Management of multisystem neurodegenerative disease necessitates that clinical care adapts to disease progression. In ataxia, speech, alongside other functional domains like upper and lower limb function often worsen over time [1,2,3,4]. Speech can deteriorate to the extent that verbal communication is no longer possible. When this happens, alternative and augmentative communication (AAC) approaches can help users meet their daily communication needs.

Traditional AAC methods are designed to assist users communicate via alternatives to natural speech. These can be low- or high-tech solutions and range from letter boards to button-activated voicing to eye tracking (see Table 1). These devices provide some capacity to communicate; however, the interaction is rarely as efficient or detailed as verbal communication.

Table 1 Current AAC resources
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In multisystem conditions like Friedreich ataxia, use of AAC is restricted by physical limitations including upper limb ataxia and visual disturbance [5]. These deficits make it challenging to efficiently use or see a cursor on screen, or manipulate buttons on a device (e.g., phone/tablet). Speech-to-text algorithms have limited capacity to recognise unclear target words, eye gaze technology has difficulty accurately tracking jerky eye movements and all approaches require training, patience, content expertise from clinicians and are fatiguing for the patient. These limitations do not mean AAC is ineffective. They do, however, dictate that some devices are useful at specific disease stages, with their utility changing when symptoms worsen.

This perennial issue is currently managed from several directions. Firstly, maintaining existing speech abilities is paramount. Speech rehabilitation remains the mainstay of clinical practice. Advances in digital therapeutics has brought treatment into the home, providing greater access to therapies for patients [6]. Secondly, efforts are underway to improve the accuracy of speech to text for dysarthric speech. Google’s Euphonia project [7], for example, has an aim to translate unclear speech into intelligible communication.

Despite these options, there is limited knowledge and evidence on AAC use in ataxia. This review describes AAC resources, assessment practices in AAC, and how management can change with disease state. We also discuss new possibilities for optimising and maintaining communication in people with ataxia where verbal speech is not viable.

Communication in ataxia

Spoken language is the primary form of communication for most people with ataxia. This is despite speech deteriorating as disease progresses. Dysarthria in ataxia is characterised by impairments across multiple speech subsystems, including respiration [8], phonation [9], articulation [10,11], resonance [12] and prosody [13]. These initially manifest as slurred and slower speech, gradually leading to a more severe phenotype, with vowel distortion, imprecise consonants, mixed nasality (predominantly hypernasality), reduced rate, and dysphonia. These combine to reduce intelligibility and naturalness of speech [14]. People with ataxia also present with difficulties across modes of communication, including hearing [15], vision [16] and writing/typing and reading impacted by upper limb impairment [17].

AAC

AAC encompasses a wide range of modalities and tools designed to assist individuals with communication difficulties. These modalities can be categorized into unaided and aided communication. Unaided communication relies on the communicator's body and doesn't involve external tools or devices. This typically takes the form of sign language, gestures, facial expressions, and body language. Unaided communication is suited to individuals who have preserved motor control but cannot rely on verbal communication [18].

Aided communication requires external tools or aids to supplement or replace speech. It includes low- and high-tech solutions. Low-tech AAC includes basic tools like communication boards, paper-based systems, and symbol books. They are often cost-effective and easy to implement. High-tech AAC encompasses advanced options like tablet apps, dedicated communication devices, specialised digital hardware, speech generating devices (SGD), and computer software. These often offer greater versatility and can sometimes be customized to suit an individual's unique needs.

SGDs are electronic devices that produce speech based on user input. They are often used by individuals with more complex communication needs, including ataxia. These devices may use text-to-speech technology, pre-programmed messages, and predictive text options. Some SGDs can be controlled through physical movements, such as head movements or eye gaze, making them accessible to individuals with severe motor impairments [19].

Assessment of complex communication needs

It is estimated that up to 0.5–1% of the world population may benefit from AAC, as they are unable to meet their daily communication needs through natural speech [20,21]. Complex communication needs manifest across a spectrum of disease severity and duration in ataxia, yielding diverse effects on an individual's engagement in domestic, professional, and other community settings. The dynamic nature of progressive ataxia warrants regular assessment of communication (see Fig. 1). Comprehensive testing is required to identify communication needs and the potential role of augmentative methods for supplementing non-functional speech [19]. There are no specific assessment procedures for evaluating communication needs in individuals with progressive ataxia [22]; instead, clinicians must establish a comprehensive picture of sensorimotor control and function alongside user preferences and participation needs.

