Neural Signatures of Parkinson's Disease: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Neural Signatures of Parkinson's Disease (NCT01990313), a na na study. The primary outcome is Change in Resting State Beta Band Power Over Time.

2. Clinical Question

The study asks whether beta band power in neural signals changes between the initial programming visit and the 12 month follow-up visit, after deep brain stimulation therapy is turned off. The registry places that question within a broader effort to measure abnormal movement and relate it to neural activity over time. The primary endpoint focuses on beta band power rather than a direct measure of movement.

3. Trial Design

This was a completed, single-group study sponsored by Stanford University. The registry reports enrollment of 15 and lists Activa PC+S as the device intervention. It does not describe a parallel control group or randomized allocation; allocation is recorded as NA. Masking is recorded as none. The registry’s design information therefore supports reading the primary analysis as a comparison of measurements over time, not as a controlled estimate of the effect of assigning one treatment rather than another.

The listed study start is 2013-10, and the primary completion is 2016-11. The primary endpoint compares beta band power at the initial programming visit with beta band power at the 12 month follow-up visit. In both cases, the description specifies that deep brain stimulation therapy was turned off for the measurement. The beta band is defined as 13-30 Hz, and power is normalized to average beta band power at the initial programming visit.

The registry describes a linear mixed model for repeated measures over time and says a regression beta coefficient was obtained to assess whether power changed significantly. The coefficient, its confidence interval, and a p-value are not reported in the registry record. The record does not report the protocol’s sample-size justification, detailed recruitment procedures, or other design features beyond the information. The intended broader purpose was to measure abnormal movements alongside neural activity and track their changes over time; the primary endpoint specifically addresses neural beta band power.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: 2 subjects excluded; 1 lost to follow-up, 1 had ECG artifact in neural signal

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 Resting State Beta Band Power Over Time, measured over Baseline and 1 Year.

The primary endpoint is change in resting state beta band power over time. It measures beta band power in a neural signal at the initial programming visit and at the 12 month follow-up visit, with deep brain stimulation turned off at both measurement occasions as described in the registry. The frequency band is 13-30 Hz. Power is normalized to the average beta band power at the initial programming visit, making the follow-up measurement interpretable relative to that baseline reference.

The registry identifies the endpoint’s unit as a regression beta coefficient. In general, a regression coefficient expresses a modeled relationship between a predictor and an outcome; in this analysis, the model relates measurement time to beta band power. A repeated-measures model is used to analyze observations taken over time from study participants. The registry says this coefficient was used to determine whether beta power changed significantly between baseline and the 12 month follow-up.

The endpoint is used to quantify a neural signal over time, consistent with the study’s stated aim of relating neural activity to abnormal movements. It is not itself a direct measure of movement. The numerical coefficient, its direction and magnitude, and measures of uncertainty are not reported in the registry record, so the amount and precision of any estimated change cannot be assessed from the record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a linear mixed model for repeated measures over time. In general, a repeated-measures analysis is designed for data in which outcomes are collected from the same participants on more than one occasion. Measurements from one person may be related to one another, so treating them as if they came from unrelated people can misrepresent uncertainty. A mixed model can represent that within-participant structure while estimating the association between measurement time and the outcome. The registry does not report the model’s detailed specification, such as its covariance structure or the exact fixed and random effects.

What does the regression coefficient represent?

In general, a regression coefficient describes the modeled change in an outcome associated with a predictor, conditional on the model’s assumptions. Here, time is the comparison of interest, and beta band power is the outcome. The registry calls the coefficient a regression beta coefficient and identifies its unit as a regression beta coefficient. It does not state the estimate, standard error, confidence interval, or p-value. As a result, the magnitude and direction of the fitted time relationship are not available for interpretation.

The registry’s endpoint description says the coefficient was used to determine whether beta power changed significantly between the initial programming visit and the 12 month follow-up. In general, statistical significance is assessed by comparing an estimate with its uncertainty under a specified model. A p-value, when reported, measures how compatible the data are with a stated null model under the analysis assumptions; it does not quantify the clinical importance of a difference. A confidence interval, when reported, gives a range of values compatible with the estimate and its uncertainty under the method used. Neither is reported for this endpoint, so the statistical evidence and precision cannot be reconstructed from the record.

How should normalization be understood?

The endpoint description states that beta band power is normalized to average beta band power at the initial programming visit. In general, normalization expresses a measurement relative to a reference value, which can make the scale easier to compare over time. Here, the baseline measurement is the reference. The registry does not provide the detailed formula used for normalization or the resulting normalized values. Thus, the precise scale and the numerical interpretation of a coefficient cannot be recovered from the description alone.

