Chronic Effects of DBS in Parkinson's Disease and Dystonia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Chronic Effects of DBS in Parkinson's Disease and Dystonia (NCT01934296), a na na study. The primary outcome is Number of Patients With Parkinson's Disease With Reliable Cortical and Sub-cortical Brain Signals.

2. Clinical Question

This is a feasibility and measurement question, rather than a comparison of treatment outcomes between groups. It asks whether reliable signals could be recorded chronically with the implanted system. The outcome is a participant count, not a measure of symptom change, disease progression, or comparative clinical benefit. The registry record does not report an observed count for this primary outcome, so the question can be described but its result cannot be inferred from the outcome definition alone.

3. Trial Design

The registry identifies this as a completed, single-group study sponsored by the University of California, San Francisco. It lists Parkinson’s disease and isolated dystonia as conditions and Activa PC+S as the device intervention. The study summary describes an investigational device used to record brain activity for 12-24 months following surgical implantation of deep brain stimulation systems. Its stated purpose was to improve understanding of brain activity in movement disorders and its relationship to deep brain stimulation, rather than to bring a new device to market.

The arm description calls the study one-arm and single-center, and characterizes it as research on the neurophysiology of human movement disorders. It describes two goals, including assessing the feasibility of chronic brain recording with a fully implantable pulse generator capable of sensing and storing local field potentials. The available arm description ends before the second goal is fully specified, so its details are not reported in the registry record.

The registry lists enrollment as 9. It records the start as 2013-11, primary completion as 2021-12, and status as COMPLETED. The primary outcome timeframe is 24 months. Although the summary gives a recording period of 12-24 months, the primary outcome itself specifies 24 months.

Allocation is NA, masking is NONE, and the study model is SINGLE GROUP. There is therefore no randomized or like-for-like control comparison to interpret. The registry record does not report a protocol-based sample-size justification, details of participant selection, or a more complete account of follow-up and study conduct. Those omissions limit what can be concluded about the design beyond the information recorded above.

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: 5 patients with Parkinson's disease

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 Number of Patients With Parkinson's Disease With Reliable Cortical and Sub-cortical Brain Signals, measured over 24 months.

The primary endpoint is the number of patients with Parkinson’s disease who had reliable cortical and subcortical brain signals recorded using Activa PC+S. The registry identifies the outcome as a count of participants and gives a timeframe of 24 months. Its population description specifies 5 patients with Parkinson’s disease.

A participant count is useful for a feasibility question because it directly describes how many people met the stated signal-reliability criterion. It is not a continuous measure of signal strength or quality, and it does not by itself describe how signal reliability varied over time. The registry record does not define the operational threshold for “reliable,” describe how recordings were assessed, or state how missing or unusable recordings would be handled. Those details are not reported in the registry record.

Interpretation depends on both the count and the population to which it applies. A count without an observed value cannot establish how often the criterion was met. Nor does the endpoint measure clinical improvement or compare outcomes with a non-device group. It addresses whether the intended cortical and subcortical recordings were obtained reliably in the specified Parkinson’s disease population during the stated timeframe. The registry lists the outcome definition, but no primary analysis is listed, so the observed endpoint result is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a binary outcome type and identifies the primary measure as a count of participants. In practical terms, each participant either meets the stated criterion for reliable cortical and subcortical signals or does not, and the endpoint is the count meeting it. The record does not report the observed count, a statistical analysis, or a confidence interval for this outcome.

What does a participant count tell the reader?

A count is a direct description of how many participants satisfy an outcome definition. It is not the same as a rate or proportion, which would require a clearly specified denominator. A count also does not communicate precision by itself. General statistical practice would pair an estimate with information about the population assessed and its uncertainty. The registry describes the primary population as 5 patients with Parkinson’s disease, but does not provide an observed endpoint count or a fuller accounting of the analyzed population.

The meaning of “reliable” is central to this endpoint. If a criterion is applied consistently and specified in advance, a count can give a clear account of how often the technical goal was met. If the criterion, recording procedures, or handling of missing recordings are unclear, readers cannot fully assess how the count would have been determined. The definition and assessment procedures are not reported in the registry record.

Why does the absence of a comparator matter?

This is a single-group study, with allocation recorded as NA and masking as NONE. General statistical interpretation of a single group focuses on outcomes observed within that group. Without a comparison group, the study cannot estimate a relative difference between device and control conditions. It also cannot use random allocation to balance other factors across groups. This does not prevent a feasibility description, but it restricts conclusions to the observed group and the outcome definition.

Because the registry does not list an analysis for the primary outcome, it is not possible to identify a prespecified inferential method, an adjustment strategy, or a model used to quantify uncertainty. The record does not report whether the primary outcome was analyzed using a confidence interval, hypothesis test, or other statistical procedure. Such choices should not be assumed from the outcome type alone.

