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Outcomes of Spinal Cord Stimulation: PatientValidation

Valerie C. Anderson, PhD*, ▪ Christina Carlson, BSN*, ▪ Deborah Shatin, PhD‡

*Department of Neurological Surgery, Oregon Health Sciences University, Portland, Oregon and‡Center for Health Care Policy and Evaluation, United Health Group, Minneapolis, Minnesota

� ABSTRACTObjective. To identify aspects ofdaily life that havebeen to social life and recreation were identified. Functional

status change, decreased ability to walk, and ability tomost affected by chronic low back pain among spinalcord stimulation (SCS) patients and to determine the perform daily household activities were rated as the

most important change from among items included inrelative contribution that improvement in each wouldmake to patients’ quality of life (QOL). examiner-read list.

Conclusions. Patients with chronic low back pain seekMaterials and Methods. Telephone survey of 44 patientswith chronic low back pain who were about to undergo improvement in multiple dimensions of QOL after SCS,

particularly increased physical activity, social relations,or had been recently implanted with an SCS system.Patients were asked to define, by open-ended response work status, and mood. It is likely that patients’ assess-

ment of SCS ‘‘success’’ correlates highly with functionaland examiner-read list, those aspects of daily life thathad been most affected by pain and to assess the rela- improvement. As such, an understanding of SCS thera-

peutic benefit and satisfaction requires that QOL betive importance that improvement in each wouldmaketo daily life. carefully assessed in future outcome trials. �Results. Patients identified 13 areas of daily function thatwere most significantly impacted by chronic low back

KEY WORDS: chronic pain; low back pain; quality ofpain.Most frequently, activities of daily living, decreasedability to work, psychological changes, and limitations life; spinal cord stimulation.

Historically, spinal cord stimulation (SCS) outcome and overall emotional experience. With this in mind,several early studies attempted to quantify the effecthas been described in terms of pain relief, with

success defined as the patient’s subjective rating of of SCS on activities of daily living (ADL), both the‘‘objective’’, i.e., return-to-work and changes in medi-50% or greater reduction in pain(1). While this sim-

ple assessment has clear clinical utility, pain relief cation use, and the more subjective outcomes. Forthe most part, though, these early studies reliedis a multidimensional combination of sensory, af-

fective, and evaluative qualities and reflects not only upon retrospective chart review and direct patientinterview using nonstandardized, invalidated instru-pain intensity but changes in quality of life (QOL)ments (Table 1).

We recently reported results from a largeReprint requests to Valerie C. Anderson, PhD, Department of Neurologi-cal Surgery, L472, Oregon Health Sciences University, 3181 SW Sam Jack- multicenter study of SCS for chronic back and lowerson Park Rd., Portland, OR 97201. Email: [email protected].

extremity pain(2). Pain relief was assessed multidi-Sponsored by an educational grant from Medtronic, Inc.

mensionally using the McGill Pain Questionnaire(MPQ)(3,4) and visual analog scales(5,6). Quality of

� 2001 International Neuromodulation Society, 1094–7159�00�$15.00�0Neuromodulation, Volume 4, Number 1, 2001 11–17 life and disability were assessed using a battery of

12 � ANDERSON ET AL

Table 1. Quality of Life Assessment in SCS Literature

QOL RatingFollow-up, years

Author (yr) Na mean (range) Subjective Objective Outcome

North et al. (1991) 62 2.1 (0.4–4.2) 8 ADLs categorically rated; Medication use; return- Most activities improved(17) Willingness to repeat for similar to-work

results

Spiegelmann and 30 1 (0.25–3.25) Unstructured patient report Medication use; return- Ambulation and sleepFriedman (1991) to-work improved(18)

Kumar et al. 94 3.3 (0.5–10) Activity level (global) by patient Medication use Activities increased(1991) (19) report

De LaPorte and 76 1–7 Daily activities (global) by patient Medication use; return- Majority improvedKelft (1993) (20) report; Satisfaction with SCS to-work

LeDoux and 22 1 Willingness to recommend to Medication use; return-Langford (1993) other patients to-work(21)

Burchiel et al. 70 1 Sickness Impact Profile; Oswestry Medication use; return- Statistically significant(1996) (2) Disability; Beck Depression to-work ADL and disability

improvement

Devulder et al. 69 4.9 � 3.3 Patient report of activities that Medication use; return-(1997) (22) can be performed to-work; SCS use

Barolat (1999) (23) 20 0.5 Sickness Impact Profile; Oswestry Improved ADL; NoDisability improved disability

aImplanted

reliable, validated instruments including the Oswes- that patients with chronic low back and/or leg painbelieve have been most affected by the pain condi-try Disability Questionnaire (ODQ)(7), Sickness Im-

pact Profile (SIP)(8,9) and Beck Depression tion and to determine the relative contribution thatimprovement in each by SCS would make to theirInventory (BDI)(10). The combination of these in-

struments allowed assessment of the four core di- quality of life. Specific assessment of these areas infuture research could lead to improved understand-mensions of QOL: functional status (physical

independence, activities of daily living, ability to ing of pain relief report and therapeutic benefit ofSCS.do work), physical symptoms (pain, sleep, fatigue),

psychological well-being (life satisfaction, anxiety,depression, concentration, etc.) and social relations(emotional support, affection, appearance)(11). METHODSAfter one year of SCS, statistically significant im-

