The Pathogenesis, Assessment and Treatment of Speech Fluency Disorders

Background: Approximately 1% of children and adolescents, 0.2% of women, and 0.8% of men suffer from stuttering, and lesser numbers from cluttering. Persistent speech fluency disorders often cause lifelong problems in communication and social participation.

Methods: In an interdisciplinary, evidence and consensus based clinical practice guideline, the current understanding of the nature, identification, diagnosis, and treatment of stuttering and cluttering was summarized. A systematic review of the literature was carried out to assess the efficacy and effectiveness of treatments for stuttering. Evidence is lacking on the etiology, pathogenesis, evaluation, and treatment of cluttering.

Results: In view of the fact that common (developmental, idiopathic) stuttering is associated with structural and functional changes of the brain, the guideline recommends that it should be called “originary neurogenic non-syndromic stuttering.” Heritability estimates for this disorder range from 70% to over 80%. For preschool children, the Lidcombe therapy has the best evidence of efficacy (Cohen’s d = 0.72–1.00). There is also strong evidence for an indirect treatment approach. For children aged 6 to 12, there is no solid evidence for the efficacy of any treatment. For adolescents and adults, there is good evidence with high effect sizes (Cohen’s d = 0.75–1.63) for speech restructuring methods such as fluency shaping; weak evidence with intermediate effect sizes for stuttering modification (Cohen’s d = 0.56–0.65); and weak evidence for combined speech restructuring and stuttering modification. The evidence does not support the efficacy of pharmacotherapy, rhythmic speaking, or breathing regulation as the sole or main form of treatment, or that of hypnosis or eclectic, unspecified stuttering therapies.

Conclusion: Stuttering is often treated in Germany with therapies for which there is inadequate evidence, and the initiation of treatment is often unnecessarily delayed. The guideline presents treatment methods whose efficacy is supported by the current evidence.

Worldwide, about 1% of children and adolescents as well as 0.2% of women and 0.8 of men suffer from stuttering (ICD-10: F98.5) (1, 2). Reported prevalence rates for cluttering (ICD-10: F98.6) are lower, but no precise numbers are known. For a considerable part of these speech fluency disorders, treatment is needed. To identify, diagnose, and treat speech fluency disorders, 17 expert societies in Germany have developed a clinical practice guideline based on consensus and evidence, and have published this on the website of the Association of Scientific Medical Societies in Germany (AWMF) as well as in book format (3, 4) (eTable 1). As the evidence relating to cluttering is less strong than that for stuttering, this article focuses primarily on stuttering.

eTable 1

Specialist scientific societies, organizations, and mandate holders involved in the guideline*

Methods

The guideline is based on a comprehensive literature search. The text was composed and agreed by the 8-member guideline author group and went through a two-stage formal voting procedure among the consensus group—initially, persons with conflicts of interests were excluded, and the vote was then repeated with these persons included. The results did not show any notable discrepancies. For the central question of the efficacy and effectiveness of therapies for stuttering we conducted a systematic literature review (eFigure 1) after four researchers (KN, HAE, HGB, SC) had independently searched the databases Web of Science, PubMed, PubPsych, and Cochrane Library. The search included publications from 2000 to April 2016. 43 publications met the methodological criteria. Two reviewers independently checked the identified publications for stuttering-specific inclusion criteria (effectiveness of measures to reduce stuttering; N ≥ 12; effect sizes reported or calculable; a minimum of two repeated measurements; follow-up period of at least 6 months).

eFigure

Flow chart of literature search (since 2000) and selection for therapies for stuttering

The evaluation of the methodological quality of the included systematic reviews and meta-analyses was based on the recommendations of the Scottish Intercollegiate Guidelines Network (SIGN) (e1); that of the randomized controlled trials and non-randomized controlled trials, non-controlled prospective case studies, retrospective treatment studies, and narrative reviews was based on two checklists from the AWMF; and the allocation of evidence levels was based on the classification of the Oxford Centre for Evidence-based Medicine (e2). The recommendations of the guideline were agreed on in a nominal group process in two consensus conferences moderated by the AWMF.

