Respiration — or breathing — is primarily under the control of the autonomic or “automatic” nervous system — the part of the central nervous system that controls vital functions such as heartbeat and respiration without conscious thought. It is unusual for MS to affect the autonomic nervous system, and therefore uncommon for breathing problems to occur in MS as a direct result of loss of autonomic control.
In MS, the most common cause of respiratory problems is loss of muscle strength and endurance. Just as a person can experience muscle weakness in the arms or legs, weakness can occur in the ventilatory muscles of the chest and abdomen that are involved in breathing. And like weakness in the other parts of the body, weakness of the ventilatory muscles can begin to occur early in the disease course and gradually worsen over time. People with weakened ventilatory muscles have to work harder to inhale and exhale. This extra effort can be quite tiring, particularly for people who already experience a significant amount of MS fatigue.
Respiratory problems can also interfere with the process of speech and voice production — making it much more difficult and tiring for people to carry on a conversation or speak loudly enough to be heard. The speech/language pathologist can recommend exercises and tools to enhance speech and communication.