About the presenter: Luc De Nil is Associate Professor and Chair of the Department of Speech-Language Pathology at the University of Toronto. He is a Senior Scientist at the Toronto Western Research Institute, an Adjunct Scientist at the Hospital for Sick Children in Toronto and a Visiting Professor at the University of Leuven (Belgium). His research interests include using behavioural testing and neuroimaging to study the neural mechanism underlying speech fluency, specifically developmental stuttering, acquired adult-onset stuttering, and Tourette's syndrome. He currently is Editor-in-Chief of the Journal of Communication Disorders.

You can post Questions/comments about the following paper to the author before October 22, 2007.

Neurogenic stuttering - so much we know, so much we still need to discover!

by Luc Du Nil
from Canada

Ann (not her real name) came to me about 15 years ago seeking help for her stuttering. She had been involved in a severe accident that resulted in a loss of consciousness. Following the accident and treatment in hospital, she continued to suffer significant physical problems, involving chronic pain, severe limitations in the use of her shoulder and arms as well as balance problems. In addition, she experienced cognitive memory and word finding problems. But most importantly to her, she developed a severe problem with her speech fluency. Since her accident, she started to experience sound and syllable repetitions, as well as speech blocks which made it very hard for her to communicate effectively with others. These disfluencies were constantly present in her speech, regardless of the listener or the situation. Her speech fluency did seem to fluctuate with the level of pain experienced. She often could talk somewhat more fluently after receiving pain medication injections, but these improvements were often short-lived. This stuttering was a real problem for her because as a business professional, she considered the ability to communicate effectively paramount to a successful professional career.

As anyone would who is dealing with stuttering, she at times encountered listeners who did not fully understand the cause and impact of her fluency problem. Those experiences led to negative self perceptions and feelings of lack of appreciation. In treatment, we worked on developing speech fluency skills such as speech rate control and gentle onsets, as well as communication coping strategies, cognitive skills and attitudes.

I saw Ann relatively regularly for a couple of years. Her speech fluency improved in treatment but transfer to other situations was very difficult, especially given her other chronic physical and cognitive problems which continued to influence her speech fluency significantly. After a couple of years, we lost contact and I had not heard from Ann until recently when she contacted me again. Her situation had not changed all that much. She still experienced significant medical problems which required repeated hospitalization, and she still had significant stuttering difficulties for which she was seeking further treatment.

Ann's case is similar to many that have been documented in the literature as examples of acquired neurogenic stuttering. These case studies typically report on persons who have no known history of developmental stuttering, but who started to show stuttering-like disfluencies, either gradually or suddenly, following a stroke, the onset of a neurodegenerative condition (such as Parkinson Disease or Multiple Sclerosis), or head trauma. While these medical conditions are the most common causes for acquired stuttering, they are by far not the only ones. Acquired stuttering has been documented following many conditions that may affect how the brain processes speech, such as the use of certain medications, surgical or other medical interventions, and even sudden changes in diet.

Sometimes, the link with a medical problem seems straightforward (e.g., developing stuttering following a stroke or after being shot in the brain with a bullet), but not always. Indeed, the link sometimes may seem somewhat less obvious due to the nature of the disorder (e.g., stuttering following a spinal examination procedure or a sudden worsening of an anorexic condition) or because the time interval between disease and stuttering onset. In some patients, stuttering onset was observed within a few hours or days following the neurological events, while in others stuttering onset was observed weeks or even months after the event. Such a long time interval may obscure the causal link between a given medical condition and stuttering. To make things even more complicated, acquired stuttering has been described in persons who experienced stuttering as a child, reported recovery, but started stuttering again following the onset of a neurological disease.

Wait, wešre not done yet! Acquired stuttering is frequently reported in the context of other speech, language, motor or cognitive problems experienced by the client, such as word finding problems, verbal apraxia, dysarthria or aphasia. If the client is experiencing additional problems affecting speech fluency, differential diagnosis can be hard to achieve. Furthermore, a number of clients also experience mental, emotional or other psychological problems following a stroke, head trauma or other medical condition, which may raise further questions as to whether the speech disfluencies are neurogenic or psychogenic in nature. Although I'm not addressing psychogenic stuttering specifically in this paper, it needs to be considered carefully when trying to understand neurogenic stuttering.

Neurogenic stuttering is clearly a complex disorder. It is also said to be an infrequent disorder. But do we really know this? I would argue that we do not really know the incidence of neurogenic stuttering. No systematic prevalence or incidence studies have been published to date and this makes it hard to assess the frequency of neurogenic stuttering in a given population, or whether it is transient or chronic in nature. When asked, clinicians will often respond that they do not recall seeing clients with neurogenic stuttering in their clinical practice. My experience, however, is that the best way to get clinicians to refer clients is to let them know that you are interested in patients who demonstrate these fluency problems. Frequently, clients start noticing the presence of potential stuttering once they start looking for it and referrals come in as a result. Indeed, my distinct impression is that neurogenic stuttering (similar to buying a particular brand of cars) does not get observed until you start looking for it. Although clinical experience does seem to support that neurogenic stuttering is not a high-incidence disorder, we do not really have any reliable incidence or prevalence figures to tell us precisely how common or uncommon it is. In our laboratory, we are currently well advanced determining the incidence in a stroke population. So maybe we will have a better idea soon at least for these patients.