Stuttering

Definitions

The guideline classifies speech fluency disorders into stuttering and cluttering and distinguishes between originary (neurogenic non-syndromic and neurogenic syndromic) and acquired (neurogenic and psychogenic) stuttering (Figure 1). As the “common stuttering,” hitherto known as “idiopathic,” is accompanied by structural and functional cerebral anomalies, the recommendation is to substitute the term by “originary neurogenic non-syndromic stuttering” or, in what follows, simply “stuttering.” The term describes a neurological impairment of speech and its planning, which develops in childhood owing to a genetic disposition. It comprises key symptoms with non-fluent speech that are typical for stuttering and also secondary symptoms with vegetative, motor, and emotional reactions to these dysfluencies. “Originary neurogenic syndromic” characterizes the kind of stuttering that can occur, for example, in trisomy 21 (Down syndrome). “Acquired neurogenic” stuttering can occur at any age after a brain injury (e3, e4). The very rare “psychogenic” stuttering develops usually after puberty acutely as a result of psychotrauma or an underlying psychiatric illness.

Figure 1

Classification of speech fluency disorders

Course

Stuttering usually starts at the age of 2–6 years. The sex ratio in the early stage is 3 boys for every two girls. Subsequently, owing to sex-specific recovery, the ratio changes to 5 : 1 (up to five men to every woman) (e5–e7).

Persons who stutter recover spontaneously in 70–80% of cases, mostly before they reach puberty. The rate of spontaneous recovery is highest in the initial two years after onset of the disorder and falls rapidly afterwards (e8–e11). Risk factors for persistent stuttering include male sex, familial stuttering (especially persistent familial stuttering), onset of the dysfluencies more than 6–12 months ago, age at onset of stuttering >3–4 years, no reduction in stuttering severity within the initial 7–12 months (e12). An individual prognosis for recovery is not possible.

Symptoms

Table 1 describes the symptoms of stuttering and distinguishes those symptoms from normal speech dysfluencies. Since fluency problems typical for stuttering are not part of a child’s normal speech development, the term “developmental stuttering” should no longer be used, and neither should the categorization into clonic and tonic stuttering.

Table 1

Symptoms of stuttering and distinction from normal speech dysfluencies

Originary neurogenic non-syndromic stuttering is present if a minimum of 3% of all spoken syllables are stuttered. Independently of the frequency of stuttered syllables, stuttering should be assumed and diagnostically evaluated in case of single stuttering events of a long duration, emotional stress, avoidance behaviors, and other accompanying symptoms (strain displayed in the stuttering symptom, physical concomitants). In childhood and adolescence, the risk increases that the affected youngster will develop social phobias independently of the severity of his/her stuttering (e13).

Genetic origin

Twin studies (5–7, e14–e18) have confirmed that stuttering has a heritability of 69–85%. As a population-based concept, this finding of heritability does not allow any conclusions regarding individual cases, but it does allow the conclusion that stuttering in biological relatives predisposes to developing it. Furthermore, these studies confirm that the family environment shared by siblings is not a causative factor, or at best to a negligible extent. Twin siblings do not have a higher concordance of stuttering just because they grow up in the same family. This finding implies that contrary to assumptions so far, the family environment in early childhood—and thus parental interactions with children—do not—or hardly at all—contribute to the development of stuttering.

The molecular genetic search for types of genetic predisposition has thus far identified more than a dozen relevant loci (8, e19–e22). Stuttering is regarded as a multifactorial polygenic disorder, with many loci of different effects and interactions between genome and environment. Since thus far, only few gene loci have been confirmed, an urgent task for molecular genetic speech fluency research is the replication of findings (8).

