Towards Selective Trial Stimulation in Spinal Cord Stimulation: Clinical and Psychological Evidence for an Individualised Implantation Strategy

Background/Objectives: The mandatory spinal cord stimulation (SCS) trial was established in the era of tonic, paresthesia-dependent stimulation, when pre-implantation outcome prediction was unreliable, validated psychological screening was unavailable, and post-implantation programming options were limited. This narrative review examines whether universal trialing remains justified in the context of contemporary paresthesia-free waveforms, mechanistically informed psychological assessment, and current evidence on the predictive utility of screening trials. The objective was to evaluate the contemporary rationale for selective rather than universal trialing and to propose a structured four-step clinical decision framework integrating contraindication screening, pain phenotype certainty, psychological risk stratification, and centre-level criteria, with the aim of identifying patients in whom a trial is most likely to add prognostic information. Methods: PubMed and the Cochrane Library were searched using predefined search strings. Eligible publications included randomised controlled trials (including the TRIAL-STIM RCT), systematic reviews, registry-based cohort studies, health-economic analyses, and consensus guidelines. Results: The evidence base comprised randomised controlled trials of trial-versus-no-trial strategies, paresthesia-free waveforms, and closed-loop stimulation (including TRIAL-STIM, SENZA-RCT, EVOKE, and ECHO-MAC), together with large registry and cohort studies, systematic reviews, qualitative patient-experience data, and current consensus guidance. Modern paresthesia-free and physiology-guided paradigms reduce several technical functions historically served by trialing, although the extent varies by waveform. The only randomised trial designed specifically to compare trial-first and no-trial strategies (TRIAL-STIM) found no difference in pain outcomes at 6 or 36 months; however, its single healthcare setting and predominantly paresthesia-based waveform mix limit generalisability. Structured pre-implantation psychological evaluation may provide prognostic information that short-duration trialing cannot replicate. At the same time, contemporary guidelines continue to recommend trialing and several clinically relevant arguments for retaining it persist, including patient experiential learning, identification of screening false negatives, and grey-zone decision-making. Conclusions: In carefully selected patients with established neuropathic pain phenotypes and comprehensive pre-implantation evaluation, selective trialing may be clinically reasonable. The proposed four-step framework offers a structured basis for allocating trial stimulation to the patients most likely to benefit from it and should be interpreted as hypothesis-generating pending prospective validation. This review does not advocate abandoning trial stimulation; rather, it argues that its role should be examined within an individualised, phenotype- and risk-stratified pathway.