The frequency range is specified as 13-30 Hz. That defines which part of the neural signal is treated as beta band power for this endpoint. The signal was measured at baseline and 1 year after turning off deep brain stimulation therapy, according to the endpoint description. The record does not provide further measurement procedures, device settings, signal-processing details, or quality-control thresholds.

What can be inferred from the design?

Because this is a single-group study and allocation is recorded as NA, the primary analysis is a longitudinal comparison rather than a randomized between-group contrast. In general, repeated observations can describe how a measured outcome varies over time, but a time comparison alone does not establish that a particular device or intervention caused the change. Other influences that vary over time may contribute, and a separate control comparison is not described in the registry.

The model choice is consistent with accounting for repeated measurements, but the registry does not report the full statistical analysis plan. The handling of missing measurements, assumptions about the distribution of model errors, model diagnostics, sensitivity analyses, and prespecified decision thresholds are not reported in the registry record. These omissions limit independent assessment of the analysis, even though the general model family and primary time comparison are stated.

The enrollment figure is 15. The primary endpoint description notes 2 subjects excluded, identifying 1 lost to follow-up and 1 with ECG artifact in the neural signal. The record does not state the final analytic sample size, whether exclusions were applied before or after model fitting, or whether all available observations were included for participants with incomplete follow-up. A mixed model can sometimes use incomplete repeated measurements under specified assumptions, but whether and how that approach was used in this study is not reported.

The registry reports 1 analysis. That count does not reveal the complete set of model choices or whether alternative analyses were conducted. A planning illustration, where included, should be understood as a planning calculation rather than observed evidence or observed power. The record does not report a trial-specific sample-size justification. No additional numerical result should be inferred from the stated model description alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures and 1 analysis, and identifies change in resting state beta band power over time as the primary endpoint. It does not report a multiplicity adjustment or a plan for interpreting multiple outcomes. In general, when several outcomes or tests are examined, the chance of at least one apparently unusual result can increase. Methods for addressing this include prespecifying a primary outcome or adjusting inference across tests. The registry record does not describe whether such methods were used. The one-analysis count does not establish that only one statistical test or endpoint was considered.

For the primary endpoint, the population description notes that 2 subjects were excluded: 1 was lost to follow-up and 1 had ECG artifact in the neural signal. The record does not report the final number analyzed, the amount or pattern of missing measurements, or whether any imputation or other missing-data method was used. It also does not specify whether the mixed model included all available observations or required complete observations at both time points.

In general, missing-data handling matters because the participants with observed follow-up measurements may differ from those without them. The potential for bias depends on the reasons for missingness and the analysis assumptions. The registry identifies reasons for the two exclusions but does not provide enough information to evaluate those assumptions or assess sensitivity to alternative missing-data approaches.

The analysis population is not otherwise defined in the registry record. It does not state whether participants were analyzed according to a prespecified population definition, nor does it describe protocol deviations or exclusions beyond the two noted for the primary endpoint. Details about an interim analysis plan, multiplicity strategy, and sensitivity analyses are not reported in the registry record.

11. Safety Results

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

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 15 participants at risk in the Activa PC+S group for serious adverse events and 0 affected. For other adverse events, it also lists 15 at risk and 0 affected. No serious adverse event terms are listed. These figures describe the registry’s reported counts for the group; they do not provide event-level detail or a stated observation window.

Zero affected in a registry entry means that no affected participants are recorded for that category in the posted results. It should not be interpreted as proof that an event is impossible or that the study rules out uncommon harms. In general, the precision of safety estimates depends on the amount of observation and the completeness of event reporting. The registry record does not provide enough detail about follow-up duration for safety reporting, event collection procedures, or the handling of events outside the listed categories to assess those aspects.

The death count is not reported in the registry record. It is therefore not appropriate to interpret the blank death figure as a reported zero. The safety entries should be read as limited descriptive counts, not as a comparative safety analysis: the study has a single listed group and no randomized control group described.

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

The registry record establishes that the study examined normalized neural beta band power at baseline and 1 year, with deep brain stimulation turned off for the measurements. It identifies the band as 13-30 Hz and describes a linear mixed model for repeated measures. It also reports enrollment of 15 and notes 2 exclusions from the primary endpoint analysis, one due to loss to follow-up and one due to ECG artifact.

What the record does not establish is the numerical amount or direction of change. The primary regression coefficient is not reported, and neither are its confidence interval or p-value. Consequently, the posted information does not allow readers to judge how large or precise the estimated change was, or whether the analysis met a statistical significance threshold. The analysis description alone is not an outcome result.

