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11 Articles in Volume 13, Issue #2
Spinal Cord Stimulation: Fundamentals
Assessment of Psychological Screeners for Spinal Cord Stimulation Success
Educating Patients About Pain Medications
Central Sensitization: Common Etiology In Somatoform Disorders
Demystifying Pain Pathways
Vibroacoustic Harp Therapy in Pain Management
Erythrocyte Sedimentation Rate and C-Reactive Protein: Old But Useful Biomarkers for Pain Treatment
Editor's Memo: Inflammatory Disease—Time to Refine Our Diagnoses
Ask the Expert: Pain Persists in Spite of High-dose Opioids
Ask the Expert: Rectally Administered Morphine
Letters to the Editor: Mistaken Hormone, Lab Values

Assessment of Psychological Screeners for Spinal Cord Stimulation Success

Candidates for spinal cord stimulator implantation are typically referred for psychological assessment as part of the screening process to evaluate the likelihood of successful outcomes. The authors review the various assessment tools and discuss which may be most beneficial for chronic pain patients.

Spinal cord stimulation (SCS) is a pain management strategy designed for patients with chronic pain (eg, neuropathic pain) that is refractory to medication and alternative or adjunct therapies, or who have experienced failed back surgery.1-3 The current literature suggests that psychological factors such as somatization, depression, anxiety, and poor coping are important predictors of poor outcome following SCS.4 Therefore, patients undergoing consideration for spinal cord stimulator implantation are typically referred for a psychological assessment as part of the process to determine their suitability and evaluate the likelihood of successful outcomes.5

For some clinicians, a brief interview may sufficiently screen for psychological factors, but in other cases, more extensive psychological testing is warranted.6 However, little information is available documenting either the role of such evaluations in categorizing potential candidates, or the utility of these assessments in predicting the likelihood of positive outcomes. Given the importance of psychological factors to treatment outcomes for a spinal cord stimulator implantation, we studied a population of patients referred for SCS-related psychological assessment to ascertain any patterns evident in their test scores. This paper reviews the results of our study.

Study Design

Eighty-six patients were identified as candidates for spinal cord stimulator implantation and underwent psychological assessments. All assessments were conducted by senior psychologists at Scott & White Healthcare/Texas A&M Health Science Center, which is located in the Central Texas region of the United States. Demographic measures (age, race/ethnicity, gender, marital status) and clinical data (prior and subsequent diagnoses, outpatient visits, and inpatient admissions) were collected from the electronic medical records and health plan data.

Psychological assessments included the following measures: Millon Behavioral Medicine Diagnostic (MBMD); Millon Clinical Multiaxial Inventory-3rd Edition (MCMI-III); Minnesota Multiphasic Personality Inventory-2nd Edition, Restructured Form (MMPI-2-RF); Shipley Institute of Living Scale (SILS); Beck Depression Inventory-II (BDI-II); and Beck Anxiety Inventory (BAI). The MBMD assesses negative health habits, psychiatric indications, coping styles, stress moderators, and treatment prognostics on scales of 0% to 100%.7 The MCMI-III assesses both acute syndromes and personality disorders, yielding scores of 0% to 100%; it was uniquely developed and normed on clinical populations.8,9 The MMPI-2-RF is a new version of the widely used MMPI-2, assessing a number of clinically relevant variables of one's emotional and personality functioning.10 The SILS assesses intellectual functioning and cognitive impairment with a self-administered 60-item instrument comprising 40 vocabulary test items and 20 items to assess abstract thinking.11 The BDI-II and BAI are self-administered checklists that assess symptoms of depression and anxiety.12,13

The analysis approach for this initial study was primarily descriptive, presenting an overall profile of this cohort of SCS candidates. Mean demographic characteristics, disclosure patterns, and summary scores for each instrument in the assessment battery were calculated, including means for each of the MBMD, MCMI-III, and MMPI-2-RF clinical subscales. Not all psychological instruments were administered to all candidates, based on the discretion of the clinician as well as the availability of tests at the time of assessment. The MBMD was administered to 79 out of the 86 participants within this sample; 62 participants completed the MCMI-III, and only 21 completed the MMPI-2-RF. The BDI-II was administered to 68 patients and the BAI was administered to 51 patients.

Study Results

Table 1 presents major findings from this study. The mean age of the sample was 52.7 years (range: 24 to 89 years), with the majority of participants being women (65.1%), white (74.4%), and married (66.6%). Participants' intellectual functioning was estimated by SILS to be in the average range (mean 99.5, SD 10.9). The mean BDI-II score denoted moderate levels of depressive symptoms (mean 20.0, SD 15.3), while average BAI scores also indicated moderate levels of anxiety (mean 16.6, SD 10.5).

Among MBMD response pattern scores, there was a notable percentage of response distortion for each of the validity scales, with about one-fifth (20.2%) of assessments showing at least a possible problem with negatively focused responding (Debasement), while more than one-quarter (27.9%) exhibited at least some possible problem with hesitation to disclose information in full (Disclosure). Nearly half (48.1%) of MBMD respondents showed possible or likely problems in their attempts to respond in a desirable manner (Desirability). In contrast, no elevations were noted for scales measuring response patterns on the MMPI-2-RF or MCMI-III. Since these two scales are primarily designed to detect psychopathology, the lack of noted elevations might not be an unusual finding.