Because a substantial proportion of the effects is of an additive nature, the currently favored model is a risk-threshold model. This means that the risk of stuttering increases with the number of loci involved, with a higher risk threshold in girls than in boys (9). It is to be expected, however, that more differentiated models will supersede the additive threshold model (8).

Cerebral findings

Stuttering is associated with morphological and functional abnormalities of the brain and is the expression of impaired interaction between auditory, somatosensory, speech planning, and speech motor neuronal networks, which is continually required in the generation of fluent speech (10–12, e23–e57).

Screening and diagnostic evaluation

One component of the regular German pediatric examinations at ages 3, 4, and 5 years is a question to parents whether their child stutters, in tandem with an assessment of the child’s speech development. The Bochum–Aachen stuttering screening (BASS) instrument for physicians is recommended for more detailed or universal screening. This can be incorporated in pediatric screening or school entry examinations ([13], www.bvss.de/images/stories/projekte/BASS_2017.pdf). If there is a risk for or suspicion of stuttering, the Screening List for Stuttering (SLS) is available (14) (German-language version: [15]).

The diagnostic approaches listed in Table 2 capture the symptoms of stuttering and the resultant socio-emotional burden. For objective assessment, different representative samples of at least 300 syllables of connected speech should be audio- or video-recorded. The recordings should be analyzed by frequency of stuttering (% of stuttered syllables), duration of the longest stuttering events, and physical concomitants and thus enable a classification by stuttering severity. Furthermore, one of two psychometric tests—the Stuttering Severity Instrument, fourth edition (SSI-4), or Test of Childhood Stuttering (TOCS)—should be administered. The Overall Assessment of the Speakers’ Experience with Stuttering (OASES) or the German Speech Questionnaire (23) should be applied to document health-related quality of life. Furthermore, ratings of speech naturalness should be conducted by non-professional listeners. If required, ratings of the severity of stuttering should be undertaken by professionals who are not involved in the treatment. In any case, such ratings should not be the only measure if they come from treating therapists themselves. If an associated psychological disorder is suspected, patients should be referred for guideline-conform diagnostic evaluation. If covert stuttering is suspected, symptoms should be provoked by means of communication-based stressors, such as interruptions or requests to speak faster, and psychological stress should be documented by one of the questionnaires mentioned earlier.

Table 2

Diagnostic instruments for stuttering

The guideline includes an algorithm for the recommended procedure for identifying, diagnosing, and treating stuttering, and monitoring its course.

Therapy

In Germany, effective, well evaluated stuttering therapies exist alongside therapies of very little efficacy. Especially in childhood, extensive individual therapies without any identifiable therapeutic strategy are often undertaken (16). Systematic reviews and meta-analyses have identified effective therapeutic components. For adolescents and adults, these are methods that

• initially practice slowed-down speech intensively
• include group therapy
• practice the transfer into situations of everyday life
• include self-assessment/self-management in programmed steps
• strive for naturally sounding speech, and
• include maintenance programs, as well as
• practice prolonged speech, soft voice onsets, rhythmic speaking, breathing control, and attitudinal changes regarding speaking (17, 18).

As a rule, this is implemented by all approaches recommended in the guideline; in particular, the German Kassel Stuttering Therapy is supported by a solid amount of evidence (19–22).

Physicians and therapists should advise patients and their relatives about therapeutic principles that have been proved to be beneficial and thus enable them to make an informed decision on the type of therapy, its emphasis, and its objectives.

According to the World Health Organization’s International Classification of Functioning, Disability and Health (ICF) model, stuttering therapies should make speaking easier primarily by eliminating stuttering symptoms (core symptoms) or reduce these in quantity and/or improve speech quality and by enabling enabling to speak with mental and motor ease, without the need for constant self-monitoring. Therapies should reduce accompanying symptoms and psychoemotional stress, and have a positive effect on social participation, an active life, and quality of life. Psychoemotional stress may mean that treatment is required even in covert stuttering because the severity of the stuttering does not correlate highly with such stress ([19, 23]; no correlation before therapy; temporarily low significant correlations post therapy, r = 0.20 and 0.44, respectively). Stress in school or at work can also be prevented by ensuring that disadvantages are compensated for (for example, equal opportunities in oral exams by allowing extra time or computer use, see www.bvss.de).

