Long-term outcome of bilateral pallidal deep brain stimulation for primary cervical dystonia

Ten patients with severe cervical dystonia (CD) unresponsive to medical treatment underwent bilateral globus pallidus internus (GPi) deep brain stimulation (DBS) and were followed for 31.9 +/- 20.9 months. At last follow-up, the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) severity score improved by 54.8%, the TWSTRS disability score improved by 59.1%, and the TWSTRS pain score improved by 50.4%. Bilateral GPi DBS is an effective long-term therapy in patients with CD.     

Long Disease Duration Interferes With Therapeutic Effect of Globus Pallidus Internus Pallidal Stimulation in Primary Cervical Dystonia

Objectives: We retrospectively investigated the correlation between disease duration and the therapeutic effect of globus pallidus internus (GPi) stimulation in patients with primary cervical dystonia (CD). Materials and Methods: Eight patients with CD unresponsive to medical treatments underwent bilateral GPi deep brain stimulation (DBS). They were followed for 63.5 ± 38.2 months (mean ± standard deviation) and were assessed before and at 1, 12, 24, and 36 months after surgery and at their final visit to our outpatient clinic using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS). Univariate analysis was performed to identify factors that affected their postoperative TWSTRS score. Results: At last follow‐up, disease severity and the degree of disability and pain on the TWSTRS were significantly improved by 70.2%, 76.1%, and 87.1%, respectively (p < 0.05, Wilcoxon signed‐rank test). Neither age nor preoperative CD severity was predictive of postoperative improvement; however, the disease duration affected their reduction rate of TWSTRS severity score at each time point investigated (p < 0.05). Conclusions: Bilateral GPi‐DBS is an effective long‐term therapy in patients with CD. The delivery of GPi stimulation in the earlier course of CD may yield greater postoperative improvement.     

Evaluation of the efficacy of deep brain stimulation in the surgical treatment of cervical dystonia

ObjectiveDeep brain stimulation (DBS) of the globus pallidus internus (GPi) is a promising therapeutic option for patients with medically refractory dystonia. We present the results after 1 year of DBS of the GPi in 4 patients with cervical dystonia.Materials and methodsFour patients with medically refractory cervical dystonia who underwent stereotactic pallidal DBS surgery between June 2010 and November 2011 were included in this retrospective study. Preoperative and postoperative evaluations at 3, 6 and 12 months after surgery were performed using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS).ResultsThe 4 patients experienced a sustained improvement, with a mean TWSTRS reduction of 74.25%, at 12 months follow-up. Disability improved by 80.5% (mean) at 1 year follow-up. No stimulation-related side effects were reported.ConclusionPallidal DBS is a valid and effective second-line treatment for patients with cervical focal dystonia. Our results support its use in patients with an insufficient response to medical treatment.     

Pallidal deep brain stimulation in patients with cranial-cervical dystonia (Meige syndrome).

Idiopathic cranial-cervical dystonia (ICCD) is an adult-onset dystonia syndrome affecting orbicularis oculi, facial, oromandibular, and cervical musculature. ICCD is frequently difficult to treat medically. Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is a highly effective treatment for idiopathic generalized dystonia, however less is known about the effect of GPi DBS on ICCD. In this article, we present the results from a pilot study assessing the effect of GPi DBS in a series of patients with ICCD. Six patients underwent bilateral stereotactic implantation of DBS leads into the sensorimotor GPi. Patients were evaluated with the Burke-Fahn-Marsden dystonia rating scale (BFMDRS) and Toronto western spamodic torticollis rating scale (TWSTRS) before surgery and 6 months postoperatively. At 6 months, patients showed a 72% mean improvement in the BFMDRS total movement score (P < 0.028, Wilcoxin signed rank test). The mean BFMDRS disability score showed a trend toward improvement (P < 0.06). The total TWSTRS score improved 54% (P < 0.043). Despite improvement in dystonia, mild worsening of motor function was reported in previously nondystonic body regions with stimulation in 4 patients. Although GPi DBS was effective in these patients, the influence of GPi DBS on nondystonic body regions deserves further investigation.     