One of the problems with neurogenic stuttering is that the patients often have such significant medical, cognitive or language problems that their stuttering is either not noticed, or at best considered to be a minor problem. As a result, the presence of stuttering may not get reported and no follow-up is provided. In my opinion, this leads to two main problems: first, because acquired stuttering often is not on the radar screen of many clinicians (unless it is really severe or a stand-alone symptom), it may be underreported and, as a result, considered to be so infrequent as to not deserving much attention. Second, little systematic research has been published on diagnostic and intervention approaches for acquired stuttering, often leading to a 'trial and error' approach in dealing with these clients. Although a number of authors have published criteria for the diagnosis of acquired stuttering (Canter, 1971, Helm-Estabrooks, 1993, Manning, 2001), these are often based on generalized impressions from personal clinical observations as well as a number of published individual case studies. It has been shown repeatedly that these criteria do not provide the differential diagnostic specificity that is needed in clinical practice (for an overview, see De Nil, et al. 2007) and more systematic research, which probably needs to be disease-specific, is needed.

One of the most interesting questions about neurogenic stuttering is whether it truly is a form of stuttering or not. Sure, people who have been identified as having an acquired form of stuttering often display significant speech disfluencies. In a number of cases these speech disfluencies look and sound a lot like those seen in persons with developmental stuttering, but in other patients this is less the case. There are different possible explanations of neurogenic stuttering. One is that it may be a late-onset form of developmental stuttering. If so, one can assume that the complexity of multiple interacting factors (genetic, biological, environmental, psychological and learning), often assumed to be causal for developmental stuttering, would be present also for the onset of acquired stuttering. One of the attractive aspects of this view is that it would allow us to investigate the neurological (and other) factors responsible for acquired stuttering in adults and make direct inferences about the role of these factors in children with the developmental type of the disorder. Of course, the observation that stuttering could essentially start at any age would raise some very interesting challenges for current models of developmental stuttering.

Another approach to understanding neurogenic stuttering is that it is one of a number of subgroups of speech fluency disorders, with developmental stuttering being a different subgroup. One could think of this as being somewhat analogous to different subgroups of aphasia. As such, the study of neurogenic stuttering would allow us to understand better the complex and various mechanisms that underlie the production of fluent speech. While this would provide important information to increase our understanding of this acquired disorder and its treatment, it may or may not yield relevant information for developmental stuttering. A third possible approach to understanding neurogenic stuttering is that it is incorrectly identified as a separate disorder and merely reflects the fact that speech fluency can be affected as part of a great number of different speech and language disorders. In other words, it is not because disruptions of fluency can be observed in a number of patients that this should necessarily be labeled as a separate disorder or syndrome. Certainly, in my experience, patients identified by their clinicians as having neurogenic stuttering can show significant variations in the type, frequency, and qualitative nature of their speech disfluencies which may provide some ammunition for the latter view.

Which one of these three possible interpretations is correct is still an open question (maybe all three are correct for different clients). The only way to find out is to encourage investigators and clinicians to engage in more systematic clinical observations and hypothesis-driven research. This will need to involve teams of investigators across multiple settings given the relatively low (although as of yet unknown) incidence. There is no better time than now to engage in these efforts, especially given the availability of sophisticated brain imaging techniques which allow us to look at functional processes, structural anatomy and the interaction between the two. This research is urgently needed. Patients with acquired stuttering (for lack of a better term as of yet) deserve it. They deserve that we try to find better and more efficient ways to help them with their speech fluency problems. Regardless of whether we come to the conclusion that acquired and developmental stuttering are related or not, acquired stuttering offers us an opportunity to learn more about processes, especially neurological ones, that are involved in speech fluency, and what their role may be. I strongly believe that such greater insights will directly or indirectly help us understand and better treat a host of other speech disorders. Yes, there is still a lot more to discover, but we have the tools to do it now. Our patients are impatiently waiting.


Manning, W. (2001) Clinical Decision Making in Fluency Disorders (2nd Edition). San Diego: Singular Publishing.

Helm-Estabrooks, N. (1993). "Stuttering associated with acquired neurological disorders." In R.F. Curlee (ed.) Stuttering and Related Disorders of Fluency (pp. 205-218). New York: Thieme.

De Nil, L.F., Jokel, R. & Rochon, E. (2007). "Etiology, symptomatology, and treatment of neurogenic stuttering". E.G. Conture & R.F. Curlee (eds.) Stuttering and Related Disorders of Fluency (third edition). New York: Thieme.

You can post Questions/comments about the above paper to the author before October 22, 2007.

September 3, 2007
Return to the opening page of the conference