Treatment results should be monitored by follow-up examinations. After three months’ therapy of at least one weekly session, notable improvements should be detectable in one of the therapeutic objectives; otherwise the therapeutic approach should be revised. Whether the therapy is intensive or extensive, delivered in an outpatient or inpatient setting, and provided as individual therapy or group therapy, the patient’s possibilities should be considered. Intensive therapy using group components could be considered, as a retrospective survey of patients about the standard therapy types with sufficiently large case numbers showed greater effectiveness for such a setting (16). Subsequently and in Table 3, the efficacy of stuttering therapies available in Germany is listed according to the literature review that forms the basis of our guideline. These include:

• Approaches of speech restructuring (such as fluency shaping, Camperdown) are behavioral therapeutic methods in which a new pattern of speaking is learnt, which prevents, or is intended to prevent, dysfluencies typical of stuttering. Strong evidence supports such methods (16–22, e58–e61); they shall be considered when deciding on a therapeutic approach.
• Approaches of stuttering modification address occurring stuttering events directly by certain speech techniques while fluent parts of speech remain untouched. Furthermore, exercises are undertaken to desensitize the speaker to the act of speaking and to stuttering. Such approaches can be used in people of all age groups who stutter (16, 24, 25).
• Combinations of speech restructuring and stuttering modifications are also effective. These can be used in children aged 12 or older and in adults (25, 26, e62). There are indications that children from age 9 may also benefit from such approaches (26, 27).
• In children, strong evidence supports the Lidcombe method, which is based on the principle of operant learning and is delivered in constant collaboration with the parents (28–31). Fluent speech is positively reinforced, and if stuttering events occur these are gently corrected. This method shall be used in children aged 3–6. It has shown robust long-term effects, as long as 7 years after the therapy (e63, e64). In Germany, it is provided by therapists with certified training.
• An indirect method uses parents’ collaboration to create the individually required conditions in which the child’s speech fluency is intended to improve—for example, slowing down of the role model for speech, linguistic simplification, and a relaxed reaction to stuttering. This should be used in children aged 3–6. Strong evidence supporting this approach comes from a single Dutch study (30).

Table 3

Efficacy of stuttering therapies available in Germany

Medication treatments shall not be used (strong negative evidence [32]). Rhythmic speech and breathing control as the sole or predominant therapeutic components, hypnosis, and unspecified stuttering therapy without a recognizable concept should not be used (weak negative evidence). Further therapeutic approaches that should not be used are procedures that: (a) do not include measures ensuring the transfer into everyday life and generalization to different speaking situations; (b) do not include measures for dealing with relapse; (c) show short-term success but for which longer-term observational studies are lacking; (d) are based solely on breathing modifications or relaxation techniques; (e) allocate responsibility for causing the stuttering or potential relapses to the patient or their family; (f) promise a cure and do not comprehensibly describe treatment objectives and approaches.

Stuttering therapy should be offered independently of the affected person’s age and onset of stuttering if impairments are present in the sense of the ICF. Stuttering children aged 3–6 shall be observed for a period of 6–12 months after onset of stuttering. Therapy shall be started if the stuttering persists after that period (33, e65). It shall, however, be started imminently if (a) several risk factors for persistent stuttering are present, (b) the key symptoms include long-term symptoms with loss of control and/or increased effort, and (c) the symptoms are experienced as stressful by the parent and/or child and cause avoidance behaviors.

In children, recovery from stuttering should be aimed for at age 3 to 6 years and the therapy should be completed before they start primary school, if possible. Complete recovery can, however, not be guaranteed. The simultaneous presence of a developmental speech-language disorder should not result in delaying indicated therapy for stuttering; if required, two treatments can be prescribed simultaneously.

