Effects of neurosurgical management of Parkinson's disease on speech characteristics and oromotor function

Subcortical Effects on Voice and Fluency in Dysarthria: Observations from Subthalamic Nucleus Stimulation

OBJECTIVE

Parkinson's disease (PD), caused by basal ganglia dysfunction, is associated with motor disturbances including dysarthria. Stimulation of the subthalamic nucleus, a preferred treatment targeting basal ganglia function, improves features of the motor disorder, but has uncertain effects on speech.We studied speech during contrasting stimulation states to reveal subcortical effects on voice and articulation. Measures were made on selected samples of spontaneous and repeated speech.

METHODS

Persons with Parkinson's disease (PWP) who had undergone bilateral deep brain stimulation of the subthalamic nucleus (DBS-STN) provided spontaneous speech samples and then repeated portions of their monologue both on and off stimulation. Excerpts were presented in a listening protocol probing intelligibility. Also analysed were a continuous phrase repetition task and a second spontaneous speech sample. Fundamental frequency (F0), harmonic-to-noise ratio (HNR), jitter, shimmer and fluency were measured in these three speech samples performed with DBS stimulation on and off.

RESULTS

During subcortical stimulation, spontaneous excerpts were less intelligible than repeated excerpts. F0 and HNR were higher and shimmer was decreased in repetition and stimulation. Articulatory dysfluencies were increased for spontaneous speech and during stimulation in all three speech samples.

CONCLUSION

Deep brain stimulation disrupts fluency and improves voice in spontaneous speech, reflecting an inverse influence of subcortical systems on articulatory posturing and laryngeal mechanisms. Better voice and less dysfluency in repetition may occur because an external model reduces the speech planning burden, as seen for gait and arm reach. These orthogonal results for fluency versus phonatory competence may account for ambivalent reports from dysarthric speakers and reveal the complexity of subcortical control of motor speech.

The Feasibility of Using Acoustic Markers of Speech for Optimizing Patient Outcomes during Randomized Amplitude Variation in Deep Brain Stimulation: A Proof of Principle Methods Study

Background

Deep brain stimulation (DBS) is an effective treatment for reducing symptoms of tremor. A common and typically subjectively determined adverse effect of DBS is dysarthria. Current assessment protocols are driven by the qualitative judgments of treating clinicians and lack the sensitivity and objectivity required to optimize patient outcomes where multiple stimulation parameters are trialed.

Objective

To examine the effect of DBS on speech in patients receiving stimulation to the posterior sub-thalamic area (PSA) via randomized manipulation of amplitude parameters.

Methods

Six patients diagnosed with tremor receiving treatment via DBS of the PSA were assessed in a double-blinded, within-subjects experimental protocol. Amplitude (i.e., voltage or current) was randomly adjusted across 10 settings, while speech samples (e.g., sustained vowel, counting to 10) were recorded to identify the patient-specific settings required for optimal therapeutic benefit (reduced tremor) with minimal adverse effects (altered speech). Speech production between stimulation parameters was quantified using acoustic analysis.

Results

Speech changed as a response to DBS but those changes were not uniform across patients nor were they generally in line with changes in amplitude with the exception of reduced vocal control and increased mean silence length in two patients. Speech outcomes did not correlate with changes in tremor.

Conclusion

Intra-individual changes in speech were detected as a response to modified amplitude; however, no clear pattern was observed across patients as a group. The use of objective acoustic measures allows for quantification of speech changes during DBS optimization protocols, even when those changes are subtle and potentially difficult to detect perceptually.

STN vs. GPi Deep Brain Stimulation: Translating the Rematch into Clinical Practice

