A Case of Esophageal Cancer With Right Vertebral Artery Variation Observed During Thoracoscopic Esophagectomy


 BackgroundVariation of the vertebral artery bifurcation is rare. This branching abnormality can make it difficult to identify the recurrent laryngeal nerve (RLN) during thoracoscopic esophagectomy. There are a few reports on abnormal branching of the vertebral artery but none related to esophagectomy. We report the case together with the results of the evaluation of vertebral artery bifurcation and length in 50 patients with esophageal cancer in our hospital.Case presentationThoracoscopic esophagectomy was performed on a 70-year-old patient with esophageal cancer. During lymph node dissection, an unusual blood vessel was found running along the right subclavian artery (RSA). This blood vessel made it difficult to identify the right RLN. We determined this blood vessel to be the right vertebral artery (RVA) branching far more centrally than usual. Because this anatomical abnormality was clarified, we could then recognize that the right RLN coursed around the RVA and the RSA and thus was running in a larger arch than usual.Conclusion﻿Knowledge of such anatomical variation is important in thoracoscopic esophagectomy to prevent iatrogenic injury of the RLN and the vertebral artery.


Abstract Background
Variation of the vertebral artery bifurcation is rare. This branching abnormality can make it di cult to identify the recurrent laryngeal nerve (RLN) during thoracoscopic esophagectomy. There are a few reports on abnormal branching of the vertebral artery but none related to esophagectomy. We report the case together with the results of the evaluation of vertebral artery bifurcation and length in 50 patients with esophageal cancer in our hospital.

Case presentation
Thoracoscopic esophagectomy was performed on a 70-year-old patient with esophageal cancer. During lymph node dissection, an unusual blood vessel was found running along the right subclavian artery (RSA). This blood vessel made it di cult to identify the right RLN. We determined this blood vessel to be the right vertebral artery (RVA) branching far more centrally than usual. Because this anatomical abnormality was clari ed, we could then recognize that the right RLN coursed around the RVA and the RSA and thus was running in a larger arch than usual.

Conclusion
Knowledge of such anatomical variation is important in thoracoscopic esophagectomy to prevent iatrogenic injury of the RLN and the vertebral artery.

Background
The vertebral artery usually takes its origin from the subclavian artery and ascends to enter the transverse foramen of the sixth cervical vertebra [1]. Different variations in the origin of the vertebral artery can make it di cult to identify the recurrent laryngeal nerve (RLN) during thoracoscopic esophagectomy. There are some reports on variations of vertebral artery bifurcation, but none as they relate to esophagectomy [2][3][4][5][6].
Knowledge of such anatomical variation is important in thoracoscopic esophagectomy to prevent iatrogenic injury of the RLN and the vertebral artery.

Case Presentation
A 70-year-old man with a height of 161.0 cm, weight of 54.6 kg, and body mass index of 21.0 kg/m 2 complained of di culty in swallowing a meal and was referred from another hospital. He was diagnosed as having thoracic esophageal cancer (T3N1M0, Stage IIIA). We performed thoracoscopic esophagectomy after chemotherapy. The thoracoscopic operation time was 299 minutes, and blood loss was 20 ml. During lymph node dissection around the right RLN, an unusual blood vessel was found running along the right subclavian artery (RSA). We con rmed from a preoperative contrast-enhanced computed tomography (CT) image that the blood vessel was the right vertebral artery (RVA), which was very long at 7.02 cm. Because this anatomical abnormality was clari ed, we could recognize that the right RLN coursed around the RVA and the RSA and thus was running in a larger arch than usual. As a result, lymph node dissection could be performed safely without damaging the right RLN, and no metastasis was found in the excised station number of 106recR (Fig. 1).

Discussion
The RSA branches from the brachiocephalic artery, runs laterally across the anterior and middle oblique muscles, and bifurcates into the RVA as its rst branch. The RVA often enters the transverse process of the sixth cervical vertebra after bifurcation. In the presented case, the RVA branched from the RSA at a very central location, so it appeared in the surgical eld during lymph node dissection around the right RLN as an unusual blood vessel running along the RSA. This unusual anatomical variant complicated the identi cation of the right RLN and had the potential for causing damage. The vertebral artery is anatomically classi ed into four segments, and that from the bifurcation of the RSA to the transverse process of the vertebral body is called the V1 segment [7]. In this patient, V1 of the left vertebral artery (LVA) was 3.78 cm long, whereas V1 of the RVA was 7.02 cm. In a study of 266 cases, Woraputtaporn et al. reported that the average length of the RVA and LVA V1 segments was 3.88 ± 1.14 cm [8]. The V1 segment of the vertebral artery of 50 esophageal cancer patients operated on at our hospital was measured on contrast-enhanced CT images. The average length of the RVA was 3.69 cm, and that of the LVA was 4.14 cm, which were almost the same as those reported by Woraputtaporn et al. (Fig. 2). Various variations have been reported at the origin of the RVA, and Newton and Potts classi ed them into six types [9]. Type A, which branches within 2 cm from the thyrocervical trunk, is reported to be the most common at 83.12%, and Type B, which branches more than 2 cm away from the thyrocervical trunk, is much less common at 8.27% (Fig. 3).
In the 50 patients with esophageal cancer in our hospital, Type A was seen in 45 patients (90%) and Type B, including that in the presented case, was seen in 5 patients (10%), which were almost the same proportions as those reported by Newton and Potts. The length of the V1 segment was compared and examined between Type A and B, and the results are expressed as the median (interquartile range) for quantitative variables. The nonparametric Wilcoxon rank sum test was used for continuous variables. A p value of less than 0.05 was considered to be statistically signi cant. The median length of the Type B RVA was 5.05 cm, which was signi cantly longer than the 3.56 cm measured in the Type A RVA, and it was proved that the length of the blood vessel was not affected by patient height or weight (Table 1).
Type B was considered to be longer than Type A because the RVA branched from the central side of the RSA. In the present patient, the RVA branched especially from the very central side of the RSA and was a very long Type B artery of 7.02 cm in length. The V1 segment of the Type B RVA may be visible in the surgical eld during lymph node dissection around the right RLN in thoracoscopic esophagectomy; therefore, attention should be paid to misidenti cation of the right RLN and the potential for damage to the vertebral artery.

Conclusion
We report a case in which the right RLN could have potentially been misidenti ed due to an abnormal bifurcation of the RVA. Knowledge of such anatomical variation is important in thoracoscopic esophagectomy to prevent iatrogenic injury of the RLN and to perform lymph node dissection safely.