Amyotrophic lateral sclerosis, dysarthria, and language disorders - type of research and approaches in different areas: an integrative literature review

Purpose: to identify the knowledge produced in national and international researches on speech and language disorders in Amyotrophic Lateral Sclerosis, regarding the type of research and approach in different areas. Methods: an integrative review performed on databases, using the following descrip -tors: Amyotrophic Lateral Sclerosis, Dysarthria, Language Disorders, Speech Production Measurement and Speech Disorders. The inclusion criteria covered articles that addressed motor speech and language disorders from 2013 to 2018, excluding duplications, and categorizing valid articles for analysis. Results: 83 articles were selected, after screening the titles and abstracts. A large scientific production from different countries and areas, mainly Speech Therapy and Neurology, was found. Most of them was clinical research (65.06%), with a main focus on speech motor disorders (42.16%), speech and language motor disorders, cognition and behavior (27.71%), and language disorders (12.06%). Conclusion: researches found were mostly clinical and aimed at determining the diag nosis of disorders in different areas of knowledge. With regard to communication, few studies have been found in Brazil, and international studies addressed high technology. The results confirmed the heterogeneous nature of the disease, which shows, in addi tion to motor impairment of speech, cognitive, behavioral and language impairments.


INTRODUCTION
Amyotrophic Lateral Sclerosis (ALS) is a heterogeneous neurodegenerative disease that results in disorders in the motor skills, cognition and behavior, highlighting serious problems in the individual´s functional skills, thus, limiting his/her possibilities of social interaction [1][2][3] .
Speech motor disorders in individuals with ALS have been described over the years, with more intensity and frequency in those individuals who show bulbar onset symptoms 2,4 . They are present in more than 80% of the cases at some point of the disease, and 75-95% of patients lose their oral communication skills 5 .
Bulbar characteristics, in the speech motor decline, evidence the impairment of all of its subsystems, especially breathing, phonation, articulation and resonance 2,6 , and are noticed insofar as the intelligibility is reduced.
In advanced stages, it evolves with anarthria, which occurs approximately 18 months after the onset of bulbar disorders 4 , interfering with the individual´s social interactions, even with family members and close friends, requiring alternative communication systems 3 in order to keep the autonomy and life quality.
Although ALS is a neurodegenerative disease that specially affects the motor neurons, which determines the loss of functional capacity for daily and practical life activities 1 , cognitive disorders are also present in 30% of the individuals, especially related to the executive function, and to the fluency, language and memory deficits. Approximately 10% of patients show frontotemporal dementia 7 .
There is an increasing interest of researches on behavior disorders, social cognition and emotional aspects 8 related to a behavioral variant of the frontotemporal dysfunction 9 . In this regard, the multidisciplinary support is necessary to minimize the effects of the disease progression 1,5,10 .
Speech and language motor disorders in ALS put the patient in a situation of communication vulnerability, characterized by any failure in the communication process between the individual and their interlocutor, interfering with their social interactions, and possibly leading them to develop emotional problems and/ or anxiety, frustration, fear and sadness 3 , gradually moving them away from social interactions, family members and close friends.
Thus, communication vulnerability represents a major impact on the lives of people with ALS, justifying the focus of this review with respect to speech and language motor disorders.
Therefore, the purpose of this research was to identify the knowledge produced in national and international researches on speech and language disorders in ALS, regarding the type of research and approaches in different areas.

METHODS
This study used the method of integrative literature review, which has the aim to concisely systematize the knowledge already produced in the scientific community, to determine a panorama of the topic to be discussed, allowing the practice based on evidences 11,12 . To that end, six steps for integrative reviews 13 were followed, in order to facilitate the synthesis and analysis of eligible articles, and to minimize possible biases found, namely: "1) Identification of the theme and selection of the research question; 2) Definition of inclusion and exclusion criteria; 3) Identification of pre-selected and selected studies; 4) Categorization of selected studies; 5) Analysis and interpretation of results; 6) Presentation of knowledge review/synthesis" 13 .
The guiding questions of this research were the following: Which knowledge fields have been studying the ALS in relation to speech and language motor disorders? What is the analysis focuses and purposes of these studies in relation to such aspects? What is the panorama of Brazilian scientific production of this theme in relation to the international one?
The search was carried out in the research portals Biblioteca Virtual em Saúde (BVS) and Pubmed; as well as in Embase and Scopus databases. These databases were selected because they gather a vast material of publications in the health field, and for being the focus of search for most of health professionals. After the survey, at first the articles titles and abstracts were analyzed, then those articles fulfilling the inclusion criteria were fully read. During the screening, those studies unrelated to dysarthria and language disorders, main focus of the study, were excluded, as well as those only addressing other pathologies not related to ALS.
After applying filters, 571 articles were found, of which 294 were excluded for being duplicated in the databases, and 194, after the titles and abstracts analysis, totalizing 83 valid articles for full reading, as described in Figure 1. Selected studies were analyzed according to the criteria of an instrument, built and applied in another research 14 (Annex 1), and for a better visualization and understanding, they were organized in tables, with absolute (n) and relative (%) frequencies, and graphs.
Valid articles were distributed in three main categories, for subsequent analysis and discussion of results, as follows: (a) Type of research and knowledge field of the study; (b) Purpose and knowledge field of the study; (c) Study focus, subcategorized in (i) Speech motor disorders; (ii) Speech, language, cognition and behavior motor disorders; and (iii) Language disorders.
For the purpose of analysis, the area of each selected study was defined, according to the main author´s department.

