The effect of deep brain stimulation on the speech motor system

Deep Brain Stimulation for Orthostatic Tremor: An Observational Study

BACKGROUND

Primary orthostatic tremor (OT) can affect patients' life. Treatment of OT with deep brain stimulation (DBS) of the thalamic ventral intermediate nucleus (Vim) is described in a limited number of patients. The Vim and posterior subthalamic area (PSA) can be targeted in a single trajectory, allowing both stimulation of the Vim and/or dentatorubrothalamic tract (DRT). In essential tremor this is currently often used with positive effects.

OBJECTIVE

To evaluate the efficacy of Vim/DRT-DBS in OT-patients, based on standing time and Quality of Life (QoL), also on the long-term. Furthermore, to relate stimulation of the Vim and DRT, medial lemniscus (ML) and pyramidal tract (PT) to beneficial clinical and side-effects.

METHODS

Nine severely affected OT-patients received bilateral Vim/DRT-DBS. Primary outcome measure was standing time; secondary measures included self-reported measures, neurophysiological measures, structural analyses, surgical complications, stimulation-induced side-effects, and QoL up to 56 months. Stimulation of volume of tissue activated (VTA) were related to outcome measures.

RESULTS

Average maximum standing time increased from 41.0 s ± 51.0 s to 109.3 s ± 65.0 s after 18 months, with improvements measured in seven of nine patients. VTA (n = 7) overlapped with the DRT in six patients and with the ML and/or PT in six patients. All patients experienced side-effects and QoL worsened during the first year after surgery, which improved again during long-term follow-up, although remaining below age-related normal values. Most patients reported a positive effect of DBS.

CONCLUSION

Vim/DRT-DBS improved standing time in patients with severe OT. Observed side-effects are possibly related to stimulation of the ML and PT.

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.

The role of the motor thalamus in deep brain stimulation for essential tremor

The advent of next-generation technology has significantly advanced the implementation and delivery of Deep Brain Stimulation (DBS) for Essential Tremor (ET), yet controversies persist regarding optimal targets and networks responsible for tremor genesis and suppression. This review consolidates key insights from anatomy, neurology, electrophysiology, and radiology to summarize the current state-of-the-art in DBS for ET. We explore the role of the thalamus in motor function and describe how differences in parcellations and nomenclature have shaped our understanding of the neuroanatomical substrates associated with optimal outcomes. Subsequently, we discuss how seminal studies have propagated the ventral intermediate nucleus (Vim)-centric view of DBS effects and shaped the ongoing debate over thalamic DBS versus stimulation in the posterior subthalamic area (PSA) in ET. We then describe probabilistic- and network-mapping studies instrumental in identifying the local and network substrates subserving tremor control, which suggest that the PSA is the optimal DBS target for tremor suppression in ET. Taken together, DBS offers promising outcomes for ET, with the PSA emerging as a better target for suppression of tremor symptoms. While advanced imaging techniques have substantially improved the identification of anatomical targets within this region, uncertainties persist regarding the distinct anatomical substrates involved in optimal tremor control. Inconsistent subdivisions and nomenclature of motor areas and other subdivisions in the thalamus further obfuscate the interpretation of stimulation results. While loss of benefit and habituation to DBS remain challenging in some patients, refined DBS techniques and closed-loop paradigms may eventually overcome these limitations.

Pallidal versus subthalamic deep brain stimulation for Meige syndrome: A systematic review and meta-analysis

Background

Globus pallidus internus (GPi) and subthalamic nucleus (STN) are two common deep brain stimulation (DBS) targets. This meta-analysis was to compared the efficacy and safety of these two DBS targets for the treatment of Meige syndrome (MS).

Methods

A systematic search was performed using EMBASE, MEDLINE, the Cochrane Library, and ClinicalTrials.gov to identify DBS trials for MS. Review Manager 5.3 was used to perform meta-analysis and the mean difference (MD) was analyzed and calculated with a random effect model. Pearson's correlation coefficients and meta-regression analyses were utilized to identify relevant predictive markers.

