Assistive Technology for Communication in Movement Disorders

Many movement disorders, such as Parkinson disease (PD), essential tremor (ET), and ataxia syndromes, result in progressive changes in speech and communication that significantly affect quality of life and increase the risk of social isolation. These changes do not usually respond effectively to medications. Nonpharmacologic interventions are the mainstay of treatment and include speech therapy programs and assistive technology. Here, we review assistive technologies aimed at restoring communication for people with speech and communication deficits due to movement disorders.

PD Hypophonia

Speech changes, a prominent feature of PD, affect ~90% of people with PD.¹ Individuals with PD may develop hypophonia, characterized by low-volume, monotone, and breathy speech.¹ Traditional treatments, such as carbidopa/levodopa and deep brain stimulation (DBS), may not improve speech and, in some cases, may worsen speech symptoms; thus, speech therapy with a speech-language pathologist (SLP) is the primary mode of treatment.¹ Therapy programs, such as Lee Silverman Voice Treatment (LSVT LOUD) and the Parkinson Voice Project SPEAK OUT!, rely on repetition, can be intensive, and may not be available in all areas.^1,2 Technologic devices addressing hypophonia can assist with these therapy programs and the learning processes involved and can improve communication in individuals who have not benefited substantially from therapy.

Portable voice accumulators, such as the Voxlog, have been used to provide external biofeedback by delivering a vibration when detecting voice levels below a set decibel threshold.² In a small study, benefit was observed primarily among participants with normal cognitive screening scores; cognitive impairment may limit successful use, but this requires further investigation.² Portable voice accumulators have thus far been used only in clinical trials. The expectation is that they could be used alongside traditional speech therapy once they become readily available.²

Devices such as the SpeechVive have been designed to use the Lombard effect (ie, the involuntary tendency of speakers to raise their voices in response to background noise). These devices consist of in-ear or over-the-ear speakers that deliver background noise with mimicked background speech or nonspeech noises and can be worn in one or in both ears.³ In small studies, these devices improved speech during the initial period of use, as noted by participants with PD as well as their companions.³ However, limited data are available on their effectiveness over longer periods. Among individuals who discontinued use early, reasons cited included distraction, difficulty thinking, annoyance, and headaches.

Speech amplification systems can increase the intelligibility of spontaneous speech in PD hypophonia.⁴ These devices may be considered when other measures have been ineffective and particularly in situations with extensive background noise. Amplifiers are available as voice amplifiers (portable or stationary) or 1-way communication systems. Portable voice amplifiers, such as the ChatterVox, include both a microphone and small amplifier worn by the individual. For a stationary voice amplifier, such as the BoomVox, the microphone and transmitter are worn by the individual and speech is directed to a larger amplifier in a set location. In comparison, 1-way communication amplifiers, such as the BeHear SMARTO, include a microphone and transmitter worn by the individual, which transmits speech directly to a receiver and headphones worn by the listener.⁴

In a small study, the use of all 3 forms of amplification systems increased intelligibility compared with no assistive device in participants with moderate to severe hypophonia.⁴ However, when background noise was introduced, overall intelligibility declined even with the use of portable or stationary speakers but was maintained with the 1-way personal communication device.⁴ Overall, speech amplification systems may be a viable option for individuals with less-controlled hypophonia, but effectiveness may be limited in higher-noise environments.

Spasmodic Dysphonia and Vocal Tremor

Spasmodic dysphonia is a type of focal dystonia that affects the muscles of the vocal folds. In the adductor type, the folds close during speech, resulting in halting and strained speech.⁵ In the abductor type, the folds open during speech, which results in quiet and breathy speech.⁵ In addition, individuals with spasmodic dysphonia may have vocal tremors similar to those seen in individuals with ET. The hallmark of treatment for spasmodic dysphonia is botulinum toxin injections to the vocal folds; however, this is not always successful in controlling the symptoms.

For individuals with spasmodic dysphonia and ET vocal tremors, vibrotactile stimulation (VTS) has been examined as a potential option to help improve voice quality. VTS uses a pair of small vibratory motors placed on the skin over the thyroid cartilage to provide laryngeal stimulation at certain frequencies (typically 60 to 100 Hz) for brief periods of time to reduce vocal strain and spasms.⁵ The hypothesis regarding the VTS effect is similar to the sensory trick (geste antagoniste) associated with cervical dystonia; the vibration stimulates the sensorimotor cortical neurons and normalizes or desensitizes their synchronization levels to ease vocal fold overactivity.⁵ Individuals responsive to VTS experience rapid improvement in vocal quality and speech effort during stimulation. However, this effect tends to wane rapidly once stimulation is halted.⁵ At present, VTS is only being used in clinical studies and is not available for consumer use.

