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Kobayashi et al. Mini-invasive Surg 2020;4:30 I http://dx.doi.org/10.20517/2574-1225.2020.12 Page 3 of 8

Table 1. Patient characteristics and surgical outcomes after technique modification
Conventional group (n = 57) Modified group (n = 20) P value
Gender 1.00
Male:Female 42:15 15:5
Age 0.71
Median (IQR) 67 (17) 64 (16)
Body mass index 0.53
Median (IQR) 21.3 (3.5) 21.0 (5.6)
Smoking yes/no 43/14 12/8 0.19
Alcohol yes/no 50/7 17/3 0.75
Location of the main tumor 0.85
Ce:Ut:Mt:Lt:Ae 1:8:16:31:1 0:3:5:12:0
Pathological type 0.32
SCC:AC:others 50:5:2 20:0:0
Prior treatment 0.22
NAC:CRT:ESD:none 26:1:4:26 10:1:1:8
AJCC Stage 0.23
I:II:III:IV 18:19:19:1 3:6:6:2
Thoracoscopic:Robotic:Open 44:13:0 0:20:0 < 0.0001
Operative time (min) 0.04
Median (IQR) 295 (71) 266 (62)
Bleeding (mL) 0.08
Median (IQR) 150 (218) 91 (255)
Number of dissected mediastinal LNs 0.04
Median (IQR) 24 (13) 29 (12)
Postoperative left RLNP (laryngoscopy) 10 (17.5%) 1 (5.0%) 0.27
Aspiration (CD2 and over) 2 (3.5%) 1 (5.0%) 1.00
Pneumonia (CD2 and over) 5 (8.8%) 4 (20.0%) 0.14
Anastomotic leakage (CD2 and over) 9 (15.8%) 2 (10.0%) 0.32
Postoperative hospital stay (days) 0.82
Median (IQR) 22 (17) 22 (7)
IQR: interquartile range; Ce: cervical esophagus; Ut: upper thoracic esophagus; Mt: middle thoracic esophagus; Lt: lower thoracic
esophagus; Ae: abdominal esophagus; SCC: squamous cell carcinoma; AC: adenocarcinoma; NAC: neoadjuvant chemotherapy; NACRT:
neoadjuvant chemoradiotherapy; ESD: endoscopic submucosal dissection; AJCC: American Joint Committee on Cancer; LNs: lymph
nodes; RLNP: recurrent laryngeal nerve paralysis; CD: Clavien-Dindo grade

presented as median and interquartile range. Differences in frequency of categorical variables were assessed
with Pearson’s chi-squared test or Fisher’s exact test, whereas continuous variables were evaluated with the
Mann-Whitney two-sample statistic as appropriate. P-values < 0.05 were considered statistically significant.

RESULTS

Detection of RLNP
Table 1 shows patients characteristics and short-term surgical results. There were 10 cases (17.5%) of RLNP
diagnosed by laryngoscopy on post-operative day 7. The cause of RLNP was determined by video analysis.
Typical causes of RLNP identified are shown in Figure 1. Table 2 lists all causes in the 10 cases of RLNP
in this study. One of the cases was excluded because the RLNP was thought to be caused by direct nerve
compression during cervical procedures. In the other nine, RLNP was found to be caused by traction in the
thoracic cavity (n = 5), compression (n = 3), and thermal injury (n = 1).

In terms of the reliability of IONM, the sensitivity (confirmed positive by IONM among verified cases of
RLNP) and specificity (negative by IONM among cases of no RLNP) were 80% (8/10) and 95.7% (45/47),
respectively [Table 3]. The positive predictive value (percentage of postoperative RLNP cases among RLNP
cases estimated by IONM) and negative predictive value (percentage of no postoperative RLNP among
patients with no RLNP estimated by IONM) were 80% (8/10) and 95.7% (45/47), respectively.

Surgical technique
Based on the above results, we modified our surgical procedure to try to avoid RLNP. To counter thermal
injury, it is necessary to identify the location of the RLN in advance by using IONM as before. We