How should uncertainty be understood?

In general, a confidence interval expresses the range of values compatible with an estimate under a specified statistical method and its assumptions. It can show how much uncertainty remains around an estimated count or proportion. A narrow interval indicates greater precision under that method, while a wide interval indicates less precision. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be judged from an interval.

General statistical methods also rely on assumptions about the data and the design. For repeated recordings over time, the observations may be related within a participant; treating related measurements as independent can understate uncertainty. The record’s primary outcome is a participant count rather than a stated repeated-measures estimate, and it does not describe whether repeated recordings were separately analyzed. No repeated-measures model should therefore be inferred.

Over-dispersion is a general concern when count data vary more than a chosen statistical model expects. It can make standard errors too small if a model assumes less variability than is present. That issue is relevant only if a count model is fitted; the registry does not report such a model for this endpoint. The primary outcome as registered is a count of participants, and the analysis method is not reported in the registry record.

What are planning calculations?

Planning calculations ask how many participants might be needed under specified assumptions to detect an effect with a chosen statistical procedure. The record describes general planning assumptions: two-sided significance level 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of an observed effect. It notes that time-to-event planning outputs concern total events, while other planning outputs concern participants per arm.

Those assumptions do not describe this trial’s actual design, which is single-group, and they are not a sample-size justification reported by the study. The registry does not report the trial’s own sample-size rationale. Any planning figures based on an observed effect would be illustrations for future planning, not observed power and not a result of this study. The assumptions alone do not establish that a particular sample size was adequate for this feasibility outcome.

The registry record’s analysis count is 0. Accordingly, there is no reported primary analysis to explain or reproduce. Statistical concepts can clarify what evidence would be useful—an observed count, its population and denominator, and an uncertainty assessment—but they cannot supply those missing results.

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("Chronic Brain Recording")
n      <- c(5)
events <- c(5)
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  Chronic Brain Recording  5  5  100.0  47.8  100.0  56.6  100.0  54.1  99.6

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and no analyses. It does not report a multiplicity plan, such as how statistical testing would be handled across multiple outcomes, timepoints, or subgroup analyses. The presence of one listed outcome measure does not establish that the study assessed only one endpoint or made no additional comparisons; details beyond the registry listing are not reported in the registry record.

Multiplicity is a general statistical concern when several hypotheses are tested. As the number of tests increases, the chance of at least one apparently unusual result can increase if no adjustment or prespecified testing strategy is used. Whether that issue applied to the study’s analyses cannot be determined because analyses and a multiplicity strategy are not reported in the registry record. No adjusted or unadjusted primary result is available to interpret.

Missing-data procedures are also not reported in the registry record. The primary endpoint concerns reliable signals, but the record does not say how absent recordings, technically unusable recordings, withdrawal, or incomplete follow-up would be classified or handled. It does not state whether the analysis would include all enrolled participants, only participants with evaluable recordings, or another population. The enrollment entry and the outcome population description do not by themselves establish the analyzed population.

These omissions matter because missing recordings could affect both the count and its interpretation. General statistical practice distinguishes a participant who does not meet an outcome criterion from one whose outcome cannot be assessed; the registry does not state how that distinction was handled. The analysis population, missingness assumptions, and any sensitivity analyses are not reported in the registry record. Conclusions about robustness to missing data or multiplicity are therefore not possible from the registry information.

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.

Most frequent non-serious adverse event terms

For the chronic brain recording group, the registry lists 9 at risk for serious adverse events and 0 affected. It lists 9 at risk for other adverse events and 2 affected. Deaths are recorded as 0. The serious adverse event terms list is empty, so no specific serious-event terms are reported in the registry record.

These entries are counts, not a comparison between study groups. The study is single-group and has no control arm, so the event counts cannot be interpreted as relative risks or as evidence of a difference from another treatment or device. The registry does not state in this information whether events were judged related to the device or study procedures. An adverse event and an event attributed to an intervention are not interchangeable concepts; attribution is not reported in the registry record.

The at-risk figures describe the recorded group denominators for these safety entries. They should not be conflated with the primary outcome population description, which identifies 5 patients with Parkinson’s disease, or used to infer how the primary endpoint was analyzed. The safety record does not report event timing, duration, severity details beyond the serious classification, or participant-level patterns. The counts describe what is listed, but do not establish the likelihood of an event in other populations or settings.

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

The registry record describes a study aimed at chronic recording of brain activity in movement disorders using Activa PC+S. Its primary endpoint asks how many patients with Parkinson’s disease had reliable cortical and subcortical signals recorded over 24 months. That is a technical feasibility question. It is distinct from asking whether deep brain stimulation improves symptoms or changes the course of a condition.

The record does not report an observed primary endpoint count or an analysis of that outcome. It therefore does not establish how many participants met the signal-reliability criterion or how precisely that count was estimated. The enrollment entry is not a substitute for the outcome result. The primary population is described as 5 patients with Parkinson’s disease, but the record does not provide a corresponding observed result or explain the relationship between this description and overall enrollment.