When formulating a deep brain stimulation (DBS) treatment plan for a patient with Parkinson's disease (PD), two critical questions should be addressed: 1- Which brain target should be chosen to optimize this patient's outcome? and 2- Should this patient's DBS operation be unilateral or bilateral? Over the past two decades, two targets have emerged as leading contenders for PD DBS; the subthalamic nucleus (STN) and the globus pallidus internus (GPi). While the GPi target does have a following, most centers have uniformly employed bilateral STN DBS for all Parkinson's disease cases (Figure 1). This bilateral STN "one-size-fits-all" approach was challenged by an editorial entitled "STN vs. GPi: The Rematch," which appeared in the Archives of Neurology in 2005. Since 2005, a series of well designed clinical trials and follow-up studies have addressed the question as to whether a more tailored approach to DBS therapy might improve overall outcomes. Such a tailored approach would include the options of targeting the GPi, or choosing a unilateral operation. The results of the STN vs. GPi 'rematch' studies support the conclusion that bilateral STN DBS may not be the best option for every Parkinson's disease surgical patient. Off period motor symptoms and tremor improve in both targets, and with either unilateral or bilateral stimulation. Advantages of the STN target include more medication reduction, less frequent battery changes, and a more favorable economic profile. Advantages of GPi include more robust dyskinesia suppression, easier programming, and greater flexibility in adjusting medications. In cases where unilateral stimulation is anticipated, the data favor GPi DBS. This review summarizes the accumulated evidence regarding the use of bilateral vs. unilateral DBS and the selection of STN vs. GPi DBS, including definite and possible advantages of different targets and approaches. Based on this evidence, a more patient-tailored, symptom specific approach will be proposed to optimize outcomes of PD DBS therapy. Finally, the importance of an interdisciplinary care team for screening and effective management of DBS patients will be reaffirmed. Interdisciplinary teams can facilitate the proposed patient-specific DBS treatment planning and provide a more thorough analysis of the risk-benefit ratio for each patient.

Effect of subthalamic stimulation on voice and speech in Parkinson's disease: for the better or worse?

BACKGROUND

Deep brain stimulation of the subthalamic nucleus, although highly effective for the treatment of motor impairment in Parkinson's disease (PD), can induce speech deterioration in a subgroup of patients. The aim of the current study was to survey (1) if there are distinctive stimulation effects on the different parameters of voice and speech and (2) if there is a special pattern of preexisting speech abnormalities indicating a risk for further worsening under stimulation.

METHODS

N = 38 patients with PD had to perform a speech test without medication with stimulation ON (StimON) and stimulation OFF (StimOFF). Speech samples were analyzed: (1) according to a four-dimensional perceptual speech score and (2) by acoustic analysis to obtain quantifiable measures of distinctive speech parameters.

RESULTS

Quality of voice was ameliorated with StimON, and there were trends of increased loudness and better pitch variability. N = 8 patients featured a deterioration of speech with StimON, caused by worsening of articulation or/and fluency. These patients already had more severe overall speech impairment with characteristic features of articulatory slurring and articulatory acceleration under StimOFF condition.

CONCLUSION

The influence of subthalamic StimON Parkinsonian speech differs considerably between individual patients, however, there is a trend to amelioration of voice quality and prosody. Patients with stimulation-associated speech deterioration featured higher overall speech impairment and showed a distinctive pattern of articulatory abnormalities at baseline. Further investigations to confirm these preliminary findings are necessary to allow neurologists to pre-surgically estimate the individual risk of deterioration of speech under stimulation.

Effect of deep brain stimulation on speech performance in Parkinson's disease

Deep brain stimulation (DBS) has been reported to be successful in relieving the core motor symptoms of Parkinson's disease (PD) and motor fluctuations in the more advanced stages of the disease. However, data on the effects of DBS on speech performance are inconsistent. While there are some series of patients documenting that speech function was relatively unaffected by DBS of the nucleus subthalamicus (STN), other investigators reported on improvements of distinct parameters of oral control and voice. Though, these ameliorations of single speech modalities were not always accompanied by an improvement of overall speech intelligibility. On the other hand, there are also indications for an induction of dysarthria as an adverse effect of STN-DBS occurring at least in some patients with PD. Since a deterioration of speech function has more often been observed under high stimulation amplitudes, this phenomenon has been ascribed to a spread of current-to-adjacent pathways which might also be the reason for the sporadic observation of an onset of dysarthria under DBS of other basal ganglia targets (e.g., globus pallidus internus/GPi or thalamus/Vim). The aim of this paper is to review and evaluate reports in the literature on the effects of DBS on speech function in PD.

Sherlock Holmes and the strange case of the missing attribution: a historical note on "The Grandfather Passage"

PURPOSE

In 1963, Charles Van Riper published "My Grandfather," a short reading passage that has evolved into a ubiquitous metric of reading ability and speech intelligibility. In this historical note, we describe several heretofore unacknowledged similarities between "The Grandfather Passage" (Darley, Aronson, & Brown, 1975) and a portion of The Valley of Fear (Conan Doyle, 1915/2006), the final novel of the Sherlock Holmes series. We also describe overlap between "My Grandfather" and "The Grandfather Passage."

METHOD

We contrasted propositions within The Valley of Fear to "My Grandfather" and "The Grandfather Passage." We also compared the respective text strings using the Turnitin antiplagiarism software application (iParadigms, 2011).

