Microelectrode-guided implantation of deep brain stimulators into the globus pallidus internus for dystonia: techniques, electrode locations, and outcomes

Interventional magnetic resonance guidance of deep brain stimulator implantation for Parkinson disease

Deep brain stimulation is increasingly being applied to movement disorders, and other novel applications are emerging. The therapy requires precise localization of the stimulation electrode at specific target sites in deep brain structures. Conventional means of implantation rely on stereotactic approaches, which lack sufficient targeting accuracy and therefore are supported by invasive physiological mapping. We review the use of interventional magnetic resonance image guidance for the implantation of deep brain stimulator electrodes in patients with moderate to advanced Parkinson disease. The methodologies used in this innovative surgical technique are presented, along with the potential benefits and limitations of such an approach. Targeting accuracies are shown to be within approximately 1 mm of the intended deep brain structure and are achieved with a single brain penetration in most cases. Preliminary evaluation of clinical outcomes indicates comparable results to that achieved with conventional implantation methods, and the technique holds promise for substantially reducing operative durations.

Induction of bradykinesia with pallidal deep brain stimulation in patients with cranial-cervical dystonia

BACKGROUND

Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is an effective and well-tolerated treatment for idiopathic generalized dystonia. More recently, it has been applied as a treatment for focal and segmental dystonias. This patient population offers an opportunity to study the effects of alteration of pallidal outflow on previously normal limb function.

METHODS

We sought to retrospectively characterize the extent of novel GPi DBS-induced adverse motor effects in patients with adult-onset cervical and cranial-cervical dystonia using a questionnaire, and compared the findings to dystonia improvement as measured by standard scales.

RESULTS

Despite significant improvement in dystonia (65% in mean Burke-Fahn-MarsdenDystonia Rating Scale motor score, p < 0.005, and 59% in mean Toronto Western Spasmodic Torticollis Rating Scale score, p < 0.008), slowing and difficulty with normal motor function was reported in previously nondystonic extremities in 10 of 11 patients. Symptoms were common in both upper and lower extremities and included new difficulties with handwriting (82%), getting up from a chair or in/out of a car (73%), and walking (45%), and were not associated with aberrant lead placement near the internal capsule.

CONCLUSION

Although GPi DBS was shown to be effective in these patients, the influence of GPi DBS on nondystonic body regions deserves further investigation.

A prospective blinded evaluation of deep brain stimulation for the treatment of secondary dystonia and primary torticollis syndromes

OBJECT

The aim of this study was to provide an objective assessment of deep brain stimulation (DBS) for groups of patients with mixed secondary dystonia and primary torticollis syndromes by a blinded evaluation of 13 consecutive patients who underwent ineffective medical treatment and botulinum toxin injections.

METHODS

Nine patients with secondary dystonia and 4 with cranial dystonia involving prominent spasmodic torticollis were selected for a DBS implant after they underwent unsuccessful medical treatment. Preoperative videos and neurological assessments were obtained and the DBS implant was inserted into the globus pallidus internus. Postoperatively, DBS parameters were adjusted to provide optimal benefit. Postoperative videotapes and quality of life scores were obtained. Blinded randomized evaluation of videotapes was performed by a neurologist specializing in movement disorders. Videos were scored using the Unified Dystonia Rating Scale, Toronto Western Spasmodic Torticollis Rating Scale, Burke-Fahn-Marsden Dystonia Rating Scale, or Abnormal Involuntary Movement Scale. Quality of life scoring was assessed using a standardized 7-point Global Rating Scale.

RESULTS

All 13 patients completed preoperative videotaping, medical assessment, and surgery. Optimal DBS programming was completed in 6.5 visits over 5.9 months. Seven patients reported marked improvement, 3 reported moderate improvement, 2 reported slight improvement or no change, and 1 was lost to follow-up. Examiner scores on the Global Rating Scale reflected patient self-reported scores.

CONCLUSIONS

Global subjective gains and notable objective improvement were observed in 11 of 13 patients. Although the benefits were variable and not fully predictable, they were of sufficient magnitude to justify offering the procedure when medications and botulinum toxin injections have failed.