LITERATURE REVIEW
Articles addressing the studied theme were found in all selected databases after the application of filters, as presented in Table 1. We observed a vast production of studies on the theme, during the years of investigation, with researches from different areas of health, such as Biomedical and Linguistic Engineering, coming from different places, like the United States, Europe, Asia and South America, as shown in Figure 2. in addition to the medical doctor, such as: speech and language pathologist, physical therapist, occupational therapist, psychologist, including specialists in palliative care, allow maintaining the life quality of individuals until the late stages of the disease, where there is no more functional capacity for the performance of routine activities 2,10 . However, most of the ALS population has no access to such services in a continued manner 1 , making it even more difficult for the patient and for the family to live with this disease.
The distribution of articles according to fields of knowledge and type of study conducted is detailed in Table 2.

(a) Type of research and knowledge field of the study
The large number of publications found shows the need of more knowledge about the fundamental physio pathological mechanisms underlying the disease, since they are still not well understood 1 . Among them, three studies from Brazilian southern and southeastern regions were found, and therefore we cannot say they represent the clinical profile of Brazilians with ALS 15 .
The different research fields found indicate the heterogeneous character of the disease, and stress the importance of a multidisciplinary care. A team comprised by caretakers, different health professionals,  Specially in Brazil, we also consider the functioning problems of the Public Health System (SUS), which makes it difficult to obtain early diagnosis and does not facilitate referencing individuals with ALS to neurological centers 15 , as well as the limitations of the governmental incentive to the research developed in public universities.

(b) Objectives of intervention and knowledge field of the study
In Table 3, it is possible to observe the distribution of clinical study articles, according to their field and objective.
Out of the 52 clinical studies, 84.61% had the aim of determining the diagnosis, using neuroimaging 17 , electromagnetic articulography 18 , ultrasound 19 , electromyography 20 , as well as subjective instruments of speech 21 and voice 22 evaluation. These finds point out to an effort to understand altered parameters of the disease, possibly in order to define disease mechanisms, which can benefit from drug segmentation and therapeutic intervention, as well as to determine those patients who will respond to these therapeutic agents 1 .
On the other hand, a reduced number of researches has focused on the possibilities of care to such a population, and only one study had the aim to evaluate the impact of therapeutic solutions on the life quality of people with ALS 23 . Such a research panorama can interfere with the care offered to this public, and consequently with their well-being and life quality. As far as speech is concerned, therapeutic intervention is regarded as more effective in the early stages, and therefore can contribute to retard the decline of inteligibility 24 , although it cannot prevent the loss of this function with the disease progress.
Furthermore, another research, considering that dysarthria negatively impacts the communication functionality and social interactions of people with ALS, has investigated the impact of speech-focused intervention and the use of Augmentative and/or Alternative Communication Systems (AACS), concluding that such systems more expressively contribute to improve or at least stabilize the life quality and mood of this population, in detriment of speech-focused intervention, and therefore AACS should be offered as early as possible 23 .
Particularly in developed countries, there is an interest in researches with communication devices of high technology. Seven articles related the use of alternative communication resources, all of them high-tech, such as the Brain Computer Interface (BCI) 25 and the Eye Tracking Communication Devices (ETCDs) 26 , to positive results, especially in the advanced stages of ALS.
In addition to these studies, others were found about the use of palatal lift prosthesis 27 to improve the dysarthric pattern, which improved the sequential movement rate, speech rate, vital capacity, sound pressure level, intelligibility and reduction of nasality in the studied individuals with ALS; and mouth micro-switch 21 , that showed to be more agile when compared to the optical micro-switch actuated by means of head movement.
With the disease progress and anarthria acceleration, the use of Augmentative and/or Alternative Communication (AAC) systems and devices becomes necessary to make communication and interaction easier. We have found researches, specially from other countries, related to the use of eye control resources with computer interface, because of the loss of voluntary muscular control 3 , restricting the autonomy. At this point, when conventional AAC devices are not sufficient 3 high-tech resources are the most viable strategies to keep and restore the possibility of communication with family members, close friends and health team, positively affecting the life quality and emotional state of people 23 , and this is possibly one of the motivations for the researches with this focus.
However, it is noteworthy that the use of those resources, especially the high-tech ones, despite being offered in the marketplace, are not affordable to most of the people, especially in Brazil, because of countless difficulties, mainly economic difficulties and the lack of investment and development of public policies that make them affordable, as well as the reduced number of qualified and specialized professionals to make use of this kind of support 28 .
Results related to the effective use of AACS highlight the discussion about the focus of therapeutic interventions in ALS, in fields such as Speech and Language Therapy and Occupational Therapy, for instance. This finding is an important contribution of this article, corroborating a study indicating that most of patients describes a positive impact of communication devices in their life quality, also evidencing mood improvement and stabilization, making them necessary since the onset of the disease 23 .
The findings point to an urgent need to debate the communication vulnerability and AACS demands and applicability in ALS, which can contribute to foment public policies aiming to provide access of users in the public health system to this kind of technology, allowing a better care to this population. Figure 3 shows the results related to the study focus, subcategorized in speech motor disorders (42.16%), followed by motor disorders of speech and language, cognition and behavior (27.71%), and language disorders (12.06%). Speech-related articles found reveal a tendency to explore articulatory kinematic and intelligibility aspects, in order to identify the most common disorder patterns and to understand how long it takes to the individual with the disease to becomes incapable of oral communication.

