An assessment of the distance between the phrenic nerve and major intrathoracic structures.

BACKGROUND: There is a lack of consensus in the literature regarding phrenic nerve proximity to thoracic structures at the level of the diaphragm. This study was undertaken to provide thoracic surgeons data on phrenic nerve location in order to reduce iatrogenic injury during invasive surgery.

METHODS: Bilateral thoracic dissection was performed on 43 embalmed human cadavers (25 males; 18 females) and data was obtained from 33 left and 40 right phrenic nerves. The site of phrenic nerve penetration into the diaphragm was identified. Calipers were used to measure the distance from each phrenic nerve to the: inferior vena cava (IVC), descending aorta, esophagus, lateral thoracic wall and anterior thoracic wall.

RESULTS: Mean thoracic diameter of male cadavers was significantly greater than that of female cadavers (P value <0.0001). There was no statistically significant difference between the distances from each phrenic nerve to visceral structures between males and females, except regarding the distance from the right phrenic nerve to the anterior thoracic wall where males exhibited significantly greater distances (P value =0.0234).

CONCLUSIONS: This study provides important data on phrenic nerve proximity to intrathoracic structures in an effort to help reduce iatrogenic injury during procedures within the thoracic cavity. Although males had a significantly larger thoracic diameter than females, the only statistically significant difference showed that the right phrenic nerve is deeper in the thoracic cavity in males. As this nerve passes closer to visceral structures it may be more susceptible to damage from pathology in surrounding vessels. This may explain the increased incidence of right phrenic nerve damage due to aortic aneurysm in males reported in the literature.