Results

Twenty trials involving 188 participants with GPi-DBS and 110 individuals with STN-DBS were eligible. Both groups showed improvement of the Burke-Fahn-Marsden Dystonia Rating Scale-Movement (BFMDRS-M) and Disability (BFMDRS-D) scores (BFMDRS-M: MD = 10.57 [7.74-13.41] for GPi-DBS, and MD = 8.59 [4.08-13.11] for STN-DBS; BFMDRS-D: MD = 5.96 [3.15-8.77] for GPi-DBS, and MD = 4.71 [1.38-8.04] for STN-DBS; all P < 0.001) from baseline to the final follow-up, while no notable disparity in improvement rates was observed between them. Stimulation-related complications occurrence was also similar between two groups (38.54 ± 24.07% vs. 43.17 ± 29.12%, P = 0.7594). Simultaneously, preoperative BFMDRS-M score and disease duration were positively connected with the relative changes in BFMDRS-M score at the final visit.

Conclusion

Both GPi-DBS and STN-DBS are effective MS therapies, with no differences in efficacy or the frequency of stimulation-related problems. Higher preoperative scores and longer disease duration probably predict greater improvement.

Neuropsychological assessment protocol in an ongoing randomized controlled trial on posterior subthalamic area vs. ventral intermediate nucleus deep brain stimulation for essential tremor

Objective

Patients with essential tremor (ET) may experience cognitive-affective impairment. Deep brain stimulation (DBS) of different targets, such as the ventral intermediate nucleus (VIM) of the thalamus or the posterior subthalamic area (PSA), has been shown to be beneficial for refractory ET. However, there is little evidence regarding the possible neuropsychological effects of PSA-DBS on patients with ET, and there are few studies comparing it with VIM-DBS in this population.In this study, we aim to present the evaluation protocol and neuropsychological battery as used in an ongoing trial of DBS for ET comparing the already mentioned targets.

Methods

As part of a randomized, double-blind, crossover clinical trial comparing the effectiveness and safety of PSA-DBS vs. VIM-DBS, 11 patients with refractory ET will undergo a multi-domain neuropsychological battery assessment. This will include a pre-/post-implantation assessment (3 months after the stimulation of each target and 6 months after an open stage of DBS on the most optimal target).

Conclusion

Evidence on the neuropsychological effects of DBS in patients with refractory ET is very scarce, particularly in lesser-explored targets such as PSA. This study could contribute significantly in this field, particularly on pre-procedure safety analysis for tailored patient/technique selection, and to complete the safety analysis of the procedure. Moreover, if proven useful, this proposed neuropsychological assessment protocol could be extensible to other surgical therapies for ET.

The Effects of Deep Brain Stimulation on Speech Motor Control in People With Parkinson's Disease

PURPOSE

Despite the overall benefits of deep brain stimulation (DBS) in Parkinson's disease (PD), its effects on speech production have been mixed when examined using auditory-perceptual and acoustic measures. This study investigated the effects of DBS on the lip and jaw kinematics during sentence production in individuals with dysarthria secondary to PD.

METHOD

Twenty-seven participants from three groups were included in the study: (a) individuals with PD and without DBS (PD group), (b) individuals with PD and with DBS (PD-DBS group), and (c) neurologically healthy control speakers (HC group). Lip and jaw movements during speech were recorded using optical motion capture and analyzed for path distance, speed, duration, articulatory stability, and interarticulator coordination.

RESULTS

The PD-DBS group showed (a) increased path distance compared with the PD and HC groups and (b) increased speed compared with the PD group but not the HC group. Both PD and PD-DBS groups exhibited lengthened sentence duration compared with the HC group. Articulatory stability was greater for the two PD groups, PD and PD-DBS, compared with the HC group. Spatial, but not temporal, coordination was lower for the PD group than for the other two groups. The only kinematic changes between the DBS on and off conditions within the PD-DBS group were increases in spatial coordination.

CONCLUSIONS

These data suggest that DBS primarily affects the amplitude scaling of articulatory movements, but not the temporal scaling, in individuals with PD. The findings are discussed with respect to the DBS-induced neural changes and their effects on speech motor control in PD.

