Because chronic pain and sleep are thought to be related, treating one may benefit the other. One such treatment is spinal cord stimulation, which has been shown to improve aspects of sleep and has been shown to be effective in treating numerous chronic pain conditions. This treatment involves an implantable spinal cord stimulator that sends low levels of electricity directly to the spinal cord to relieve pain. However, its impact on patients’ lives has not yet been determined.
For the study, participants completed a battery of certified outcome measures of sleep, pain, functional status, and overall quality of life at various time points throughout the study. These questionnaires were given preoperatively and six months or one year postoperatively. Participants were asked whether they were satisfied with the spinal cord stimulation procedure and whether they would undergo the procedure again.
Researchers examined the relationship between pain outcome measures using the Insomnia Severity Index, a clinical screening tool that assesses the severity of both nighttime and daytime components of insomnia. With this tool, they identified a minimal clinically significant difference—the smallest noticeable change that a patient perceives as clinically significant and that could indicate a change in their management. A minimal clinically important difference is particularly useful in evaluating new treatments because there is a smaller group to compare them to for statistical significance.
The study was published in the journal Stereotactic and Functional Neurosurgery, Minimal clinically significant difference ranges successfully established for the insomnia severity index outcome measure to help measure insomnia improvement after spinal cord stimulation.
The results showed that the insomnia severity index improved by 30 percent or more in 39.1 percent of the participants, and the Epworth sleepiness scale improved by 30 percent or more in 28.1 percent of the participants. Minimally clinically significant difference values between 2.4 and 2.6 were associated with improvement in disability and depression in participants.
“The physiological mechanisms of both pain and sleep are complex, and the relationship between the two is poorly understood,” said Julie Pilitsis, MD, Ph.D., senior author and dean and vice president for medical affairs, FAU Schmidt College of Medicine.
Spinal cord stimulation success was measured by the change between scores before surgery and scores six to 12 months after surgery. The Insomnia Severity Index asks seven questions to assess an individual’s level of insomnia, with higher scores indicating increased nighttime sleep disturbance. The Epworth Sleepiness Scale quantifies daytime sleepiness based on the patient’s likelihood of falling asleep during eight daily activities, with higher scores indicating increased daytime sleepiness. To determine which patients had improved sleep, the researchers looked for a 30 percent or greater improvement in the insomnia severity index, or Epworth sleepiness scale.
“Our study included sleep conditions in our analysis because the interaction between sleep and chronic pain is important to consider in patients undergoing spinal cord stimulation,” said Pilitsis, who is a member of FAU’s Stiles-Nicholson Brain Institute. “As more research is done on minimal clinically significant difference thresholds, the assessment of clinical response to spinal cord stimulation will improve. Thus, we can better understand the type of patient who may benefit most from this treatment.”
Co-authors of the study are Phillip M. Johansen, a fourth-year medical student at FAU; Frank A. Trujillo, third-year FAU medical student; Vivian Hagerty, MD, FAU general surgery resident; FAU Schmidt College of Medicine; and neurosurgeons Tessa Harland, MD; and Gregory Davis, MD, both with Albany Medical Center.