Noninvasive Spinal Stimulation in Stroke: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Noninvasive Spinal Stimulation in Stroke (NCT03714282), a randomized na study. The primary outcome is Change in Step-length Symmetry Using Symmetry Index.

2. Clinical Question

3. Trial Design

This was a randomized, parallel-group trial comparing noninvasive spinal stimulation with gait training against conventional gait training. The registry lists the study as completed, with enrollment of 8. The study began on 2018-10-18 and its primary completion date was 2020-05-14. The phase is listed as NA. Masking is listed as none, so the record does not describe a masked comparison.

Both groups were assigned locomotion training. In the stimulation group, transcutaneous spinal cord stimulation was combined with training; the conventional group trained without stimulation. Each arm description allows up to 50 min of locomotion training. The time spent in side-lying locomotion, treadmill training, and overground training could vary with individual tolerance and progression. The registry does not report how training time or progression actually differed between participants.

The primary outcome was change in step-length symmetry using a symmetry index. It was measured before and after the intervention, which the record describes as 8 weeks of training and 24 sessions in total. Secondary outcomes listed were changes in self-selected and fast velocity on the 10 Meter Walk Test, the 6 Minute Walk Test, and PCI during the 6 Minute Walk Test. The record identifies 6 outcome measures, but does not provide a reduced primary-outcome comparison or report analysis results.

The small enrollment and absent outcome analysis limit what can be concluded about comparative effects. Randomization describes the intended assignment method; it does not by itself establish that groups were balanced on important characteristics or that the planned intervention was delivered uniformly. Details about the randomization procedure, allocation concealment, eligibility criteria, and adherence are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Change in Step-length Symmetry Using Symmetry Index, measured over Pre and Post intervention (8 weeks of training, Post = after all training sessions completed. 3 training sessions/week x8 weeks = 24 sessions total).

The primary endpoint was change in step-length symmetry using a symmetry index. The registry describes measuring participants as they walked along a GAITRite electronic walkway at their self-selected and safe fast gait speeds. It says the walkway was to be at least 14 feet long. The index is based on the relationship between the nonparetic and paretic sides and is designed so that its maximum value is 100%, regardless of which limb has the greater value. The record states that positive changes indicate improvement and that higher scores are better.

Step-length symmetry is used as a measure of gait pattern. The registry describes the GAITRite data capture as a measure of overall gait quality, while the index focuses on symmetry in spatiotemporal gait parameters. Comparing the measure before and after training is intended to capture change over the intervention period. Because the record identifies an endpoint and its direction but does not report the observed values or a between-group estimate, it does not establish how either group changed or whether their changes differed.

The endpoint is a continuous measure, with the mean and standard deviation identified as the planned summary form. A mean can describe the group’s average measurement, while the standard deviation describes variation among participants. The registry does not report the actual means, standard deviations, or a primary analysis result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Randomization is a method for assigning participants to study groups by chance. In general, it is intended to reduce systematic differences between groups at the time of assignment. This trial is listed as randomized and parallel-group, meaning the comparison was between separate groups. The registry does not describe the sequence-generation method, allocation concealment, or whether any restrictions were used in assignment. Those details are not reported in the registry record, so the quality of those procedures cannot be assessed from the record.

What does a continuous endpoint mean?

A continuous outcome can take a range of numerical values rather than representing only a category. Step-length symmetry is described using a symmetry index, and the planned summary is the mean with standard deviation. The mean represents the average measurement in a group. The standard deviation describes how dispersed individual measurements are around that average. They answer different questions: a group can have an average value while still containing substantial variation between participants.

For a pre-and-post outcome, change is commonly understood as a measure after the intervention compared with a measure before it. The registry identifies these measurement occasions but does not report actual observations, group summaries, or a comparison of changes. It also does not report the analysis model used. Consequently, no estimate of the average change or difference in average change can be interpreted from the posted results.

Why is a between-group estimate important?

When a trial compares two groups, the central statistical question is usually whether the groups’ outcomes differ, and by how much. An estimate describes the size and direction of a contrast. A confidence interval, as a general statistical concept, expresses the range of values compatible with the observed data under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval. Neither an estimate nor an interval is reported for this primary endpoint in the registry record. Without them, the magnitude and precision of any comparative effect are unknown.

A test result alone would not answer every question about importance. Statistical compatibility with no difference and the size of a possible difference are distinct considerations. In this record, no primary test result is reported, so even that limited description is unavailable. The endpoint’s stated direction—higher scores are better—defines its interpretation but does not provide evidence about the result.

