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Page 2 of 8 Kobayashi et al. Mini-invasive Surg 2020;4:30 I http://dx.doi.org/10.20517/2574-1225.2020.12

Keywords: Minimally invasive surgery, thoracoscopic esophagectomy, recurrent laryngeal nerve paralysis

INTRODUCTION
Surgery for thoracic esophageal cancer has a high rate of postoperative complications [1-3] including
recurrent laryngeal nerve paralysis (RLNP), which can lead to aspiration pneumonia and voice hoarseness,
and greatly affects the postoperative course. Inflammatory complications can also affect the patient’s long-
[4,5]
term prognosis . Of note, RLNP occurs more frequently on the left, which adds to the clinical challenge.
As such, we introduced intraoperative neural monitoring (IONM) in 2015 and have previously reported on
[6]
its success in reducing the incidence of RLNP at our hospital . This can be attributed to three factors: (1)
mapping of the recurrent laryngeal nerve (RLN) location; (2) RLN path navigation; and (3) learning effect.
Nevertheless, RLNP has not been eliminated completely, largely because the type(s) of surgical maneuver
that is responsible is not known.

We hypothesized that with IONM and intra-operative video analysis, the surgical maneuver leading to
postoperative RLNP can be identified. Herein, we report our findings from our experiences in applying
IONM to esophagectomy. We also describe a modified procedure to prevent RLNP, especially on the left,
and the short-term surgical results.

METHODS
Patients
Seventy-seven consecutive patients who underwent prone esophagectomy with radical lymph node
dissection at our institution from July 2015 to December 2019 were identified. Of 57 cases treated up to
January 2019, 10 (17.5%) developed RLNP and were subjected to detailed video analysis and a preventive
surgical technique for RLNP was developed. Since RLNP on the right hardly occurred, we focused on
the left. Patients were divided into two groups: conventional surgery (July 2015 to January 2019, n = 57)
and modified surgery (February 2019 to December 2019, n = 20) and short-term surgical outcomes were
compared. Cancer staging was performed preoperatively according to the 8th edition of the American
Joint Committee on Cancer Staging Manual by endoscopy, enhanced computed tomography, and positron
[7]
emission tomography . Postoperative RLNP was evaluated by laryngoscopy on postoperative day 7.
We also recorded Clavien-Dindo Grade 2 and higher complications such as aspiration, pneumonia, and
anastomotic leakage. In all cases, the first author (Kobayashi H), who had performed more than 100
thoracoscopic esophagectomies prior to this study, performed or supervised the surgery. This study was
approved by the institutional review board.

IONM and modified surgical technique
[6]
The use of IONM has been described previously . The modified surgical technique is described in
the Result section. Briefly, patients were positioned prone and an electromyographic tracheal tube
(Medtronic, Jacksonville, FL, USA), one-lung ventilation with blocker, no muscle relaxation, and NIM
Nerve Monitoring System 3.0 (Medtronic) were used. The RLN in the thoracic cavity was localized and
confirmed by IONM. At the end of the surgery, the vagal nerve was stimulated with a probe to confirm
nerve functioning. Video analyses was performed by the first (Kobayashi H) and second authors (Kondo
M) independently. When there was concordance between assessment by the two authors, that particular
maneuver would be considered the cause of RLNP.

Statistical analyses
Statistical analyses were performed using JMP version 12.0 software (SAS Institute Inc., Cary, NC, USA).
Categorical variables were reported as absolute values and percentages and continuous variables are