Basic and Clinical Sciences (BCSE) Practice Exam

Unilateral paralysis of the diaphragm is a common cause of dyspnoea in lung cancer due to its direct impact on respiratory mechanics. In cases of lung cancer, particularly if the tumor is located in the apex of the lung or involves the mediastinum, it can encroach on the phrenic nerve, which innervates the diaphragm. When this nerve is affected, it can lead to paralysis of that side of the diaphragm, resulting in impaired respiratory function and difficulty in adequate ventilation. This dysfunction can manifest as shortness of breath or dyspnoea, especially during physical exertion when the demand for respiratory capacity is greater.

While infections of the lungs, allergic reactions to medications, and heart complications can also contribute to dyspnoea, they are not as directly associated with the pathophysiological changes observed in lung cancer as unilateral paralysis of the diaphragm. In lung cancer cases, the structural and functional impact on the diaphragm is particularly noteworthy and is a significant contributor to the respiratory symptoms experienced by patients.