RESULTS

"My Grandfather" and "The Grandfather Passage" are nearly identical passages with 88% string overlap. In addition, both passages show similarities with text from The Valley of Fear.

CONCLUSIONS

Darley et al. (1975) did not acknowledge Van Riper (1963) as the original author of "The Grandfather Passage." In addition to this citation oversight, neither Darley et al. nor Van Riper attributed Conan Doyle as original source material. We describe the colorful history of this passage that has seen a remarkable breadth of utility in speech and language sciences.

A preliminary report on disordered speech with deep brain stimulation in individuals with Parkinson's disease

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has proven effective in treating the major motor symptoms of advanced Parkinson's disease (PD). The aim of this study was to learn which laryngeal and articulatory acoustic features changed in patients who were reported to have worse speech with stimulation. Six volunteers with PD who had bilateral STN electrodes were recorded with DBS turned on or off. Perceptual ratings reflected poorer speech performance with DBS on. Acoustic measures of articulation (corner vowel formants, diphthong slopes, and a spirantization index) and phonation (perturbation, long-term average spectrum) as well as verbal fluency scores showed mixed results with DBS. Some speakers improved while others became worse on individual measures. The magnitude of DBS effects was not predictable based on the patients' demographic characteristics. Future research involving adjustments to stimulator settings or electrode placement may be beneficial in limiting the negative effects of DBS on speech.

Acoustic Analysis of PD Speech

According to the U.S. National Institutes of Health, approximately 500,000 Americans have Parkinson's disease (PD), with roughly another 50,000 receiving new diagnoses each year. 70%-90% of these people also have the hypokinetic dysarthria associated with PD. Deep brain stimulation (DBS) substantially relieves motor symptoms in advanced-stage patients for whom medication produces disabling dyskinesias. This study investigated speech changes as a result of DBS settings chosen to maximize motor performance. The speech of 10 PD patients and 12 normal controls was analyzed for syllable rate and variability, syllable length patterning, vowel fraction, voice-onset time variability, and spirantization. These were normalized by the controls' standard deviation to represent distance from normal and combined into a composite measure. Results show that DBS settings relieving motor symptoms can improve speech, making it up to three standard deviations closer to normal. However, the clinically motivated settings evaluated here show greater capacity to impair, rather than improve, speech. A feedback device developed from these findings could be useful to clinicians adjusting DBS parameters, as a means for ensuring they do not unwittingly choose DBS settings which impair patients' communication.

Effects of medication and subthalamic nucleus deep brain stimulation on tongue movements in speakers with Parkinson's disease using electropalatography: a pilot study

Parkinson's disease (PD) affects speech in the majority of patients. Subthalamic nucleus deep brain stimulation (STN-DBS) is particularly effective in reducing tremor and rigidity. However, its effect on speech is variable. The aim of this pilot study was to quantify the effects of bilateral STN-DBS and medication on articulation, using electropalatography (EPG). Two patients, PT1 and PT2, were studied under four conditions: on and off medication and ON and OFF stimulation. The EPG protocol consisted of a number of target words with alveolar and velar stops, repeated 10 times in random order. The motor part III of the Unified Parkinson Disease Rating Scale (UPDRS) indicated significantly improved motor scores in the ON stimulation condition in both patients. However, PT1's articulation patterns deteriorated with stimulation whereas PT2 showed improving articulatory accuracy in the same condition. The results revealed different effects of stimulation and medication on articulation particularly with regard to timing. The study quantified less articulatory undershoot for velar stops in comparison to alveolars. Furthermore, the findings provided preliminary evidence that stimulation with medication has a more detrimental effect on articulation than stimulation without medication.

Subthalamic nucleus deep brain stimulation changes velopharyngeal control in Parkinson's disease

PURPOSE

Adequate velopharyngeal control is essential for speech, but may be impaired in Parkinson's disease (PD). Bilateral subthalamic nucleus deep brain stimulation (STN DBS) improves limb function in PD, but the effects on velopharyngeal control remain unknown. We tested whether STN DBS would change aerodynamic measures of velopharyngeal control, and whether these changes were correlated with limb function and stimulation settings.

METHODS

Seventeen PD participants with bilateral STN DBS were tested within a morning session after a minimum of 12h since their most recent dose of anti-PD medication. Testing occurred when STN DBS was on, and again 1h after STN DBS was turned off, and included aerodynamic measures during syllable production, and standard neurological ratings of limb function.

RESULTS

We found that PD participants exhibited changes with STN DBS, primarily consistent with increased intraoral pressure (n=7) and increased velopharyngeal closure (n=5). These changes were modestly correlated with measures of limb function, and were correlated with stimulation frequency.

