DBS Under General Anesthesia: Comparison To The Standard Technique: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for DBS Under General Anesthesia: Comparison To The Standard Technique (NCT01997398), a registered phase not stated study. The primary outcome is "Off" and "On" Medication Unified Parkinson's Disease Rating III Score (UPDRS).

2. Clinical Question

The clinical question is whether the described approach to electrode placement can be evaluated against the standard technique using motor-function assessments. The registry describes an initial experience with direct anatomical targeting under general anesthesia without neurophysiology, rather than a clearly randomized comparison. That distinction matters: a difference between groups, if reported, could not automatically be attributed to the surgical approach without considering how participants entered each group and whether the groups were comparable.

The primary measure captures motor impairment using a clinician-administered rating scale. The registry also lists Parkinson’s Disease Quality-39 Score as a secondary outcome. It does not report outcome values for either measure, so the record does not establish the direction or size of any change or comparison. Details of the standard technique and the comparison groups are not reported in the registry record.

3. Trial Design

The record describes a completed study titled “DBS Under General Anesthesia: Comparison To The Standard Technique.” Its official title identifies the general-anesthesia approach as an initial experience and comparison with the standard technique. The listed condition is Parkinson’s disease. The sponsor is St. Joseph’s Hospital and Medical Center, Phoenix. The registry gives a start date of 2012-11, a primary completion date of 2014-12, a status of COMPLETED, and an enrollment of 35.

The study summary describes placing deep brain stimulation electrodes under general anesthesia without microelectrode recordings. A portable head CT scanner was used to verify accuracy intra-operatively. The listed group is bilateral GPi DBS surgery under general anesthesia. The record does not describe the comparator procedure in enough detail to characterize it beyond the title’s reference to the standard technique.

The allocation method is not stated. The registry information also indicates that the arms are not a like-for-like control comparison. Therefore, the design should not be read as a randomized trial establishing a causal contrast between techniques. The record does not explain how participants were assigned or selected for the different approaches, or whether other factors differed between groups.

The primary outcome was the mean “Off” and “On” Medication Unified Parkinson’s Disease Rating III Score, assessed pre-operatively and 6 months post-operatively. A trained movement disorders clinician performed prospective baseline and follow-up assessments. Parkinson’s Disease Quality-39 Score is listed as a secondary outcome. Although the record is marked completed, it does not report numerical results for these outcomes or explain the detailed analysis plan.

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.

Before assignment: Patients with advanced Parkinson's disease eligible for deep brain stimulation (DBS) surgery

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.

Population: Patients who underwent bilateral GPi DBS surgery under general anesthesia

6. Primary Endpoint

The registry lists the primary outcome as "Off" and "On" Medication Unified Parkinson's Disease Rating III Score (UPDRS), measured over pre-operatively and 6 months post-operatively.

The primary endpoint is the mean score on the MDS modified UPDRS III, a clinician-administered assessment of motor function. The registry describes assessments before surgery and 6 months post-operatively, with participants assessed in both off-medication and on-medication states. The off-medication assessment followed holding Parkinson’s disease medications for 12 h. The scale ranges from 0, indicating no motor function deficit, to 132, indicating the highest motor function deficit; higher scores therefore represent greater motor deficit on the scale.

A motor rating scale is used to quantify clinical status in a consistent way, allowing scores to be described and compared across assessment times or groups. Reporting both medication states distinguishes the assessments made under those stated conditions; it does not, by itself, tell whether a change is attributable to surgery or to another factor. The registry says there were no subscales.

The record identifies the mean as the summary measure and standard deviation as the measure of dispersion. A mean describes the average score, while a standard deviation describes how spread out individual scores are around that average. Neither the baseline nor follow-up means and standard deviations are reported in the registry record, and no comparative estimate or confidence interval is reported. Consequently, the endpoint definition is clear, but the posted record does not permit interpretation of the observed motor-score results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a continuous primary outcome summarized by a mean and standard deviation. These are descriptive statistics: the mean locates the average score, and the standard deviation describes how much individual scores vary around that average. The outcome is the MDS modified UPDRS III, assessed in two medication states at baseline and 6 months post-operatively. Those assessment conditions and times define what the registered endpoint concerns; they do not specify the statistical model used to compare measurements.