In case of comorbidities, such as anxiety disorders and depression, the sequence of treatment should be prioritized (34). The exclusive treatment of stuttering-associated anxiety disorder does not reduce the frequency of stuttering and exclusive treatment of the speech fluency disorder does not reduce the anxiety disorder (35). Psychotherapy that does not address the problem of the speech fluency disorder directly should not be applied as the only treatment.

Devices and software that imposes a time meter for speech or that feed back the patient’s own speech with a delay or changed frequency can eliminate stuttering during the period of their use (e66), but cannot be recommended as routine treatment components (e67). Software for improvement of speech fluency should be used only within the setting of recommended stuttering therapies and under the supervision of a therapist. Speech signal or electromyography (EMG) mediated biofeedback methods could be considered as a therapeutic component (36).

Participation in self-help groups—for example, through the Bundesvereinigung Stottern & Selbsthilfe (the Federal Association for Stuttering & Self-Help, BVSS, www.bvss.de)—is recommended on the basis of a clinical consensus.

Cluttering

Cluttering is characterized by speech that is perceived as too rapid and/or irregular, and/or with irregularly occurring phonetic/phonological abnormalities, contraction or omission of syllables, abnormal pauses, syllable stress, and speech rhythm, as well as dysfluencies that are untypical for stuttering (37). These symptoms often impact the intelligibility of people who clutter. Etiologically, genetic factors have been assumed to be causal (38, e68, e69). Neuroimaging techniques and electrophysiological findings have shown cerebral anomalies in the speech–language relevant networks (e70). Differences between cluttering and stuttering are shown in eTable 2.

eTable 2

Distinguishing characteristics of cluttering and stuttering (37, 39)

The Predictive Cluttering Inventory (e71) is available for the purpose of screening for cluttering. For the diagnostic evaluation, the medical history sheet by Sick (37) is available, as is the fluency assessment battery (39), and speech samples have to be audio(video)-recorded.. The few therapeutic studies have shown successes especially for speech restructuring strategies from stuttering therapy (40; see also eTable 3).

eTable 3

Treatment of cluttering

Needs for action and research

The guideline confirms the need for therapeutic research, among others, of the long-term effectiveness and efficiency of therapeutic approaches and their settings (individual therapy versus group therapy, extensive versus intensive/interval therapy), of predictors for therapeutic success and relapses, of how to define effectiveness-oriented, evidence-based indications for different therapeutic methods, and of patients’ reasons for deciding on certain therapeutic methods. The German remedies directives should be adapted to reflect the current state of knowledge.

Acknowledgment
We thank all our colleagues and the organizations that participated in developing the guideline, especially Peter Schneider, Georg Thum, Stephan Baumgartner†, Christian Glück; Burkhard Lawrenz, Christine Metten, Martina Rapp, and Ina Kopp. Many thanks also go to Emmanouela Dimitrakopoulou and Paul Ziemba for their editorial input in putting together the manuscript.

Conflict of interest statement
Dr. Sandrieser is in receipt of royalties for a book on the same topic from Thieme publishers.

Prof Bosshardt has received author fees for publications on the same topic from Hogrefe publishers.

The remaining authors declare that no conflict of interests exists.

Manuscript received on 18 March 2017, revised version accepted on 24 March 2017.

Translated from the original German by Birte Twisselmann, PhD.

Corresponding author
Prof. Dr. med. Katrin Neumann
Abteilung für Phoniatrie und Pädaudiologie
Klinik für Hals-, Nasen- und Ohrenheilkunde, Kopf- und Halschirurgie
St. Elisabeth-Hospital
Ruhr-Universitat Bochum

Bleichstr. 16
44787 Bochum, Germany

Supplementary material
For eReferences please refer to:
www.aerzteblatt-international.de/ref2217

eFigure, eTables:
www.aerzteblatt-international.de/17m0383

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