Deep brain stimulation in posterior subthalamic area for Holmes tremor: Case reports with review of the literature

Background

Holmes tremor (HT) is a refractory tremor associated with cortico-basal ganglia loops and cerebellothalamic tract abnormalities. Various drug treatments have been attempted; however, no treatment method has yet been established. Historically, thalamic deep brain stimulation (DBS) has been performed in medically refractory cases. Recently, the posterior subthalamic area (PSA) has been used for HT. Here, we report cases of HT and review the effectiveness and safety of PSA-DBS for HT.

Cases

We conducted a retrospective chart review of two patients with HT who underwent PSA-DBS. Improvement in tremors was observed 1 year after surgery without apparent complications.

Literature review

We identified 12 patients who underwent PSA-DBS for HT, including our cases. In six patients, PSA was targeted alone; for the rest, the ventralis intermediate nucleus (Vim) of the thalamus and PSA were simultaneously targeted. The Fahn-Tolosa-Marin Tremor Rating Scale improvement rates were 56.8% (range, 33.9-82.1%; n = 6) and 77.8% (range, 42.6-100%; n = 5) for the PSA-DBS and PSA+Vim-DBS, respectively.

Conclusion

Reasonable improvements in HT were observed after PSA-DBS. PSA might be an appropriate target for improving the symptoms of HT. Long-term observations, accumulation of cases, and randomized studies are required in future.

Which one is the superior target? A comparison and pooled analysis between posterior subthalamic area and ventral intermediate nucleus deep brain stimulation for essential tremor

Background/Aims

The efficacy and safety of posterior subthalamic area (PSA) and ventral intermediate nucleus (VIM) deep brain stimulation (DBS) in the treatment of essential tremor (ET) have not been compared in large‐scale studies. We conducted a secondary analysis to identify the superior target of ET‐DBS treatment.

Methods

PubMed, Embase, Cochrane Library, and Google Scholar were searched for relevant studies before September 2021. The tremor‐suppression efficacy and rate of stimulation‐related complications (SRCR) after PSA‐DBS and VIM‐DBS treating ET were quantitatively compared. Secondary outcomes, including tremor subitem scores and quality of life results, were also analyzed. Subgroup analyses were further conducted to stratify by follow‐up (FU) periods and stimulation lateralities. This study was registered in Open Science Framework (DOI: 10.17605/OSF.IO/7VJQ8).

Results

A total of 23 studies including 122 PSA‐DBS patients and 326 VIM‐DBS patients were analyzed. The average follow‐up time was 12.81 and 14.66 months, respectively. For the percentage improvement of total tremor rating scale (TRS) scores, PSA‐DBS was significantly higher, when compared to VIM‐DBS in the sensitivity analysis (p = 0.030) and main analysis (p = 0.043). The SRCR after VIM‐DBS was higher than that of PSA‐DBS (p = 0.022), and bilateral PSA‐DBS was significantly superior to both bilateral and unilateral VIM‐DBS (p = 0.001).

Conclusions

This study provided level IIIa evidence that PSA‐DBS was more effective and safer for ET than VIM‐DBS in 12–24 months, although both PSA‐DBS and VIM‐DBS were effective in suppressing tremor in ET patients. Further prospective large‐scale randomized clinical trials are warranted in the future.

Chronic embedded cortico-thalamic closed-loop deep brain stimulation for the treatment of essential tremor

Deep brain stimulation (DBS) is an approved therapy for the treatment of medically refractory and severe movement disorders. However, most existing neurostimulators can only apply continuous stimulation [open-loop DBS (OL-DBS)], ignoring patient behavior and environmental factors, which consequently leads to an inefficient therapy, thus limiting the therapeutic window. Here, we established the feasibility of a self-adjusting therapeutic DBS [closed-loop DBS (CL-DBS)], fully embedded in a chronic investigational neurostimulator (Activa PC + S), for three patients affected by essential tremor (ET) enrolled in a longitudinal (6 months) within-subject crossover protocol (DBS OFF, OL-DBS, and CL-DBS). Most patients with ET experience involuntary limb tremor during goal-directed movements, but not during rest. Hence, the proposed CL-DBS paradigm explored the efficacy of modulating the stimulation amplitude based on patient-specific motor behavior, suppressing the pathological tremor on-demand based on a cortical electrode detecting upper limb motor activity. Here, we demonstrated how the proposed stimulation paradigm was able to achieve clinical efficacy and tremor suppression comparable with OL-DBS in a range of movements (cup reaching, proximal and distal posture, water pouring, and writing) while having a consistent reduction in energy delivery. The proposed paradigm is an important step toward a behaviorally modulated fully embedded DBS system, capable of delivering stimulation only when needed, and potentially mitigating pitfalls of OL-DBS, such as DBS-induced side effects and premature device replacement.

