Highlights
In a retrospective cross-sectional study from a tertiary thyroid surgery center, systematic postdissection vagal stimulation (V2) achieved 100% sensitivity for postoperative vocal cord palsy, compared with 57.9% for postdissection recurrent laryngeal nerve stimulation (R2) alone.
Nine nerves at risk showed intact R2 responses but absent V2 signals; 7 of these cases were followed by impaired postoperative vocal mobility, indicating that RLN-only assessment can miss clinically important dysfunction.
Routine V2 testing altered intraoperative decision-making, including unexpected conversion from planned total thyroidectomy to lobectomy in patients with first-side loss of signal, a strategy intended to avoid bilateral vocal cord palsy.
The study reinforces the International Nerve Monitoring Study Group recommendation that the complete stimulation sequence should include V1, R1, R2, and V2 rather than stopping at RLN reassessment alone.
Background and Clinical Context
Thyroidectomy is among the most commonly performed endocrine operations, and although generally safe in experienced hands, injury to the recurrent laryngeal nerve (RLN) remains one of its most feared complications. Unilateral RLN dysfunction may produce hoarseness, weak cough, aspiration risk, and reduced quality of life. Bilateral vocal cord palsy is less common but potentially catastrophic, with postoperative airway compromise that may require urgent reintubation or tracheostomy.
Visual identification of the RLN is a long-standing surgical standard, but intraoperative neuromonitoring (IONM) has become widely adopted as an adjunct, particularly in bilateral thyroid surgery, reoperative cases, cancer operations, and other higher-risk settings. The most clinically important value of IONM may be less about preventing every nerve injury and more about helping the surgeon detect a loss of signal (LOS) on the first side. When a convincing first-side LOS occurs during a planned total thyroidectomy, many surgeons will consider staging the procedure and defer the contralateral resection, thereby reducing the risk of bilateral vocal cord paralysis.
For that strategy to work safely, the monitoring protocol must be sensitive enough to identify true functional compromise. The International Nerve Monitoring Study Group has recommended a standardized stimulation sequence: V1, predissection vagus nerve stimulation; R1, predissection RLN stimulation; R2, postdissection RLN stimulation; and V2, postdissection vagus nerve stimulation. The rationale is physiologically important. Distal RLN stimulation confirms that the segment of nerve being stimulated can conduct, but proximal vagal stimulation tests the full neural pathway from the vagus through the RLN to the laryngeal muscles. A discrepancy between preserved R2 and absent V2 may indicate a proximal lesion, traction injury, or other conduction abnormality not detected when stimulating only the exposed distal RLN.
The study by Van Den Berg, Griffin, and Sheahan addresses a practical question with major implications for operative strategy: does systematic V2 stimulation identify postoperative vocal cord palsy more reliably than relying on R2 alone?
Proposed Article Structure
This article is organized into five clinically oriented sections: background and rationale; study design and methods; key results; expert commentary and implications for surgical strategy; and conclusion, funding, and references. This structure mirrors how practicing surgeons and perioperative clinicians interpret operative monitoring studies: first understanding the clinical problem, then assessing methodological strength, then focusing on actionable findings.
Study Design and Methods
Design and setting
This was a retrospective cross-sectional study performed at an academic tertiary referral center for thyroid surgery. The investigators evaluated consecutive patients undergoing thyroidectomy between February 2024 and October 2025 with intermittent IONM performed in the full sequence V1, R1, R2, V2.
Participants
Eligible patients were those undergoing thyroidectomy with intermittent IONM and postoperative laryngoscopy. Exclusion criteria were sensible and clinically relevant: preoperative vocal cord palsy, deliberate or inadvertent RLN section, or absence of postoperative laryngoscopic assessment. These exclusions help isolate electrophysiologic prediction of postoperative dysfunction rather than confounding from known preexisting or transection injuries.
Comparator
The principal internal comparison was the diagnostic performance of R2 versus V2 stimulation for predicting impaired vocal cord mobility on the first postoperative day. The investigators also compared the findings with a previous cohort comprising 1159 nerves at risk in which vagal stimulation had been performed selectively rather than systematically.
Outcome measures
The primary endpoint was postoperative vocal mobility on day 1 laryngoscopy. The authors report standard test-performance metrics, including sensitivity, specificity, negative predictive value, and positive predictive value. In the context of surgical decision-making, sensitivity is particularly important because a false-negative result may encourage completion thyroidectomy despite occult first-side nerve dysfunction.
Key Findings
Study population
The study included 240 patients with a mean age of 50 years (SD, 15 years); 188 patients, or 78.3%, were female. Across these operations, there were 353 nerves at risk (NARs), the conventional unit of analysis in thyroid surgery nerve monitoring studies.
