National Physical Therapy Examination (NPTE) Practice Exam

Which characteristic is commonly associated with amyotrophic lateral sclerosis (ALS)?

1. Increased lung expansion

2. Decreased lung capacity

3. Improved respiratory function

4. Normal pulmonary function tests

The correct answer is: Decreased lung capacity

In amyotrophic lateral sclerosis (ALS), one of the hallmark features is the progressive degeneration of motor neurons, which can lead to significant respiratory complications due to weakness of the respiratory muscles. As the disease progresses, patients often experience a decrease in lung capacity because the muscles responsible for breathing, including the diaphragm and intercostal muscles, become weakened. This muscle weakness results in a reduced ability to take deep breaths and fully expand the lungs, ultimately leading to hypoventilation and impaired gas exchange. Lung function tests in ALS typically reveal a restrictive pattern, characterized by decreased vital capacity and total lung capacity. This decreased lung capacity is a major concern in ALS management, as it can lead to respiratory failure, necessitating further medical interventions such as ventilatory support. In contrast, characteristics such as increased lung expansion, improved respiratory function, or normal pulmonary function tests do not align with the typical progression of ALS. These would suggest an absence of respiratory muscle involvement, which is not typical of the disease. Thus, decreased lung capacity is indeed the characteristic commonly associated with ALS.