1. 2020;23;E19-E30Fantastic Four: Age, Spinal Cord Stimulator Waveform, Pain Localization and History of Spine Surgery Influence the Odds of Successful Spinal Cord Stimulator Trial
   Observational Study
   Beth Collins, RN, Shihab Ahmed, MBBS, David Hao, MD, Kimberly Ting, MD, Ruby Kwak, BS, and Charles Odonkor, MD.

BACKGROUND: There is a dearth in our understanding of the factors that are predictive of successful spinal cord stimulator (SCS) trials and eventual conversion to permanent implants. Knowledge of these factors is important for appropriate patient selection and treatment optimization.

OBJECTIVES: Although previous studies have explored factors predictive of trial success, few have examined the role of waveform in trial outcomes. This study sought to establish the relationship of neuraxial waveform and related measures to trial outcomes.

STUDY DESIGN: This study used a retrospective chart review design.

METHODS: Data were retrospectively collected on 174 patients undergoing SCS trials upon institutional review board approval of the study protocol. Indications for SCS were: complex regional pain syndrome, failed back surgery syndrome with radicular symptoms, peripheral neuropathy, and axial low back pain. Descriptive statistics and logistic regression analyses were used to assess the association of demographic and clinical variables with SCS trial outcomes.

RESULTS: The study population comprised 56% women, had a median age of 55 (interquartile range [IQR], 44-64), and 32 of 174 (18%) patients failed SCS trials. Individuals with successful trials (>= 50% pain relief) were significantly younger and had a median age of 54 years (IQR, 42-60) compared to those who failed SCS trials (median age 66 years; IQR, 50-76; P = .005). Adjusting for age, gender, number of leads, pain category, and diagnoses: surgical history (odds ratio [OR] = 4.4; 95% confidence interval [CI], 1.3-15.8) and paresthesia-based tonic-stimulation (OR = 10.3; 95% CI, 1.7-62.0), but not burst or high frequency, were significantly associated with successful trials. Of note, the number of leads (whether dual or single), pain duration, characteristics, and category (nociceptive vs neuropathic) were not significant factors. An interaction between surgical spine history and lower extremity pain was significantly associated with a positive trial (P = .005).

LIMITATIONS: This study was limited by its retrospective nature and focus on a patient population at a single major academic medical center.

CONCLUSIONS: Paresthesia-based tonic stimulation, age, and surgical history have significant effects on SCS trials. Prospective and randomized controlled studies may provide deeper insights regarding impact on costs and overall outcomes.
IRB Approval #: 2018P002216

KEY WORDS: Pain duration, pain location, spinal cord stimulator trial, stimulator waveform, surgical history