Is stuttering characterized by subtypes?

Ehud Yairi, Ph.D.
University of Illinois
Summer 2007

With few exceptions, every entity in the universe can find its place within a system of classification. These have an important role in the organization and enhancement of knowledge. Although certain features of stuttering are relatively consistent, such as the age at onset of the disorder and the presence of certain core speech disfluencies, there are large differences in many aspects of the disorder across people who stutter, including variations in expression of symptoms and their severity.

In addition to symptom diversity, in many ways the disorder of stuttering is inter-woven with linguistic, phonetic, cognitive, social, emotional, physiological domains, as well as other domains.

It has also been explained as emerging from a wide range of possible etiologies.Still, for a long time stuttering has been considered to be a unitary disorder. St. Onge and Calvert's (1964) remark that stuttering has been viewed as a 'pathognomonic monolith' nicely summarizes this perspective.

These two scholars posed the questions: "What are we studying when we study stuttering? Whatever it is, is it one, several, or many?" Thus, the issue of whether stuttering is a single disorder or one that includes discrete subtypes gains great importance. If subtypes exist, do they differ in terms of etiology or relative contributions of various factors? Do they follow different developmental courses? Does the nature of the disorder vary significantly among them? The implications to theory and research design are obvious. Not lessimportant is the question of whether subtypes respond differentially to various treatments.

The concept of stuttering subtypes was already entertained several hundred years ago when it was proposed that the disorder is caused by either brain hyper-excitability or by emotionality. New classifications have surfaced throughout the modern history of speech pathology as reflected in the writings of Froeschels (1943), and the more recent work of Riley and Riley (2000) and Alm (2004), reflecting diverse views on the issue.

These classifications can be grouped in many ways. For example, based on:

(a) etiology, such developmental stuttering in children and acquired stuttering when onset occurs in adults, or on several subtypes of psychogenic etiologies (Brill, 1923),

(b) prominent stuttering characteristics, such as repetitions vs. sound elongations (Froeschels, 1943; Schwartz & Conture, 1988), or exteriorized vs. interiorized stuttering (Douglas & Quarrington, 1952),

(c) biological characteristics, such as sex (Silverman & Zimmer(1979), family history of stuttering (Poulos & Webster, 1991), or cerebral lateralization (Hinkle, 1971; Sommers, Brady, & Moore, 1975),

(d) concomitant disorders, such as stuttering associated with motor or with language deficits (J. Riley, 1971),

(e) developmental course, such as Van Riper's (1971) scheme that differentiates among four different tracks.

Although a good number of ideas have been offered, only limited research concerned specifically with stuttering subtypes has been conducted. More typically, researchers have focused on a single dimension of stuttering, e.g., disfluency characteristics, motorskills, personality, brain hemispheric lateralization, thereby over-looking the multifaceted character of the stuttering disorder.

These studies were also limited to small groups of participants, and often fell short of adequate experimental controls. Perhaps due to these limitations they have not succeeded in generating strong evidence for straightforward typologies. So far, none of the proposed classification systems for stuttering as a disorder has been adopted by a significant number of either researchers or clinicians.

The current decade, however, has seen renewed theoretical and experimental interests in stuttering subtypes. For example, Feinberg, Griffin, and Levey (2000) studied people who stutter with afocus on the old idea of clonic vs. tonic stuttering; Foundas, Corey,and Hurley (2004) investigated brain lateralization; Yairi andAmbrose (2005) further pursued their persistent and naturallyrecovered subtypes; and Suresh, Ambrose, Roe, et al. (2006) looked atchromosomal markers.

Currently, a large research project devoted to the subtypes notion, supported by the National Institute On Deafness and Other Communication Disorders, is being carried out at the University of Illinois Stuttering Research Program with the participation of several other centers (e.g., Universities of Chicago, Iowa, Wisconsin at Milwaukee, Arkansas, Northern Illinois, Eastern Illinois, and the Michael Palin Center in London).

Contrary to most previous research, this project incorporates multiple aspects, such as epidemiology, speech, language, motor, personality, and more, and includes a large corpus of children and adults who stutter. Along the lines of multiple factors, variables not previously examined simultaneously in the same individuals overtime are being explored.

If subtypes of stuttering are identified and recognized, then our theories and models of stuttering will need to be sufficiently dynamic to accommodate the requisite divisions and subdivisions. As mentioned above, significant practical implications to counseling, treatment, and research design may result.

Although we are enthusiastic about the prospects, one must keep in mind the possibility that the difficulties encountered thus far inisolating stuttering subtypes could mean that stuttering is, after all, a unitary disorder and that well-defined subtypes may not exist.

References
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