Pallidal stimulation in cervical dystonia: clinical implications of acute changes in stimulation parameters

Background and purpose:  Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is successful in dystonia, but the role of each electrical parameters of stimulation is unclear. We studied the clinical effects of acute changes of different parameters of GPi–DBS in cervical dystonia (CD).
Methods:  Eight CD patients with bilateral GPi–DBS at 28.6 ± 19.2 (mean ± SD) months after surgery were recruited. Mean improvement in the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) severity score was 54.5% compared to before surgery. Ten settings, including a combination of a wide range of pulse widths (PWs), low and high frequencies and voltage, were administered in a randomized double blinded fashion. Clinical benefit was assessed by two raters using the TWSTRS and by the patients using an analogue rating scale.
Results:  The TWSTRS severity scores were reduced by 56.7% with stimulation at the best settings. Improvement was significantly associated with high frequency (≥60 Hz) and high voltage. Stimulation at 130 Hz showed the best clinical improvement. Increasing PWs (from 60 to 450 μs) did not result in a significant improvement.
Conclusion:  Frequency and amplitude appear to be the most important factors in the acute anti-dystonic effects in GPi–DBS patients with CD.     

Chronic deep brain stimulation in patients with tardive dystonia without a history of major psychosis

Tardive dystonia usually occurs with a delay after neuroleptic exposure in patients with major psychosis. A subgroup of patients, however, is given such medication for “mild depression” or “neurasthenia.” Tardive dystonia, in general, may respond favorably to pallidal deep brain stimulation (DBS). Nevertheless, it remains unclear thus far whether or not similar beneficial outcome is achieved with pallidal DBS in different subgroups of patients with tardive dystonia. Four women (mean age 59 years at surgery) underwent stereotactic pallidal DBS in the frame of an observational study. Tardive dystonia occurred secondary to medication with fluspirilene and haloperidol, and injection of long‐acting depot neuroleptics prescribed for mild depression or “nervousness.” Assessment included the Burke‐Fahn‐Marsden (BFM) scale preoperatively and at 12 months follow‐up. Extended follow‐up was available at a mean of 27.3 months postoperatively (range 16–36 months). There were no surgically related complications. All 4 patients experienced sustained statistically significant benefit from pallidal DBS. Mean improvement at 12 months was 77% for the BFM motor score (range, 45–91%; P = 0.043), and 84% at the last available follow‐up (range, 70–91%; P = 0.03). This was paralleled by improvement of the BFM disability score. Chronic pallidal DBS in patients with tardive dystonia without a history of major psychosis provides sustained improvement which is similar to that in other subgroups of patients with tardive dystonia. This effect is stable on extended follow‐up for up to 3 years. © 2010 Movement Disorder Society     

Deep brain stimulation for dystonia: outcome at long-term follow-up

OBJECTIVE: Deep brain stimulation (DBS) has emerged as a useful therapeutic option for patients with insufficient benefit from conservative treatment. METHODS: Nine patients with chronic DBS who suffered from cervical dystonia (4), generalized dystonia (2), hemidystonia (1), paroxysmal dystonia (1) and Meige syndrome (1) were available for formal follow-up at three years postoperatively, and beyond up to 10 years. All patients had undergone pallidal stimulation except one patient with paroxysmal dystonia who underwent thalamic stimulation. RESULTS: Maintained improvement was seen in all patients with pallidal stimulation up to 10 years after surgery except in one patient who had a relative loss of benefit in dystonia ratings but continued to have improved disability scores. After nine years of chronic thalamic stimulation there was a mild loss of efficacy which was regained when the target was changed to the pallidum in the patient with paroxysmal dystonia. There were no major complications related to surgery or to chronic stimulation. Pacemakers had to be replaced within 1.5 to 2 years, in general. CONCLUSION: DBS maintains marked long-term symptomatic and functional improvement in the majority of patients with dystonia.     

