Anatomical observation of phrenic nerve branch variations at the cervicothoracic junction and upper mediastinum: two case reports

This study reports two types of branch and communication variations of the phrenic nerve at the cervicothoracic junction and upper mediastinum. However, the main trunk course within the mediastinum and terminal distribution at the diaphragm remained relatively constant overall. Understanding these variations helps enrich phrenic nerve anatomical data and provides anatomical basis for identification and protection of the phrenic nerve during related cervical, mediastinal, and minimally invasive surgeries.