Providing Brain Control of Extracorporeal Devices to Patients With Quadriplegia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Providing Brain Control of Extracorporeal Devices to Patients With Quadriplegia (NCT01849822), a na na study. The primary outcome is Number of Participants With Patient Control Over the End Effector (Virtual or Physical).

2. Clinical Question

The study asks whether a neural prosthetic system can enable a person with tetraplegia due to high spinal cord injury to control an external device using brain signals. The registry describes control of a virtual or physical end effector, such as a computer cursor or robotic limb. Its stated primary effectiveness objective is to evaluate control of these devices, with accuracy compared against chance performance.

This is a feasibility question about device control in an individual clinical context, not a comparative estimate of treatment effects between groups. The record names the Action Research Arm Test, the Canadian Occupational Performance Measure, and the Quality-of-Life Inventory among the methods intended to assess effectiveness or related outcomes. It does not report their results or specify how those measures relate to a threshold for declaring control.

3. Trial Design

The registry describes a completed, single-group study with an enrollment of 1. Allocation is listed as NA, and masking is listed as NONE. The study therefore does not have a randomized comparator arm, and the record does not support a like-for-like comparison between intervention and control participants. The phase is not reported in the registry record.

The intervention is the Neural Prosthetic System, a device-based brain-machine interface. The registry describes two NeuroPort Arrays implanted in the posterior parietal cortex. The study objective is to evaluate whether brain signals can be used to control virtual or physical end effectors. The brief description characterizes the system and implantation procedure as experimental and states that they had not been approved by the FDA.

The study started in 2013-02, had primary completion in 2019-01, and is listed as COMPLETED. The primary outcome timeframe is six years after array implantation. These record dates describe the trial timeline; they do not establish when outcome assessments took place or whether every planned assessment was completed.

The registry record does not report a formal protocol rationale for the enrollment target, a statistical analysis plan, or a sample-size justification. It also does not report details such as how many task sessions were conducted, how success was defined, or whether assessment procedures changed during follow-up. Those details matter when interpreting a feasibility study because device performance can depend on task definition, measurement conditions, and the way control is classified.

With a single participant and no concurrent comparison group, the design is suited to describing the experience and recorded outcomes of that participant. It cannot by itself estimate between-group differences or establish how often similar performance would occur in a broader population. The registry record does not report a basis for generalizing beyond the enrolled participant.

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

Analysis population for the primary outcome, as defined in the registry: tetraplegic patient

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.

Population: 1 participant

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Patient Control Over the End Effector (Virtual or Physical), measured over Six years after array implantation.

The primary outcome is titled “Number of Participants With Patient Control Over the End Effector (Virtual or Physical).” Its unit is participants, and its timeframe is six years after array implantation. It is a count-based endpoint: it is intended to record how many participants meet the study’s criterion for control, rather than to report a mean score or a change on a continuous scale.

The endpoint addresses the central feasibility objective: whether the Neural Prosthetic System can translate brain signals into control of an external device. The record describes accuracy as a way to assess control and states that task performance would be compared with chance. It also lists standardized tests and the Quality-of-Life Inventory among assessment methods. The record does not specify a numerical accuracy threshold, the exact rule for classifying a participant as having control, or how results across the different assessments would be combined.

A participant count can communicate whether the stated outcome was recorded, but it gives limited detail about the quality or consistency of control. It does not, on its own, describe accuracy across tasks, performance over time, or the participant’s experience. Those interpretations would require the underlying outcome data and operational definitions, which are not reported in the registry record. The primary outcome result is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical interpretation depends on what was measured, how it was summarized, and what comparison was planned. The registry identifies a count of participants with control over an end effector as the primary outcome, but the result is not reported. It also does not report the analysis method, an estimate of accuracy, or an uncertainty interval. No numerical effectiveness conclusion can therefore be drawn from the posted results.

What does a count endpoint represent?

A count endpoint records how many participants meet a defined outcome criterion. For this study, the criterion concerns patient control over a virtual or physical end effector. A count is straightforward to understand, but its meaning depends on a clear definition of control. For example, an analysis needs a prespecified rule for classifying a task as successful and for combining results across tasks or sessions. The registry does not report such a rule or a numerical threshold for accuracy.

When a study includes only a small number of participants, a count can change substantially in response to the outcome of an individual. In this record, enrollment is 1, so the result would describe that participant rather than provide a stable estimate of performance across a population. This is a general limitation of interpreting counts from very small studies; it does not reveal what the unreported result was.

What does comparison with chance require?

The registry states that task accuracy would be compared with chance performance. In general, a chance benchmark represents the performance expected without meaningful control under a defined task and response setup. To interpret a comparison, readers need to know how the task was structured, how chance was calculated, how many observations contributed to the accuracy estimate, and whether repeated observations were treated as independent. The registry record does not report those details or the comparison result.