Globus pallidus deep brain stimulation for adult-onset axial dystonia

IntroductionGeneralized dystonia, both primary and secondary forms, and axial dystonias such as tardive dystonia, and idiopathic cervical dystonia are responsive to globus pallidus interna (GPi) DBS. There is a paucity of investigations probing the impact of DBS on adult-onset axial dystonia. We assessed the efficacy of GPi DBS in four patients with rare adult-onset axial dystonia.MethodsPrimary outcome measure was improvement in the motor component of the Burke-Fahn-Marsden (BFM) rating scale. Secondary outcome measures were quality of life as determined by the SF-36 questionnaire, time to achieve best possible benefit and DBS parameters that accounted for the best response. In patients with prominent concomitant cervical dystonia we also used the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS).ResultsGPi DBS improved BFM scores by 87.63 ± 11.46%. Improvement in total severity scale of TWSTRS was 71.5 ± 12.7%. Quality of life also remarkably improved as evidenced by 109.38 ± 82.97 and 7.05 ± 21.48% percent change in psychometrically-based physical component summary (PCS), and a mental component summary (MCS) score respectively.ConclusionsGPi DBS is a very effective treatment for adult-onset axial dystonia. Considering its refractoriness to medical therapy and significant impact on quality of life DBS should be considered for this disorder.     

Pallidal deep brain stimulation is effective, and improves quality of life in primary segmental and generalized dystonia

Background –  Dystonia is one of the most prevalent movement disorders, and may lead to abnormal postures, pain, significant disability and social isolation if not well treated. In widespread segmental or generalized dystonia efficient treatment options were lacking until the recent introduction of deep brain stimulation of the internal globus pallidus (pallidal DBS).
Methods –  The first case series and single-blinded controlled study showed promising results regarding the effect of pallidal DBS on dystonic movements, pain and disability, but the impact of this treatment on health-related quality of life (HRQoL) remained uncertain. Then, as part of the first randomized, and sham stimulation-controlled trial performed by the DBS for Dystonia Study Group, HRQoL was evaluated using the Short Form-36 Health Survey (SF-36) at baseline, after the 3 months sham-controlled phase, and after 6 months of continuous pallidal DBS, in 40 patients with severe primary segmental or generalized dystonia.
Results –  The 3-month sham-stimulation controlled phase resulted in significant improvement of dystonic movements, pain and disability in the active stimulation group, and four of the eight SF-36 domain scores also improved significantly compared with the sham-stimulated group. After 6 months of active stimulation in all patients, significant improvement in all eight SF-36 domains was observed, with comparable improvement in the segmental and generalized dystonia groups.
Conclusion –  Convincing evidence has been obtained that pallidal DBS effectively reduces dystonia-related symptoms, and markedly improves HRQoL in patients suffering from otherwise intractable, primary segmental or generalized dystonia, thus providing new opportunities for this patient group.     

Psychiatric co-morbidity is highly prevalent in idiopathic cervical dystonia and significantly influences health-related quality of life: Results of a controlled study

IntroductionThe aim of this study was to systematically investigate the prevalence of psychiatric disorders and factors influencing health-related quality of life (HR-QoL) in cervical dystonia (CD) patients, in the context of objective dystonia motor severity.MethodsWe studied 50 CD patients and 50 matched healthy controls. Psychiatric assessment included the MINI–PLUS interview and quantitative questionnaires. Dystonia motor severity (based on video evaluation), pain and disability were determined with the TWSTRS rating scale. In addition, severity of tremor and jerks was evaluated with the 7-point CGI-S scale. HR-QoL was determined with the RAND-36 item Health Survey and predictors of HR-QoL were assessed using multiple regression analysis.ResultsIn CD patients, the MINI-PLUS revealed a significantly higher prevalence of psychiatric disorders (64% vs. 28%, p = 0.001), with substantially more depression (32% vs. 14%) and anxiety disorders (42% vs. 8%). This was confirmed by the quantitative rating scales. Disease characteristics did not differ between patients with and without a psychiatric diagnosis. HR-QoL in dystonia patients was significantly lowered. The most important predictors of HR-QoL appeared severity of depressive symptoms, pain and disability, but not severity of motor symptoms.ConclusionPsychiatric co-morbidity is highly prevalent and is an important predictor of HR-QoL in CD patients, rather than dystonia motor severity. Our findings support the theory of a shared neurobiology for motor and non-motor features and highlight the need for systematic research into psychiatric disorders in dystonia. Adequate treatment of psychiatric symptoms could significantly contribute to better overall quality of life of CD patients.     

