Discerning a smile - The intricacies of analysis of post-neck dissection asymmetry

Variability of the Cervical Branch Depending on the Facial Nerve Branching Pattern and Anthropometric Type of the Head

(1) Background: Considering that the specialty literature supplies only general data about the variability of the cervical branch of the facial nerve, this study aimed to determine this branch's variation and individual peculiarities depending on the nerve branching pattern and anthropometric type of the head. (2) Methods: The study was conducted on 75 hemifaces of adult formalized cadavers. Ahead of anatomical dissection, each head was measured to establish the anthropometric type, according to Franco and colleagues. The branching patterns were then distributed according to the Davis classification. (3) Results: The number of cervical branches (CB) of the facial nerve varied from one to five branches, with the following rate: 1 CB (61.3%), 2 CB (28%), 3 CB (6.7%), 4 CB (2.7%), and 5 CB (1.3%). Seven branching patterns of the facial nerve were revealed: Type I in 18.7%, Type II in 14.7%, Type III in 20%, Type IV in 14.6%, Type V in 5.3%, Type VI in 18.7%, and Type NI in 8% (bizarre types). According to the branching pattern, the mean numbers of the cervical branches were as follows: Type I-1.6 ± 1.02; Type II-1.4 ± 0.50; Type III-1.4 ± 0.50; Type IV-1.4 ± 0.67; Type V-2.0 ± 1.41; Type VI-1.8 ± 1.12; and Type-NI-1.8 ± 0.75; p = 0.599. According to the anthropometric type of the head, the mean number of CB in the mesocephalic type (MCT) was 1.5 ± 0.82, in the dolichocephalic type (DCT), 1.7 ± 0.87, and in the brachycephalic type, (BCT) 1.8 ± 1.04; p = 0.668. (4) Conclusions: The cervical branch of the facial nerve varies depending on the facial nerve branching pattern and the anthropometric type of the head. The highest degree of variation was characteristic of BCT and Type V and the lowest, of MCT and Types II, III, and IV.

Use of neuromuscular blockade for neck dissection and association with iatrogenic nerve injury

BACKGROUND

Cranial nerve injury is an uncommon but significant complication of neck dissection. We examined the association between the use of intraoperative neuromuscular blockade and iatrogenic cranial nerve injury during neck dissection.

METHODS

This was a single-center, retrospective, electronic health record review. Study inclusion criteria stipulated patients > 18 years who had ≥ 2 neck lymphatic levels dissected for malignancy under general anesthesia with a surgery date between 2008 - 2018. Use of neuromuscular blockade during neck dissection was the primary independent variable. This was defined as any use of rocuronium, cisatracurium, or vecuronium upon anesthesia induction without reversal with sugammadex prior to surgical incision. Univariate tests were used to compare variables between those patients with, and those without, iatrogenic cranial nerve injury. Multivariable logistic regression determined predictors of cranial nerve injury and was performed incorporating Firth's estimation given low prevalence of the primary outcome.

RESULTS

Our cohort consisted of 925 distinct neck dissections performed in 897 patients. Neuromuscular blockade was used during 285 (30.8%) neck dissections. Fourteen instances (1.5% of surgical cases) of nerve injury were identified. On univariate logistic regression, use of neuromuscular blockade was not associated with iatrogenic cranial nerve injury (OR: 1.73, 95% CI: 0.62 - 4.86, p = 0.30). There remained no significant association on multivariable logistic regression controlling for patient age, sex, weight, ASA class, paralytic dose, history of diabetes, stroke, coronary artery disease, carotid atherosclerosis, myocardial infarction, and cardiac arrythmia (OR: 1.87, 95% CI: 0.63 - 5.51, p = 0.26).

CONCLUSIONS

In this study, use of neuromuscular blockade intraoperatively during neck dissection was not associated with increased rates of iatrogenic cranial nerve injury. While this investigation provides early support for safe use of neuromuscular blockade during neck dissection, future investigation with greater power remains necessary.