Even if a numerical change were available, a single-group comparison over time would describe the observed trajectory rather than isolate the causal effect of a device. No randomized treatment comparison is described. Changes across visits could reflect the study conditions as well as other influences over time, and the registry does not report a control group that would help distinguish those possibilities.

The broader study purpose concerns objective measurement of abnormal movements in relation to neural activity and tracking how they change over time. The primary endpoint is a neural signal measure, not a direct clinical measure of movement or a patient-centered outcome. The record does not report whether the endpoint was associated with a change in movement, nor does it report a treatment benefit or lack of benefit.

The adverse-event entries record 0 affected for both serious and other events among 15 at risk in the listed group. The death count is not reported in the registry record. These entries are limited safety descriptions and do not establish the absence of risk. Taken together, the record is informative about the study question, measurement timing, and intended analysis, but it does not contain the numerical primary result needed to evaluate the observed change.

13. Why This Trial Matters Statistically

This study is statistically notable for framing a neural measurement as a longitudinal endpoint. Repeated measurements can be useful when the research question concerns change within participants over time. The registry’s use of a linear mixed model reflects a method designed for repeated observations, where measurements from the same person may be statistically related. The endpoint also makes the reference explicit: beta band power is normalized to the initial programming visit.

The record illustrates why a method description and a result are not interchangeable. It states that a regression beta coefficient was used to assess change, but does not report the coefficient or its uncertainty. Without those quantities, readers cannot evaluate the direction, magnitude, or precision of the estimated relationship. Statistical interpretation depends not only on naming a model but also on reporting its estimate and uncertainty.

The design is also important. A single-group study can describe the pattern in an enrolled cohort, but the within-study comparison over time is not a randomized contrast. That distinction limits causal interpretation. The study’s stated purpose—to relate abnormal movements to neural activity over time—also encompasses a broader scientific aim than this primary endpoint alone. Beta band power is a neural signal measure, and the registry does not report a direct relationship between that endpoint and movement outcomes.

Finally, the registry notes exclusions related to loss to follow-up and signal artifact, while not detailing the final analysis population or missing-data strategy. These reporting gaps matter because readers need to understand who contributed data and how incomplete observations were handled. The statistical value of the record lies in its explicit endpoint and general model description, alongside a clear reminder that incomplete reporting can prevent assessment of the primary result.

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 most important limitation for interpreting the primary endpoint is that the numerical regression coefficient is not reported in the registry record. No confidence interval, standard error, or p-value is given. The direction, size, and precision of the estimated change therefore cannot be assessed from the record.

The design is single-group, with allocation recorded as NA and masking recorded as none. The endpoint compares two time points rather than randomized groups. This design can describe within-study change but does not provide a randomized control comparison for attributing any change to the device or separating it from other time-related influences.

The registry reports enrollment of 15 and says 2 subjects were excluded from the primary endpoint analysis: 1 was lost to follow-up and 1 had ECG artifact in the neural signal. It does not report the final analyzed count, how missing measurements were handled, or whether the analysis included participants with incomplete repeated observations. The details needed to judge potential bias from missingness are not reported in the registry record.

Further methodological details are also absent. The record names a linear mixed model but does not give its full specification, diagnostics, or sensitivity analyses. It does not report a multiplicity strategy, a trial-specific sample-size justification, or an interim analysis plan. The primary endpoint concerns beta band power, not a direct movement outcome, and the record does not report a numerical link between the signal and abnormal movements. Safety entries are descriptive, with no event terms listed and the death count not reported.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Neural Signatures of Parkinson's Disease — NCT01990313.
• Registry record last updated 2018-02-20; status last verified 2018-01.
• Results first posted 2018-01-16.
• 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

NCT01990313, titled “Neural Signatures of Parkinson's Disease,” is a completed, single-group study sponsored by Stanford University. The registry lists enrollment of 15, a study start of 2013-10, and primary completion in 2016-11. Activa PC+S is listed as the device intervention. Allocation is recorded as NA and masking as none.

The primary endpoint compares normalized resting state beta band power at the initial programming visit and the 12 month follow-up, with deep brain stimulation turned off. The band is defined as 13-30 Hz, and the registry describes analysis with a linear mixed model for repeated measures. It notes 2 subjects excluded from the primary analysis, 1 lost to follow-up and 1 with ECG artifact.

The primary coefficient and its uncertainty are not reported in the registry record. The listed group has 15 at risk and 0 affected for serious and other adverse events; the death count is not reported.