Patientsprovement in pain was measured by visual analogscale and MPQ. Disability, as measured by the ODQ, Forty-four patients with chronic nonmalignant low

back and/or extremity pain who were about to un-and activities of daily life, as measured by the totalscore and physical and psychosocial subscales of the dergo a trial of SCS (N � 22; 50%) or who had been

implanted with a PISCES-Quad or RESUME (Med-SIP, were also significantly improved. Additionally,patients were less depressed after one year of SCS. tronic, Inc., Minneapolis, MN) stimulating system for

less than 6 months (N � 22; 50%) were contacted byDespite these improvements, only 35% of patientsdescribed pain relief as good or excellent and en- telephone from March 1994 to September 1997.

The mean age of respondents was 58.1 � 13.4 yearsdorsed SCS as a beneficial and worthwhile therapy.One possible explanation for these results is that (range 37–85). Chronicity of the pain complaint was

reflected in the 10.0 � 8.3 years mean pain dura-the functional areas assessed by the SIP and ODQmay be relatively unimportant to SCS patients, while tion. Fifty-five percent (24/44) of the population

was female. The majority of patients (33/44; 75%)other areas that are more important to patients arenot adequately evaluated. The purpose of the pres- suffered from mixed nociceptive-neuropathic pain,

most of whom (29/33; 88%) were diagnosed withent study was to identify those aspects of daily life

SCS Outcome Validation � 13

failed back surgery syndrome. Nine patients (9/44; jects felt that their health status had been reducedprior to onset of low back pain due to diabetes or20%) had predominantly neuropathic pain as a result

of peripheral (5/44; 11%) or diabetic (1/44; 2%) urologic problems.Subjects were first asked to identify, throughneuropathy, arachnoiditis (1/42; 2%), or chronic

lower extremity pain (2/44; 5%). open-ended response, any changes in daily functionthat had occurred after pain onset and to determinethe area that had been the most significantlyStudy Procedureschanged by pain. Only one patient said that pain

Study participants were identified from clinic re- had not produced any significant lifestyle change.cords and contacted by an investigator uninvolved The remaining 43 patients rated a total of 13 differ-in patient care. Participants were first asked to de- ent areas as having been most significantly impactedscribe in general terms their level of function prior by the pain condition. Most frequently, an inabilityto onset of the pain condition. In subsequent ques- to walk ‘‘normal’’ distances without pain was identi-tions (s)he was asked to describe via an open-ended fied as the most important change in patients’ dailyquestion the aspects of daily life that had been most life (8/43; 19%). Inability/decreased ability to work,affected and to assess the relative importance that a decrease in general activity level (typically definedimprovement in each would make to daily life. Pa- in relation to household activities or ability to ‘‘gettients were then asked to rank each identified life- around’’), and changes in mood (depression, loss ofstyle change as ‘‘most significant,’’ ‘‘very important,’’ independence, irritability) were cited by 14% each‘‘important,’’ or ‘‘minor.’’ (6/43). Decreased ability to continue normal hob-

Subjects were then read a list of 12 areas of daily bies and recreation was cited as the most signifi-life commonly affected by chronic low back pain, cant change by another four subjects (4/43; 9%).including personal care, lifting, walking, sitting, Other items that patients identified as having beenstanding, ability to use stairs, sleeping, sex life, social most significantly impacted by the pain includedlife, traveling, irritability, and hobbies/recreation. limitations to social life (3/43; 7%), an inability toItems mentioned as an area of concern during open- sit without pain (3/43; 7%), and anunacceptably highended questioning were not repeated. For each ac- medication intake (2/43; 5%). Increased sexual activ-tivity identified as an area of concern, subjects were ity, ability to sleep, lift, manage personal care, andasked to rank categorically (‘‘very important,’’ ‘‘im- stand were identified as the most significant changesportant,’ or ‘‘minor’’) the importance that improve- by one patient each. Results are shown in Fig. 1.ment in that area would have on daily life and to Subjects then continued to rank all previouslyidentify the most significant area of concern. Finally, mentioned lifestyle changes in terms of the impor-subjects were given the opportunity to comment tance that restoration to pre-pain levels would makeon any aspect of the pain condition as it related to to daily life. Overall, 12 areas were identified asdaily function that had not previously been ad- important or very important contributors to whatdressed. patients considered a ‘‘normal’’ lifestyle (Fig. 2). The

ability to perform household duties was cited mostData Analysis often (13/43; 30%) as an important change produced

