This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Automatic Periodic Stimulation and Continuous Electromyography (EMG) for Facial Nerve Monitoring During Parotidectomy (NCT03172520), a na na study. The primary outcome is Change in Electromyography (EMG).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03172520 |
| Phase | NA |
| Condition | Parotid Gland Disorders |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 10 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Mayo Clinic |
| Results posted | Yes |
2. Clinical Question
Population
The registry identifies parotid gland disorders and describes monitoring during parotidectomy. It does not report detailed eligibility criteria or a fuller description of the intended participant population. The registry lists enrollment as 10, but the primary outcome record says the study was terminated before data were collected.
Intervention
The planned approach combined a Facial Nerve Monitor with an automatic periodic stimulating electrode, referred to as the APS electrode, during parotidectomy surgery. The stated purpose was to document the device's safety and potentially prevent postoperative facial nerve weakness. The registry does not report procedural details or whether the planned monitoring was carried out.
Comparator
No separate comparator group is described. The study is listed as single-group, with allocation recorded as NA. It therefore does not set up a like-for-like comparison between APS monitoring and another monitoring strategy or no monitoring. Without a comparator, the registry record cannot establish a comparative treatment effect.
Primary question
The primary outcome was change in electromyography, with measurements planned at baseline and approximately 3 hours. The registry describes EMG as a technique for recording electrical activity produced by skeletal muscles. Although the study's stated purpose also mentions safety and possible prevention of postoperative facial nerve weakness, the primary outcome listed is EMG change. The record says data were not collected.
3. Trial Design
NCT03172520 is registered as an interventional study of device-based facial nerve monitoring during parotidectomy. The registry lists the study as single-group, with no allocation and no masking. The described group was to receive Facial Nerve Monitor use together with an APS electrode during surgery. No separate control arm is listed, so this design does not provide a randomized or concurrent comparison.
The registry lists enrollment as 10. It gives a start date of 2017-01-01 and a primary completion date of 2017-06-30, and the study status is terminated. The primary outcome record states that termination occurred because of limitations in timing and personnel and that data were not collected. Thus, the enrollment entry should not be read as evidence that outcome data were obtained from 10 participants.
The primary outcome was change in EMG, with a timeframe of baseline and approximately 3 hours. The record lists one outcome measure and no analyses. The phase is recorded as NA. The registry does not report a statistical analysis plan, a sample-size justification for the trial, interim analyses, detailed eligibility criteria, or further information about how the planned measurements were to be summarized. The design description identifies an intended monitoring procedure, but the record does not establish that the procedure was implemented or that the planned outcome assessments took place.
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
| Stage | Facial Nerve Monitoring With APS Electrode |
|---|---|
| STARTED | 10 |
| COMPLETED | 0 |
| NOT COMPLETED | 10 |
Analysis population for the primary outcome, as defined in the registry: Study terminated due to limitations in timing and personnel. Data was not collected
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.
| Characteristic | Unit | Facial Nerve Monitoring With APS Electrode |
|---|---|---|
| Participants analysed | 10 | |
| Age, Continuous | years | 59.67 (SD 14.47) |
| Sex: Female, Male: Female | Participants | 2 |
| Sex: Female, Male: Male | Participants | 8 |
| Race and Ethnicity Not Collected | Participants | — |
| Region of Enrollment: United States | participants | 10 |
6. Primary Endpoint
The registry lists the primary outcome as Change in Electromyography (EMG), measured over baseline, approximately 3 hours.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is titled change in electromyography (EMG), with assessment planned at baseline and approximately 3 hours. EMG records electrical activity produced by skeletal muscles. In this study's context, the endpoint was intended to capture an electrical signal associated with facial nerve monitoring during parotidectomy. The registry gives no unit, summary parameter, or measure of dispersion for this endpoint, so it does not define a specific numerical scale or the planned form of the change calculation.
In general, a change endpoint compares a measurement after an intervention or procedure with a baseline measurement. This can describe how a measured signal changes over time within the assessed group. It does not, by itself, show what would have happened under a different monitoring approach; a comparator is needed to estimate a between-group contrast. Nor does a change in an electrical signal necessarily answer every clinical question named in a study's rationale. The record's broader stated purpose includes documenting device safety and potentially preventing postoperative facial nerve weakness, but the listed primary endpoint is EMG change.
