The Upper Aerodigestive Tract: Control of Voice, Speech, Swallowing, and Cough
Parkinson disease (PD) impacts almost every system in the body. Voice, speech, swallowing, and coughing are all crucial activities of daily living that can be impacted by Parkinson’s. These important functions are all part of what speech language pathologists call the upper aerodigestive tract. The upper aerodigestive tract consists of the nose, lips, mouth, tongue, throat (pharynx), voice box (larynx), upper part of the windpipe (trachea), and food tube (esophagus). This post will explore the interconnection of activities in this region and is a teaser to what you’ll hear in the Comprehensive Care Session IV at the WPC Virtual Congress.
Image by Alessandra Alê from Pixabay; used under Creative Commons license
Voice
The voice is the source of sound for our speech. It is generated through vibrations by the vocal cords, which are complex tissues within the larynx. To create voice, we take a breath in, bring the vocal cords close together, and breathe out. The force of the air we exhale sets the vocal cords vibrating. This vibration results in changes to the air pressure and is perceived by our ears as sound.
Image by OpenStax CNX; used under Creative Commons license
PD can influence breathing and laryngeal movements, impacting the quality of voice. Often, voices of individuals with PD can sound soft, breathy, or harsh.
Speech
Once we set the vocal cords into vibration, we use muscles in our pharynx, soft palate, tongue, and lips to shape that sound into what we recognize as speech. These movements must be precisely planned and coordinated so we can be understood by others.
Speech movements in persons with PD can be rushed and imprecise. This, combined with a soft voice can make it difficult to be understood. These are the reasons why speech therapy approaches, such as Lee Silverman Voice Treatment (LSVT) and SPEAK OUT focus on increasing the effort and intention behind speech production.
Swallowing
Swallowing uses most of the same structures and muscles as voice and speech, but in a different way. We take food and liquid into the mouth (chewing as necessary) and bring it together into a bolus. We push the tongue against the roof of the mouth to propel the food into the throat, triggering the reflex swallow. In the reflex swallow, we close off the nasal cavity and larynx to protect the airway. The pharynx contracts to push the bolus from the throat into the esophagus. The esophagus then constricts from top to bottom until the bolus enters the stomach.
Changes to motor control of muscles in the mouth, pharynx, larynx, and esophagus in PD can lead to changes in swallowing function. Swallowing may be inefficient when the bolus moves slowly through the mouth, throat, and esophagus, with residue left over. Swallowing can also be unsafe when the bolus enters the larynx and airway, increasing the risk for aspiration pneumonia.
Cough
Coughing is another vital function of the larynx. If an irritant enters the larynx, it triggers the cough reflex. To cough, we take a deep breath in, close the vocal cords, build up air pressure underneath the vocal cords, then open the vocal cords to release a sharp burst of air and expel the source of irritation. Coughing is one way that we can protect our airway and is a good example of the multiple function of the larynx.
Summary
The upper aerodigestive tract consists of structures and muscles that work together to perform multiple necessary functions. PD impacts sensation and motor control, which in turn effects activities of the upper aerodigestive tract, including voice, speech, swallowing, and cough.
Neurological control of movements in voice, speech, swallowing, and cough differs from that of movements in the limbs and is impacted by PD. Thus, treatments that improve signs and symptoms of PD in the limbs have limited effects in the upper aerodigestive tract. It is important for those with PD to monitor for changes to voice, speech, swallowing, and cough, as changes can result in health and well-being consequences.
An evaluation by a speech-language pathologist (sometimes called a speech and language therapist) is needed to fully characterize changes to function in the upper aerodigestive tract. There are several evidence-based treatment approaches for voice, speech, swallowing, and cough that can improve health and quality of life for individuals with PD.
Please join us for a clinical and research update from experts in upper aerodigestive function and neural control at WPC Virtual: Advancing the Science, Care, & Living with Parkinson’s!
Corinne A. Jones, PhD, CCC-SLP is an Assistant Professor in the Departments of Neurology and Speech, Language, & Hearing Sciences at The University of Texas at Austin. She is also a licensed and certified speech-language pathologist at UT Health Austin. Dr. Jones will be presenting The How and WHY Vocal Break and moderating a Comprehensive Care session on upper aerodigestive function in May at the WPC Virtual Congress
Ideas and opinions expressed in this post reflect that of the author(s) solely. They do not necessarily reflect the opinions of the World Parkinson Coalition®