Is stuttering characterized by subtypes?

Ehud Yairi, Ph.D.
University of?ÿ Illinois

With few exceptions, every entity in the universe can find its place?ÿwithin a system of classification.?ÿ These have an important role in?ÿthe organization and enhancement of knowledge.?ÿ Although certain?ÿfeatures of stuttering are relatively consistent, such as the age at?ÿonset of the disorder and the presence of certain core speech?ÿdisfluencies, there are large differences in many aspects of the?ÿdisorder across people who stutter, including variations in?ÿexpression of symptoms and their severity.

In addition to symptom diversity, in many ways the disorder of?ÿstuttering is interwoven with linguistic, phonetic, cognitive,?ÿsocial, emotional, physiological domains, as well as other domains.?ÿ

It has also been explained as emerging from a wide range of possible?ÿetiologies.?ÿStill, for a long time stuttering has been considered to?ÿ
be a unitary disorder.?ÿSt. Onge and Calvertƒ??s (1964) remark that?ÿstuttering has been viewed as a ƒ??pathognomonic monolithƒ?? nicely?ÿsummarizes this perspective.

These two scholars posed the questions: ƒ??What are we studying when?ÿwe study stuttering??ÿ Whatever it is, is it one, several, or many?ƒ???ÿ?ÿThus, the issue of whether stuttering is a single disorder or one?ÿthat includes discrete subtypes gains great importance.?ÿ If subtypes?ÿexist, do they differ in terms of etiology or relative contributions?ÿof various factors??ÿ Do they follow different developmental courses??ÿDoes the nature of the disorder vary significantly among them??ÿ The?ÿimplications to theory and research design are obvious.Not less?ÿimportant is the question of whether subtypes respond differentially?ÿto various treatments.

The concept of stuttering subtypes was already entertained several?ÿhundred years ago when it was proposed that the disorder is caused by?ÿeither brain hyper-excitability or by emotionality.?ÿNew?ÿclassifications have surfaced throughout the modern history of speech?ÿpathology as reflected in the writings of Froeschels (1943), and the?ÿmore recent work of Riley and Riley (2000) and Alm (2004), reflecting?ÿdiverse views on the issue.

These classifications can be grouped in many ways.?ÿFor example,?ÿbased on:

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

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

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

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

(e) developmental course, such as Van Riperƒ??s (1971) scheme that?ÿdifferentiates among four different tracks.

Although a good number of ideas have been offered, only limited?ÿresearch concerned specifically with stuttering subtypes has been?ÿconducted. More typically, researchers have focused on a single?ÿdimension of stuttering, e.g., disfluency characteristics, motor?ÿskills, 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?ÿoften fell short of adequate experimental controls. Perhaps due to?ÿthese limitations they have not succeeded in generating strong?ÿevidence for straightforward typologies.?ÿSo far, none of the?ÿproposed classification systems for stuttering as a disorder has been?ÿadopted by a significant number of either researchers or clinicians.

The current decade, however, has seen renewed theoretical and?ÿexperimental interests in stuttering subtypes.?ÿ For example,?ÿFeinberg, Griffin, and Levey (2000) studied people who stutter with a?ÿfocus on the old idea of clonic vs. tonic stuttering; Foundas, Corey,?ÿand Hurley (2004) investigated brain lateralization; Yairi and?ÿAmbrose (2005) further pursued their persistent and naturally?ÿrecovered subtypes; and Suresh, Ambrose, Roe, et al. (2006) looked at?ÿchromosomal markers.?ÿ

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

Contrary to most previous research, this project incorporates?ÿmultiple aspects, such as epidemiology, speech, language, motor,?ÿpersonality, and more, and includes a large corpus of children and?ÿadults who stutter.?ÿ Along the lines of multiple factors, variables?ÿnot previously examined simultaneously in the same individuals over?ÿtime are being?ÿ explored.

If subtypes of stuttering are identified and recognized, then our?ÿtheories and models of stuttering will need to be sufficiently?ÿdynamic to accommodate the requisite divisions and subdivisions.?ÿ As?ÿmentioned above, significant practical implications to counseling,?ÿtreatment, and research design may result.

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

References
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