(c) Focus of the Study
Longitudinal study points out the loss of speech skills in 60% of the participants during the 2-year follow-up, although in such individuals´ speech as well as functional communication remained adequate for 18 months in average after the onset of the first bulbar symptoms 4 .
However, individuals with bulbar onset ALS lose the speech skills in average seven months after the first speech and language therapy intervention, which results in a limited time to them to adapt to an appropriate AAC resource. On the other hand, persons with spinal onset ALS, since they are already followed up because of other symptoms, are referred to the speech and language pathologist earlier and have more time for that adaptation 4 , increasing the chances of maintaining communication even in advanced stages of the disease.
In addition to that, some indicators showed to be sensible to the early bulbar decline, such as the articulatory and phonatory dysfunction, which are altered even before the deterioration of the speech intelligibility and the substantial reduction of the speech rate 6 .
According to some authors, the speech rate reduction to 120 words per minute (WPM) marks the beginning of the fast decline of intelligibility in oral communication 29 . In this regard, since ALS patients start to have difficulties to be understood, they constantly need to repeat the words and phrases, and thus decide to avoid communicating with others 2 . This situation evidences the experienced vulnerability and implies restrictions in the communicative participation, throughout the course of the disease, caused by the difficulty in performing tasks, and because of the negative feelings involved in each experience 10 .
In general, we observe a constancy in the use of instruments and objective measures 6 to evaluate the characteristics and seriousness of dysarthria in such individuals, such as the software Phonatory Aerodynamic System (PAS) (KayPentax, USA), used to evaluate the respiratory sub-system and that allows measuring eight speech measurements, pause patterns and two sub-glottal pressure measurements; the Multidimensional Voice Profile (MDVP, Model 5105) and PRAAT 29 for the acoustic evaluation of voice and speech; devices to identify articulatory movements; nasometer for the test of the velopharyngeal function effectiveness; and also intelligibility measuring instruments, such as the Sentence Intelligibility Test (SIT) 30 .
In view of such findings, the speech evaluation by the speech and language pathologist is very important, being part of the differential diagnosis, indicating the onset of bulbar disorders and facilitating the intervention as early as possible.

