatment, and the one used in the retrospective study, is an open surgical procedure. The approach requires a bilateral laminectomy 1 level above and 1 level below the fistula. Recovery times range from 2 days to more than a week—similar to those for a laminectomy for degenerative spine disease.

Recently, endovascular percutaneous embolization has been proposed as an alternate treatment for some SDAVFs. Embolization has the advantage of being less invasive with a shorter recovery time than open surgery, but recurrence rates are higher.

In addition, embolization is not optimal for every patient. In some cases, angiography may reveal tortuous intradural vessels that are too difficult to navigate with a catheter. In other cases, the fistula may be so large that the embolization material could flow into the spinal column.

Dural arteriovenous fistula

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To manage such cases, Dr. Birch and colleagues have been performing an innovative surgical technique that allows them to address SDAVFs with a microendoscopic approach. They have used this approach to thoracolumbar fistulas involving single-vessel communication in a series of patients:

• All of the patients had gait instability.
• Some patients also had bowel and bladder dysfunction and back pain.
• Ligation was successful, and no significant complications occurred during or after surgery.
• Hospital stays ranged from overnight to 3 days.
• Neurologic deficits were improved or stabilized in all patients.
• Follow-up imaging showed obliteration of the SDAVFs at the 1-year follow-up visit.

As is true of other minimally invasive techniques, the small size of the incision in this new technique reduces the risk of infection following the procedure and minimizes the blood loss during it.

Specialized experience is required to manage the fistula through such a small opening, but Dr. Birch notes that "it means less pain for the patient and potentially less chance of spinal fluid leakage through the incision."

His neurosurgical colleague Naresh P. Patel, M.D., adds that that the microendoscopic approach appears to be a viable alternative for certain SDAVFs that cannot be treated endovascularly, providing the surgeon with an additional management strategy and enhancing individualized patient care.