Surgery for movement disorders

Movement disorders, such as Parkinson's disease, tremor, and dystonia, are among the most common neurological conditions and affect millions of patients. Although medications are the mainstay of therapy for movement disorders, neurosurgery has played an important role in their management for the past 50 years. Surgery is now a viable and safe option for patients with medically intractable Parkinson's disease, essential tremor, and dystonia. In this article, we provide a review of the history, neurocircuitry, indication, technical aspects, outcomes, complications, and emerging neurosurgical approaches for the treatment of movement disorders.

siRNA knock-down of mutant torsinA restores processing through secretory pathway in DYT1 dystonia cells

Most cases of the dominantly inherited movement disorder, early onset torsion dystonia (DYT1) are caused by a mutant form of torsinA lacking a glutamic acid residue in the C-terminal region (torsinADeltaE). TorsinA is an AAA+ protein located predominantly in the lumen of the endoplasmic reticulum (ER) and nuclear envelope apparently involved in membrane structure/movement and processing of proteins through the secretory pathway. A reporter protein Gaussia luciferase (Gluc) shows a reduced rate of secretion in primary fibroblasts from DYT1 patients expressing endogenous levels of torsinA and torsinADeltaE when compared with control fibroblasts expressing only torsinA. In this study, small interfering RNA (siRNA) oligonucleotides were identified, which downregulate the levels of torsinA or torsinADeltaE mRNA and protein by over 65% following transfection. Transfection of siRNA for torsinA message in control fibroblasts expressing Gluc reduced levels of luciferase secretion compared with the same cells non-transfected or transfected with a non-specific siRNA. Transfection of siRNA selectively inhibiting torsinADeltaE message in DYT fibroblasts increased luciferase secretion when compared with cells non-transfected or transfected with a non-specific siRNA. Further, transduction of DYT1 cells with a lentivirus vector expressing torsinA, but not torsinB, also increased secretion. These studies are consistent with a role for torsinA as an ER chaperone affecting processing of proteins through the secretory pathway and indicate that torsinADeltaE acts to inhibit this torsinA activity. The ability of allele-specific siRNA for torsinADeltaE to normalize secretory function in DYT1 patient cells supports its potential role as a therapeutic agent in early onset torsion dystonia.

Pallidal neuronal discharge in Huntington's disease: support for selective loss of striatal cells originating the indirect pathway

Chorea is the predominant motor manifestation in the early symptomatic phase of adult onset Huntington's disease (HD). Pathologically, this stage is marked by differential loss of striatal neurons contributing to the indirect pathway. This pattern of neuronal loss predicts decreased neuronal firing rates in GPi and increased firing rates in GPe, the opposite of the changes in firing rate known to occur in Parkinson's disease (PD). We present single-unit discharge characteristics (33 neurons) observed in an awake patient with HD (41 CAG repeats) undergoing microelectrode guided surgery for pallidal deep brain stimulation. Pallidal single-unit activity at "rest" and during voluntary movement was discriminated off line by principal component analysis and evaluated with respect to discharge rate, bursting, and oscillatory activity in the 0-200 Hz range. 24 GPi and 9 GPe units were studied, and compared with 132 GPi and 50 GPe units from 14 patients with PD. The mean (+/-SEM) spontaneous discharge rate for HD was 58+/-4 for GPi and 73+/-5 for GPe. This contrasted with discharge rates in PD of 95+/-2 for GPi and 57+/-3 for GPe. HD GPi units showed more bursting than PD GPi units but much less oscillatory activity in the 2-35 Hz frequency range at rest. These findings are consistent with selective early loss of striatal cells originating the indirect pathway.