Pallidal deep brain stimulation in cervical dystonia: clinical outcome in four cases

OBJECTIVE: Report on the clinical results following bilateral globus pallidus interna deep brain stimulation in four patients (one female and three males) with severe cervical dystonia, mean age 48 years (range 37-67). METHODS: All four patients had failed extensive medical and botulinum toxin treatment. The mean duration of the disease was nine years (range 4-15 years). Patients were assessed pre and postoperatively using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS). Pre-operatively, the mean TWSTRS total score was 43.2 (range 28-60.5). Posteroventral pallidal deep brain stimulators were inserted using MRI and microelectrode recording guidance. Last follow-up was 15 months for the four patients. RESULTS: Mean reduction in the TWSTRS total scores at last follow- up was 73% (range 61- 85%). Improvement in pain occurred soon after deep brain stimulation surgery. Motor improvement was delayed and prolonged over several months. Frequent adjustment in the stimulation parameters was necessary in the first three months. CONCLUSION: Bilateral pallidal stimulation is effective in management of selected cases of intractable cervical dystonia.     

A family with a hereditary form of torsion dystonia from Northern Sweden treated with bilateral pallidal deep brain stimulation

To evaluate pallidal DBS in a non‐DYT1 form of hereditary dystonia. We present the results of pallidal DBS in a family with non‐DYT1 dystonia where DYT5 to 17 was excluded. The dystonia is following an autosomal dominant pattern. Ten members had definite dystonia and five had dystonia with minor symptoms. Four patients received bilateral pallidal DBS. Mean age was 47 years. The patients were evaluated before surgery, and “on” stimulation after a mean of 2.5 years (range 1–3) using the Burke‐Fahn‐Marsden scale (BFM). Mean BFM score decreased by 79 % on stimulation, from 42.5 ± 24 to 9 ± 6.5 at the last evaluation. Cervical involvement improved by 89%. The 2 patients with oromandibular dystonia and blepharospasm demonstrated a reduction of 95% regarding these symptoms. The present study confirms the effectiveness of pallidal DBS in a new family with hereditary primary segmental and generalized dystonia. © 2009 Movement Disorder Society     

Long‐Term Follow‐Up Study of Chronic Deep Brain Stimulation of the Subthalamic Nucleus for Cervical Dystonia

Objectives. Medically refractory cervical dystonia has recently been treated using deep brain stimulation (DBS), targeting the subthalamic nucleus (STN). There has been limited literature regarding short‐term outcomes and no literature regarding long‐term outcomes for refractory cervical dystonia following DBS of the STN. Materials and Methods. Two patients with medically refractory cervical dystonia underwent STN DBS. Patients were rated using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) preoperatively and immediately postoperatively as well as just prior to turning on the stimulators and subsequently at 24–48 hours, six months, one, two, and three years after stimulation. Microrecordings were used to identify the STN and substantia nigra reticulata (SNr). Results. Significant immediate and sustained long‐term improvements were seen in motor, disability, pain, and total TWSTRS scores. In one patient, only unilateral stimulation was required. The STN and SNr were easily identified as having activity similar to off‐state Parkinson's patients. Conclusions. DBS therapy for cervical dystonia utilizing the STN as the surgical target may be novel and may be an alternative target to the globus pallidus internus as supported by this first long‐term outcome report. Further studies need to be performed to confirm these conclusions.     