Crucially, the registry says that data were not collected because the study was terminated due to limitations in timing and personnel. There is therefore no observed EMG change to interpret, and no reported endpoint estimate or uncertainty interval. The measurement rationale can be described, but the endpoint cannot be used to draw a conclusion from this registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central statistical fact is that the planned primary outcome has no collected data in the registry record. The study was terminated because of limitations in timing and personnel, and the primary outcome record explicitly states that data were not collected. Consequently, no change in EMG, group summary, treatment contrast, confidence interval, or hypothesis test result is reported. The record lists no analyses.
The listed enrollment is 10, but that number does not supply an endpoint result. It should not be interpreted as the number of participants with usable EMG observations: the primary outcome record says those data were not collected. The registry also does not give a participant flow account that would clarify how many people were approached, enrolled, treated, or assessed before termination. Those details are not reported in the registry record.
The design is single-group and has no comparator. Even if EMG measurements had been available, a within-group change would describe change over time in the monitored group; it would not alone distinguish the effect of the APS electrode from the effects of surgery, other aspects of care, or changes in measurement conditions. A comparative causal estimate would require an appropriate comparison and a plan for handling differences between groups. No such comparator is listed.
The adverse-event record lists 10 at risk, 0 affected by serious events, 0 affected by other events, and 0 deaths. These are the registry's recorded counts, not a substitute for the missing EMG outcome. The absence of listed affected participants should be interpreted cautiously because the study was terminated and the record does not describe the completeness or duration of adverse-event ascertainment. It cannot establish that no adverse events occurred.
The registry includes assumptions for a planning illustration based on a stated fraction of an observed effect, two-sided significance level 0.05, equal allocation between two arms, and a normal approximation. Those assumptions do not create an observed effect or an analysis result. Since the record reports no collected primary outcome data, it provides no trial-specific observed effect on which to base a substantive interpretation. Any sample-size illustration is planning information, not observed power or evidence of an effect.
Overall, the record describes an intended device-monitoring study and its planned EMG endpoint, but not a completed outcome analysis. Its results cannot establish whether EMG changed, whether the device was safe, or whether postoperative facial nerve weakness was prevented. These questions remain unanswered by the posted results.
9. Statistical Methods Explained
The statistical interpretation begins with the design. The registry classifies the study as single-group, with allocation recorded as NA and masking recorded as NONE. The intervention description combines the Facial Nerve Monitor and APS electrode during parotidectomy. No separate comparator group is listed. These features matter because statistical methods can only estimate contrasts that the design and collected data support. Here, the record reports that the primary outcome data were not collected, so no endpoint analysis is available to evaluate.
What does a single-group design estimate?
General statistical context: a single-group study can describe measurements within the participants who receive the intervention, such as a baseline value and a later value. If observations are collected, a change summary may quantify the average or distribution of within-person changes, depending on the prespecified analysis. A single-group change does not, by itself, isolate the effect of the intervention. Events over time, surgery, measurement conditions, and other influences may also contribute to observed change. A concurrent comparator can help address the question of what would have occurred under an alternative approach, though interpretation still depends on design and analysis.
For this registry record, the primary endpoint is change in EMG from baseline to approximately 3 hours. The record does not give a unit, a statistical parameter, a dispersion measure, or a detailed analysis method. It also reports that no data were collected. Thus, it is not possible to identify an actual estimand from the posted results: there is no reported endpoint quantity estimated from participant data. The intended outcome can be described, but no mean change, median change, individual trajectory, or other numerical summary is reported.
Why are effect estimates and confidence intervals absent?
General statistical context: an effect estimate summarizes the quantity an analysis aims to describe, while a confidence interval expresses the precision of that estimate under the assumptions of the method. A confidence interval is not a guarantee that the true value lies within its limits; it is a statistical procedure for representing uncertainty. Its usefulness depends on having relevant observations and a defined analysis. With no collected EMG data, this record has no estimate to accompany with an interval. The lack of an interval is not evidence of a precise null result; it reflects the lack of endpoint analysis.
A hypothesis test would likewise require an analysis question, data, and an applicable model. The registry reports zero analyses and no result for the primary endpoint. Therefore, there is no reported p-value to interpret. A non-significant result would mean something different from no result: the former would be a test outcome based on data, whereas the latter is the situation described in this record.
What role would dispersion and distributional assumptions play?
