An analysis of vascular pattern in modified P1 zone and relationship with recurrent laryngeal nerve

Modified P1 zone is defined as the zone related to the recurrent laryngeal nerve(RLN) 1 cm proximal to the nerve entry point to the larynx, where the vessels cross the nerve at a vertical plane. RLN injuries are common in this zone during thyroidectomy. This study aims to describe the vascular pattern at the modified P1 zone.

This prospective analysis included 131 consecutive subjects who underwent thyroid surgery between October 2023 and June 2024. Various clinical, radiological, histopathological and intraoperative parameters were studied.

The study included 212 nerves at risk(NAR). The mean age of the study population was 43 ± 12.6 years. Immediate post-operative vocal cord palsy was noted in 3.3% of NAR. 100% of patients had at least one vessel in relation to RLN in the modified P1 zone. The mean number of vessels in this zone was 3 ± 1.2. Type 3 vascular pattern(presence of vessels anterior and posterior to the nerve) was the most common(68.9%). Multivariate analysis showed the presence of Pelizzo grade 2 tubercle of Zuckerkandl (OR 2.4; 95% CI: 1.07-5.37, p = 0.033) and the presence of stage 2 or 3 tumor stage(OR 2.2; 95% CI: 1.10- 4.55, p = 0.026) were independent predictors of the increased number of vessels(> 2 vessels).

The study describes the consistent vascular pattern and its relationship with RLN in the modified P1 zone. Awareness of this may help surgeons to prevent RLN injury during thyroid surgery and effectively tackle the vessels in modified P1 zone.