by the pain condition. Performing routine daily activ-Descriptive statistics were performed using JMP Sta-ities without pain and continuing recreational activi-tistical Visualization Software (SAS Institute, Cary,ties were also cited frequently (11/43; 26% each).NC). Collection of data and statistical analyses wereOther items mentioned by at least two patients in-performed by an unbiased observer uninvolved included walking and standing without pain, lifting,patient care(12).and an ability to work. Mood, sleep, personal hy-giene, and sexual activity were also mentioned byseveral subjects. The frequency of all items de-RESULTSscribed by patients as important or very importantchanges produced by the chronic pain conditionForty-two respondents (42/44; 95%) felt that their

level of function had been similar to others around are shown in Fig. 2. After all items had been ranked,subjects were then asked if there were other im-them prior to the onset of the pain condition and

had been without any special limitations. Two sub- portant changes that they had not previously de-


patients were asked to rate the effect that improve-ment would make on their daily life. Results areshown in Fig. 3. Consistent with the open-endedresponse, walking was most frequently identified(34/44; 77%) as the activity that would make animportant or very important improvement in pa-tients’ daily life. Sitting and standing were alsodeemed important or very important areas for alarge majority of patients. Although mentioned lessfrequently in the open-ended discussion, 75% ofpatients (33/44) felt that sleep improvement wouldmake a very important change in their life. Areas ofrelative unimportance included lifting, going up anddown stairs, and personal hygiene, with many re-spondents stating that they had adapted their life-style such that these activities were no longerproblematic.

Overall, 10 of the 12 items on the examiner-readFigure 1. Most significant lifestyle change affected by low list were also cited by patients in the open-endedback pain condition (N � 43). Areas identified by more than10% of participants are labeled; For additional details, see text.

questioning. Figure 4 shows a normalized compari-son of the frequency with which each of the 10 itemswas rated as important or very important in both theopen-ended and examiner-read list of activities. Asscribed. In response, lifestyle factors of increasedshown, improvement in ability to walk was ratedalcohol consumption and decreased weight controlof highest priority in both assessments. By eitherwere mentioned by two patients.method, recreation/hobbies, an ability to travel, andFollowing the above discussion, subjects weresleep were also important to the majority of patients.read a list of 12 areas of daily function assessed byPersonal hygiene, sex life, and lifting were the leastthe ODQ and SIP and asked if the difficulty associ-problematic to patients by both assessments.ated with performing each was increased by the pain

condition. For those areas identified as problematic,

Figure 2. Patient-identified im-portant or very important functions af-fected by chronic low back pain (N� 43).


Figure 3. Relative importance ofsuggested activities: very important(solid); important (stripe); minor (dot-ted); not important (open) (N � 44).

Figure 4. Normalized frequency ofresponses rated important or very im-portant from the patient-identified(open)and suggested (solid) list ofac-tivities (N � 43).

DISCUSSION pression. While the combination of these instru-ments does include all four QOL core dimensions offunctional status, physical symptoms, psychologicalChronic low back pain affects multiple dimensions

of patients’ lives and each contributes to the overall well-being, and social relations, we wondered howimportant these areas were to low back pain patientsreport of ‘‘pain relief.’’ Therefore, to improve the

benefit and worth to patients, pain management and to what extent improvement by SCS would beconsidered beneficial.therapies must address more than the physical symp-

tom of pain. In a previous study, we assessed out- By both the open-ended and examiner-suggesteditem approach, functional status was the most im-come after one year of SCS using several

instruments: the Sickness Impact Profile, a 131-item portant dimension of QOL among the study popula-tion. Improvement in activity level, specificallymeasure of quality of life; the Oswestry Disability

Questionnaire, a disability scale developed specifi- walking, standing, and those physical activities nec-essary to perform everyday household chores inde-cally for the low back pain population; and the Beck

Depression Inventory, a widely used measure of de- pendently, was consistently considered the most


important benefit that patients hoped to gain from of physical symptoms, especially pain, to improveclinical relevance.SCS (Figs 1 and 3). This result suggests that patients’

perception of everyday physical limitations must becarefully assessed, as it is likely to correlate highlywith perceived benefit and worth of the therapy. CONCLUSIONReturn to work or an increase in the existing work

These results confirm that patients with chronic lowload, although not included in the examiner-readback pain seek improvement in multiple dimensionslist of activities, was also very important to manyof QOL, particularly increased physical activity lev-patients and substantiates the importance of workels, social relations, work status, and mood. In fact,status as an important functional outcome amongpatients’ assessment of SCS ‘‘success’’ may correlateSCS patients. Unfortunately, we and others haveas much or more with functional improvement asfound that the debilitating and refractory nature ofwith ‘‘pain relief.’’ We conclude that an understand-chronic low back pain makes work resumption aftering of therapeutic benefit and satisfaction requirestreatments for intractable pain such as SCS an un-that QOL be carefully assessed in future outcomelikely outcome(2,13).research on chronic low back pain.Social relations, as established through hobbies

and recreation, travel, and social activities, wereconsistently rated as important areas that patients

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