The study’s single-group design also sets boundaries on interpretation. Without a comparator, there is no direct estimate of a difference between people using the recording system and a control group. The record cannot support a comparative treatment-effect conclusion. Its stated research aim is to better understand brain activity and how it relates to deep brain stimulation, not to bring a new device to market. The listed primary endpoint measures recorded signals rather than clinical benefit.

The adverse-event counts should be read as descriptive entries for the chronic brain recording group, not as comparative safety evidence. The registry lists serious adverse events, other adverse events, and deaths, but does not list serious-event terms or provide attribution details in the information recorded. The counts alone do not determine whether an event was caused by the device or procedure.

In short, the record establishes the study’s purpose, broad design, and intended primary measure, but it does not report the primary outcome analysis. The result, uncertainty, analysis population, and handling of missing recordings are not reported in the registry record. Those gaps prevent a conclusion about the observed feasibility outcome, while leaving the stated technical research question clear.

14. Why This Trial Matters Statistically

This study illustrates the distinction between a clinical outcome and a technical feasibility outcome. The registered primary measure is a participant count based on whether cortical and subcortical signals were recorded reliably. Such an endpoint can be relevant when the research goal is to develop or evaluate chronic measurement capability. It does not, on its own, answer whether a clinical condition improved.

The case also shows why an outcome definition and an outcome result must be kept separate. The registry describes the measure, population, and timeframe, but lists no analysis. Without the observed count, readers cannot assess how often the recording criterion was met. Without an uncertainty estimate, they cannot judge how precise an estimate might be. An enrollment entry does not fill either gap.

Design also shapes the question a study can answer. A single-group study can describe what was observed in its study group, but it does not offer a randomized comparison. The absence of a comparator is not a flaw to be repaired by statistical language; it is a boundary on the claims supported by the design. For a feasibility study, that boundary helps keep interpretation focused on the recording objective rather than an unmeasured comparative treatment effect.

Finally, registry transparency matters for interpreting feasibility. A reproducible reading would benefit from an operational definition of reliable signals, the handling of missing or unusable recordings, a clearly described analysis population, and a reported primary result with uncertainty. These details are not reported in the registry record. Their absence makes it difficult to assess the endpoint’s precision and reproducibility, while the stated research purpose and design still show why chronic brain-signal recording was the central statistical question.

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 consequential limitation for interpreting the primary endpoint is that the registry record does not report its observed result or analysis. Although the outcome is defined as a count of patients with reliable cortical and subcortical signals, no count meeting that definition is listed. No confidence interval or other uncertainty measure is reported, so the endpoint’s precision cannot be assessed.

The definition of signal reliability is not reported in the registry record. The record also does not describe the assessment process, how repeated recordings contributed to the endpoint, or how recordings that were absent or unusable were handled. These details are important to understanding how consistently the endpoint could be applied and what a participant count represents.

The study is single-group, with no comparator. Its design does not provide a randomized between-group estimate. Masking is recorded as NONE, and the record does not give further detail about outcome assessment procedures. These features should be considered when interpreting an outcome that may involve judgments about signal reliability, although the registry does not describe how those judgments were made.

The record lists enrollment as 9 and describes the primary outcome population as 5 patients with Parkinson’s disease, but does not explain the relationship between the figures or identify the primary analysis population. It does not report a sample-size justification, multiplicity strategy, missing-data methods, or sensitivity analyses. The arm description is incomplete, and the details of its second stated goal are not reported in the registry record. Together, these limits leave the registered purpose and endpoint identifiable, but constrain assessment of conduct, analysis, and results.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Chronic Effects of DBS in Parkinson's Disease and Dystonia — NCT01934296.
• Registry record last updated 2023-04-24; status last verified 2023-04.
• Results first posted 2023-04-24.
• 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

NCT01934296 is a completed, single-group study titled “Chronic Effects of DBS in Parkinson's Disease and Dystonia,” sponsored by the University of California, San Francisco. It lists Parkinson’s disease and isolated dystonia as conditions and Activa PC+S as the device intervention. The study summary describes chronic brain recording following surgical implantation of deep brain stimulation systems, with the aim of understanding brain activity in movement disorders and its relationship to deep brain stimulation.

The registry lists enrollment as 9, a start of 2013-11, and primary completion of 2021-12. The primary outcome is the number of patients with Parkinson’s disease with reliable cortical and subcortical signals recorded using Activa PC+S, with a 24-month timeframe. The record lists one outcome measure and no analyses; an observed primary outcome result is not reported in the registry record.

For the chronic brain recording group, the record lists 0 affected by serious adverse events, 2 affected by other adverse events, and 0 deaths. No serious adverse event terms are listed.