CONCLUSION

Our findings suggest that STN DBS may change velopharyngeal control during syllable production in PD, with greater benefit associated with low frequency stimulation. However, DBS demonstrates a more subtle influence on speech-related velopharyngeal control than limb motor control. This distinction and its underlying mechanisms are important to consider when assessing the impact of STN DBS on PD.

LEARNING OUTCOMES

As a result of this activity, the participant will be able to (1) describe the effects of deep brain stimulation on limb and speech function; (2) describe the effects of deep brain stimulation on velopharyngeal control; and (3) discuss the possible reasons for differences in limb outcomes compared with speech function with deep brain stimulation of the subthalamic nucleus.

Subthalamic nucleus deep brain stimulation changes speech respiratory and laryngeal control in Parkinson's disease

Adequate respiratory and laryngeal motor control are essential for speech, but may be impaired in Parkinson's disease (PD). Bilateral subthalamic nucleus deep brain stimulation (STN DBS) improves limb function in PD, but the effects on respiratory and laryngeal control remain unknown. We tested whether STN DBS would change aerodynamic measures of respiratory and laryngeal control, and whether these changes were correlated with limb function and stimulation parameters. Eighteen PD participants with bilateral STN DBS were tested within a morning session after a minimum of 12 h since their most recent dose of anti-PD medication. Testing occurred when DBS was on, and again 1 h after DBS was turned off, and included aerodynamic measures during syllable production, and standard clinical ratings of limb function. We found that PD participants exhibited changes with DBS, consistent with increased respiratory driving pressure (n = 9) and increased vocal fold closure (n = 9). However, most participants exceeded a typical operating range for these respiratory and laryngeal control variables with DBS. Changes were uncorrelated with limb function, but showed some correlation with stimulation frequency and pulse width, suggesting that speech may benefit more from low-frequency stimulation and shorter pulse width. Therefore, high-frequency STN DBS may be less beneficial for speech-related respiratory and laryngeal control than for limb motor control. It is important to consider these distinctions and their underlying mechanisms when assessing the impact of STN DBS on PD.

Patient-specific model-based investigation of speech intelligibility and movement during deep brain stimulation

BACKGROUND/AIMS

Deep brain stimulation (DBS) is widely used to treat motor symptoms in patients with advanced Parkinson's disease. The aim of this study was to investigate the anatomical aspects of the electric field in relation to effects on speech and movement during DBS in the subthalamic nucleus.

METHODS

Patient-specific finite element models of DBS were developed for simulation of the electric field in 10 patients. In each patient, speech intelligibility and movement were assessed during 2 electrical settings, i.e. 4 V (high) and 2 V (low). The electric field was simulated for each electrical setting.

RESULTS

Movement was improved in all patients for both high and low electrical settings. In general, high-amplitude stimulation was more consistent in improving the motor scores than low-amplitude stimulation. In 6 cases, speech intelligibility was impaired during high-amplitude electrical settings. Stimulation of part of the fasciculus cerebellothalamicus from electrodes positioned medial and/or posterior to the center of the subthalamic nucleus was recognized as a possible cause of the stimulation-induced dysarthria.

CONCLUSION

Special attention to stimulation-induced speech impairments should be taken in cases when active electrodes are positioned medial and/or posterior to the center of the subthalamic nucleus.

A noninvasive imaging approach to understanding speech changes following deep brain stimulation in Parkinson's disease

PURPOSE

To explore the use of noninvasive functional imaging and "virtual" lesion techniques to study the neural mechanisms underlying motor speech disorders in Parkinson's disease. Here, we report the use of positron emission tomography (PET) and transcranial magnetic stimulation (TMS) to explain exacerbated speech impairment following subthalamic nucleus deep brain stimulation (STN-DBS) in a patient with Parkinson's disease.

METHOD

Perceptual and acoustic speech measures, as well as cerebral blood flow during speech as measured by PET, were obtained with STN-DBS on and off. TMS was applied to a region in the speech motor network found to be abnormally active during DBS. Speech disruption by TMS was compared both perceptually and acoustically with speech produced with DBS on.

RESULTS

Speech production was perceptually inferior and acoustically less contrastive during left STN stimulation compared to no stimulation. Increased neural activity in left dorsal premotor cortex (PMd) was observed during DBS on. "Virtual" lesioning of this region resulted in speech characterized by decreased speech segment duration, increased pause duration, and decreased intelligibility.