DBS of the globus pallidus interna (GPi) or thalamic ventral intermediate nucleus (VIM) is an investigational therapeutic option for individuals with spasmodic dysphonia who are refractory to standard treatments.⁶ Between these 2 targets, GPi DBS may provide better control of dystonia and can also treat some tremor.⁷ VIM DBS is more effective than GPi for treatment of tremor but is less effective for dystonic symptoms.⁷ In one small study, VIM DBS was safe and improved perception of vocal quality in many participants with spasmodic dysphonia.^8,9 In another study evaluating participants with spasmodic dysphonia with VIM DBS in the stimulation “on” or “off” state, every participant reported an improvement in quality of life and voice quality with stimulation “on,” although this trend did not reach statistical significance due to the small sample size. Likewise, examiner speech scores also improved with DBS stimulation in this study but did not reach significance.⁸ Another small study found that stimulation of thalamic sensorimotor regions was associated with symptomatic improvement, although no consistent group-level stimulation “sweet spot” was identified.⁹ Studies evaluating GPi DBS in participants with spasmodic dysphonia have demonstrated improvement in speech fluency and reduction in voice breaks in the adductor variant.¹⁰ Additional studies are needed to define optimal targets, individual selection, and stimulation protocols.

Similar to individuals with spasmodic dysphonia, individuals with ET-associated vocal tremors have limited response to first-line pharmacotherapies, such as propranolol and primidone, and may benefit from more targeted treatments, such as botulinum toxin injections to the vocal folds.¹¹ For treatment-refractory individuals, both DBS and focused ultrasound (FUS) targeting thalamic VIM can be considered. A small study compared fundamental frequency variability during sustained vowel vocalization and blinded expert perceptual voice tremor rating in participants who underwent unilateral FUS vs bilateral DBS implantation. Both groups showed significant improvement in fundamental frequency variability and expert voice tremor rating scores. Larger studies are warranted to elucidate better the potential benefits and comparative efficacy of both procedures in vocal tremor control, especially now that bilateral FUS is Food and Drug Administration–approved for ET.¹¹

Ataxic Speech and Advanced Speech Deficits

In atypical parkinsonian conditions, individuals may experience hypophonia and dysarthria, as seen in PD; however, symptoms tend to be more prevalent early and progress more rapidly. In addition, conditions such as progressive supranuclear palsy or corticobasal syndrome can result in apraxia of speech, which causes dysfunction in planning and programming of speech.¹² Some individuals with progressive supranuclear palsy and the parkinsonian-predominant variant of multiple system atrophy may have hypokinetic-spastic speech with a more strangled voice quality.¹² Ataxic speech can be seen in many progressive ataxia conditions and in the cerebellar-predominant variant of multiple system atrophy, resulting in a more scanning type of speech, with increased pausing, decreased prosody, and potential progression to dysphonia.^12,13 In later stages of disease, speech can be severely impaired and may progress to anarthria.

Severe speech impairment or minimal intelligibility can result in difficulty communicating or an inability to communicate. At this point, it is important to consider augmentative and alternative communication (AAC) strategies or devices. AAC encompasses both low-technology aids, such as pen and paper, communication notebooks, and alphabet boards, and high-tech speech-generative devices, which often use text-to-speech and may be accessible using modern technologies, such as a gyroscopic mouse, eye-tracking cameras, and EMG switches to accommodate upper extremity deficits.^13,14 Individuals should be referred to an SLP for evaluation before choosing an AAC device based on their needs and functional limitations, with those needs reevaluated as disease progresses and abilities change.^13,14 As ataxic conditions advance, text-to-speech or pointing can become challenging, in which case devices that track eye movements can potentially be of benefit to maintain communication. These devices may be complicated to set up and to use properly, especially for individuals with a greater degree of cognitive impairment. Often, as cognitive–linguistic function declines, individuals will need to transition from high-tech to low-tech tools.¹³ Overall, when effectively tailored to individual needs, AAC can facilitate or restore communication for individuals with severe speech difficulties.

Figure. Clinical approach to the selection of assistive communication technologies in movement disorders. This pathway provides guidance for selecting assistive technology based on the predominant communication problem and the individual’s functional abilities. Illustration created using ChatGPT 5.1 (OpenAI, San Francisco, CA) based on content in this article. Abbreviations: AAC = alternative and augmentative communication; DBS = deep brain stimulation; EMG = electromyography; ET = essential tremor; GPi = globus pallidus internus; PD = Parkinson disease; SD = spasmodic dysphonia; SLP = speech-language pathologist; VIM = ventral intermediate nucleus; VTS = vibro-tactile stimulation.

Discussion

Many movement disorders may present with or result in deficits in speech and communication, which can worsen in severity with disease progression. The mainstay of treatment continues to be evaluation and therapy by SLPs, but new potential technologic treatment avenues are opening. Devices are being designed to provide assistance with improving volume or production of speech and communication (Figure). This is a newer area of research, and many of these devices are only used in clinical trials. Individuals with communication impairment should be referred to SLPs to discuss potential treatment options and obtain recommendations to enhance their independence and ability to communicate. Additional research and standardization will be needed to help guide the use of these technologies and inform treatment recommendations.