Speech Function Following Deep Brain Stimulation of the Caudal Zona Incerta: Effects of Habitual and High-Amplitude Stimulation

Purpose Deep brain stimulation (DBS) is often successful in alleviating motor symptoms of essential tremor (ET); however, DBS may also induce adverse speech effects. The caudal zona incerta (cZi) is a promising DBS target for tremor, but less is known about the consequences of cZi DBS for speech. This preliminary study examined how habitual cZi DBS and cZi stimulation at high amplitudes may affect speech function in persons with ET. Method Fourteen participants with ET were evaluated: off stimulation, on habitual cZi DBS, and with unilateral cZi stimulation at increasing stimulation amplitudes. At each stimulation condition, the participants read three 16-word sentences. Two speech-language pathologists made audio-perceptual consensus ratings of overall speech function, articulation, and voice using a visual sort and rate method. Rated functions when off stimulation, on habitual cZi DBS, and at maximal-amplitude stimulation were compared using Friedman nonparametric tests. For participants with bilateral habitual DBS (n = 5), the effects of bilateral and unilateral stimulation were described in qualitative terms. Results Habitual cZi DBS had no significant group-level effect on any of the investigated speech parameters. Maximal-amplitude stimulation had a small but significant negative effect on articulation. Participants with reduced articulatory precision (n = 9) had more medially placed electrodes than the nonaffected group (n = 5). Bilateral and unilateral left stimulation had comparable effects on speech. Conclusions Findings from this preliminary study of cZi DBS indicate that speech is generally not affected by stimulation at habitual levels. High-amplitude cZi stimulation may, however, induce adverse effects, particularly on articulation. Instances of decreased articulatory function were associated with stimulation of more medial electrode contacts, which could suggest cerebello-rubrospinal involvement.

Deep-Brain Stimulation for Essential Tremor and Other Tremor Syndromes: A Narrative Review of Current Targets and Clinical Outcomes

Tremor is a prevalent symptom associated with multiple conditions, including essential tremor (ET), Parkinson's disease (PD), multiple sclerosis (MS), stroke and trauma. The surgical management of tremor evolved from stereotactic lesions to deep-brain stimulation (DBS), which allowed safe and reversible interference with specific neural networks. This paper reviews the current literature on DBS for tremor, starting with a detailed discussion of current tremor targets (ventral intermediate nucleus of the thalamus (Vim), prelemniscal radiations (Raprl), caudal zona incerta (Zi), thalamus (Vo) and subthalamic nucleus (STN)) and continuing with a discussion of results obtained when performing DBS in the various aforementioned tremor syndromes. Future directions for DBS research are then briefly discussed.

Network Fingerprint of Stimulation-Induced Speech Impairment in Essential Tremor

OBJECTIVE

This study was undertaken to gain insights into structural networks associated with stimulation-induced dysarthria (SID) and to predict stimulation-induced worsening of intelligibility in essential tremor patients with bilateral thalamic deep brain stimulation (DBS).

METHODS

Monopolar reviews were conducted in 14 essential tremor patients. Testing included determination of SID thresholds, intelligibility ratings, and a fast syllable repetition task. Volumes of tissue activated (VTAs) were calculated to identify discriminative fibers for stimulation-induced worsening of intelligibility in a structural connectome. The resulting fiber-based atlas structure was then validated in a leave-one-out design.

RESULTS

Fibers determined as discriminative for stimulation-induced worsening of intelligibility were mainly connected to the ipsilateral precentral gyrus as well as to both cerebellar hemispheres and the ipsilateral brain stem. In the thalamic area, they ran laterally to the thalamus and posteromedially to the subthalamic nucleus, in close proximity, mainly anterolaterally, to fibers beneficial for tremor control as published by Al-Fatly et al in 2019. The overlap of the respective clinical stimulation setting's VTAs with these fibers explained 62.4% (p < 0.001) of the variance of stimulation-induced change in intelligibility in a leave-one-out analysis.

