-->PONE-D-25-62561-->-->Neurological events and unanticipated risks after locoregional anesthesia (NEURAL): protocol for a multicenter prospective observational study-->-->PLOS One

Dear Dr. De Cassai,

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Richa Gupta

Academic Editor

PLOS One

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Additional Editor Comments:

EDITORIAL DECISION

This is a well-written and engaging manuscript that addresses an important topic. The study is clearly structured, and the findings are presented in a coherent manner. After careful evaluation of the reviewers’ comments and a thorough assessment of the overall quality, originality, and relevance of the submission, the editorial decision is: MINOR REVISION.

The reviewers have provided constructive suggestions aimed primarily at improving clarity, presentation, and minor methodological or interpretative aspects. Please find attached reviewer’s comments:

REVIEWER 1 – MINOR REVISION

The NEURAL study is a large, multicenter prospective observational project designed to determine the true incidence of complications—such as nerve injury, hematoma, pneumothorax, and LAST—following single-shot regional anesthesia. It will enroll over 3,396 adult patients across more than 40 Italian centers, with follow-up extending up to one year for persistent neurological deficits. The study collects detailed patient, procedural, and follow up data to identify both overall incidence and modifiable risk factors. Ultimately, its findings aim to improve patient safety, refine clinical practices, and support updated evidence based guidelines.

Minor revisions:

1. Lack of methods to account for clustering

The protocol does not address the implications of enrolling patients across more than 40 centers, where outcomes may be correlated within institutions due to shared practices, operator skill, equipment, or workflow. Without incorporating statistical methods that account for clustered data—such as multilevel (mixed effects) models, generalized estimating equations (GEE), or random effects logistic regression—standard errors may be underestimated, leading to inflated Type I error rates. Clarifying how center level variation will be handled is essential.

2. No stated strategy for handling missing data

Given the extended follow up period (up to one year for neurological deficits), loss to follow up and incomplete covariate data are likely. The protocol does not describe any approach for addressing missingness, such as multiple imputation, inverse probability weighting, or sensitivity analyses. A predefined plan is necessary to ensure unbiased estimates and transparent reporting.

3. Absence of multiple comparison considerations

With numerous block types, predictors, and secondary outcomes, the probability of false positive findings increases. Although it is reasonable for exploratory observational studies to avoid overly conservative adjustments, the protocol should acknowledge this issue and clarify whether procedures such as Bonferroni correction, false discovery rate control, or hierarchical testing will be considered in interpreting results.

4. Rare event logistic regression concerns

The expected incidence of complications (~0.5%) presents challenges for conventional logistic regression, which can yield biased or unstable estimates when events are sparse. The protocol does not discuss alternative methods tailored to rare events, such as Firth penalized likelihood or exact logistic regression, which may improve model performance and inferential reliability.

REVIEWER 2 – ACCEPT

Dear Authors!

Seems to be a well planed study. I don't say it is absolute necessary, but worth thinking to incorporate the early signs of local anaesthetic systemic toxictiy (or is it included in neurological alteration?) and whether they needed intervention or not.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

-->Comments to the Author

1. Does the manuscript provide a valid rationale for the proposed study, with clearly identified and justified research questions?

The research question outlined is expected to address a valid academic problem or topic and contribute to the base of knowledge in the field.-->

Reviewer #1: Yes

Reviewer #2: Yes

**********

-->2. Is the protocol technically sound and planned in a manner that will lead to a meaningful outcome and allow testing the stated hypotheses?

The manuscript should describe the methods in sufficient detail to prevent undisclosed flexibility in the experimental procedure or analysis pipeline, including sufficient outcome-neutral conditions (e.g. necessary controls, absence of floor or ceiling effects) to test the proposed hypotheses and a statistical power analysis where applicable. As there may be aspects of the methodology and analysis which can only be refined once the work is undertaken, authors should outline potential assumptions and explicitly describe what aspects of the proposed analyses, if any, are exploratory.-->

Reviewer #1: Yes

Reviewer #2: Yes

**********

-->3. Is the methodology feasible and described in sufficient detail to allow the work to be replicable?

Descriptions of methods and materials in the protocol should be reported in sufficient detail for another researcher to reproduce all experiments and analyses. The protocol should describe the appropriate controls, sample size calculations, and replication needed to ensure that the data are robust and reproducible.-->

Reviewer #1: Yes

Reviewer #2: Yes

**********

-->4. Have the authors described where all data underlying the findings will be made available when the study is complete?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception, at the time of publication. The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception, at the time of publication. The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.-->

Reviewer #1: No

Reviewer #2: Yes

**********

-->5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.-->

Reviewer #1: Yes

Reviewer #2: Yes

**********

-->6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above and, if applicable, provide comments about issues authors must address before this protocol can be accepted for publication. You may also include additional comments for the author, including concerns about research or publication ethics.

