How damage to the central nervous system can impact speech production
February 15, 2014
Stuttering, a speech disorder in which sounds, syllables or words are repeated or prolonged, makes communicating with others difficult. Stuttering impacts the quality of life of 3 million people living in the U.S., according to the U.S. Department of Health & Human Services.
Neurogenic stuttering, also known as neurogenic disfluency, impairs an individual's ability to generate normal rate of speech, achieve prosody, and communicate in a smooth manner, according to Marissa A. Barrera, MS, MPhil, MCSC, CCC-SLP, doctoral candidate at CUNY Graduate Center and owner of New York Neurogenic Speech-Language Pathology P.C. in New York, NY.
Unlike developmental stuttering, the more commonly known form of disfluent speech, neurogenic stuttering is an acquired fluency disorder resulting from some form of damage to the central nervous system.
Some disorders associated with neurogenic disfluencies include but are not limited to traumatic brain injury, stroke, progressive multifocal leukoencephalitis, AIDS, meningitis, tumors, neoplasms and degenerative diseases such as multiple sclerosis and Parkinson's disease.
In cases of neurogenic stuttering, the various components of speech cannot be properly coordinated because of signaling problems between the brain and nerves or muscles. "This diagnosis is different from the developmental form of stuttering or stuttering with a psychogenic etiology," explained Hunter Manasco, PhD, CCC-SLP, Misericordia University in Dallas, Pa.
Developmental vs. Neurogenic Stuttering
According to Barrera, neurogenic disfluency is similar to other types of fluency disorders, however, the age of onset and type of onset are significantly different. Developmental stuttering during childhood is perceptually similar to neurogenic disfluency, but neurogenic disfluency is triggered following trauma, injury or disease.
No two individuals with neurogenic disfluencies will present in exactly the same manner. "Perceptually, however, the person's speech may sound effortful and halting paired with intermittent interruptions and interjections," Barrera said.
Barrera shared some symptoms to watch for when evaluating an individual suspected of having neurogenic disfluencies. These symptoms include:
• Repetition of parts of words (phonemes or syllables)
• Prolongations of sound
• Repetition of entire phrases and words ("My, my, my name is .")
• Pauses or stops during atypical moments in communication
• Interjections such as repeating "um"
• Moments of accelerated rate of speech
The disfluencies of speech associated with neurogenic stuttering are usually not as varied as the disfluencies observed in developmental stuttering, Manasco observed. "A recent client, for example, displayed phoneme and syllable repetitions in the initial position as is seen usually in developmental stuttering," he said. "But the client also displayed the repetitions equally in the medial and final positions, which would be odd to see in developmental stuttering. He clearly had disfluent speech."
Additionally, Manasco stated, individuals with neurogenic stuttering do not become more fluent in situations such as choral reading and singing. These activities, however, tend to be fluency enhancing for those with a developmental form of stutter.
"Neurogenic stuttering commonly does not improve when individuals engage in singing, group reading, or when speaking in the presence of background noise and delayed auditory feedback, whereas, this is frequently helpful for persons with developmental stuttering," Barrera said.
There are other patterns of speech that set developmental stuttering apart from neurogenic stuttering.
Developmental stuttering is most often associated with contents words. In contrast, neurogenic disfluences can occur in any words in any place within an utterance, Barrera explained.
Further, neurogenic stutterers do not become less fluent in situations where those with developmental stuttering become less fluent, Manasco shared.
Some evidence exists that individuals who had once stuttered during childhood may experience a reappearance of disfluent speech following a disruption to the CNS in adulthood, Barrera told ADVANCE.
Diagnosis & Treatment
Individuals who have difficulty communicating smoothly should have an in-depth motor speech and fluency evaluation with a speech-language pathologist. According to Barrera, the individual is best served by a clinician who has experience treating and caring for patients with neurogenic disorders.
Barrera is a graduate school instructor of acquired motor speech and voice disorders at CUNY Lehman College. Barrera's neurorehabilitation center actively treats more than 300 patients, most of whom have acquired neurological disorders. More than 25 % of the clinic's patient population presents with neurogenic disfluencies secondary to injury or disease.
Barrera suggests that the evaluating SLP collect a comprehensive case history including current medications, medical status and history of stuttering earlier in one's life. The evaluation should also be used to determine the presence of additional communication impairment(s).
"A thorough evaluation is essential to determine if the individual had normal speech production prior to onset of injury or disease and to identify if another communication disorder is influencing fluent speech production," Barrera said.
The therapists at the Speech-Language-Hearing Center at Misericordia University see a large number of referrals of individuals with disfluency disorders. Manasco attributes most of the neurogenic cases he has seen to stroke, traumatic brain injury, and degenerative conditions such as dementia, Parkinson's disease, and multiple systems atrophy.
Treatment varies widely depending on several factors, according to Manasco. These factors include how severe the disfluencies are, what type of disfluencies the client is exhibiting, what the associated deficits are, what the underlying disease process creating the disfluency is, and whether or not the client is aware of and concerned with his disfluencies.
"Because neurological etiologies of stuttering tend to be damage to the brain or some degenerative process, the disfluency in speech often may not be a major concern to the client," observed Manasco.
Most commonly, the therapist employs a combination of traditional stuttering therapies developed for the treatment of the developmental stuttering population alongside other necessary therapies to treat any other language or speech deficits.
In individuals with Parkinsonism, the SLP may need to teach overt control and self-awareness of rate of speech, Manasco told ADVANCE. "These individuals often become more fluent simply by consciously and deliberately slowing and pacing their speech more appropriately," he said.
Manasco believes that speech therapy is best combined with necessary counseling for depression or social avoidance behaviors. "This approach may prove useful for those clients who are reacting negatively to their situation by withdrawing or participating less in normal social activities," he said.
Due to the disruption of the CNS as the underlying etiology of neurogenic disfluency, Barrera indicates that these individuals may also exhibit co-existing motor speech and cognitive-communication disorders including anomia, verbal apraxia, oral apraxia, dysarthria, aphasia, dysphagia and reduced executive function/cognition.
"Because neurogenic stuttering is essentially the result of some form of brain damage, it can be reasonably expected that these individuals will most often display deficits in other areas," Manasco stated.
According to Manasco, it's unlikely that a stroke, degenerative disease, or a traumatic brain injury will knock out a single skill or ability leaving all other skill levels and abilities intact.
The associated deficits exhibited by these patients are the same deficits that any SLP would associate with stroke, traumatic brain injury, or neurodegenerative disease, Manasco explained.
A speech-language therapist with experience in this area can teach patients certain strategies to improve speech fluency while developing a positive attitude toward communication.
Rebecca Mayer Knutsen is on staff at ADVANCE. Contact: firstname.lastname@example.org