INTERPRETATION

This study demonstrates that SID in essential tremor patients is associated with both motor cortex and cerebellar connectivity. Furthermore, the identified fiber-based atlas structure might contribute to future postoperative programming strategies to achieve optimal tremor control without speech impairment in essential tremor patients with thalamic DBS. ANN NEUROL 2021;89:315-326.

Multiparametric laryngeal assessment of the effect of thalamic deep brain stimulation on essential vocal tremor

OBJECTIVE

EVT is a refractory voice disorder that significantly affects quality of life. This work aims to conduct a multiparametric assessment of the effect of deep brain stimulation (DBS) of the thalamic ventral intermediate nucleus (VIM) on essential vocal tremor (EVT) and investigate the relation between DBS lead location and EVT outcomes.

METHODS

Nine participants underwent DBS for essential tremor and were diagnosed with co-occurring EVT in this prospective cohort study. Objective measurements including acoustic evaluation of vocal fundamental frequency (F0) and intensity modulation and subjective measurements including physiologic evaluation of the oscillatory movement of the laryngeal muscles and vocal tract and perceptual ratings of tremor severity were collected PRE and POST DBS. Finally, we investigated the relation between DBS lead location and EVT outcomes.

RESULTS

Acoustic modulations of F0 and intensity were significantly improved POST DBS. Physiologic assessment showed a POST DBS reduction of oscillatory movement in the laryngeal muscles and vocal tract, but not significantly. Listener and participant perception, of EVT severity was also significantly reduced. Finally, our results indicate better EVT control with increased distance to midline of left VIM thalamic stimulation.

CONCLUSIONS

By employing a battery of objective and subjective measures, our study supports the benefit of DBS for the treatment of EVT and specifies the acoustic and physiologic mechanisms that mediate its positive effect. We further provide preliminary results on the relation between lead location and EVT outcomes, laying the foundation for future studies to clarify the optimal DBS target for the treatment of EVT.

Effect of thalamic deep brain stimulation on swallowing in patients with essential tremor

Objective

Deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) is a mainstay treatment for severe and drug‐refractory essential tremor (ET). Although stimulation‐induced dysarthria has been extensively described, possible impairment of swallowing has not been systematically investigated yet.

Methods

Twelve patients with ET and bilateral VIM‐DBS with self‐reported dysphagia after VIM‐DBS were included. Swallowing function was assessed clinically and using by flexible endoscopic evaluation of swallowing in the stim‐ON and in the stim‐OFF condition. Presence, severity, and improvement of dysphagia were recorded.

Results

During stim‐ON, the presence of dysphagia could be objectified in all patients, 42% showing mild, 42% moderate, and 16 % severe dysphagia. During stim‐OFF, all patients experienced a statistically significant improvement of swallowing function.

Interpretation

VIM‐DBS may have an impact on swallowing physiology in ET‐patients. Further studies to elucidate the prevalence and underlying pathophysiological mechanisms are warranted.

Intraoperative Evaluation of Essential Vocal Tremor in Deep Brain Stimulation Surgery

Purpose Essential vocal tremor (EVT) is a prevalent and difficult-to-manage voice disorder. There is evidence that deep brain stimulation (DBS) of the ventral intermediate nucleus (Vim) of the thalamus may be beneficial for treating EVT. The objective of this preliminary investigation was to conduct intraoperative voice assessments during Vim-DBS implantation in order to evaluate immediate voice outcomes in medication-refractory essential tremor patients with co-occurring EVT. Method Seven adult subjects diagnosed with EVT undergoing Vim-DBS surgery participated in this investigation. Voice samples of sustained vowels were collected by a speech-language pathologist preoperatively and intraoperatively, immediately following Vim-DBS electrode placement. Voice evaluation included objective acoustic assessment of the rate and extent of EVT fundamental frequency and intensity modulation and subjective perceptual ratings of EVT severity. Results The rate of intensity modulation, extent of fundamental frequency modulation, and perceptual rating of EVT severity were significantly reduced intraoperatively as compared to preoperatively. Moderate, positive correlations were appreciated between a subset of acoustic measures and perceptual severity ratings. Conclusions The results of this study demonstrate a speech-language pathologist can conduct intra-operative evaluation of EVT during DBS surgery. Using a noninvasive, simple acoustic recording method, we were able to supplement perceptual subjective observation with objective assessment and demonstrate immediate, intraoperative improvements in EVT. The findings of this analysis inform the added value of intraoperative voice evaluation in Vim-DBS patients and contribute to the growing body of literature seeking to evaluate the efficacy of DBS as a treatment for EVT.