Repeated task observations can carry less independent information than the same number of observations from unrelated participants when results within a person are correlated. General statistical principle: analyses should reflect the unit of observation and account for dependence when repeated measurements are related. The record does not describe the unit-level data or the method used to handle repeated tasks, so it is not possible to assess whether or how this issue was addressed.

What can a significance test establish?

A significance test evaluates how compatible observed data are with a specified null model, given the assumptions of the test. The study description refers to accuracy being significantly greater than chance, but the registry does not report a test statistic, p-value, or analysis result. A stated hypothesis is not a reported finding. Without the observations and analysis, readers cannot determine whether the proposed comparison was conducted or what conclusion it produced.

General statistical principle: statistical significance does not by itself communicate the size, practical meaning, or precision of an effect. An estimate and its confidence interval help describe the range of values reasonably compatible with the data under the analysis assumptions. No confidence interval is reported for the primary outcome. The registry record also does not report an effect estimate from which precision could be assessed.

How should planning calculations be read?

The planning assumptions describe illustrations using a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. These assumptions describe hypothetical planning scenarios. They do not match the single-group design recorded for this study, and the illustrations should not be read as the study’s actual enrollment plan or as evidence of observed power.

General statistical principle: a sample-size calculation depends on the target effect, variability, statistical test, type I error level, desired power, and design structure. Altering those assumptions can alter the resulting planning estimate. A calculation based on a fraction of an observed effect is particularly scenario-dependent: it asks what planning might look like under an assumed effect size, rather than measuring the probability that the completed trial detected an effect. The registry does not report a trial-specific sample-size justification.

Because the study has one group and no randomized comparator, calculations that assume equal allocation between two arms are not an account of the actual design. The calculations can at most serve as planning illustrations under their stated assumptions. They cannot supply a missing treatment comparison, outcome result, or uncertainty estimate.

What information is missing for statistical review?

The registry record does not report the primary outcome result, an inferential analysis, a success threshold, task-level accuracy, or a confidence interval. It does not report the analysis population, how missing assessments were handled, or whether any interim analyses were conducted. These items should not be inferred from study completion status or from the fact that outcomes were registered. A fuller statistical review would require the outcome data, the operational definitions, and the analysis methods, none of which are reported in the registry record.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Neural Prosthetic System")
n      <- c(1)
events <- c(1)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Neural Prosthetic System  1  1  100.0  2.5  100.0  20.7  100.0  15.8  98.7

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures, with the participant-control count identified as the primary outcome. It also describes several assessment approaches: standardized tests, comparison of task performance with chance, and the Quality-of-Life Inventory. The record does not report how the different outcomes or assessment methods were prioritized in the analysis, whether they were tested separately, or whether any adjustment for multiple comparisons was planned.

In general, evaluating multiple outcomes or repeated tests can increase the chance of finding at least one apparently notable result when each is considered separately. Multiplicity procedures are methods for controlling or describing that issue. Whether such procedures were needed depends on the prespecified analysis and the number and structure of comparisons. Those details are not reported in the registry record, so no multiplicity adjustment can be confirmed or assumed.

The record does not report missing-outcome counts, missing-data handling, or whether all planned assessments were completed. Enrollment of 1 does not reveal whether data were available at each assessment or at the six-years-after-implantation timeframe. General statistical principle: conclusions can depend on why observations are missing and how the analysis handles them. The record does not provide enough information to evaluate that issue.

The analysis population is also not reported in the registry record. There is no description of whether the analysis included all enrolled participants, only participants with usable device data, or another defined set. With no reported outcome results or analysis entries, the registry does not show how the primary endpoint was analyzed. These omissions limit reproducibility and prevent readers from assessing whether the reported analysis, if any, followed a prespecified plan.

12. 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 the Neural Prosthetic System group with 1 participant at risk for serious adverse events and 0 affected. It also lists 1 participant at risk for other adverse events and 0 affected. Deaths are listed as 0, and no top serious adverse-event terms are listed.

These figures are counts in the registry record, not rates estimated from a large sample. With enrollment of 1, a zero count means that no affected participant is recorded in the corresponding category; it does not establish that an event is impossible or that risk is absent. General statistical principle: safety counts from very small samples are imprecise, and the range of possible event rates compatible with such limited observation can be broad.

The record does not provide event narratives, exposure time for safety outcomes, or details about how events were collected and classified. The primary outcome timeframe is six years after implantation, but the safety fields alone do not specify the observation period for each adverse-event category. These counts should therefore be read as the registry’s reported tallies, not as a complete description of all safety considerations.