You may also provide optional suggestions and comments to authors that they might find helpful in planning their study.

(Please upload your review as an attachment if it exceeds 20,000 characters)-->

Reviewer #1: The NEURAL study is a large, multicenter prospective observational project designed to determine the true incidence of complications—such as nerve injury, hematoma, pneumothorax, and LAST—following single-shot regional anesthesia. It will enroll over 3,396 adult patients across more than 40 Italian centers, with follow-up extending up to one year for persistent neurological deficits. The study collects detailed patient, procedural, and follow‑up data to identify both overall incidence and modifiable risk factors. Ultimately, its findings aim to improve patient safety, refine clinical practices, and support updated evidence‑based guidelines.

Minor revisions:

1. Lack of methods to account for clustering

The protocol does not address the implications of enrolling patients across more than 40 centers, where outcomes may be correlated within institutions due to shared practices, operator skill, equipment, or workflow. Without incorporating statistical methods that account for clustered data—such as multilevel (mixed‑effects) models, generalized estimating equations (GEE), or random‑effects logistic regression—standard errors may be underestimated, leading to inflated Type I error rates. Clarifying how center‑level variation will be handled is essential.

2. No stated strategy for handling missing data

Given the extended follow‑up period (up to one year for neurological deficits), loss to follow‑up and incomplete covariate data are likely. The protocol does not describe any approach for addressing missingness, such as multiple imputation, inverse‑probability weighting, or sensitivity analyses. A predefined plan is necessary to ensure unbiased estimates and transparent reporting.

3. Absence of multiple‑comparison considerations

With numerous block types, predictors, and secondary outcomes, the probability of false‑positive findings increases. Although it is reasonable for exploratory observational studies to avoid overly conservative adjustments, the protocol should acknowledge this issue and clarify whether procedures such as Bonferroni correction, false discovery rate control, or hierarchical testing will be considered in interpreting results.

4. Rare‑event logistic regression concerns

The expected incidence of complications (~0.5%) presents challenges for conventional logistic regression, which can yield biased or unstable estimates when events are sparse. The protocol does not discuss alternative methods tailored to rare events, such as Firth‑penalized likelihood or exact logistic regression, which may improve model performance and inferential reliability.

Reviewer #2: Dear Authors!

Seems to be a well planed study. I don't say it is absolute necessary, but worth thinking to incorporate the early signs of local anaesthetic systemic toxictiy (or is it included in neurological alteration?) and whether they needed intervention or not.

**********

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Reviewer #1: No

Reviewer #2: Yes: Istvan BataiIstvan Batai

**********

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Neurological events and unanticipated risks after locoregional anesthesia (NEURAL): protocol for a multicenter prospective observational study

PONE-D-25-62561R1

Dear Dr. De Cassai,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Richa Gupta

Academic Editor

PLOS One

Additional Editor Comments (optional):

The authors have adequately addressed all the concerns raised by the reviewers. The revisions have improved the clarity, accuracy, and overall quality of the manuscript. In its current form, the article is suitable for acceptance.

Reviewers' comments:

Reviewer's Responses to Questions

-->Comments to the Author

1. Does the manuscript provide a valid rationale for the proposed study, with clearly identified and justified research questions?

The research question outlined is expected to address a valid academic problem or topic and contribute to the base of knowledge in the field.-->

Reviewer #1: Yes

**********

-->2. Is the protocol technically sound and planned in a manner that will lead to a meaningful outcome and allow testing the stated hypotheses?

The manuscript should describe the methods in sufficient detail to prevent undisclosed flexibility in the experimental procedure or analysis pipeline, including sufficient outcome-neutral conditions (e.g. necessary controls, absence of floor or ceiling effects) to test the proposed hypotheses and a statistical power analysis where applicable. As there may be aspects of the methodology and analysis which can only be refined once the work is undertaken, authors should outline potential assumptions and explicitly describe what aspects of the proposed analyses, if any, are exploratory.-->

Reviewer #1: Yes

**********

-->3. Is the methodology feasible and described in sufficient detail to allow the work to be replicable?

Descriptions of methods and materials in the protocol should be reported in sufficient detail for another researcher to reproduce all experiments and analyses. The protocol should describe the appropriate controls, sample size calculations, and replication needed to ensure that the data are robust and reproducible.-->

Reviewer #1: Yes

**********

-->4. Have the authors described where all data underlying the findings will be made available when the study is complete?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception, at the time of publication. The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception, at the time of publication. The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.-->

Reviewer #1: Yes

**********

-->5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.-->

Reviewer #1: Yes

**********

-->-->

**********

-->7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our For information about this choice, including consent withdrawal, please see our Privacy Policy..-->

Reviewer #1: No

**********