No abstract

Background:The branching pattern of vessels emerging from the external carotid artery varies considerably. Knowledge of this variation is critical for clinicians who perform neck procedures. This study assessed the origin of the four primary caudal branches of the external carotid artery (superior thyroid, lingual, facial, and occipital arteries) with regard to sex and side. The position of common carotid artery bifurcation was also analyzed with regard to sex and side. Methods: The carotid arterial system of 79 cadavers from the eastern United States (37 male, 42 female) was dissected bilaterally. The position of carotid bifurcation relative to a midpoint between the suprasternal notch and mastoid process was measured with digital fractional calipers. Origin of the caudal branches was determined and the distance from the carotid bifurcation measured. Results: On the right, the superior thyroid artery emerged from the carotid bifurcation/external carotid more frequently than it did from the common carotid (67% and 31%, respectively); however, on the left, it emerged more frequently from the common carotid (57% and 43%, respectively) (p = 0.003). No side-dependent differences were observed for the remaining three caudal branches. The occipital artery emerged below the origin of the facial artery more frequently than at/above (55% and 44%, respectively). No significant differences were found for the origin of the caudal four branches with regard to sex. There was no significant difference in the location of the carotid bifurcation with regard to sex or side. Conclusions: The origin of the superior thyroid artery differed when comparing neck side, while the origin of the occipital artery frequently emerged caudal to that of the facial artery. Both findings are inconsistent with most anatomical atlases. The positions of the carotid bifurcation as well as the origin of the remaining caudal branches were no different with regard to either parameter.

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.

The purpose of this article is to provide background information and the current understanding of a less familiar cause of female breast cancer; exposure to ultraviolet light at night. Breast cancer is a common disease that causes significant morbidity and mortality in women. There are several risk factors for breast cancer, most of which are genetic and environmental in nature. An often-overlooked risk factor is exposure to blue light during night shift work, which decreases melatonin production. One of the many cancer-preventing properties of melatonin is to limit estrogen production. Increased lifetime exposure to estrogen is a well-known cause of breast cancer. Awareness of nighttime blue light exposure as a breast cancer risk factor by women doing night shift work and those exposed to nighttime light via smartphones and laptops, is essential information to know so that protective measures can be taken.