General statistical context: dispersion describes how much individual observations vary around a summary. It matters because uncertainty in an estimated mean or contrast depends on both the amount of information and variability in the observations. Distributional assumptions concern the shape or behavior of the data or model errors, and can affect the validity of an analysis. For repeated EMG measurements, an analysis would also need to account for the relationship between observations from the same participant. The registry does not report a chosen model, a dispersion statistic, or distributional diagnostics, and the absence of collected data means none can be assessed from the posted results.
More generally, a method should be chosen to match the endpoint scale, design, and data structure. If a continuous measurement is analyzed as a change score, the analyst needs a clear definition of that score and an approach to missing or unusable measurements. If repeated observations are modeled directly, their within-participant dependence should be recognized. These are general methodological considerations, not descriptions of analyses performed in this study.
How should planning illustrations be distinguished from trial results?
The record describes assumptions for a sample-size planning illustration: two-sided significance level 0.05, equal allocation between two arms, normal approximation, and an effect to detect expressed as a stated fraction of the observed effect. The general purpose of a planning calculation is to explore how many participants might be needed under specified assumptions. Such a calculation is not an observed treatment effect, does not show what the trial found, and is not observed power. The record's actual study design is single-group, while the illustration's assumptions refer to equal allocation between two arms; those planning assumptions should not be mistaken for the design that was conducted.
Planning based on an observed effect also depends on having an observed effect estimate. The primary outcome record says data were not collected, so the posted results do not establish an observed EMG effect for this study. Any planning illustration associated with the record should therefore be read only as a conditional calculation under its stated assumptions, not as evidence from an endpoint analysis. The registry does not report the trial's own sample-size justification.
What can be concluded from the available statistical record?
The available information supports a description of the intended study structure and endpoint, along with the explicit statement that the study was terminated before data collection. It does not support estimation of EMG change, statistical precision, a comparative effect, or a test of a clinical hypothesis. General statistical methods can explain what those analyses would mean if suitable observations were available, but they cannot replace absent data. The registry does not report an analysis plan, handling of repeated observations, missing-data method, or analysis population. No particular method should be attributed to the investigators beyond the information recorded.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one outcome measure and no analyses. It identifies change in EMG as the primary outcome, planned at baseline and approximately 3 hours. It does not describe a multiplicity strategy, such as how statistical error would be controlled if several outcomes, time points, or subgroup comparisons were tested. Since the record reports no collected data and no analyses, there are no reported tests whose multiplicity can be evaluated. A multiplicity adjustment should not be inferred.
The missing-data issue is more fundamental than a small number of incomplete measurements. The primary outcome record says data were not collected because the study was terminated due to limitations in timing and personnel. The registry does not report whether any participants had partial measurements, whether any other outcomes were collected, or whether there were observations outside the primary endpoint. Those details are not reported in the registry record. There is no basis for describing an imputation method, complete-case analysis, or sensitivity analysis as having been used.
The registry does not identify an analysis population, such as all enrolled participants or participants with an evaluable measurement. It lists enrollment as 10, but does not provide participant flow or an endpoint-specific analysis count. The enrollment entry therefore cannot be taken as an analysis denominator. General statistical context: defining the analysis population and documenting missingness help readers understand which participants contribute to an estimate and how missing observations might affect it. In this record, no endpoint estimate is reported, and the analysis population is not reported in the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Facial Nerve Monitoring With APS Electrode | 0 | 10 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Facial Nerve Monitoring With APS Electrode | 0 of 10 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Facial Nerve Monitoring With APS Electrode | 0 of 10 |
The adverse-event record lists the Facial Nerve Monitoring With APS Electrode group with 10 participants at risk for serious events and 0 affected; it also lists 10 at risk for other events and 0 affected. The recorded death count is 0. These figures describe what is entered in the registry, not a complete demonstration that no events occurred.
The primary outcome record says the study was terminated because of limitations in timing and personnel and that data were not collected. The registry does not explain how adverse events were collected, the observation period, or the completeness of safety follow-up. It is therefore unclear what exposure or follow-up the at-risk counts represent. The zero affected counts should be read as zero events recorded in these registry fields, not proof of zero risk or assurance that the device is safe. The posted safety counts also do not answer the missing primary EMG question.
12. What the Result Does, and Does Not, Mean
The record establishes that investigators planned to use a Facial Nerve Monitor with an APS electrode during parotidectomy, and that they identified change in EMG as the primary outcome. It also records a study status of terminated and explains that data were not collected because of limitations in timing and personnel. Those details describe the study's intent and why its primary outcome is unavailable.