What would a mean comparison describe?

In general, a comparison of means describes the difference in average scores between defined groups or assessment times. To interpret that comparison, the analysis needs to identify the observations being contrasted, the population included, and the handling of participants without complete measurements. Repeated assessments on the same participant are related rather than independent. A suitable analysis must account for that relationship if it models measurements together. The registry record does not report whether the analysis used a repeated-measures approach, separate comparisons, or another method.

For an outcome measured in both off-medication and on-medication states, the contrast also needs a clear definition. It could concern a change over time within a state, a comparison between groups at a time point, or another prespecified quantity. These are different statistical questions. The registry gives the assessment states and times but does not report the exact contrast or model specification. It is therefore not possible to infer which estimate the listed analysis was intended to produce.

How should uncertainty be read?

In general, a confidence interval expresses uncertainty around an estimate under the stated statistical model and assumptions. A narrow interval indicates greater precision than a wide interval, but precision does not establish that an estimate is unbiased or clinically important. The interval also does not correct for a weak comparison design. The registry record does not report a confidence interval or a numerical estimate for the primary outcome.

A standard deviation is not the same as a standard error or confidence interval. The standard deviation describes variation among participant scores; a standard error describes uncertainty in an estimated quantity. Conflating these measures can lead to incorrect conclusions about how precisely the average or group contrast has been estimated. Although the registered outcome specifies standard deviation as its dispersion measure, no observed values are reported.

What can the design support?

In general, random allocation can help balance measured and unmeasured prognostic factors across groups, though it does not guarantee balance in a particular study. Here, the allocation method is not stated, and the registry indicates that the arms are not a like-for-like control comparison. The record does not explain how the groups were formed or provide the information needed to evaluate their comparability. A statistical adjustment, if one was used, cannot be assumed: adjustment variables and methods are not reported in the registry record.

The title’s comparison with the standard technique is not sufficient to establish that the comparison was randomized or controlled in a way that supports causal attribution. General statistical interpretation distinguishes an observed association between group membership and outcome from a causal effect of the procedure. The latter requires design and analysis assumptions that cannot be assessed from the available description.

What do the planning assumptions mean?

The registry’s planning illustration is described as using the observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It is explicitly a planning illustration rather than the trial’s own design justification. For continuous outcomes, such illustrations can show how a hypothetical future study’s required participants per arm would vary with the assumed effect to detect. Planning for a fraction of the observed effect represents a smaller target effect than planning for the full observed effect. These calculations are sensitive to the observed estimate and its uncertainty, and they should not be treated as evidence of observed power or as proof that the study was adequately sized.

The outcome estimates needed to assess the observed effect are not reported in the registry record. The sample-size justification for the original study is also not reported in the registry record. The planning assumptions therefore should not be mistaken for a documented prospective design decision, and no conclusion about adequacy of the completed study’s size can be drawn from them.

For a continuous endpoint, the normal approximation is a modeling assumption used in the planning illustration. General statistical practice considers whether the outcome distribution and sampling behavior make such an approximation reasonable. The registry does not report distributional checks or a justification for the approximation. That absence does not establish that the approximation was inappropriate; it means its suitability cannot be assessed from the record.

Which analysis details remain unknown?

The record lists one analysis, but does not report its method, estimand, covariates, handling of repeated measures, or treatment of missing outcome observations. It also does not report whether the analysis was adjusted or unadjusted. These omissions matter because different analysis choices can target different quantities and can produce estimates with different uncertainty. Without the specification and results, there is no basis to reconstruct the sponsor’s analysis or to make a recalculated estimate.

