Multiple Sclerosis (MS) is a chronic disease of the central nervous system where the immune system attacks the protective myelin sheath surrounding nerve fibers in the brain and spinal cord. This damage disrupts communication pathways between the brain and the rest of the body, leading to a wide range of physical and cognitive symptoms. MS lesions can interrupt the precise neural signals required for coordinating the muscles of the mouth, throat, and respiratory system. This interference affects two closely related functions: the ability to produce clear speech and the complex act of swallowing, making communication and mealtimes challenging.
The Neurological Mechanisms Behind These Symptoms
Difficulties with speaking and swallowing are rooted in the damage MS causes to specific areas of the brain and spinal cord. MS lesions, which are areas of demyelination, often occur in the brainstem, the cerebellum, and the motor cortex. These three regions form a network responsible for the strength, coordination, and timing of the muscles involved in speech and swallowing.
Damage to the brainstem, which controls facial, laryngeal, and pharyngeal muscles, causes weakness and slowness. Lesions in the cerebellum disrupt the fine-tuning of movement, leading to a lack of coordination known as ataxia. Damage to the motor cortex impairs the strength and control needed for precise muscle actions. This multi-site neurological damage often results in a mixed motor speech disorder, typically a combination of spasticity and ataxia.
Manifestation of Speech Difficulties
The motor speech disorder associated with MS is medically termed dysarthria, resulting from the weakness or incoordination of the muscles used to speak. A common manifestation is a change in the clarity of articulation, where the lips, tongue, and jaw struggle to form sounds precisely, leading to slurred or imprecise speech.
The voice itself is often affected, a condition called dysphonia, which presents as reduced volume or projection. Voice quality may also become hoarse, strained, or breathy due to poor control over the vocal cords and respiratory muscles. MS can also disrupt the natural rhythm and melody of speech, known as prosody. This can lead to a monotonic delivery or an uneven, jerky pattern called “scanning speech,” characterized by abnormally long pauses between syllables or words. These speech changes are often more pronounced when an individual is fatigued.
Understanding Swallowing Impairment
Swallowing impairment, or dysphagia, affects a significant number of people with MS, with prevalence estimates ranging from 33% to 43%. Normal swallowing involves three highly coordinated stages: the oral, pharyngeal, and esophageal phases. MS-related damage primarily impacts the oral and pharyngeal stages by weakening muscles and delaying reflex timing.
In the oral phase, individuals may have difficulty chewing food or controlling the food bolus, sometimes leading to food “pocketing” in the cheeks. During the pharyngeal phase, delayed or uncoordinated throat muscles can fail to adequately protect the airway. This failure results in aspiration, where food or liquid mistakenly enters the trachea and lungs. Aspiration is a serious health risk because it can lead to aspiration pneumonia, which is a common cause of hospitalization and mortality in people with advanced MS.
Symptoms indicating dysphagia include frequent coughing or throat clearing during or after eating, a sensation of food getting stuck, or recurrent chest infections. Because muscle weakness can be subtle, people may experience “silent aspiration” without visible signs like coughing, making early professional evaluation important.
Strategies for Managing Communication and Eating
Speech-Language Pathologists (SLPs) are the primary specialists who evaluate and treat both speech and swallowing difficulties in MS.
Managing Communication
For communication difficulties, the SLP introduces specific techniques to improve speech clarity and projection. Pacing strategies, such as consciously slowing the rate of speech, give articulatory muscles more time for precise movements. Exercises focused on breath control and strengthening respiratory muscles help increase vocal volume and sustain longer phrases. When verbal communication is severely compromised, the SLP recommends Augmentative and Alternative Communication (AAC) devices. These tools, which range from simple communication boards to electronic speech-generating devices, provide a reliable means of expression when speaking is difficult due to fatigue or disease progression.
Managing Swallowing
For managing swallowing impairment, the SLP develops individualized strategies to ensure safe eating and hydration. Compensatory techniques involve changing head or body posture during the swallow, such as turning the head or tucking the chin, to redirect the food’s path and protect the airway. Dietary modifications are often recommended, including altering food textures to softer consistencies or thickening liquids to reduce aspiration risk. The SLP may also prescribe muscle strengthening exercises to improve the function of the tongue and throat muscles, helping to maintain swallowing efficiency.