The Effects of Deep Brain Stimulation on Speech Intelligibility in Persons With Essential Tremor

Purpose The aim of this study was to investigate how deep brain stimulation (DBS) of the caudal zona incerta (cZi) affects speech intelligibility in persons with essential tremor. Method Thirty-five participants were evaluated: off stimulation, on chronic stimulation optimized to alleviate tremor, and during unilateral stimulation at increasing amplitude levels. At each stimulation condition, the participants read 10 unique nonsense sentences from the Swedish Test of Intelligibility. Two listeners, blinded to stimulation condition, transcribed all recorded sentences orthographically in a randomized procedure. A mean speech intelligibility score for each patient and stimulation condition was computed, and comparisons were made between scores off and on stimulation. Results Chronic cZi-DBS had no significant effect on speech intelligibility, and there was no difference in outcome between bilateral and unilateral treatments. During unilateral stimulation at increasing amplitudes, nine participants demonstrated deteriorating speech intelligibility. These nine participants were on average older and had more superior contacts activated during the evaluation compared with the participants without deterioration. Conclusions Chronic cZi-DBS, optimized for tremor suppression, does not generally affect speech intelligibility in persons with essential tremor. Furthermore, speech intelligibility may be preserved in many individuals, even when stimulated at high amplitudes. Adverse effects of high-amplitude unilateral stimulation observed in this study were associated with stimulation originating from a more superior location, as well as with the participants' age. These results, highlighting age and stimulation location as contributing to speech intelligibility outcomes, were, however, based on a limited number of individuals experiencing adverse effects with high-amplitude stimulation and should, therefore, be interpreted with caution.

Deep Brain Stimulation Programming for Movement Disorders: Current Concepts and Evidence-Based Strategies

Deep brain stimulation (DBS) has become the treatment of choice for advanced stages of Parkinson's disease, medically intractable essential tremor, and complicated segmental and generalized dystonia. In addition to accurate electrode placement in the target area, effective programming of DBS devices is considered the most important factor for the individual outcome after DBS. Programming of the implanted pulse generator (IPG) is the only modifiable factor once DBS leads have been implanted and it becomes even more relevant in cases in which the electrodes are located at the border of the intended target structure and when side effects become challenging. At present, adjusting stimulation parameters depends to a large extent on personal experience. Based on a comprehensive literature search, we here summarize previous studies that examined the significance of distinct stimulation strategies for ameliorating disease signs and symptoms. We assess the effect of adjusting the stimulus amplitude (A), frequency (f), and pulse width (pw) on clinical symptoms and examine more recent techniques for modulating neuronal elements by electrical stimulation, such as interleaving (Medtronic®) or directional current steering (Boston Scientific®, Abbott®). We thus provide an evidence-based strategy for achieving the best clinical effect with different disorders and avoiding adverse effects in DBS of the subthalamic nucleus (STN), the ventro-intermedius nucleus (VIM), and the globus pallidus internus (GPi).