In general, statistical significance and clinical importance answer different questions. A small p-value, if one were available, would not indicate the size or practical importance of a difference. A substantial estimate with a wide confidence interval could remain uncertain. In this record, neither numerical estimates nor inferential statistics are posted, so the findings cannot be classified by magnitude, precision, or statistical significance.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Pre-DBS Bilateral GPi DBS Under General Anesthesia", "Post-DBS Bilateral GPi DBS Under General Anesthesi", "Pre-DBS Bilateral GPi DBS Under General Anesthesia", "Post-DBS Bilateral GPi DBS Under General Anesthesi")
n   <- c(35, 34, 35, 34)
m   <- c(48.4, 28.9, 23.52, 22.56)
sp  <- c(13.8, 12.5, 10.4, 12.8)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Pre-DBS Bilateral GPi DBS Under General Anesthesia  35  48.400  13.800  43.660  53.140
CARM  Post-DBS Bilateral GPi DBS Under General Anesthesi  34  28.900  12.500  24.539  33.261
CARM  Pre-DBS Bilateral GPi DBS Under General Anesthesia  35  23.520  10.400  19.947  27.093
CARM  Post-DBS Bilateral GPi DBS Under General Anesthesi  34  22.560  12.800  18.094  27.026

11. Multiplicity, Missing Data and Analysis Populations

The registry identifies the MDS modified UPDRS III as the primary outcome and Parkinson’s Disease Quality-39 Score as a secondary outcome. It also lists one analysis. The record does not describe how the analysis relates to the outcomes, medication states, assessment times, or comparison groups. It does not report a multiplicity strategy, such as a prespecified hierarchy or an adjustment for testing several contrasts. Therefore, the record does not show how the risk of chance findings across multiple questions was addressed.

Multiplicity is a general statistical concern when several outcomes or contrasts are examined. The more opportunities there are to identify an apparently notable result, the more important it is to distinguish prespecified primary questions from exploratory analyses. The existence of a primary and secondary outcome does not itself reveal how many tests were conducted or how their results were interpreted. Those details are not reported in the registry record.

Missing-data methods are also not described. The record does not report completion of the 6-month assessments, the number of observations included in outcome analyses, reasons for missing measurements, or any imputation or sensitivity analysis. These details are important because analyses based only on participants with observed follow-up can be affected if missingness is related to outcome or group assignment.

The analysis population is not reported in the registry record. It is therefore unclear which enrolled participants contributed to each outcome analysis or whether a defined intention-to-treat or other population was used. The listed enrollment should not be assumed to be the denominator for every analysis. Without these details, neither the potential influence of missing data nor the scope of the reported population can be assessed.

12. 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 a group titled bilateral GPi DBS surgery under general anesthesia. For serious adverse events, it reports 35 participants at risk and 0 affected. For other adverse events, it reports 35 at risk and 0 affected. These figures describe the posted counts for that listed group; they do not establish that events were absent outside the recorded definitions or observation period.

A zero count is not equivalent to proof of zero risk. In general, an event count is interpretable only alongside the event definitions, follow-up duration, ascertainment procedures, and completeness of reporting. Those details are not reported in the registry record. The figures therefore provide a limited description of the posted safety information rather than a comprehensive assessment of safety.

Deaths are not reported in the registry record. No serious adverse-event terms are listed. The record does not provide enough detail to determine whether the absence of listed terms reflects no events, the scope of event coding, or another reporting feature. These safety counts should be read separately from the primary motor-function outcome, which also lacks posted numerical results.

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

The record establishes that a completed study examined an approach to bilateral GPi deep brain stimulation under general anesthesia and named the standard technique as a comparison. It documents an approach using direct anatomical targeting without microelectrode recordings and intra-operative portable head CT verification. It also defines a motor-function endpoint assessed before surgery and 6 months after surgery in off-medication and on-medication states.

What the record does not establish is the size or direction of any outcome change, whether the intervention differed from the standard technique on motor scores, or how precise any such difference was. Numerical primary and secondary outcome results are not reported in the registry record. The record therefore cannot support a conclusion that one technique produced better or worse motor function or quality of life.

The non-randomized status and lack of a like-for-like control comparison also limit causal interpretation. Allocation is not stated, and the group formation and comparator details are not reported. In general, differences between non-equivalent groups may reflect characteristics of the groups as well as the procedures being compared. Statistical adjustment can sometimes address measured differences, but no adjustment method or covariates are reported, and adjustment cannot be presumed to remove all bias.