Frequency of loss of signal
Among the 353 NARs, 43 nerves (12.2%) had LOS, of which 33 (9.3%) represented persistent LOS. These rates deserve attention. They are higher than permanent RLN injury rates typically reported in expert practice, which reflects the fact that electrophysiologic LOS includes transient and potentially recoverable conduction abnormalities in addition to clinically evident palsy.
The critical discordance: intact R2 but absent V2
The most important result is that 9 of the 33 persistent LOS events (27.3%) were identified only on V2 stimulation, without preceding LOS or other electrophysiologic warning events on the RLN. In other words, more than one-quarter of persistent signal losses would have been missed if the surgeon had relied only on distal postdissection RLN stimulation.
This discordant pattern is not just an electrical curiosity. Of the 9 cases with intact R2 but absent V2 response, 7 patients, or 77.8%, had impaired postoperative vocal mobility. Clinically, this means that a seemingly reassuring R2 trace may be misleading when proximal conduction failure exists.
Diagnostic performance
The sensitivity of R2 stimulation for postoperative vocal cord palsy was 57.9%, whereas the sensitivity of V2 stimulation was 100%. This is the central finding of the paper. A test used to decide whether to proceed with contralateral thyroid resection should ideally have very high sensitivity, because missed injuries carry asymmetric clinical consequences. In this regard, systematic V2 appears markedly superior.
The abstract does not provide the full set of raw data needed to independently reconstruct specificity, negative predictive value, and positive predictive value for the present cohort, but the authors state these metrics were compared. The headline message remains that V2 improved identification of patients with postoperative vocal dysfunction relative to R2 alone.
Impact on intraoperative strategy
Six patients who had been planned for total thyroidectomy instead underwent lobectomy only because the operative plan was changed intraoperatively. Notably, 2 of these changes were triggered by unexpected V2 LOS. This is a meaningful practice-level outcome: V2 did not simply improve diagnostic sensitivity on paper; it changed what the surgeon did in real time.
That point is central to the study’s stated clinical relevance. The practical purpose of first-side nerve monitoring is to support safer bilateral surgery. If systematic V2 identifies occult first-side dysfunction that would otherwise be missed, then routine V2 may help prevent the highest-stakes complication of all, bilateral vocal cord palsy.
Comparison with prior selective-vagal cohort
In the earlier cohort in which vagal nerve stimulation was performed selectively, the overall sensitivity of IONM for impaired vocal cord mobility was 83.3%. By comparison, the current systematic-V2 approach reached 100% sensitivity. Although this is not a randomized comparison and likely reflects differences in case mix and practice patterns over time, it supports the authors’ argument that selective vagal stimulation is inferior to routine completion of the full monitoring sequence.
Expert Commentary and Clinical Interpretation
Why V2 can outperform R2
The physiologic explanation is persuasive. Distal RLN stimulation after dissection tests only the segment of nerve distal to the stimulation point. If injury occurs proximally, at the vagus-RLN junction, or if there is traction-related conduction block that is not traversed by distal stimulation, then R2 may remain present despite clinically relevant laryngeal dysfunction. Postdissection vagal stimulation tests the entire efferent motor pathway more proximally and therefore better approximates true functional integrity.
This finding is consistent with the broader IONM literature, which has long emphasized that vagal stimulation is required both at the start and the end of the case to document circuit integrity, exclude equipment-related artifact, and confirm that the response persists after thyroid lobe mobilization and hemostasis.
Implications for staged thyroidectomy
The study matters most for surgeons performing planned bilateral procedures. When first-side LOS occurs, the surgeon faces a difficult choice: proceed and risk bilateral dysfunction, or stage the operation and accept a second anesthetic and possible delay in definitive treatment. That choice depends heavily on confidence in the monitoring result. A protocol with limited sensitivity may falsely reassure the surgeon into completing the contralateral side. The present data suggest that stopping at R2 may create exactly that problem.
From a patient-safety perspective, the threshold for abandoning contralateral surgery should be lower when there is unexplained V2 loss, even if the exposed RLN still stimulates distally. This is especially relevant in benign bilateral disease, Graves disease, compressive goiter, and low-risk differentiated thyroid cancer where delayed completion surgery is often feasible. In contrast, in invasive malignancy or airway-threatening disease, surgeons may still need to proceed despite signal abnormalities, but such decisions should be individualized and documented.
Methodological strengths
The study has several strengths. It examined a consecutive clinical series at a high-volume tertiary center, used a standardized stimulation sequence aligned with international recommendations, and required postoperative laryngoscopy rather than relying on subjective voice symptoms alone. The endpoint, postoperative vocal mobility on day 1, is objective and clinically relevant.
