Single-Photon Emission Computerized Tomography (SPECT) as a Tool For Spinal Pain Management
By Patrick Roth, MD MHA FAANS FACS, Founder, New Jersey Brain and Spine, Chairman, Department of Neurosurgery, Hackensack University Medical Center
Pain management as a healthcare subspecialty faces numerous barriers that serve to undermine its efficacy. As a neurosurgeon, interested in pain that arises from the spine (the majority of which comprises a pain management practice), I have found the emerging technology of SPECT scan to be extremely helpful.
Background: Pain management is a complex undertaking that is falsely perceived by sufferers as a simple task- find and treat the pain generator. The treatment of pain is rarely this simple, however. Spinal pain, in particular, must be understood as “part of life”, like a headache or a cold. At any given time, 20% of the world’s population experiences significant back pain. Yet, in westernized cultures, there is a relatively higher incidence of suffering from back pain and disability from back pain. This distinction has less to do with the real cause or pain generator of back pain than it does with the influence of culture on the sensation of back pain. Patients routinely imagine that their pain represents an injury. As such, the injury must heal or be repaired in order for the pain to subside. In addition, patients believe that activity will exacerbate the injury. In fact, activity is usually more helpful than harmful and most back pain improves with time.
When patients present with pain, particularly chronic unilateral pain, the SPECT scan can be invaluable in specifying the anatomical origin of the pain.
In addition, the careless use of narcotic pain medication has created a simultaneous epidemic of deleterious side effects and stigma around the use of narcotics. Part of the blame lies with the belief that pain, itself, is bad and ought to be dialed down with medications or alleviated with procedures. We ought to look at pain more holistically and use a combination of mind and body therapies to address the experience of pain rather than focus on dialing down the pain itself.
Interventionalists who treat pain often limit their treatment to the idea of deciphering and then targeting the pain generator. This can be achieved by a host of approaches with a spectrum of invasiveness. Complicating the matter, our fee-for-service healthcare system incentivizes these approaches and, remarkably, reimburses these procedures whether or not they are effective. Pain management, practiced I the community, routinely indicates procedures based on an “educated guess” as to what is causing the pain. The guess is frequently based on the physical examination, the clinical nature of the pain, and the results of the MRI or CT scan. SPECT scan adds a different dimension to the assessment. Whereas the MRI and CT scans are anatomical studies that offer the origin of the pain through inference, the SPECT scan provides a physiologically-based, distinct radiographic image that complements the aforementioned components of the educated guess.
SPECT scanning for back pain involves an intravenous injection of a radiotracer (technetium-99m biphosphonate) followed by obtaining images captured by a gamma camera from the release of gamma ray emission after the radioisotope has bound with the target organ (bone). Initially, the images were only planar (two-dimensional), but technological advances have allowed for three-dimensional images by either rotating the camera around the patient or by applying a technology to layer the planar SPECT image onto a previously obtained 3-D MRI or CT scan. The result of the process is a SPECT derived signal showing up in those bones that are metabolically active. The 3-D component allows for precise identification of the location of the uptake of the radiotracer. In the case of spinal pain, the radiotracer uptake serves as a surrogate for inflammation. It measures metabolic activity related to osteoclastic remodeling, which occurs in reaction to inflammation. The SPECT scan can be more sensitive than the MRI or CT, as, osteoclastic activity often precedes anatomical changes and is more specific because aging brings with it natural, asymptomatic anatomical changes.
When patients present with pain, particularly chronic unilateral pain, the SPECT scan can be invaluable in specifying the anatomical origin of the pain. The MRI and CT scans will often show many degenerative changes, but we know from MRI and CT studies that these changes are commonly seen with aging and are often asymptomatic. Thus, inferring that changes on MRI or CT as a source of pain has a high false positive result. When SPECT scan implicates an anatomical change seen on MRI or CT scan, the false positive rate goes down and the predictive efficacy of targeted treatment goes up.
The diagnostic strategy that I use for pain of presumed spinal origin often includes a SPECT scan in addition to an MRI or CT scan. This has greatly increased the success rate of the subsequent targeted treatments (both injections and surgical procedures). It has also eliminated unnecessary treatments for those patients who have negative SPECT scans.
I emphasize that this great technology must be applied as part of a holistic approach to pain, one that not only targets the pain generator, but one that targets the experience of pain. I find it helpful to always consider a three-tier origin of the pain. There is a stimulus for which the aforementioned imaging can be helpful in identifying. This is what patients expect as an explanation for their pain. In addition, there are always bodily adaptations to the stimulus. For example, muscle spasms, postural changes, and changes in our body that come from avoiding activity that triggers the pain generator. These adaptations can, themselves, be pain generators. Physical therapy has its greatest impact on this 2nd tier aspect of pain. Finally, the experience of pain is judged and contextualized by our brains. This is ultimately related to our culture, upbringing, and previous experiences. This is where cognitive behavioral therapy has its greatest impact. Unfortunately, we are woefully inadequate in addressing this 3rd tier of pain. In my opinion, all three tiers are addressed in all cases of pain for optimal treatment. Management of the stimulus (1st tier) is greatly enhanced with the technology of the SPECT scan.