Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disorder impacting motor neurons, specialized nerve cells controlling voluntary muscle movements. ALS is the most common form of motor neuron diseases. The progressive loss of these neurons ultimately affects a person’s ability to move, speak, eat, and breathe.
How ALS Impacts Speech
ALS directly affects speech by causing the degeneration of motor neurons that supply the muscles involved in speech production. These bulbar neurons, located in the brainstem, send messages to the muscles of the lips, tongue, soft palate, jaw, and voice box. As these motor neurons degenerate, muscle weakness, stiffness, and wasting occur.
The weakening of these muscles directly impairs the three main components of speech: respiration, phonation, and articulation. Respiration, the foundation of speech, is affected by diaphragm weakness, reducing the airflow needed to produce sounds. Phonation, the production of voice, relies on the vocal cords vibrating as air passes through them, and muscle weakness can hinder this vibration. Articulation, the formation of clear sounds, becomes difficult as the muscles of the tongue, lips, and jaw lose strength and coordination.
Specific Speech Impairments
Individuals with ALS commonly experience specific speech difficulties, collectively known as dysarthria. This motor speech disorder affects the speed, strength, accuracy, range, tone, or duration of movements required for speech control. Dysarthria in ALS often presents as slow, slurred, or difficult-to-understand speech due to muscle weakness affecting articulation.
Another common impairment is dysphonia, involving changes in voice quality. This can manifest as a hoarse, breathy, or strained voice, often due to laryngeal muscle involvement. Individuals may also experience changes in speech volume, making projection difficult, and a reduced speaking rate. Hypernasality, where too much air escapes through the nose during speech, can also occur, making speech sound muffled.
Progression of Speech Changes
The progression of speech difficulties in ALS varies among individuals, but these impairments tend to worsen over time. In individuals with bulbar-onset ALS, where initial symptoms involve speech or swallowing, speech problems often appear earlier in the disease course. For instance, significant reductions in speaking rate may occur around 23 months after symptom onset, with speech becoming somewhat unintelligible by 32 months.
Conversely, those with limb-onset ALS, where weakness begins in the arms or legs, may retain functional speech for a longer duration, potentially up to 60 months after symptom onset. As the disease advances, muscle weakness and atrophy spread, leading to increasing difficulty in being understood. In later stages, most voluntary muscles involved in speaking can become paralyzed, which may eventually lead to a complete loss of verbal communication.
Strategies for Communication
Early intervention with a speech-language pathologist (SLP) is beneficial for individuals with ALS to address communication changes. SLPs can help develop personalized strategies to enhance speech clarity and intelligibility. Compensatory techniques, such as speaking slowly, exaggerating mouth movements, and pausing between words, can improve understanding.
As speech declines, various assistive communication technologies can help maintain communication. Voice banking involves digitally recording one’s voice to create a synthetic voice, allowing individuals to use their own voice with speech-generating devices. Message banking allows for the recording of specific phrases in one’s natural voice, preserving unique intonations. Augmentative and alternative communication (AAC) tools, ranging from low-tech communication boards to high-tech text-to-speech devices and eye-gaze technology, become valuable as verbal speech becomes more difficult.