Pallidal deep brain stimulation in patients with cervical dystonia and severe cervical dyskinesias with cervical myelopathy

OBJECTIVES: Surgical treatment of complex cervical dystonia and of cervical dyskinesias associated with cervical myelopathy is challenging. In this prospective study, the long term effect of chronic pallidal stimulation in cervical dystonia and on combining the technique with spinal surgery in patients with severe cervical dyskinesias and secondary cervical myelopathy is described. METHODS: Eight patients with a history of chronic dystonia who did not achieve adequate benefit from medical treatment or botulinum toxin injection participated in the study. Five patients had complex cervical dystonia with tonic postures and phasic movements. Three patients had rapidly progressive cervical myelopathy secondary to severe cervical dyskinesias and dystonia in the context of a generalised movement disorder. Quadripolar electrodes were implanted in the posteroventral lateral globus pallidus internus with stereotactic CT and microelectrode guidance. In the three patients with secondary cervical myelopathy, spinal surgery was performed within a few weeks and included multilevel laminectomies and a four level cervical corporectomy with spinal stabilisation. RESULTS: Improvement of the movement disorder was noted early after pallidal surgery, but the full benefit could be appreciated only with a delay of several months during chronic stimulation. Three months after surgery, patients with cervical dystonia had improved by 38% in the severity score, by 54% in the disability score, and by 38% in the pain score of a modified version of the Toronto western spasmodic torticollis rating scale. At a mean follow up of 20 months, the severity score had improved by 63%, the disability score by 69%, and the pain score by 50% compared with preoperatively. There was also sustained amelioration of cervical dyskinesias in the three patients who underwent spinal surgery. Lead fractures occurred in two patients. The mean amplitude needed for chronic deep brain stimulation was 3.8 V at a mean pulse width of 210 micros, which is higher than that used for pallidal stimulation in Parkinson's disease. CONCLUSIONS: Chronic pallidal stimulation is effective for complex cervical dystonia and it is a useful adjunct in patients with cervical dyskinesias and secondary cervical myelopathy who undergo spinal surgery.     

Good long-term efficacy of pallidal stimulation in cervical dystonia: a prospective, observer-blinded study

Background and purpose: Deep brain stimulation of the internal globus pallidus (GPi‐DBS) is established as an effective treatment of primary generalised dystonia in controlled studies. In cervical dystonia (CD), only one previous study has reported observer‐blinded outcome assessment of long‐term GPi‐DBS, with 1‐year follow‐up. Methods: In this prospective, single‐centre study, eight patients with CD (7 women:1 man, 4 focal:4 segmental) treated with bilateral GPi‐DBS for median (range) 30 (12–48) months, were evaluated by the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS; Severity, Disability and Pain scores), the Short‐Form Health Survey‐36 (SF‐36), and the Becks Depression Index in an open design. In addition, a blinded rater assessed the TWSTRS Severity score from videos obtained preoperatively and at the last follow‐up. Results: In the blinded evaluation, median (range) TWSTRS Severity score improved from 25 (19–30) to 8 (4–23) (P = 0.028), thus a 70% (23–82) score reduction. In the open evaluation, median Severity score improvement at the last follow‐up was 73%, representing a significant further improvement from 50% at 6 months. The Disability and Pain scores improved by median 91% and 92%, respectively, and the SF‐36 subdomain scores improved significantly. A reversible right hemiparesis and aphasia occured in one patient 4 days postoperatively, because of reversible oedema around the left electrode. No other serious adverse effects and no permanent morbidity were observed. Conclusions: This single‐blinded study shows good long‐term efficacy of GPi‐DBS in CD patients and supports using this treatment in those who have insufficient response to medical treatment.     

