Dysarthria in pallidal Deep Brain Stimulation in dystonia depends on the posterior location of active electrode contacts: a pilot study

Speech, voice, and language outcomes following deep brain stimulation: A systematic review

BACKGROUND

Deep brain stimulation (DBS) reliably ameliorates cardinal motor symptoms in Parkinson's disease (PD) and essential tremor (ET). However, the effects of DBS on speech, voice and language have been inconsistent and have not been examined comprehensively in a single study.

OBJECTIVE

We conducted a systematic analysis of literature by reviewing studies that examined the effects of DBS on speech, voice and language in PD and ET.

METHODS

A total of 675 publications were retrieved from PubMed, Embase, CINHAL, Web of Science, Cochrane Library and Scopus databases. Based on our selection criteria, 90 papers were included in our analysis. The selected publications were categorized into four subcategories: Fluency, Word production, Articulation and phonology and Voice quality.

RESULTS

The results suggested a long-term decline in verbal fluency, with more studies reporting deficits in phonemic fluency than semantic fluency following DBS. Additionally, high frequency stimulation, left-sided and bilateral DBS were associated with worse verbal fluency outcomes. Naming improved in the short-term following DBS-ON compared to DBS-OFF, with no long-term differences between the two conditions. Bilateral and low-frequency DBS demonstrated a relative improvement for phonation and articulation. Nonetheless, long-term DBS exacerbated phonation and articulation deficits. The effect of DBS on voice was highly variable, with both improvements and deterioration in different measures of voice.

CONCLUSION

This was the first study that aimed to combine the outcome of speech, voice, and language following DBS in a single systematic review. The findings revealed a heterogeneous pattern of results for speech, voice, and language across DBS studies, and provided directions for future studies.

Electrophysiological insights into deep brain stimulation of the network disorder dystonia

Deep brain stimulation (DBS), a treatment for modulating the abnormal central neuronal circuitry, has become the standard of care nowadays and is sometimes the only option to reduce symptoms of movement disorders such as dystonia. However, on the one hand, there are still open questions regarding the pathomechanisms of dystonia and, on the other hand, the mechanisms of DBS on neuronal circuitry. That lack of knowledge limits the therapeutic effect and makes it hard to predict the outcome of DBS for individual dystonia patients. Finding electrophysiological biomarkers seems to be a promising option to enable adapted individualised DBS treatment. However, biomarker search studies cannot be conducted on patients on a large scale and experimental approaches with animal models of dystonia are needed. In this review, physiological findings of deep brain stimulation studies in humans and animal models of dystonia are summarised and the current pathophysiological concepts of dystonia are discussed.

Physiology of dystonia: Human studies

In this chapter, we discuss neurophysiological techniques that have been used in the study of dystonia. We examine traditional disease models such as inhibition and excessive plasticity and review the evidence that these play a causal role in pathophysiology. We then review the evidence for sensory and peripheral influences within pathophysiology and look at an emergent literature that tries to probe how oscillatory brain activity may be linked to dystonia pathophysiology.

Effects of thalamic and basal ganglia deep brain stimulation on language-related functions - Conceptual and clinical considerations

Deep Brain Stimulation (DBS) is a therapy for various neurological movement disorders. It acts predominantly on motor symptoms, but may unfold a number of mostly subtle cognitive effects. In this regard, reports on particular language-related DBS sequels are comparably frequent, but difficult to overlook, given the heterogeneity of targeted structures in the brain, treated diseases, assessment methods and results reported. Accordingly, available knowledge was organized with respect to important aspects, such as the main DBS loci and surgical versus neuromodulatory therapy actions. Current views of biolinguistic underpinnings of the reviewed data, their clinical relevance and potential implications are discussed.

Surgical Management for Dystonia: Efficacy of Deep Brain Stimulation in the Long Term