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

The study addresses a technically demanding feasibility question: whether an implanted neural prosthetic system can use brain signals to control virtual or physical end effectors for a person with tetraplegia. The registry specifies a primary outcome centered on participant control and describes accuracy relative to chance as a driving hypothesis. It also names standardized assessments and a quality-of-life measure as parts of its evaluation approach.

The registry record does not report the primary outcome result, task accuracy, comparison with chance, or results from the other outcome measures. As a result, it does not establish whether control was achieved, how reliable any control was, or how performance changed over time. The stated objective and hypothesis should not be treated as findings. Likewise, an absent result is not a report of failure; it is an information gap in the registry record.

The design is single-group and includes 1 participant. There is no randomized control group, and the chance benchmark described for accuracy is not a participant comparator. Thus, the record cannot provide a randomized estimate of the difference between the device and a control intervention. Nor can a result from this design, even if reported, by itself establish how commonly similar outcomes would occur in a broader group.

The study is listed as completed, with primary completion in 2019-01. Completion status describes registry status rather than the completeness of public outcome reporting. The record does not report whether all planned assessments were performed or how missing information was handled. The available information supports an account of the registered study question, intervention, and design, but not a conclusion about effectiveness or the magnitude and precision of any outcome.

Interpretation should therefore remain at the level of what was planned and recorded. The intervention is described as experimental, and no medical recommendation follows from the registry information. A fuller assessment would require the outcome data, definitions of successful control, task-level methods, and analysis results.

14. Why This Trial Matters Statistically

This trial matters statistically because it brings together a highly specialized device intervention, a small single-group design, and an outcome that depends on defining successful control. A clear operational definition is essential: without a specified criterion, a count of participants with control can be difficult to interpret or reproduce. The registry identifies the general outcome but does not report the threshold or classification rule.

The stated comparison with chance also highlights the importance of measurement design. Chance performance is meaningful only in relation to the task, response options, and observation process. General statistical principle: a benchmark should be specified in a way that matches the data-generating task, and repeated observations should be analyzed with attention to their dependence. The registry record does not report the task-level data or analysis details needed to evaluate these choices.

The enrollment of 1 makes the distinction between an individual feasibility observation and a population estimate especially important. A study can be useful for describing whether an approach can be tested and for informing future research, but a single-group record cannot estimate a comparative effect against a concurrent control group. The primary result is not reported, so the registry also cannot support a participant-level performance description.

Finally, this record illustrates that a completed status and registered outcome definitions do not substitute for posted results. Transparent reporting of outcome values, analysis methods, missing-data handling, and uncertainty would allow readers to assess what the study found and how precisely. Those results are not reported in the registry record.

15. 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 most direct limitation is that the primary outcome result is not reported in the registry record. The record therefore does not show the count of participants meeting the control outcome, task accuracy, or the comparison with chance described in the study objective. Results for the other outcome measures are also not reported.

The enrollment is 1, and the design is single-group. There is no randomized comparator arm, so the study does not support a between-group treatment-effect estimate. The small enrollment also limits how much can be inferred about variation across people. These are design limitations, independent of whether the device-control objective was achieved.

The registry does not report the operational definition of patient control, a numerical accuracy threshold, the chance benchmark, or task-level measurement details. It does not report the statistical analysis plan, an inferential analysis, an uncertainty interval, the analysis population, or missing-data methods. The relationship among the primary outcome, standardized tests, and Quality-of-Life Inventory is not specified in the record.

The record describes the intervention as experimental and states that it had not been approved by the FDA. It does not provide the full clinical and technical detail needed to assess the experience of implantation or device use. The safety fields report zero affected participants in the listed categories, but do not provide event narratives or category-specific observation periods.

These limitations mean the registry record is useful for describing the intended feasibility question and the broad design, but insufficient for judging the observed level of control, its precision, or how broadly any result might apply.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Providing Brain Control of Extracorporeal Devices to Patients With Quadriplegia — NCT01849822.
• Registry record last updated 2021-04-30; status last verified 2021-04.
• Results first posted 2021-04-30.
• 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.

19. Record Summary

NCT01849822 is a completed, single-group study of the Neural Prosthetic System for brain control of virtual or physical end effectors in a person with tetraplegia. The registry records an enrollment of 1, allocation as NA, and masking as NONE. The study started in 2013-02 and had primary completion in 2019-01.

The primary outcome is the number of participants with patient control over an end effector, assessed at six years after array implantation. The registry describes accuracy relative to chance and names standardized assessments and the Quality-of-Life Inventory as evaluation approaches. The primary outcome result and analysis results are not reported in the registry record.

The safety listings record 0 serious adverse events, 0 other adverse events, and 0 deaths among the listed at-risk counts. The record does not report a trial-specific sample-size justification, detailed analysis methods, missing-data handling, or a randomized comparison.