(ii) Motor disorders of speech and language, cognition and behavior
Several studies of speech and language motor disorders found have their focus associated to cognition and behavior disorders, generally related to frontotemporal dysfunction found in 50 to 60% of ALS population, even without the presence of the genetic component, and which can show dementia, cognitive and behavior disorders, as well as social cognition and language deficits 31 .
Through an international consensus, criteria were developed to help differentiating and diagnosing such condition that take into consideration clinical, electrophysiological, neuropsychological, genetic and neuropathological aspects. It recognizes that ALS can be a pure syndrome or coexist with a Frontotemporal Dementia (ALS-FTD) 9 , and refers to the behavioral and/ or cognitive variant as the two mains clinical profiles of non-motor manifestations in not demented patients with ALS 32 .
The Frontotemporal Dementia (FTD) is present in approximately 15% of the individuals, and is usually found as a behavior variant, which is characterized for being an progressive syndrome that leads to an disorder in the interpersonal conduct regulation and emotional dullness, and which can be described by caretakers as uncommon irritability, selfishness or lack of interest 9 .
Cognitive disorders in ALS consist of fluency, language, social cognition, executive functions and verbal memory deficits 7 . In turn, behavioral disorders most common in ALS include apathy, disinhibition and irritability, and in a lower degree, abnormal eating habits, stereotyped behaviors, as well as sensorial abnormalities 33 . Apathy is the behavior most frequently identified, being detected in as much as 70% of the patients 8,9,32 .
Depression can be a psycho-behavioral symptom associated to ALS, and when present it interferes with the cognitive performance 34 , although it is not intensely described in the scientific literature 33 . Depression tends to be observed in the early phase of the disease, close to the diagnosis and frequently associated to caretakers also having the same symptom 31 .
It is noteworthy that such disorders can be present before the occurrence of motor manifestations, and once the ALS-FTD and/or disorder of the executive function is diagnosed, the prognosis is worse in comparison to those having it in its pure form, with the reduction of the survival by one year 31 .

(iii) Language disorders
Cognitive disorders in ALS have been intensely described in the scientific literature in the past few years, mainly related to the impairment of the executive function, although it is known that they are not restricted to this domain and can also represent the deterioration of language skills. Some authors say that the cognitive impairment profile in ALS has a heterogeneous nature, with some patients showing disorders predominantly in the executive function, while others have it exclusively in language or a mixed pattern 8 . It is still unknown the reason why such domains are affected, however language processing aspects have been related to the frontal pathology in ALS 34 .
A study performed with 241 individuals, of which 185 with the behavioral variant and 56 with ALS-FTD, evidences that behavioral and affective changes are more frequent in the first group, while language deficiencies were more common in the second group. The impairment of the executive function equally occurs in both groups 8 . According to the same research, language disorders more frequently found are anomy, difficulty in finding words during conversation, echolalia, verbal perseveration, repetition of words and phrases, phonological disorders, agrammatism (in spontaneous speech or written), impaired comprehension, superficial dyslexia and orthographic deficiency 8 .

Limitation of the Study
According to the survey data, most of the studies reviewed in this research has a limited sampling number, and therefore does not show a good degree of external generality. Therefore, a future systematic validation is necessary, with larger samples, in order to get a deeper knowledge of speech and language motor disorders in people with ALS, especially regarding the possibilities of available therapeutics, and thus allowing a more assertive therapeutic conduction.
Another important topic to be considered is the limited number of national researches, which makes it impossible to obtain epidemiological data representing the Brazilian population, as well as therapeutic resources more consistent with Brazilian socioeconomic reality.

CONCLUSION
A large scientific production related to speech and language motor disorders was found, with studies coming from different countries and various fields of knowledge, especially Neurology and Speech and Language Therapy. A reduced number of national researches was found, as compared to the international researches, which allows us to infer that issues related to the development of public policies, incentive to the research production, in addition to sociodemographic characteristics of the Brazilian population, as well as their difficult access to public services, can interfere with this matter.
Results confirm the heterogeneous nature of ALS that evidences, in addition to motor disorders, cognitive, behavioral and language impairments. Such findings stress the need of a multidisciplinary care, starting from the diagnosis, which should be intensified with the progress of the disease to provide life quality to the studied population, considering the few possibilities offered in therapeutic interventions.
Most of the researches aimed to diagnose disorders, in order to understand the disease itself and its underlying mechanisms.0} To that end, the use of instruments and more objective measurements, in detriment of subjective evaluations with the use of perceptual parameters, were constant, indicating this trend of the studies in the field.
Motor disorders of speech were the predominant analysis focus, evidencing speech intelligibility as the main concern because of the disease evolution to dysarthria and anarthria. There was also a major interest of researchers in the cognitive and behavioral disorders present in the ALS, associated or not to dementia.
Another important finding is the lack of researches addressing efficient care and therapeutic resources to assist ALS population, which were restricted to the use of high-tech communication devices (brain-computer interface), especially in developed countries, however, distant from the Brazilian reality.
In view of this panorama, we reaffirm the importance of findings related to the communication vulnerability in ALS and to the need to foment studies on therapeutic intervention in such population, and thus, providing them with better quality of life, as well as communication and social participation. Also, in this sense, the work of a speech and language pathologist is extremely important, since the initial evaluation, to allow the observation of existing disorders, also contributing to the differential diagnosis, and allowing an intervention as early as possible.
On this path, findings more precisely highlight the scientific evidences of the theme, in order to guide the clinical practice of the speech and language pathologist and of other professionals alike, and to raise the interest in the still little explored fields of research, allowing a better care to such a population, this being, therefore, the major contribution of this article.