Fig. 1
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Changing AAC suitability across disease stages in ataxia

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AAC assessment and subsequent intervention typically requires active involvement from a team of individuals, including the person who requires AAC; their family members, caregivers, and communication partner(s); and clinical specialists [23]. Families, caregivers, and communication partners (e.g., teachers, employers, co-workers) play a key role in AAC assessments since—beyond the candidates themselves—this group of individuals is most likely to be affected by any decisions made toward an AAC intervention. The lack of family involvement in the assessment and intervention process has been cited as a significant factor in AAC device abandonment [24,25]. The involvement of a multidisciplinary team of specialists is crucial to identify an intervention that addresses the candidate’s unique communication challenges, which can include psychophysiological (e.g., sensory-perceptual, motor, cognitive-linguistic, and literacy impairments) and environmental considerations. The team of clinical specialists can therefore include professionals such as speech-language pathologists, physical therapists, occupational therapists, social workers, vocational coaches, medical personnel (e.g., audiologist, primary care physician), and psychologists, among other professionals. Together, this team is responsible for performing AAC assessments and, in turn, using assessment results to implement and modify AAC interventions as needed.

AAC intervention is recommended by the American Speech-Language-Hearing Association (ASHA)26 to be considered as early as possible, regardless of communication impairment aetiology. Beukelman and Mirenda developed the Participation Model in 1988 as a framework to systematically implement AAC assessments; the model has since been revised in 2014. The revised Participation Model is recommended by the ASHA to guide AAC assessment and intervention as a dynamic process that needs to be revisited as AAC users learn new skills or as their disabilities progress (i.e., a change in “participation level”). According to the Participation Model, the focus of an AAC assessment is to gather information about the candidate’s participation patterns and needs, and then to plan, implement and evaluate the effectiveness of AAC interventions. Progress is then monitored and re-evaluated as needed based on how the user participates in their environments (see Fig. 2).

Fig. 2
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Schematized framework for assessing communication in ataxia, based on the revised Participation Model from Beukelman and Mirenda (2014)

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A comprehensive assessment includes collecting a case history, identifying communication skills and needs, characterizing facilitators and barriers, and assessing sensorimotor abilities (e.g., hearing, vision, motor). The goal of testing is to identify factors that contribute to communication success for the individual who relies on AAC as well as for their communication partners. AAC assessments should ideally take place over multiple days to gain clear insight into how an individual’s environment (e.g., lighting, device positioning, noise, familiarity, communication partner) and personal behaviours (e.g., attention, fatigue, motivation) affects their needs or skills.

Interviewing the candidate and exploring their social network are both valuable methods to delineate the candidate’s life experiences, goals, capabilities and strengths, limitations, and fears, and—most importantly—their unmet communication needs. This process can be used to highlight the candidate’s cultural, socio-economic, and linguistic background, as well as contextual factors (both personal and environmental), structural or functional impairments, comorbid deficits, and perspectives toward AAC. One popular instrument called the Social Networks Inventory is useful for characterizing interpersonal relationships, specifically in how the user feels about their relationships with significant others in their life and how they think those others feel about that relationship [27]. Speech and language assessments should be also conducted to comprehensively assess the candidate’s natural speech, expressive and receptive language, reading and writing abilities, symbol representation, and cognitive-linguistic organization. This largely includes informal assessments via interviews and observations with the user, but are often supplemented by standardized assessments such as the Comprehensive Aphasia Test [28](word- and sentence-level understanding), or the Peabody Picture Vocabulary Test–Fifth Edition (PPVT-5) [29] for receptive language.

Sensorimotor capabilities can be evaluated in areas of motor control, vision, and hearing. Motor control can be assessed by observing reflex patterns that may interfere with volitional control and characterizing the candidate’s ability to make gestures, manual signs, or dynamic movements. The latter is important when considering the ability of a person with ataxia to access aided AAC—such as using a finger to reliably select letters on a touchscreen—as they may have significant difficulty quickly and accurately controlling hand movements. Aided AAC modalities can be accessed by direct selection or scanning. Direct selection may involve pressing real or virtual buttons using different body parts (e.g., head, hands, fingers), or through hi-tech modalities such as head tracking, gaze selection, or eye tracking. If an individual has difficulty directly selecting items, then scanning may be used as an alternative; here, the AAC team must consider possible motor control sites as well as switch types that are used to make selections one at a time. This involves a process of trial and error, where users try a range of switches, movements, and positions to identify a combination that provides the most successful access to an activity. It is important to consider observe user position, movement patterns and concerns, control sites, type and positioning of switches, user skill levels, and the user’s preferred choice(s). Though primarily an informal and person-centered process, various frameworks exist to guide the AAC team with the process of a switch assessment. For instance, the ACE Centre in the UK developed the Switch Assessment and Planning Framework for Individuals with Physical Disabilities [30] to guide AAC teams in establishing a switch access method that offers the easiest, quickest, and most successful method of access. Observations from motor control assessments are used to identify the best option, options that offer future potential with further practice or training, options that could be used for limited activities, and no-go options based on physical needs and abilities.