Dysgeusia in deep brain stimulation for essential tremor

Dysgeusia, or foul taste, is a rarely reported side effect in patients who have undergone deep brain stimulation (DBS) in the thalamus for essential tremor. This retrospective study evaluated the incidence, nature, neurophysiological and anatomical location of dysgeusia following DBS. Of 52 patients who had undergone DBS for essential tremor, eight (15%) reported dysgeusia, which was described as a "metallic," "sour," "foul," or "cold" taste in the mouth. Dysgeusia was separate and distinguishable from paresthesia. Dysgeusia was more frequently reported with bilateral than unilateral DBS implants (6 of 27 (22%) vs. 2 of 25 (8%) patients, respectively). The anatomical locations of the contacts causing dysgeusia were measured on postoperative MRI, and compared to those from seven control patients who did not experience dysgeusia after receiving bilateral DBS implants. Leads causing dysgeusia were more posterior than non-dysgeusia-associated leads (4.5 ± 1.2 vs. 5.7 ± 1.8 mm anterior to the posterior commissure, respectively, P < .001). Intraoperative microelectrode recording indicated that these contacts were in the sensory region of the thalamus. Intraoperative testing found that low sensory threshold for paresthesia predicted the development of dysgeusia postoperatively (1.5 ± 0.5 V vs. 3.3 ± 1.9 V; P < .05). These data indicate that taste perception can be altered in the human through DBS, with posterior leads likely within the sensory region of the thalamus. Dysgeusia can be reduced by changing stimulation parameters, or surgical revision of the lead.

DBS of the PSA and the VIM in essential tremor

Objective

To evaluate deep brain stimulation (DBS) of the posterior subthalamic area (PSA) in essential tremor (ET) and compare it to the ventral intermediate nucleus of the thalamus (VIM) in terms of stimulation efficacy, efficiency, and side effects.

Methods

DBS leads were implanted such that contacts were placed in the VIM, on the intercommissural line, and in the PSA. Thirteen patients with ET entered a randomized, double-blind crossover phase and completed a 1-year follow-up.

Results

PSA-DBS significantly reduced tremor severity and improved quality of life. There were no relevant differences in quality and frequency of stimulation side effects between VIM and PSA, with a tendency toward greater tremor improvement with PSA stimulation. Clinical benefit was achieved at significantly lower stimulation amplitudes in the PSA. The majority of patients remained with PSA-DBS after 1 year.

Conclusion

In accordance with previous retrospective investigations, our prospective data suggest that PSA-DBS is at least equally effective as but possibly more efficient than VIM-DBS.

Classification of evidence

This study provides Class I evidence that for patients with essential tremor, PSA-DBS is not significantly different from VIM-DBS in suppressing tremor, but clinical benefit from PSA-DBS is attained at lower stimulation amplitudes.

The effects of Thalamic Deep Brain Stimulation on speech dynamics in patients with Essential Tremor: An articulographic study

Acoustic studies have revealed that patients with Essential Tremor treated with thalamic Deep Brain Stimulation (DBS) may suffer from speech deterioration in terms of imprecise oral articulation and reduced voicing control. Based on the acoustic signal one cannot infer, however, whether this deterioration is due to a general slowing down of the speech motor system (e.g., a target undershoot of a desired articulatory goal resulting from being too slow) or disturbed coordination (e.g., a target undershoot caused by problems with the relative phasing of articulatory movements). To elucidate this issue further, we here investigated both acoustics and articulatory patterns of the labial and lingual system using Electromagnetic Articulography (EMA) in twelve Essential Tremor patients treated with thalamic DBS and twelve age- and sex-matched controls. By comparing patients with activated (DBS-ON) and inactivated stimulation (DBS-OFF) with control speakers, we show that critical changes in speech dynamics occur on two levels: With inactivated stimulation (DBS-OFF), patients showed coordination problems of the labial and lingual system in terms of articulatory imprecision and slowness. These effects of articulatory discoordination worsened under activated stimulation, accompanied by an additional overall slowing down of the speech motor system. This leads to a poor performance of syllables on the acoustic surface, reflecting an aggravation either of pre-existing cerebellar deficits and/or the affection of the upper motor fibers of the internal capsule.

Probabilistic mapping of deep brain stimulation effects in essential tremor

Objective

To create probabilistic stimulation maps (PSMs) of deep brain stimulation (DBS) effects on tremor suppression and stimulation-induced side-effects in patients with essential tremor (ET).

Method

Monopolar reviews from 16 ET-patients which consisted of over 600 stimulation settings were used to create PSMs. A spherical model of the volume of neural activation was used to estimate the spatial extent of DBS for each setting. All data was pooled and voxel-wise statistical analysis as well as nonparametric permutation testing was used to confirm the validity of the PSMs.