Introduction: Dystonia is a movement disorder substantially affecting the quality of life. Botulinum Neurotoxin (BoNT) is used intramuscularly as a treatment for dystonia; however, not all dystonia patients respond to this treatment. Deep brain stimulation (DBS) is an established treatment for Parkinson’s disease (PD) and essential tremor, but it can help in dystonia as well. Objectives: We studied a total of 67 dystonia patients who were treated with DBS over a period of 7 years to find out the long-term efficacy of DBS in those patients. First, we calculated patient improvement in post-surgery follow-up programs using the Global Dystonia Severity scale (GDS) and Burke–Fahn–Marsden dystonia rating scale (BFMDRS). Secondly, we analyzed the scales scores to see if there was any statistical significance. Methods: In our study we analyzed patients with ages from 38 to 78 years with dystonia who underwent DBS surgery between January 2014 and December 2020 in four different centers (India, Kuwait, Egypt, and Turkey). The motor response to DBS surgery was retrospectively measured for each patient during every follow-up visit using the GDS and the BFMDRS scales. Results: Five to 7 years post-DBS, the mean reduction in the GDS score was 30 ± 1.0 and for the BFMDRS score 26 ± 1.0. The longitudinal change in scores at 12 and 24 months post-op was also significant with mean reductions in GDS and BFMDRS scores of 68 ± 1.0 and 56 ± 1.0, respectively. The p-values were <0.05 for our post-DBS dystonia patients. Conclusions: This study illustrates DBS is an established, effective treatment option for patients with different dystonias, such as generalized, cervical, and various brain pathology-induced dystonias. Although symptoms are not completely eliminated, continuous improvements are noticed throughout the post-stimulation time frame.

A practical guide to troubleshooting pallidal deep brain stimulation issues in patients with dystonia

High frequency deep brain stimulation (DBS) of the internal portion of the globus pallidus has, in the last two decades, become a mainstream therapy for the management of medically-refractory dystonia syndromes. Such increasing uptake places an onus on movement disorder physicians to become familiar with this treatment modality, in particular optimal patient selection for the procedure and how to troubleshoot problems relating to sub-optimal efficacy and therapy-related side effects. Deep brain stimulation for dystonic conditions presents some unique challenges. For example, the frequent lack of immediate change in clinical status following stimulation alterations means that programming often relies on personal experience and local practice rather than real-time indicators of efficacy. Further, dystonia is a highly heterogeneous disorder, making the development of unifying guidelines and programming algorithms for DBS in this population difficult. Consequently, physicians may feel less confident in managing DBS for dystonia as compared to other indications e.g. Parkinson's disease. In this review, we integrate our years of personal experience of the programming of DBS systems for dystonia with a critical appraisal of the literature to produce a practical guide for troubleshooting common issues encountered in patients with dystonia treated with DBS, in the hope of improving the care for these patients.

Deep Brain Stimulation in KMT2B-Related Dystonia: Case Report and Review of the Literature With Special Emphasis on Dysarthria and Speech

Objective: KMT2B-related dystonia is a progressive childhood-onset movement disorder, evolving from lower-limb focal dystonia into generalized dystonia. With increasing age, children frequently show prominent laryngeal or facial dystonia manifesting in dysarthria. Bilateral deep brain stimulation of the globus pallidus internus (GPi-DBS) is reported to be an efficient therapeutic option. Especially improvement of dystonia and regaining of independent mobility is commonly described, but detailed information about the impact of GPi-DBS on dysarthria and speech is scarce. Methods: We report the 16-months outcome after bilateral GPi-DBS in an 8-year-old child with KMT2B-related dystonia caused by a de-novo c.3043C>T (p.Arg1015^*) non-sense variant with special emphasis on dysarthria and speech. We compare the outcome of our patient with 59 patients identified through a PubMed literature search. Results: A remarkable improvement of voice, articulation, respiration and prosodic characteristics was seen 16 months after GPi-DBS. The patients' speech intelligibility improved. His speech became much more comprehensible not only for his parents, but also for others. Furthermore, his vocabulary and the possibility to express his feelings and wants expanded considerably. Conclusion: A positive outcome of GPi-DBS on speech and dysarthria is rarely described in the literature. This might be due to disease progression, non-effectiveness of DBS or due to inadvertent spreading of the electrical current to the corticobulbar tract causing stimulation induced dysarthria. This highlights the importance of optimal lead placement, the possibility of horizontal steering of the electrical field by applying directional stimulation with segmented leads as well as the use of the lowest possible effective stimulation intensity.