Beyond motor control, vision and hearing must be evaluated to fully characterize the user’s needs. Vision assessments are typically carried out by ophthalmologists, optometrists, or vision specialists and are crucial to understand the needs of the candidates to be able to provide visual accommodations (e.g., bigger text) when necessary. Similarly, evaluating auditory capabilities is necessary to determine whether AAC candidates are effectively receiving auditory input in their environment. Hearing assessments focus on candidate responses to spoken instructions, questions, responses, and feedback from text-to-speech outputs on AAC technologies.

Ultimately selecting an AAC method requires close liaison with motor control specialists (e.g., occupational and physiotherapists) to consider vision and hearing abilities alongside physical requirements such as posture and fine motor skills. Interdisciplinary AAC collaborations are imperative in ataxia, which can affect multiple sensorimotor domains. For instance, Friedreich’s ataxia is associated with partial vision and/or hearing loss as well as physical symptoms affecting motor control skills (e.g., peripheral neuropathy). Involving an interdisciplinary team ensures that the selected AAC intervention addresses any communication needs while also considering the interplay with other aspects of the user’s sensorimotor function.

It is important that communication partner dynamics and environmental supports are identified to develop an operational profile for intervention. This encompasses legislative or regulatory information that either supports or imposes restrictions on the utilization of AAC interventions for the candidate. Community attitudes—from family and co-workers to the broader public—should be identified so that opportunities for participation as well as their understanding of AAC and skills are known.

Pooled information from the multifaceted AAC assessment process (spanning case history, communication skills and needs, and sensorimotor capabilities) helps the team identify short- and long-term goals for intervention [31], which is the second area of focus of the Participation Model. Many times, trials with specific AAC modalities are important for the team to home in on the most effective intervention. It may be that different AAC techniques are better suited for some environments. For example, an SGD may be effective in a quiet setting at home, but not in a noisy restaurant. Proactive planning for future intervention is essential since the needs and skills of a person with ataxia change over time. In turn, this may alter their ability to use their current intervention [31].

Eye tracking

Eye tracking technology can be useful where ataxia limits the use of traditional input devices such as a keyboard or mouse due to impaired coordination of movement. Eye-tracking technology can be effectively used as a mode of AAC in the context of ataxia (see Consumer Case Study 1). Eye-tracking devices can be used without requiring any physical touch, which is advantageous for people with ataxia where impaired movement can limit timing and accuracy of touch. Users can type out messages by looking at on-screen keyboards where the eye tracker can select keys based on where the user is looking, and the selection can be made by dwelling on a key for a certain period or by using blink or switch activation. Like other AAC modalities, this is often combined with predictive text and phrase selection to minimize the amount of typing required. Once a message is composed, eye-tracking AAC devices can use in conjunction with text-to-speech technology to verbalise the message.

Beyond communication, eye-tracking technology can also give users with ataxia greater control of their environment. This can include full control of a computer, enabling users to navigate the web, use software, and even create art or music, depending on the software’s capabilities. It can extend to operating household electronics, computers, and even wheelchairs, providing a greater degree of independence.