The listed safety counts are limited to the registry’s recorded figures: 0 serious adverse events and 0 other adverse events among 35 participants at risk in the listed group. They do not establish complete safety ascertainment, and deaths are not reported in the registry record. Taken together, the record is useful for identifying the study question, intervention description, endpoint, and a small amount of safety information. It is not a complete report of comparative effectiveness or a basis for a clinical recommendation.

14. Why This Trial Matters Statistically

This record illustrates why a clearly named endpoint and a completed status do not by themselves provide enough information to judge a clinical comparison. The motor-function outcome is defined with its scale range, assessment states, and timing. Yet without the observed means, standard deviations, comparative estimate, and uncertainty, readers cannot determine the magnitude, direction, or precision of the outcome findings. Registration details and posted results answer different questions.

It also highlights the importance of design information. A comparison named in a study title can sound straightforward, but the allocation method is not stated and the arms are not a like-for-like control comparison. Those features shape what a group contrast can mean. Statistical methods cannot make a non-equivalent comparison automatically causal; the design, group formation, and analysis assumptions all matter.

The record further shows why outcome reporting should include more than a score definition. An interpretable analysis would ordinarily make clear which contrast was estimated, which participants contributed, how repeated measurements and missing observations were handled, and how uncertainty was quantified. Those details are not reported in the registry record, so readers cannot evaluate robustness or precision.

Finally, the adverse-event counts demonstrate the limits of reading zeros without context. Event definitions, observation period, and completeness of ascertainment are essential for interpreting a zero count, but are not reported. The statistical lesson is not that the posted information has no value: it identifies what was studied and what was measured. Rather, careful conclusions must stay within the boundary between a registered study description and numerical evidence that the record does not contain.

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 registry record leaves important design and reporting details unresolved. Allocation is not stated, and the arms are not a like-for-like control comparison. The standard technique is named as the comparator, but its procedural details and the way the groups were formed are not reported in the registry record. These omissions limit assessment of comparability and causal interpretation.

The primary outcome is described in detail, but its numerical results are absent. The record does not report baseline or follow-up means and standard deviations, group contrasts, confidence intervals, or p-values. It likewise does not report numerical results for the listed quality-of-life outcome. Consequently, the direction, size, and precision of the clinical outcomes cannot be evaluated.

The record does not report the analysis population, the number of observations contributing to each outcome, missing-data methods, or the analysis model. It also does not describe adjustment variables, handling of the repeated assessments, or the multiplicity strategy. Without these details, the analysis cannot be reproduced or assessed for sensitivity to alternative assumptions.

Safety reporting is limited to the posted counts for the listed group. Event definitions, ascertainment procedures, follow-up completeness, and the period over which adverse events were collected are not reported in the registry record. Deaths are not reported. The planning assumptions are explicitly described as an illustration rather than the study’s own design justification, and the original sample-size justification is not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: DBS Under General Anesthesia: Comparison To The Standard Technique — NCT01997398.
• Registry record last updated 2016-01-01; status last verified 2015-12.
• Results first posted 2015-11-25.
• 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

NCT01997398 is a completed study of bilateral GPi deep brain stimulation under general anesthesia for Parkinson’s disease, with the standard technique named as a comparison. The summary describes electrode placement without microelectrode recordings and intra-operative accuracy verification using a portable head CT scanner. The registry lists an enrollment of 35, a start date of 2012-11, and a primary completion date of 2014-12.

The primary outcome is the mean MDS modified UPDRS III motor score, assessed pre-operatively and 6 months post-operatively in off-medication and on-medication states. Parkinson’s Disease Quality-39 Score is listed as a secondary outcome. Numerical outcome results and detailed analysis methods are not reported in the registry record. Allocation is not stated, and the arms are not a like-for-like control comparison. The listed safety figures are 0 serious adverse events and 0 other adverse events among 35 participants at risk in the listed group; deaths are not reported.