Dysarthria and Speech Intelligibility Following Parkinson’s Disease Globus Pallidus Internus Deep Brain Stimulation

Background: Although earlier studies reported variable speech changes following subthalamic nucleus (STN) deep brain stimulation (DBS) in Parkinson’s disease (PD) patients, the effects of globus pallidus internus (GPi) DBS on speech performance in PD remain largely unknown. Objective: We aimed to characterize speech changes following PD GPi-DBS. Methods: We retrospectively analyzed clinical and speech outcomes of 25 PD patients treated with bilateral GPi-DBS at a single center. Outcome measures included the Unified Parkinson’s Disease Rating Scale (UPDRS), speech subsystem domains (respiratory, laryngeal, resonance, orofacial, rate, prosody, rhythm, and naturalness), and overall speech intelligibility. Scores at baseline were compared with those at 6 months, 1 year, and the longest clinical follow-up available. Results: In the off-medication state, activities of daily living and motor function based on UPDRS II and III significantly improved postoperatively. We observed unique patterns of speech changes in patients with PD following GPi-DBS in the short- (n = 25) and longer-term (n = 8) follow-up periods. Velopharyngeal (resonance), laryngeal components, and prosody worsened after bilateral GPi-DBS (p < 0.015). Speech intelligibility did not worsen after GPi-DBS in the short-term, but there was a trend to deteriorate at long-term follow-up (e.g., one year and beyond). We observed worsening of hypokinetic dysarthria in individual patients. Also, a minority of patients developed stuttering, spastic dysarthria, or ataxic dysarthria. Conclusion: Bilateral GPi-DBS worsened several modalities of parkinsonian speech without compromising overall speech intelligibility. GPi-DBS can potentially worsen or induce hypokinetic dysarthria, stuttering, spastic dysarthria, or ataxic dysarthria. GPi-DBS may have different and variable effects on speech function when compared to STN-DBS.

Auditory-Perceptual Evaluation of Deep Brain Stimulation on Voice and Speech in Patients With Dystonia

OBJECTIVE

To determine the effects of globus pallidus interna (GPi) deep brain stimulation (DBS) on speech and voice quality of patients with primary, medically refractory dystonia.

METHODS

Voices of 14 patients aged ≥18 years (males = 7 and females = 7) with primary dystonia (DYT1 gene mutation dystonia = 4, cervical dystonia = 6, and generalized dystonia = 4) with bilateral GPi DBS were assessed. Five blinded raters (two fellowship-trained laryngologists and three speech/language pathologists) evaluated audio recordings of each patient pre- and post-DBS. Perceptual voice quality was rated using the Grade, Roughness, Breathiness, Asthenia, and Strain scale and changes in speech intelligibility were assessed with the Clinical Global Impression scale of Severity instrument. Inter-rater and intrarater reliability rates for perceptual voice ratings were assessed using the kappa coefficient.

RESULTS

Voice quality parameters showed mean improvements in Grade (P < 0.0001), Roughness (P = 0.0043), and Strain (P < 0.0001) 12 months post-DBS. Asthenia increased from baseline to 6 months (P = 0.0022) and declined significantly from 6 to 12 months (P = 0.0170). Breathiness did not change significantly over time. Speech intelligibility also improved from 6 to 12 months (P = 0.0202) and from pre-DBS to 12 months post-DBS (P = 0.0022). Grade and Strain ratings had nearly perfect and substantial inter-rater agreement (0.84 and 0.71, respectively).

CONCLUSIONS

Voice and speech intelligibility improved after bilateral GPi DBS for dystonia. GPi DBS may emerge as a potential treatment option for patients with medically refractory laryngeal dystonia.

Functional and Structural Connectivity Patterns Associated with Clinical Outcomes in Deep Brain Stimulation of the Globus Pallidus Internus for Generalized Dystonia

BACKGROUND AND PURPOSE

Deep brain stimulation is a well-established treatment for generalized dystonia, but outcomes remain variable. Establishment of an imaging marker to guide device targeting and programming could possibly impact the efficacy of deep brain stimulation in dystonia, particularly in the absence of acute clinical markers to indicate benefit. We hypothesize that the stimulation-based functional and structural connectivity using resting-state fMRI and DTI can predict therapeutic outcomes in patients with generalized dystonia and deep brain stimulation.

MATERIALS AND METHODS

We performed a retrospective analysis of 39 patients with inherited or idiopathic-isolated generalized dystonia who underwent bilateral globus pallidus internus deep brain stimulation. After electrode localization, the volumes of tissue activated were modeled and used as seed regions for functional and structural connectivity measures using a normative data base. Resulting connectivity maps were correlated with postoperative improvement in the Unified Dystonia Rating Scale score.