The Influence of Deep Brain Stimulation Intensity and Duration on Symptoms Evolution in an OFF Stimulation Dystonia Study

BackgroundDeep brain stimulation (DBS) of the internal globus pallidus (GPi) is an established therapy for primary generalized dystonia. However, the evolution of dystonia symptoms after DBS discontinuation after years of therapy has only rarely been reported. We therefore longitudinally studied the main physiological measurements known to be impaired in dystonia, with DBS ON and then again after termination of DBS, after at least five years of continuous DBS.ObjectiveWe studied whether dystonia evolution after DBS discontinuation in patients benefiting from long-term GPi DBS is different from that observed in earlier stages of the therapy.MethodsIn eleven DYT1 patients treated with bilateral GPi DBS for at least 5 years, dystonia was assessed ON-DBS, immediately after switch-off (OFF-DBS1) and 48 h after DBS termination (OFF-DBS2). We studied the influence of DBS intensity on dystonia when DBS was discontinued.ResultsOn average a significant difference in symptoms was measured only between ON-DBS and OFF-DBS1 conditions. Importantly, none of the patients returned to their preoperative dystonia severity, even 48 h after discontinuation. The amount of clinical deterioration in the OFF conditions positively correlated with higher stimulation current in the chronic ON-DBS condition.ConclusionsThe duration of DBS application influences symptom evolution after DBS termination. DBS intensity seems to have a prominent role on evolution of dystonic symptoms when DBS is discontinued. In conclusion, DBS induces changing modulation of the motor network with less worsening of symptoms after long term stimulation, when DBS is stopped.     

Pallidal surgery for the treatment of primary generalized dystonia: long-term follow-up

OBJECTIVE: To describe the results and long-term follow-up after functional surgery of the internal segment of the globus pallidus (GPi) in 10 patients with primary generalized dystonia. PATIENTS AND METHODS: Nine of the 10 patients were positive for the DYT1 gene mutation. Bilateral deep brain stimulation (DBS) of the GPi was performed in three cases, bilateral pallidotomy in two, and combined surgery (unilateral GPi lesion with contralateral stimulation) in the remaining five. All patients were evaluated with the Burke-Fahn-Marsden dystonia scale (BFMDS) before, immediately after surgery, at 3 weeks, 3 and 6 months and then yearly. Follow up time ranged from 15 to 105 months (mean: 66.1 months) with six patients having more than 6 years follow up. RESULTS: All patients improved after surgery. All patients with unilateral or bilateral DBS experienced an immediate improvement before starting stimulation. The magnitude of this initial micro lesion effect did not predict the magnitude of the long-term benefit of DBS. The mean decrease in the in the BFMDS was 34%, 55%, and 65% in the movement scale; and 32%, 48%, and 49% in the disability scale for patients with bilateral pallidal DBS, combined unilateral DBS and contralateral pallidotomy, and bilateral pallidotomy, respectively. Worsening of dystonia after a plateau of sustained benefit was observed in three patients. Two patients required multiple pallidal surgeries. Adverse events included: permanent anarthria (1), misplacement of the electrode requiring further surgery (2), scalp infection (1), and hardware related problems (3). CONCLUSIONS: This long-term follow up study confirms the beneficial effect of pallidal DBS or pallidotomy in primary generalized dystonia. In addition, our results extent previous observations by showing that, in these patients, (1) the microlesion effect of DBS is not predictive of long-term benefit; (2) combined DBS with contralateral pallidotomy appears to be more effective than bilateral pallidal DBS; and (3) dystonia can reappear after an initial good response during long term follow up.     