Limitations
Several caveats should temper interpretation. First, the study is retrospective and observational, so it cannot eliminate confounding or fully establish that systematic V2 itself caused better outcomes. Second, the sample size is modest, especially for the number of palsy events, which means performance estimates may have wide uncertainty even though confidence intervals are not reported in the abstract. Third, comparisons with the earlier selective-vagal cohort are historical rather than concurrent, leaving room for temporal changes in surgical technique, monitoring expertise, equipment, and case complexity.
Another limitation is that the primary endpoint was day 1 vocal mobility, not long-term permanent palsy. Early dysfunction is important, but some deficits recover. Still, for intraoperative decision-making, immediate postoperative function is the correct operational endpoint because it is what staged-thyroidectomy strategy aims to protect.
The study also does not resolve whether all centers using intermittent IONM can reproduce these results. Performance may vary with anesthetic management, endotracheal tube positioning, stimulation parameters, troubleshooting protocols, and surgeon experience. Continuous IONM, increasingly used in some settings, may detect impending injury earlier than intermittent stimulation and could modify the relative importance of end-of-case V2 testing, though not replace it entirely.
Alignment with guidelines and prior evidence
The International Nerve Monitoring Study Group has previously published standardized guidelines emphasizing the V1-R1-R2-V2 sequence for both quality assurance and interpretability. The present study offers contemporary empirical support for that recommendation. It also complements the broader literature showing that the most meaningful benefit of IONM may lie in preventing bilateral palsy through staged surgery rather than simply lowering aggregate RLN injury rates across all cases.
For clinicians and health systems, the message is practical: an incomplete monitoring sequence may undermine the very rationale for using IONM in bilateral thyroidectomy. If monitoring is adopted, it should be performed in a technically rigorous and standardized manner.
Clinical Takeaways for Practice
First, postoperative vagal stimulation should not be viewed as optional quality control. Based on these data, it is a core component of functional nerve assessment at the end of thyroid lobe dissection.
Second, preserved R2 alone should not automatically reassure the surgeon that the first-side nerve is intact. Discordant intact R2 and absent V2 appears clinically meaningful and may predict postoperative vocal cord dysfunction.
Third, when unexpected V2 LOS occurs during a planned total thyroidectomy, particularly in benign or low-urgency disease, consideration should be given to halting the operation after the first side and staging completion surgery.
Fourth, any center using IONM should ensure standardized troubleshooting algorithms for signal loss, including checks of tube position, equipment integrity, anesthetic factors, and stimulation consistency before major operative decisions are made.
Conclusion
This study by Van Den Berg and colleagues suggests that routine postdissection vagal stimulation substantially improves the sensitivity of intraoperative neuromonitoring for postoperative vocal cord palsy compared with postdissection RLN stimulation alone. The clinically important observation is not merely better signal detection, but better identification of patients in whom completing bilateral surgery may be unsafe. In modern thyroid surgery, systematic V2 stimulation appears less like an optional extra step and more like the functional endpoint that makes IONM actionable. Prospective multicenter studies would help define generalizability, but the current evidence supports treating systematic V2 stimulation as the procedural standard when IONM is used to guide strategy during thyroidectomy.
Funding and ClinicalTrials.gov
The abstract does not report a funding source. No ClinicalTrials.gov registration number is provided, which is not unusual for a retrospective cross-sectional study.
References
1. Van Den Berg NH, Griffin J, Sheahan P. Systematic Postdissection Vagal Stimulation and Surgical Strategy During Thyroidectomy. JAMA Otolaryngology–Head & Neck Surgery. Published online May 7, 2026. PMID: 42096212. Available at: https://pubmed.ncbi.nlm.nih.gov/42096212/
2. Randolph GW, Dralle H, Abdullah H, et al. Electrophysiologic recurrent laryngeal nerve monitoring during thyroid and parathyroid surgery: international standards guideline statement. Laryngoscope. 2011;121 Suppl 1:S1-S16.
3. Schneider R, Sekulla C, Machens A, Lorenz K, Thanh PN, Dralle H. Dynamics of loss and recovery of the nerve monitoring signal during thyroidectomy predict early postoperative vocal fold function. Head Neck. 2016;38 Suppl 1:E1144-E1151.
4. Dionigi G, Bacuzzi A, Boni L, et al. International neuromonitoring study group guidelines for intraoperative monitoring of thyroid and parathyroid surgery. Although terminology and updates vary across publications, guideline-based standardized vagal and RLN stimulation remains central to contemporary monitored thyroidectomy practice.