Results

PSMs showed tremor suppression to be more pronounced by stimulation in the zona incerta (ZI) than in the ventral intermediate nucleus (VIM). Paresthesias and dizziness were most commonly associated with stimulation in the ZI and surrounding thalamic nuclei.

Discussion

Our results support the assumption, that the ZI might be a very effective target for tremor suppression. However stimulation inside the ZI and in its close vicinity was also related to the occurrence of stimulation-induced side-effects, so it remains unclear whether the VIM or the ZI is the overall better target. The study demonstrates the use of PSMs for target selection and evaluation. While their accuracy has to be carefully discussed, they can improve the understanding of DBS effects and can be of use for other DBS targets in the therapy of neurological or psychiatric disorders as well. Furthermore they provide a priori information about expected DBS effects in a certain region and might be helpful to clinicians in programming DBS devices in the future.

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A revised method to create probabilistic stimulation maps for large DBS datasets

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Data for DBS in essential tremor targeting the ventral intermediate nucleus (VIM).

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Zona incerta shows higher tremor suppression but also more side effects than VIM.

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Insights into the possible neuroanatomical origins of different DBS side effects

Deep brain stimulation of the posterior subthalamic area and the thalamus in patients with essential tremor: study protocol for a randomized controlled pilot trial

BACKGROUND

Deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) of the thalamus is effective in medication refractory essential tremor (ET). In recent years, evidence has accumulated that the region ventral to the VIM, the posterior subthalamic area (PSA), might be an equally or even more effective target for electrode implantation. However, this evidence is primarily based on case series, cross-sectional observations, and retrospective data.

METHODS/DESIGN

A prospective crossover pilot study investigating the effects of PSA stimulation in medication refractory ET patients was designed. In this study, bilateral electrodes are implanted such that at least one of the electrode contacts is located in the PSA and VIM, respectively. This implantation approach allows (1) a prospective double-blind investigation of the effects of PSA stimulation compared to baseline, as well as (2) a crossover comparison between VIM and PSA stimulation with respect to tremor suppression and side effect profiles.

DISCUSSION

The results of this double-blinded, prospective study will allow a better understanding of the effects and side effects of PSA compared to VIM-DBS in patients with ET.

TRIAL REGISTRATION

German Clinical Trials Register: DRKS00004235 . Registered on 4 July 2012.

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.

Individualized current-shaping reduces DBS-induced dysarthria in patients with essential tremor

Objective:

To investigate in patients with essential tremor (ET) treated with thalamic/subthalamic deep brain stimulation (DBS) whether stimulation-induced dysarthria (SID) can be diminished by individualized current-shaping with interleaving stimulation (cs-ILS) while maintaining tremor suppression (TS).

Methods:

Of 26 patients screened, 10 reported SID and were invited for testing. TS was assessed by the Tremor Rating Scale and kinematic analysis of postural and action tremor. SID was assessed by phonetic and logopedic means. Additionally, patients rated their dysarthria on a visual analog scale.

Results:

In 6 of the 10 patients with ET, DBS-ON (relative to DBS-OFF) led to SID while tremor was successfully reduced. When comparing individualized cs-ILS with a non–current-shaped interleaving stimulation (ILS) in these patients, there was no difference in TS while 4 of the 6 patients showed subjective improvement of speech during cs-ILS. Phonetic analysis (ILS vs cs-ILS) revealed that during cs-ILS there was a reduction of voicing during the production of voiceless stop consonants and also a trend toward an improvement in oral diadochokinetic rate, reflecting less dysarthria. Logopedic rating showed a trend toward deterioration in the diadochokinesis task when comparing ON with OFF but no difference between ILS and cs-ILS.

Conclusion:

This is a proof-of-principle evaluation of current-shaping in patients with ET treated with thalamic/subthalamic DBS and experiencing SID. Data suggest a benefit on SID from individual shaping of current spread while TS is preserved.

Classification of evidence:

This study provides Class IV evidence that in patients with ET treated with DBS with SID, individualized cs-ILS reduces dysarthria while maintaining tremor control.