Stuttering: an overview

American Family Physician,  May 1, 2008  by Jane E. Prasse,  George E. Kikano

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Speech dysfluency (stuttering) is common in children. Although stuttering often resolves before adulthood, it can cause significant anxiety for children and their families. Stuttering speech patterns are often easily identifiable; when a child is learning to talk, repetition of sounds or words, prolonged pauses, or excessively long sounds in words usually occur. Secondary behaviors (e.g., eye blinking, jaw jerking, involuntary head or other movements) that accompany stuttering can further embarrass the child, leading to a fear of speaking. The etiology of stuttering is controversial, but contributing factors may include cognitive abilities, genetics, sex of the child, and environmental influences. Research has shown that more than 80 percent of stuttering cases are classified as developmental problems, although stuttering can also be classified as a neurologic or, less commonly, psychogenic problem. The initial assessment of patients who stutter addresses the severity of dysfluency; secondary behaviors; and the impact of stuttering, such as patient distress. Further testing is useful in assessing the need for therapy. Pharmacologic therapy has not been shown to improve stuttering. Encouraging patients to talk slowly and the use of fluency-shaping mechanisms such as delayed auditory feedback devices to slow the speech rate can help minimize or eliminate stuttering. For patients with persistent stuttering, controlled fluency or stuttering modification therapy may be effective.

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Speech dysfluency (stuttering) occurs in approximately 1.4 percent of children younger than 10 years. (1) stuttering occurs in persons of all ages, but it is most common in young children who are developing and learning language and speech. Stuttering resolves by adulthood in nearly 80 percent of children with developmental stuttering. Less than 1 percent of adults stutter, (1) 80 percent of whom are men. (2) The prevalence of stuttering is similar across different social, economic, cultural, and ethnic groups. (1)

Definitions and Concepts

Stuttering is typically defined as involuntary dysfluency in verbal expression. Usually, stuttering manifests as repetitions of sounds, syllables, or words or as speech blocks or prolonged pauses between sounds and words.

Secondary behaviors associated with stuttering include eye blinking, jaw jerking, and head or other involuntary movements. These behaviors are learned approaches to minimize the increasing severity of stuttering and can add to the patient's embarrassment and fear of speaking. Older children and adults often develop additional secondary behaviors to hide stuttering. These linguistic escape and avoidance behaviors include word substitutions, use of interjections, and sentence revisions.

Classification

Stuttering is classified as developmental, neurogenic, or psychogenic. Developmental stuttering is the most common form. It is initially noted in children between three and eight years of age and accounts for more than 80 percent of stuttering cases in the general population. (3) Approximately 75 percent of preschoolers with developmental stuttering spontaneously recover within four years. (2) Patients with developmental stuttering initially present with mild symptoms that resolve or progress to more serious symptoms with secondary behaviors.

Neurogenic stuttering usually follows a neurologic event, such as traumatic brain injury, stroke, or other brain damage. Developmental stuttering can be differentiated from acquired stuttering because, with the developmental form, stuttering occurs at the beginning of words and the secondary behaviors are more obvious than with acquired stuttering.

Psychogenic stuttering is rare and involves rapid repetition of initial sounds. It usually occurs in adults with a history of psychiatric problems following a psychological event or emotional trauma; there may be no other known etiology. (4)

Etiology

A variety of factors may influence stuttering events, although the etiology of the condition is unclear. Possible contributing factors include cognitive processing abilities, genetics, sex of the patient, and environmental influences. Research on the skills and behaviors of persons who stutter typically includes the assessment of confirmed adult stutterers.

COGNITIVE ABILITY

Recent studies have shown that some adults who stutter have different cognitive processing abilities than those who do not stutter. (5,6) One small study reported that adults who stutter have longer reaction times than fluent speakers when presented with increasingly complex cognitive tasks. (5) In persons who stuttered, these cognitive processes involved more use of the right hemisphere of the brain than was used in fluent speakers.

Another study that compared functional magnetic resonance imaging scans of persons who stutter with those who do not stutter found that neural systems activate differently during the generation and production of speech. (6) Persons who stuttered required greater ongoing attention to processing and reduced the amount of "conceptual work" to limit their stuttering. Because there are no studies of brain scans in children who stutter, the link between cognitive function and childhood stuttering has not been determined.