Injury of the external branch of the superior laryngeal nerve in thyroid surgery.

The external branch of the superior laryngeal nerve (EBSLN) innervates the cricothyroid muscle (CTM) to promote lengthening and thinning of the vocal fold, thus increasing voice pitch. The close relation with the superior thyroid vessels (STV) puts the EBSLN in risk every time the superior pole of the thyroid is dissected. It travels downward to innervate the CTM, lateral to the thyroid cartilage and to the inferior pharyngeal constrictor muscle (IPCM), being eventually covered by this muscle fibers as it approaches its entry point. During its descending course, the EBSLN curves and crosses the STV posteriorly. The lower this crossing occurs in the neck, the higher the risk of surgical damage to the nerve by transection, traction, entrapment, thermal damage or disrupted blood supply. The chances of surgical trauma are also increased by size and weight of the specimen, shorter neck length and non-white ethnicity. Voice changes following thyroid surgery are common and multifactorial. The actual rate of vocal impairment due to EBSLN injury is unclear, since changes to the everyday speaking voice can be minimal and laryngeal findings are usually subtle and controversial. CTM electroneuromyography (EMG) is the most accurate tool to diagnose abnormal EBSLN conductivity, but it is technically difficult and barely applicable in routine practice. Recommended approaches to prevent injury include: (I) individual distal ligature of the STV by the thyroid capsule; (II) visual identification of the nerve and its trajectory and (III) electrostimulation with either observation of CTM twitch or intraoperative nerve monitoring (IONM) via dedicated endotracheal tube electrodes. There is accumulating evidence that a combination of visual and standardized electrophysiological EBSLN identification with meticulous division of the STV improves preservation rates. IONM bears the additional benefits of prognostication, quantification and documentation of neural function once it allows intraoperative laryngeal EMG.

Primary tumor staging for oral cancer and a proposed modification incorporating depth of invasion: an international multicenter retrospective study.

IMPORTANCE: The current American Joint Committee on Cancer (AJCC) staging system for oral cancer demonstrates wide prognostic variability within each primary tumor stage and provides suboptimal staging and prognostic information for some patients. OBJECTIVE: To determine if a modified staging system for oral cancer that integrates depth of invasion (DOI) into the T categories improves prognostic performance compared with the current AJCC T staging. DESIGN, SETTING, AND PARTICIPANTS: Retrospective analysis of 3149 patients with oral squamous cell carcinoma treated with curative intent at 11 comprehensive cancer centers worldwide between 1990 and 2011 with surgery ± adjuvant therapy, with a median follow-up of 40 months. MAIN OUTCOMES AND MEASURES: We assessed the impact of DOI on disease-specific and overall survival in multivariable Cox proportional hazard models and investigated for institutional heterogeneity using 2-stage random effects meta-analyses. Candidate staging systems were developed after identification of optimal DOI cutpoints within each AJCC T category using the Akaike information criterion (AIC) and likelihood ratio tests. Staging systems were evaluated using the Harrel concordance index (C-index), AIC, and visual inspection for stratification into distinct prognostic categories, with internal validation using bootstrapping techniques. RESULTS: The mean and median DOI were 12.9 mm and 10.0 mm, respectively. On multivariable analysis, DOI was a significantly associated with disease-specific survival (P < .001), demonstrated no institutional prognostic heterogeneity (I² = 6.3%; P = .38), and resulted in improved model fit compared with T category alone (lower AIC, P < .001). Optimal cutpoints of 5 mm in T1 and 10 mm in T2-4 category disease were used to develop a modified T staging system that was preferred to the AJCC system on the basis of lower AIC, visual inspection of Kaplan-Meier curves, and significant improvement in bootstrapped C-index. CONCLUSIONS AND RELEVANCE: We propose an improved oral cancer T staging system based on incorporation of DOI that should be considered in future versions of the AJCC staging system after external validation.

Minimum nodal yield in oral squamous cell carcinoma: defining the standard of care in a multicenter international pooled validation study.

PURPOSE: There is evidence to suggest that a nodal yield <18 is an independent prognostic factor in patients with clinically node negative (cN0) oral squamous cell carcinoma (SCC) treated with elective neck dissection (END). We sought to evaluate this hypothesis with external validation and to investigate for heterogeneity between institutions. PATIENTS AND METHODS: We analyzed pooled individual data from 1,567 patients treated at nine comprehensive cancer centers worldwide between 1970 and 2011. Nodal yield was assessed with Cox proportional hazard models, stratified by study center, and adjusted for age, sex, pathological T and N stage, margin status, extracapsular nodal spread, time period of primary treatment, and adjuvant therapy. Two-stage random-effects meta-analyses were used to investigate for heterogeneity between institutions. RESULTS: In multivariable analyses of patients undergoing selective neck dissection, nodal yield <18 was associated with reduced overall survival [hazard ratio (HR) 1.69; 95 % confidence interval (CI) 1.22-2.34; p = 0.002] and disease-specific survival (HR 1.88; 95 % CI 1.21-2.91; p = 0.005), and increased risk of locoregional recurrence (HR 1.53; 95 % CI 1.04-2.26; p = 0.032). Despite significant differences between institutions in terms of patient clinicopathological factors, nodal yield, and outcomes, random-effects meta-analysis demonstrated no evidence of heterogeneity between centers in regards to the impact of nodal yield on disease-specific survival (p = 0.663; I (2) statistic = 0). CONCLUSION: Our data confirm that nodal yield is a robust independent prognostic factor in patients undergoing END for cN0 oral SCC, and may be applied irrespective of the underlying patient population and treating institution. A minimum adequate lymphadenectomy in this setting should include at least 18 nodes.