CONCLUSIONS

This case report provides evidence that impaired speech production accompanying STN-DBS may result from unintended activation of PMd. Clinical application of functional imaging and TMS may lead to optimizing the delivery of STN-DBS to improve outcomes for speech production as well as general motor abilities.

Effect of bilateral stimulation of the subthalamic nucleus on different speech subsystems in patients with Parkinson's disease

The effect of deep brain stimulation on the two speech-production subsystems, articulation and phonation, of nine Parkinsonian patients is examined. Production parameters (stop closure voicing; stop closure, VOT, vowel) in fast syllable-repetitions were defined and measured and quantitative, objective metrics of vocal fold function were obtained during vowel production. Speech material was recorded for patients (with and without stimulation) and for a reference group of healthy control speakers. With stimulation, precision of the glottal and supraglottal articulation as well as the phonatory function is reduced for some individuals, whereas for other individuals an improvement is observed. Importantly, the improvement or deterioration is determined not only on the basis of the direction of parameter change but also on the individuals' position relative to the healthy control data. This study also notes differences within an individual in the effects of stimulation on the two speech subsystems. These findings qualify the value of global statements about the effect of neurostimulatory operations on Parkinsonian patients. They also underline the importance of careful consideration of individual differences in the effect of deep brain stimulation on different speech subsystems.

Speech, Language, and Swallowing Disorders in the Older Adult

The geriatric population has become a major component in the practice of medical speech-language pathology. This article discusses normal and abnormal functions of speech, voicing, language, cognition, and swallowing. Particular attention is given to disorders affecting the geriatric population. Evaluation, treatment, and ethical issues are explored in addition to the role of the speech-language pathologist on the interdisciplinary team.

An Internet-based telerehabilitation system for the assessment of motor speech disorders: a pilot study

PURPOSE

This pilot study explored the feasibility and effectiveness of an Internet-based telerehabilitation application for the assessment of motor speech disorders in adults with acquired neurological impairment.

METHOD

Using a counterbalanced, repeated measures research design, 2 speech-language pathologists assessed 19 speakers with dysarthria on a battery of perceptual assessments. The assessments included a 19-item version of the Frenchay Dysarthria Assessment (FDA; P. Enderby, 1983), the Assessment of Intelligibility of Dysarthric Speech (K. M. Yorkston & D. R. Beukelman, 1981), perceptual analysis of a speech sample, and an overall rating of severity of the dysarthria. One assessment was conducted in the traditional face-to-face manner, whereas the other assessment was conducted using an online, custom-built telerehabilitation application. This application enabled real-time videoconferencing at 128 kb/s and the transfer of store-and-forward audio and video data between the speaker and speech-language pathologist sites. The assessment methods were compared using the J. M. Bland and D. G. Altman (1986, 1999) limits-of-agreement method and percentage level of agreement between the 2 methods.

RESULTS

Measurements of severity of dysarthria, percentage intelligibility in sentences, and most perceptual ratings made in the telerehabilitation environment were found to fall within the clinically acceptable criteria. However, several ratings on the FDA were not comparable between the environments, and explanations for these results were explored.

CONCLUSIONS

The online assessment of motor speech disorders using an Internet-based telerehabilitation system is feasible. This study suggests that with additional refinement of the technology and assessment protocols, reliable assessment of motor speech disorders over the Internet is possible. Future research methods are outlined.

Changes in gait and symptoms after bilateral pallidotomy: a client with Parkinson's disease

A single-subject, time-series design was used to describe a female with young-onset Parkinson's disease who, after a period of 15 years, was demonstrating long term side effects of medication in addition to the progression of Parkinson's disease. She underwent a bilateral pallidotomy to address these problems. Prior to her surgery, her spatiotemporal gait kinematics were measured at intervals before and after medication ingestion. The identical procedures were undertaken one month and at four months post-pallidotomy. In all three sessions, the Webster Scale scored her symptoms while her medication was not working (Off) and again when effective (On). After surgery, she was interviewed to obtain a qualitative impression of the outcome. Before the surgery, the gait parameters demonstrated a fluctuating profile. Forty-five minutes post-medication, her gait parameters approached normal levels but significant dyskinetic movements were evident. Her Webster Scale scores indicated advanced Parkinson's disease particularly when Off One-month post-pallidotomy, her gait parameters were more consistent with dyskinesias mildly present. Her Webster Scale scores were reduced while both Off and On. Four months post-pallidotomy her gait parameters were entirely consistent and within normal limits. Her Webster Scale scores were the same Off and On and no dyskinesias were detectable. The excellent result was probably enhanced by the patient's dedication to regular exercise designed to minimize secondary physical complications.