Psychological Screening of Patients for Spinal Cord Stimulator Treatment
By Tory McJunkin, MD, Paul Lynch, MD, Jack Anderson, MD, Joshua Kanner, BAS, & Edward Swing, PhD
Dear Arizona Pain Specialists,
I am looking for ways to enhance my practice and would like to be able to provide spinal cord stimulation to some of my patients. My understanding is that this requires psychological screening. What kind of screening is required? How is this important to patient outcomes?
Dear Seeking Stimulation,
In treating chronic pain with neuromodulation devices, such as spinal cord stimulators (SCS), it is imperative to select the appropriate patients to achieve the best outcomes. Many factors have been considered as possible influences on patient outcomes. Psychosocial influences are recognized as potentially important determinants of response to SCS treatment.1 This, in part, has led to the widespread use of pre-surgical psychological evaluations. Moreover, many insurance companies mandate psychological screening prior to surgery. Understanding the impact of psychiatric illnesses is particularly important, given that an estimated 20-45% of chronic pain patients concurrently suffer from psychiatric illness.2 The growing role of neuromodulation treatment for pain has led researchers to attempt to better understand how psychiatric illnesses relate to SCS efficacy.
Evaluating the evidence:
A number of studies have examined the role of psychological illness in the efficacy of spinal cord stimulation treatment. Two recent systematic reviews found that treatment success was related to co-morbid psychological illness.1,3 Successful outcomes were deﬁned as decreased pain, increased function, returning to work, and reduced medical treatment (e.g., reduced pain medication dosage). Different screening tools were used across studies, but most studies used the Minnesota Multiphasic Personality Inventory (MMPI or MMPI-2). In some cases, clinical interviews assessing patient’s psychological state were used to make recommendations of risk instead of questionnaire assessments.4,5 Studies varied in the time of evaluation, with some evaluating the SCS trial period only and others following patient outcomes for six months to seven years after implantation. Despite differing methodologies, systematic reviews find that depression consistently has a negative effect on SCS treatment outcomes. This finding is consistent with the broader pain medicine literature. Depressed patients suffering from low back pain have been found to have poorer responses to treatment in general and greater persistence of pain over time.6
Additionally, some studies found SCS treatment to be less effective for patients higher in anxiety, catastrophizing, paranoia, and psychopathic deviation.7-9 Though fewer studies have identified these traits as affecting SCS outcomes, the available evidence may justify forgoing SCS implantation for patients high in anxiety, catastrophizing, paranoia, or psychopathic deviation. Conversely, SCS treatment was found to be more effective in patients high in joy and mania.7,8,10 Joy and mania may be associated with greater optimism and fewer symptoms of depression, possibly explaining the positive association with SCS treatment success. The research findings for other traits have been inconsistent. Hysteria and hypochondriasis were associated with better SCS outcomes in some studies7,10 and worse outcomes in others. 5,9,10
Spinal Cord Stimulator treatment may improve psychological functioning:
Though many studies have found depression to relate to worse SCS treatment outcomes, some studies in which depressed individuals were treated with SCS found reductions in these patients’ level of depression.10,12 There are several possible explanations for this finding. Though depressed patients were less likely to achieve a significant reduction in pain, those patients whose pain did decrease may have become less depressed as a result of improved pain symptoms. This may have been particularly true for depressed individuals whose depression was a secondary consequence of their chronic pain. Chronic pain can be debilitating, robbing people of their quality of life, thus contributing to depression. It is plausible that this subset of the depressed population would actually experience both relief in their underlying chronic pain and improvements in their depressive symptoms.
Alternatively, it may be that depression was reduced because SCS treatment offers inherent psychosocial treatment. These patients are regularly monitored and invited to attend clinics for follow-up and regular care. This may provide ongoing social support and legitimization of pain symptoms that is beneficial for their psychological functioning.
A third possibility is that the improvement in depression following SCS treatment might be explained through the physiological mechanisms of neuromodulation. Neuromodulation devices, such as spinal cord stimulators act on the same noradrenergic and seratonergic pathways targeted by SSRI antidepressant medications.3 The efficacy of deep brain stimulation for treating depression is another example of a therapeutic use of neuromodulation in depression. Spinal cord stimulators may reduce depression by producing effects on the neural pathways that are similar to deep brain stimulation and antidepressant medications.
More evidence will be needed to determine which of these explanations account for the finding that SCS treatment improves depression. To the extent that SCS treatment tends to improve depression, this might suggest that depression need not be an exclusion criterion but alternatively a psychological characteristic that could be considered as a target of SCS treatment alongside pain relief. This may also suggest treating depression prior to an SCS trial or implantation.
It is common practice to perform psychological screening, either based on a questionnaire, such as the MMPI-2, or through a clinical interview, before proceeding with spinal cord stimulator implantation. Such screening is frequently required for insurance approval of this procedure. The research evidence to date provides some support for the use of these methods of screening. Generally, patients with psychiatric diagnoses are less likely to have favorable outcomes as a result of treatment.1,3 The amount of evidence indicating less favorable SCS treatment outcomes varies for different psychiatric disorders and traits. The evidence is clearest that depression is associated with poorer outcomes. Additionally, higher levels of anxiety, catastrophizing, paranoia, and psychopathic deviation have each been found to relate to worse SCS outcomes in some studies. For other psychiatric conditions and traits, there is mixed or limited evidence of relevance to SCS trial success.
It should be noted that even among groups found to have a lower success rate for SCS, such as depressed patients, many do get significant relief. The use of psychological screening is complicated by the finding that some depressed patients seem to get relief from their depression symptoms after SCS treatment. Though multiple issues (e.g., reimbursement, alternative treatments, risks of implantation, and the likelihood of success) need to be considered in the decision to pursue SCS treatment, psychiatric conditions need not necessarily rule out the use of SCS treatment. The use of other treatments for psychological symptoms before pursuing SCS may also alleviate some concerns. Additionally, if the patient responds very well during the SCS trial period, this could indicate the potential to benefit despite their current psychological state, given that psychosocial variables appear to have broadly similar effects on both SCS trials and permanent implants. We hope that future research can continue to differentiate between psychological conditions that do or do not reduce SCS treatment effectiveness so that patients are not excluded from this treatment unnecessarily.
Dr. Lynch and Dr. McJunkin own and operate Arizona Pain Specialists, a comprehensive pain management practice that provides minimally invasive, clinically proven treatments, with three locations in the greater Phoenix area. Dr. Lynch and Dr. McJunkin also provide consulting services to other pain doctors around the country through their partner company, Boost Medical. For more information, visit ArizonaPain.com and BoostMedical.com.
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