The record does not show an observed EMG change. It does not provide a result indicating whether the electrical activity increased, decreased, or remained similar from baseline to approximately 3 hours. No effect estimate, confidence interval, or analysis result is reported. The absence of such a result must not be treated as evidence that the device had no effect or that it had a particular effect.
The study's stated purpose includes documenting safety and potentially preventing postoperative facial nerve weakness. But the registry does not report an analyzed outcome for postoperative weakness, and it reports no collected primary endpoint data. The adverse-event fields list zero affected participants, but the record does not describe enough about ascertainment and follow-up to turn those entries into a conclusion about safety. No comparison group is listed, so the record also cannot support a comparative claim against another monitoring strategy.
General statistical context: the strength of a conclusion depends on the data collected, the design, and the precision of the estimates. A study plan alone does not establish an outcome. In this case, the appropriate interpretation is that the posted results leave the planned clinical and statistical questions unanswered. This is different from a finding of no difference, no risk, or no clinical benefit; none of those conclusions is reported.
13. Why This Trial Matters Statistically
This trial matters statistically because it illustrates the distinction between a registered study plan and an analyzable result. A registry entry can describe the intervention, endpoint, and intended timing, yet still contain no outcome evidence if data are not collected. For NCT03172520, the intended EMG assessment is identifiable, but the record states that termination occurred before data collection. Recognizing that distinction prevents an empty result from being misread as a null finding.
The design also clarifies why questions and methods must align. The stated broader purpose includes safety and potential prevention of postoperative facial nerve weakness, while the listed primary endpoint is EMG change. Those are related but distinct questions. A physiological measurement can describe a signal; it is not automatically a direct measure of every clinical outcome named in a rationale. The registry does not report results for either question.
The single-group structure is another important statistical feature. Without a comparator, a change within the monitored group would not by itself estimate what would have happened under another approach. Here, no change can be summarized because data were not collected, but the design description still matters for understanding what kinds of conclusions the planned study could support.
Finally, the registry's planning assumptions should be kept separate from observed evidence. Sample-size calculations are conditional on assumptions about the target effect, design, and statistical method. They are not observed power and do not recover information absent from the trial. The record does not report a trial-specific sample-size justification. Together, these features make careful reading of registry status, endpoint definitions, analysis availability, and design essential when judging what a clinical study can tell readers.
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 direct limitation is that the registry states that data were not collected. The study was terminated due to limitations in timing and personnel, so the primary EMG outcome has no posted result. This prevents assessment of the planned change from baseline to approximately 3 hours and precludes estimation of its precision.
The record also lists no analyses and no comparator group. Its single-group design would limit comparative interpretation even if within-group measurements had been available. The registry does not report detailed eligibility criteria, participant flow, the number with completed procedures, or an endpoint analysis population. Enrollment is listed as 10, but the record does not establish how many participants contributed outcome observations.
Important endpoint details are absent: no unit, summary parameter, or dispersion measure is specified. The statistical analysis plan, handling of repeated measurements, and missing-data methods are not reported in the registry record. The registry also does not report interim analyses or the study's own sample-size justification. These omissions limit evaluation of planned statistical methods, though the absence of collected outcome data is the primary barrier to interpreting results.
Safety interpretation is limited by the lack of reported detail about event definitions, ascertainment, and follow-up. Although the registry lists zero affected participants in its serious and other event fields, these entries cannot establish complete event capture or rule out risk. The record's termination and missing outcome data should remain central when interpreting all reported counts.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Automatic Periodic Stimulation and Continuous Electromyography (EMG) for Facial Nerve Monitoring During Parotidectomy — NCT03172520.
- Registry record last updated 2020-01-18; status last verified 2020-01.
- Results first posted 2020-01-18.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
NCT03172520 is a terminated, single-group device study of Facial Nerve Monitor use with an APS electrode during parotidectomy. The registry lists enrollment as 10 and gives a study start of 2017-01-01 and primary completion of 2017-06-30. Masking is recorded as NONE, allocation as NA, and the phase as NA.
The primary outcome was change in EMG, planned from baseline to approximately 3 hours. The registry states that the study was terminated because of limitations in timing and personnel and that data were not collected. It lists one outcome measure and no analyses. The adverse-event fields record 0 affected by serious events, 0 affected by other events, and 0 deaths among 10 at risk in each event category. These entries do not replace the missing endpoint data or establish complete safety ascertainment.