乌鸦传媒

An abrupt loss of pain relief in a woman whose syringomyelia-caused pain had been mitigated by a spinal cord stimulation device appears to have been caused by recurrent falls, which in turn subtly damaged an electrode-lead contact, researchers suggested at the virtual meeting of the .

When the 38-year-old woman reported that the device no longer seemed to be working, the team of Baylor College of Medicine, Houston, investigators started hunting for the cause, reported lead poster author Maxwell Lee, BA, a Baylor medical student. He was part of a team that included Jay Karri, MD, academic chief resident at Baylor, and Brian Bruel, MD, an interventional pain specialist affiliated with Memorial Hermann Health System, The Woodlands, Texas.

"The overall prevalence of complications associated with spinal cord stimulation devices is estimated to range between 30% to 40%," Lee and colleagues reported. "Mechanical compromise represents the majority of spinal cord stimulation associated complications and is most often secondary to electrode lead migration, fracture, improper connection, or malfunction."

But when the researchers imaged the connections in this women, they were unable to observe anything that appeared out of place. "Electrode lead malfunction not secondary to overt structural malfunction, while a theoretical risk, has been reported very rarely in the literature," Lee noted.

In this case, the woman had been diagnosed with primary syringomyelia which had chronic axial low back pain as one symptom. It had been managed successfully with a tonic waveform spinal cord stimulator for 2 years before she presented with acute pain recurrence. In addition to the low back pain, the patient also reported numerous falls, presumably a secondary complication of spinal weakness caused by syringomyelia. She reported that her back pain had returned to the pre-implantation level.

The researchers then ran tests on the device. "Lumbar X-ray imaging revealed no evidence of structural deficits within the device or electrodes and no electrode migration," the researchers reported. But they did find high impedance on three contacts in one electrode.

In a subsequent revision procedure for the device, the doctors could find no overt fracture at the electrode contacts or across the length of the lead. Still, they replaced the lead anyway. Further interrogation of the device found no impedance across all leads.

At week one, the woman reported that pain relief had returned, and at week 4 she was still experiencing benefit, Lee reported.

"In our patient with recurrent falls," he suggested, "we postulate that repetitive trauma produced intrinsic damage to the spinal cord stimulator lead and resulted in lead malfunction. Given the acuity of reported lead malfunction, we believe direct damage to the electrode contact interface may be the likely underlying etiology."

The researchers suggested several possible causes of electrode lead malfunction, including scar tissue formation which can cause impedance; deficits in polyurethane insulation of the leads or decrease compliance along the platinum-iridium alloy electrode contacts may both contribute to inconspicuous structural lead malfunction.

The researchers suggested, that while the case represents a rare phenomenon, "judicious patient selection and proper implementation of fall prevention measures are instrumental for device preservation in patients with frequent falls."

In commenting on the study, Varun Channagiri, MD, a resident in anesthesiology at Rutgers New Jersey Medical School in Newark, told 乌鸦传媒, "Having damage caused by recurrent falls is not something we see often, but I can see how that could occur."

He noted that replacing leads or batteries can be accomplished with minimal surgery on an outpatient basis. "It usually can be done in about an hour," Channagiri said.