RESULTS

Structural connectivity between the volumes of tissue activated and the primary sensorimotor cortex was correlated with Unified Dystonia Rating Scale improvement, while more anterior prefrontal connectivity was inversely correlated with Unified Dystonia Rating Scale improvement. Functional connectivity between the volumes of tissue activated and primary sensorimotor regions, motor thalamus, and cerebellum was most correlated with Unified Dystonia Rating Scale improvement; however, an inverse correlation with Unified Dystonia Rating Scale improvement was seen in the supplemental motor area and premotor cortex.

CONCLUSIONS

Functional and structural connectivity with multiple nodes of the motor network is associated with motor improvement in patients with generalized dystonia undergoing deep brain stimulation. Results from this study may serve as a basis for future development of clinical markers to guide deep brain stimulation targeting and programming in dystonia.

Deep brain stimulation for dystonia in Finland during 2007-2016

BACKGROUND

Dystonia is a movement disorder substantially affecting the quality of life and the ability to work. A proportion of patients does not respond to first line pharmacotherapy. Deep brain stimulation (DBS) is established as a primary operative treatment option for severe drug resistant dystonia. We studied dystonia patients treated with DBS in Finland between the years 2007-2016 to evaluate the use and outcomes of DBS treatment.

METHODS

We analysed the hospital records of dystonia patients, who underwent DBS operation during 2007-2016 in Finland. The clinical and technical parameters were recorded as well as preoperative assessments and treatments. The response to DBS was evaluated retrospectively using the Global Dystonia Rating Scale (GDS).

RESULTS

Out of 585 dB implantations during the study period, 37 were done for dystonia. The clinical response improved significantly with time in the isolated focal dystonia group, and at 12 months, 22 of 32 patients had over 50% alleviation of the GDS score. There was only one subclinical intracerebral haemorrhage, and four infections leading to revision. Speech impairment and limb coordination problems were common stimulation- related adverse events and were mostly resolved or relieved with the adjustment of stimulation parameters.

CONCLUSIONS

DBS seems to be beneficial in dystonia. Although DBS is indicated for dystonia in Finland, the number of operations did not increase at the same rate as DBS operations in general. DBS appears to be a safe and effective treatment for focal as well as generalized dystonia.

Effect of pallidal deep-brain stimulation on articulation rate in dystonia

Pallidal deep-brain stimulation of the internal globus pallidus (GPi-DBS) is an effective treatment for dystonia. However, GPi-DBS may cause important stimulation-induced side effects such as hypokinetic dysarthria, which is particularly manifested by articulation rate abnormalities. However, little data regarding the effect of the location of the electrode and stimulation parameters for pallidal stimulation on articulation rate in dystonia is available. Speech data were acquired from 18 dystonic patients with GPi-DBS and 18 matched healthy controls. Each of dystonic patients was tested twice within 1 day in both the GPi-DBS ON and GPi-DBS OFF stimulation conditions. Compared to healthy controls, the decreased diadochokinetic rate and slower articulation rate in dystonic patients were observed in both stimulation conditions. No significant differences in speech rate measures between stimulation conditions were detected with no relation to contact localization and stimulation intensity. Our findings do not support the use articulation rate as a surrogate marker of stimulation-induced changes to the speech apparatus in dystonia.

Subthalamic deep brain stimulation in patients with primary dystonia: A ten-year follow-up study

BACKGROUND

Subthalamic deep brain stimulation (STN-DBS) is a promising intervention for primary dystonia; however, evidence regarding its efficacy is lacking. Thus, a long-term follow-up is indispensable.

OBJECTIVE

This trial was designed to examine the efficacy and consistency of subthalamic deep brain stimulation in patients with primary dystonia over the long term.

METHOD

This was a retrospective study involving 14 patients with primary dystonia who underwent STN-DBS and consented to a follow-up of at least 10 years. The Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) and 36-item Short-Form General Health Survey were employed, at five time points (pre-operation [baseline], 1 month post-operation, 1 year post-operation, 5 years post-operation, and last follow-up), to assess improvement of dystonic symptoms and changes in quality of life.

OUTCOMES

All patients gained extensive clinical benefits from STN-DBS therapy, without experiencing serious adverse effects. Improvements of 59.0% at 1 month, 85.0% at 1 year, and 90.8% at 5 years after the operation, and up to 91.4% at the last follow-up, were demonstrated by movement evaluation with the BFMDRS. All patients achieved a substantial improvement in quality of life.

CONCLUSION

Subthalamic deep brain stimulation is an effective and persisting alternative to pallidal deep brain stimulation, and importantly, it is very safe even with extremely long-term chronic stimulation.