Chronic bilateral pallidal stimulation in patients with generalized primary dystonia - multi-contact cathodal stimulation is superior to bipolar stimulation mode. Preliminary results

Background and purposePrimary generalized dystonia (PGD) is a medically refractory progressive disease of the brain causing near total handicap of affected patients. The aim of the study was to assess the efficacy and safety of bilateral pallidal stimulation in patients with PGD.Material and methodsThe study population is composed of 5 patients with PGD. The formal objective assessment included the Burke-Fahn-Marsden dystonia rating scale (BFMDRS). All stereotactic procedures were performed in general anaesthesia using a Leksell G stereotactic head frame without electrophysiological guidance. Immediately after insertion of deep brain stimulation (DBS) leads, the internal pulse generators (Itrel II or Soletra) were implanted subcutaneously in the chest wall or abdominal region.ResultsThere were no complications related to the stereotactic procedures. The hardware-related complications (two broken DBS leads) were replaced successfully. There were no infections or erosions of implanted hardware. It has been observed that in the long-term follow-up period primary set bipolar stimulation mode lost its benefit achieved previously. Various stimulation combinations were investigated. Monopolar cathodal or especially multi-contact cathodal stimulation was the most effective one. The efficacy of bilateral pallidal stimulation was proved by the objective validated BFMDRS at long-term follow-up.ConclusionsResponse to DBS may improve with the number of activated cathodal contacts within the globus pallidus internus.     

Deep brain stimulation in the treatment of severe dystonia

A retrospective study of a consecutive series of 19 patients with medically intractable dystonia treated with uni- or bilateral deep brain stimulation (DBS) is reported. A minimal follow-up of 6 months was available, up to eleven years in one patient. The first twelve consecutive patients (4 with primary and 8 with secondary dystonia) were treated with chronic stimulation of the posterior part of the ventrolateral thalamic nucleus (VLp). In this group global functional outcome was improved in 8 patients, although dystonia movement and disability scale scores did not show significant improvement. Of the 12 patients treated first by VLp DBS, three (1 primary and 2 secondary dystonia) underwent pallidal (GPi) DBS after the VLp DBS failed to improve their symptoms. The last seven consecutive patients (5 primary and 2 secondary dystonia) were treated directly with GPi DBS. Extracranial infection prevented chronic GPi DBS in one patient. In another GPi patient, preliminary negative tests with the electrodes discouraged implantation of the stimulators, and the patient was not treated with chronic DBS. In the remaining group of eight patients including those previously treated with VLp DBS, chronic GPi DBS resulted in a significant improvement in the dystonia movement scale and disability scores. Although this is a retrospective study dealing with dystonia of heterogeneous etiology, the results strongly suggest that GPi DBS has a better outcome than VLp DBS Received: 22 January 2001 / Received in revised form: 28 February 2001 / Accepted: 1 March 2001     

Intermuscular coherence as biomarker for pallidal deep brain stimulation efficacy in dystonia

ObjectiveFinding a non-invasive biomarker for Globus Pallidus interna Deep Brain Stimulation (GPi-DBS) efficacy. Dystonia heterogeneity leads to a wide variety of clinical response to GPi-DBS, making it hard to predict GPi-DBS efficacy for individual patients.MethodsEEG-EMG recordings of twelve dystonia patients who received bilateral GPi-DBS took place pre- and 1 year post-surgery ON and OFF stimulation, during a rest, pinch, and flexion task. Dystonia severity was assessed using the BFMDRS and TWSTRS (pre- and post-surgery ON stimulation). Intermuscular coherence (IMC) and motorcortex corticomuscular coherence (CMC) were calculated. Low frequency (4–12 Hz) and beta band (13–30 Hz) peak coherences were studied.ResultsDystonia severity improved after 1 year GPi-DBS therapy (BFMDRS: 30%, median 7.8 (IQR 3–10), TWSTRS: 22%, median 6.8 (IQR 4–9)). 86% of IMC were above the 95% confidence limit. The highest IMC peak decreased significantly with GPi-DBS in the low frequency and beta band. Low frequency and beta band IMC correlated partly with dystonia severity and severity improvement. CMC generally were below the 95% confidence limit.ConclusionsPeak low frequency IMC functioned as biomarker for GPi-DBS efficacy, and partly correlated with dystonia severity.SignificanceIMC can function as biomarker. Confirmation in a larger study is needed for use in clinical practice.