What does the analysis count tell us?

The registry identifies 6 outcome measures and 0 analyses. This indicates that outcome measures are listed but analysis entries are not reported in the record. A listed endpoint is not the same as a reported result. To interpret an analysis, readers would ordinarily need information such as the participants included, the model or comparison used, the estimate, and its uncertainty. These analysis details are not reported in the registry record.

The record also says that the primary outcome has several categories or time points and was not reduced to one comparison. That matters because multiple measurements can represent different questions: for example, measurements at separate times or distinct categories should not automatically be treated as interchangeable. Selecting one result after examining several can also affect how evidence is interpreted. The record does not describe how the outcome’s categories or time points were intended to be analyzed, or how any selection among them would be handled.

Why do planning calculations differ from trial results?

Sample-size calculations are planning tools. In general, they ask how many participants would be needed under specified assumptions to detect a chosen effect with a chosen level of statistical power. The registry describes its illustrations as based on the observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. These calculations are planning illustrations, not evidence that the enrolled study achieved a particular power.

Participants-per-arm values in a planning illustration are hypothetical requirements under those assumptions. They are not observed enrollment, and they do not demonstrate that the planned effect is real. Because no reduced primary comparison is available in the record, a reader should not treat such calculations as a substitute for the primary estimate, uncertainty interval, or trial analysis. The registry does not report the trial’s own sample-size justification.

How should uncertainty be understood in this record?

Uncertainty arises both from limited observations and from incomplete reporting of the analysis. With 8 participants enrolled, the amount of information available for estimating group differences is inherently limited in scope. However, the record does not give outcome distributions or an effect estimate, so the precision cannot be quantified. It would be inappropriate to infer a confidence interval, p-value, or effect size from the enrollment count alone. The posted registry results therefore permit a design-level description, but not a quantitative assessment of comparative efficacy.

10. Multiplicity, Missing Data and Analysis Populations

Multiplicity refers, in general, to the statistical complication that can arise when several outcomes, time points, groups, or analyses are examined. The registry lists 6 outcome measures, including several walking measures, and notes that the primary outcome has several categories or time points. It was not reduced to one comparison. The record does not describe a multiplicity adjustment, a hierarchy of outcomes, or a prespecified strategy for selecting among time points or categories. These details are not reported in the registry record. Without an analysis plan or results, it is not possible to assess how multiplicity was handled.

Missing-data handling is also not reported in the registry record. The record does not state whether all enrolled participants completed outcome measurements, how missing observations were treated, or whether any imputation or sensitivity analysis was used. This matters because an analysis based only on participants with complete measurements can differ from one that addresses missing values, particularly if missingness is related to outcomes or group assignment. This is a general concern, not evidence that missing data occurred in this trial.

The record does not report the analysis population. It is therefore not possible to tell whether analyses, if conducted outside the registry record, followed randomized assignment, included only participants who completed training, or used another population definition. Such distinctions can affect the interpretation of randomized comparisons. The registry lists 0 analyses, so the analysis populations and their results are not reported in the registry record.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry lists 4 participants at risk for serious adverse events in the noninvasive spinal stimulation with gait training group and 4 in the conventional gait training group. It reports 0 serious adverse events in each group. It also lists 4 participants at risk for other adverse events in each group, with 0 other adverse events in either group. Deaths are listed as 0 in both groups.

These figures describe the adverse-event counts in the registry record. A zero count means no events of that listed type were reported for the participants counted; it does not prove that the intervention carries no risk or that every possible event would have been detected. The record does not describe event definitions, collection procedures, monitoring duration, or completeness of reporting. These details are not reported in the registry record.

The safety counts should be read in the context of enrollment of 8 and the small number of participants at risk in each group. They provide a limited description of the recorded events, not a precise estimate of event frequency in a wider population. No medical conclusion should be drawn from the absence of reported events alone.

12. What the Result Does, and Does Not, Mean

The trial record identifies a clinically relevant statistical question: whether adding noninvasive spinal stimulation to gait training is associated with a different change in step-length symmetry than conventional gait training. It also identifies the population, intervention, comparator, and measurement schedule. These details make the intended comparison understandable, even though the registry does not report an analyzed result.

The result does not establish that one group improved more than the other. The endpoint description states that positive values indicate improvement, but the record gives no observed changes, between-group estimate, confidence interval, or test result. It is therefore not possible to tell from the posted registry results whether the groups’ outcomes were similar or different, or to quantify any possible difference.