The MBMD assesses the following health habits: alcohol, drugs, eating, caffeine, inactivity, and smoking. If a patient exhibited "likely" or "possible" problems for each habit, they were classified as having a negative behavior in that area. In this study, the most frequent problem areas observed among patients were overeating and inactivity. More than half (58.3%) of the participants had at least a possible issue with overeating, while close to two-thirds (68.4%) of participants indicated an issue with inactivity. About one-third (39.2%) of participants reported to have problems with smoking. Among MBMD clinical scales (denoted as prevalence rates or PR), several clinically significant elevations (ie, PR>75) were noted. These include the MBMD Stress Moderator scales for Illness Apprehension (mean 77.1, SD 13.4), Functional Deficits (mean 86.3, SD 14.1), and Pain Sensitivity (mean 97.0, SD 14.5). The MBMD Management Guides scale for Adjustment Difficulties also was elevated (mean 84.4, SD 11.3). This slight elevation would not be unusual for this population, given the patients' struggles with chronic pain. Also, this elevation would not necessarily prevent these patients from proceeding with the spinal cord stimulator implantation.

None of the MCMI-III scales were clinically elevated above the cutoff base rate score of 75. However, several mean scores for MMPI-2-RF clinical scales (presented as t-scores) were elevated above the clinical cutoff of 65. One elevated clinical scale denotes somatic complaints and preoccupation with health concerns (RC1: mean 68.3, SD 12.1). Other clinically significant mean scores were noted for sub-scale components of RC1, including malaise (mean 72.0, SD 11.0), head pain (mean 65.5, SD 10.8), and neurologicalcomplaints (mean 69.1, SD 13.7).

Discussion

The present study sought to describe a sample of patients presenting for a psychological evaluation as candidates for spinal cord stimulator implantation. Demographically, the majority of participants were middle-aged, married, white women, with an estimated average intellectual functioning. In terms of depressive symptoms, participants were experiencing mild to moderate levels, while levels of anxiety-related symptoms were within the moderate range. Validity scales on the MBMD showed about half of participants responded to questions in a way that attempted to portray themselves in a positive light. This might be expected given that the primary goal of these participants is to be eligible for implantation. Such a finding, when contrasted with validity scales on the other measures, leaves open the question of equivalent sensitivity among validity scales on these major assessment measures.

A significant portion (68.4%) of participants had reported at least some problem with inactivity. Chronic pain sufferers, including those with intractable and refractory chronic pain, can often express fear that exercise or any other physical activity will exacerbate pain. Studies have shown an association between physical activity and exercise and a lower prevalence of chronic musculoskeletal complaints, although the question of whether chronic pain is a cause or consequence of inactivity remains unanswered.14

Overeating was also a common issue in about half of participants. It may be that depression may lead one to overeat in response to negative emotions, and findings of moderate levels of depressive symptoms in this sample may suggest such a relationship. Following this, some suggest that there may be a link between chronic pain and overeating, although such a relationship has been found more so with obese patients who are also suffering from chronic pain.15 Nevertheless, the relationship between chronic pain and overeating appears to be little explored, and thus warrants further investigation.

Several mean clinical scores on various psychometric instruments were elevated in this sample. These included several stress moderator scales on the MBMD—illness apprehension, functional deficits, and pain sensitivity. In addition, adjustment difficulties were noted as a possibility in terms of treatment prognosis and management issues. The lack of any findings of depression or anxiety on these larger measures (ie, MBMD, MCMI-III, and MMPI-2-RF) stand in contrast against the findings of moderate levels of depressive and anxiety-related symptoms as denoted by the BDI-II and BAI. Sampling issues may have played a role in this, as was the case with the limited number of respondents who completed the MMPI-2-RF. However, such a discrepancy may be a function of how each measure is designed, with the BDI-II and BAI generally examining symptoms, while the larger measures take into account a wider range of variables.

Symptoms of depression and anxiety as denoted on the BDI-II and BAI may also reflect aspects of a physical syndrome, such as chronic pain, and the functional limitations imposed by chronic pain may in turn resemble depression. This is supported by significant findings on the MMPI-2-RF involving a wide range of somatic complaints and an overall preoccupation with health concerns. Such findings make sense intuitively, given that all participants presented with chronic pain, and the research literature is replete with findings that chronic pain has wide-ranging psychosocial and functional implications.16,17

Study Limitations

Several limitations are inherent in this study. One important limitation involves missing scores from some participants due to the fact that not all measures were administered to all participants who underwent psychological testing; it is important to note that this may sometimes be the case in clinical practice, depending on test availability and practitioner discretion. The issue of test availability is most notable with the MMPI-2-RF, with only about one quarter of the participants being administered this test. Our relatively small sample also limits the generalizability of these results to the wider population, although they do highlight some trends that warrant further investigation.

Conclusion

Chronic pain has wide-ranging implications in terms of overall functioning and psychosocial adjustment. There may be characteristic levations with certain psychological test scores in patients presenting for a pre-surgical psychological evaluation as candidates for spinal cord stimulator implantation; however, further research is needed to clarify whether these factors actually represent predictors for a negative treatment outcome. Further research efforts will examine such important clinical outcomes as overall pain reduction, treatment follow up, additional surgical needs, and quality of life, along with potential associations to the battery of psychological assessments presented here. Additional research also is needed on several issues, including the relationships between overeating and inactivity to chronic pain, and the use of commonly used assessment instruments for the evaluation of chronic pain populations.

Last updated on: October 28, 2014
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