Potential limitations of technological AAC solutions

There are multiple reasons why AAC options are not adopted or are discontinued by potential users [32] (see also see Consumer Case Study 2). Progressive neurological diseases lead to changes in abilities (Fig. 1). This means that AAC approaches need to be adaptable over time. Technology that works well at one stage may become less effective with degeneration. High-tech solutions like eye-tracking devices may be complex to set up and use, especially for individuals who are not technologically able or are experiencing cognitive decline. The learning requirements can be burdensome with some individuals finding it difficult or frustrating to use these technologies effectively [33]. Motor control and coordination issues common in ataxia, including spasticity can interfere with the use of assistive technologies [34]. In ataxia specifically, involuntary eye movements or difficulties with maintaining steady head and neck control can affect the accuracy of eye-tracking systems [35]. Advanced assistive technologies can be prohibitively expensive and may not be covered by insurance or healthcare systems. This can limit access to those who might benefit from them the most, especially as individuals with significant disability are often underemployed or unemployed [36]. The dynamic and individual nature of communication needs in progressive neurological disease mandates that AAC approaches need to be customised. There is often a significant need for individual customization of assistive devices, which can be time-consuming and requires professional expertise, making it less accessible for those in remote or under-resourced areas. Alongside the factors of cost and customisation, technology often presents with technical and maintenance issues. Dependence on technology means that technical failures can leave individuals without a means of communication or control over their environment. Similarly, regular maintenance and troubleshooting can be challenging for users and caregivers. AAC devices are often used in conjunction with other approaches, requiring integration and interaction between approaches. Technology may not always integrate seamlessly with other devices and services needed for daily living. Compatibility issues can restrict the functionality and efficiency of assistive devices. To optimise set up, access and continued use of approaches, adequate training for users and ongoing support is needed. Caregivers and family members also often benefit from training to assist effectively.

Personal factors outside of the technology or approach itself can alter a user’s experience. Fatigue is common in mitochondrial disorders and neurodegenerative diseases generally [37]. Using assistive technologies often requires sustained attention and concentration, which impacts access and an individual’s ability to use an approach for extended periods. This is related to the interaction with cognitive functioning, where some individuals with ataxia may experience cognitive decline, impacting their ability to effectively use or adapt to new technologies. Lastly, AAC approaches can present a social barrier where the use of assistive technology is stigmatized or misunderstood by others. This can lead to feelings of isolation or embarrassment for the user.

Future directions

The future of AAC will likely incorporate brain computer interfaces (BCI), building on recent work examining non-invasive brain signal interpretation. There are some recent advancements that will be relevant for people with ataxia. Meta's work on decoding speech from non-invasive brain recordings was recently published in Nature Machine Intelligence [38]. Their work aimed to amalgamate neurological signals and artificial intelligence through magnetoencephalography and electroencephalography. Apple recently patented technology that detects bio-signals using dynamic selection of electrodes" [39] within AirPods. Effectively interpreting brain signals through the ear using sensors embedded within ear pods. Alongside this work there is a strong push for supporting voice of the patient through voice banking. This has gained traction in conditions like Amyotrophic Lateral Sclerosis where disease trajectory is steep, and perseveration of communication is a priority [40]. The role of voice banking in slowly progressive but ultimately fatal disorders like ataxia is less clear. Where disease onset is in childhood, voice banking with an immature voice for later use as an adult is undesirable. As disease worsens, your own ‘healthy’ voice deteriorates. The best way to integrate a stored voice in an AAC set up that caters to multiple physical restrictions incumbent in the condition is also unclear. Trials are underway to evaluate the utility of voice banking in progressive neurological disease. In a recent ground-breaking development, a paralysed woman in the US successfully communicated using a digital avatar controlled through a BCI [41]. This was achieved by using high-density surface recordings of the speech cortex in a clinical-trial participant presenting with severe limb and vocal paralysis. The aim was to achieve real-time decoding across three interconnected speech-related output modalities: text, speech audio, and facial-avatar animation, encompassing lip sync and emotional expressions. These are tangible examples of the fusion between brain-computer interfaces with voice banking and the advancement of language AI. This integration holds the potential to enable individuals to preserve their voice, even in instances where they have lost the ability to speak.

Recommended approaches when investigating suitability and allocation of AAC for people with ataxia

People with a hereditary ataxia should all receive a comprehensive assessment of their communication. This could include a clinical speech examination accompanied by patient reported outcomes and establishment of baseline function. Following establishment of needs, and whether AAC would enhance communication outcomes, a thorough assessment by a speech-language pathologist and potentially an occupational therapist specialized in AAC could be conducted to determine the most suitable system (see Table 1 for AAC resources). The chosen system needs to be evaluated and accurately calibrated for the individual’s use. Systems can be customised according to each interface and the individual’s preferences and abilities, possibly adjusting the sensitivity and latency times. Adequate training and support are needed for all AAC users, caregivers, and communication partners.

To address these limitations, continuous support from healthcare providers, regular assessments, and updates to technology are required. Manufacturers and service providers must work towards creating more adaptable, user-friendly, and integrated solutions that can evolve with the progression of the disease and the changing needs of the individual. Additionally, advocacy for better insurance coverage and more widespread adoption can help make these technologies more accessible to those in need.