The record also does not establish whether training was completed as planned by each participant. The intervention descriptions allow training up to 50 min and say that the activity mix depended on tolerance and progression. Actual attendance, exposure, and adherence are not reported in the registry record. The design description alone cannot show what participants received in practice.

Similarly, the listed secondary outcomes do not amount to evidence of effects on walking speed, walking distance, or PCI. Results for these outcomes are not reported in the registry record. The safety counts show no serious or other adverse events reported in the listed groups, but the record does not provide enough detail to conclude that adverse-event monitoring was comprehensive.

Finally, planning calculations should not be read as evidence of trial success or failure. They represent sample-size illustrations under stated assumptions, not observed power and not a substitute for reported estimates. The main limitation for interpretation is the absence of a reduced primary comparison and analysis results. The appropriate conclusion is about what the registry records: a completed randomized study with an identified endpoint and enrollment of 8, but no reported primary effect estimate in this record.

13. Why This Trial Matters Statistically

This trial is statistically notable because it asks a clear comparative question but the registry record does not provide the analysis needed to answer it. The design identifies random assignment, two parallel groups, an intervention, a comparator, and a continuous primary endpoint. Yet the record lists 0 analyses and does not reduce the primary outcome’s several categories or time points to a single comparison. That gap illustrates why trial registration and outcome descriptions are not interchangeable with posted results.

For clinical researchers, a result is most informative when it includes a group contrast and a measure of uncertainty. An outcome’s definition and direction are important, but they cannot show the observed change. Without an estimate and precision measure, readers cannot distinguish a small, uncertain difference from a larger, more precisely estimated one. In this record, neither can be assessed.

The enrollment of 8 also underscores the importance of transparent reporting in small trials. A small study may produce imprecise estimates, but the size and direction of its estimate still matter for interpreting what was observed. Here, no estimate is reported, so the issue is not merely that the estimate may be uncertain; the registry record does not present it for evaluation.

The entry also shows why planning illustrations require careful interpretation. Sample-size requirements based on an observed effect are hypothetical calculations under assumptions. They do not establish that an effect exists, that the study had sufficient information, or that a result was statistically significant. Such calculations are useful for planning but cannot replace the reported analysis.

Finally, safety counts are most useful when read alongside clear definitions, monitoring methods, and follow-up information. The registry lists no adverse events, but does not report the details needed to evaluate completeness. The broader statistical lesson is that a transparent account of methods, analysis populations, missing data, outcome selection, and uncertainty is needed to make a randomized comparison interpretable.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record describes the study as completed but does not provide a reduced primary-outcome comparison or analysis results. This prevents assessment of the direction, magnitude, and precision of the primary outcome. The record lists 0 analyses, and results for the secondary outcomes are not reported in the registry record.

Enrollment was 8, which limits the amount of information available for estimating comparative effects. The record does not report participant characteristics or baseline outcome values, so the similarity of the groups at baseline cannot be assessed. It also does not describe the randomization procedure or allocation concealment. Masking is listed as none, but the record does not explain whether outcome assessment was otherwise protected from knowledge of group assignment.

The intervention descriptions allow variation in training activities according to participant tolerance and progression. Actual training exposure, attendance, adherence, and progression are not reported in the registry record. The record also does not report the analysis population, handling of missing data, or the approach to multiple outcome categories and time points. These omissions make it difficult to evaluate whether the intended comparisons were carried out as planned.

Safety reporting is limited to counts and numbers at risk. Event definitions, monitoring procedures, and follow-up completeness are not reported in the registry record. These limitations are specific to the information available for this trial and do not establish that events or data were missing; they mean those aspects cannot be assessed from the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Noninvasive Spinal Stimulation in Stroke — NCT03714282.
• Registry record last updated 2026-03-17; status last verified 2026-03.
• Results first posted 2026-03-17.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry record describes a completed randomized, parallel-group trial of noninvasive spinal stimulation with gait training versus conventional gait training in individuals with hemiplegic stroke. It lists enrollment of 8, no masking, and phase NA. The primary endpoint was change in step-length symmetry using a symmetry index, measured before and after an intervention described as 8 weeks of training and 24 sessions total.

Secondary outcomes include walking speed, walking distance, and PCI during the 6 Minute Walk Test. The registry lists 6 outcome measures and 0 analyses. It states that the primary outcome has several categories or time points and was not reduced to one comparison. Consequently, the primary effect estimate and analysis results are not reported in the registry record. Safety listings show no serious adverse events, other adverse events, or deaths reported in either group, with 4 participants at risk in each group for each adverse-event category.