Treatment of dystonia with deep brain stimulation

Pallidal deep brain stimulation (DBS) is an established treatment option for medically refractive dystonia. The mechanism by which globus pallidus pars interna (GPi) DBS improves dystonia is still unclear. Primary generalized dystonia usually responds well to this therapy, as recently confirmed in two well-designed, double-blind, controlled trials; however, predictors of outcome within this population are not well known. The role of GPi DBS in idiopathic cervical dystonia resistant to treatment with botulinum toxin, in tardive dystonia, and in some types of secondary dystonia are emerging as populations of patients who may also benefit, but outcomes are not well documented. Serious complications from this therapy are rare. Future research will likely continue to address the most appropriate programming settings for various populations of dystonia, the mechanism by which DBS affects dystonia, and the possibility of alternative brain targets that might have less associated side effects or greater efficacy than the GPi.

Opposite effects of internal globus pallidus stimulation on pallidal neurones activity

Besides clinical efficacy, the mechanisms of action of deep brain stimulation (DBS) are still debated. To shed light on this complex issue, we have taken the opportunity to record the response of globus pallidus internus (GPi) neurones to 100 Hz stimulations in a case of Lesch-Nyhan syndrome (LNS) where four pallidal electrodes were implanted. Three types of response were observed, 2/19 neurones were unaffected by DBS. About 7/19 neurones were inhibited during DBS stimulation and 10/19 neurones were excited during DBS stimulation. Both effects ceased when DBS was turned off. Inhibited neurones were situated lower that exited ones on the trajectory (1.25 and 4.65 mm above the center of GPi respectively). These observations suggest that locally DBS induces a reversible inhibition of neurone firing rate while at the same time distantly exciting the main afferents to and/or efferents from the GPi. Both actions would result in a strong GPi inhibition that does not preclude increased outflow from the GPi.

Location of Active Contacts in Patients with Primary Dystonia Treated with Globus Pallidus Deep Brain Stimulation

Objective:

Deep brain stimulation of the globus pallidus internus has been used for the treatment of various forms of dystonia, but the factors influencing postoperative outcomes remain unknown. We compared the location of the contacts being used for stimulation (active contacts) in patients with cervical dystonia, generalized dystonia, and Parkinson's disease and correlated the results with clinical outcome.

Methods:

Postoperative magnetic resonance scans of 13 patients with cervical dystonia, six patients with generalized dystonia, and five patients with Parkinson's disease who underwent globus pallidus internus deep brain stimulation were analyzed. We assessed the location of the active contacts relative to the midcommisural point and in relation to the anteroposterior and mediolateral boundaries of the pallidum. Postoperative outcome was measured with the Toronto Western Spasmodic Torticollis Rating Scale (for cervical dystonia) and the Burke-Fahn-Marsden Dystonia Rating Scale (for generalized dystonia) during the last follow-up.

Results:

We found that the location of the active contacts relative to the midcom-misural point and the internal boundaries of the pallidum was similar across the groups. In our series, the contacts used for stimulation were clustered in the posterolateral region of the pallidum. Within that region, we found no correlation between the location of the contacts and postoperative outcome.

Conclusion:

The location of the active contacts used for globus pallidus internus deep brain stimulation was similar in patients with cervical dystonia, generalized dystonia, and Parkinson's disease.

Modeling parkinsonian circuitry and the DBS electrode. II. Evaluation of a computer simulation model of the basal ganglia with and without subthalamic nucleus stimulation

Treatment with deep brain stimulation (DBS) for Parkinson's disease (PD) has become routine over the past decade, particularly using the subthalamic nucleus (STN) as a target and utilizing microelectrode recordings to ensure accurate placement of the stimulating electrodes. The clinical changes seen with DBS in the STN for PD are consistently beneficial, but there continues to be only marginal understanding of the mechanisms by which DBS achieves these results. Using an analytical model of the typical DBS 4-contact electrode and software developed to simulate individual neurons and neural circuitry of the basal ganglia we compare the results of the model to those of data obtained during DBS surgery of the STN. Firing rate, interspike intervals and regularity analyses were performed on the simulated data and compared to results in the literature.

Neuronal responses to passive movement in the globus pallidus internus in primary dystonia

Abnormal sensory processing has been implicated in the pathophysiology of primary dystonia. In the globus pallidus internus (GPi), the primary output structure of the basal ganglia, many neurons respond to sensory (proprioceptive) stimulation. Here we have characterized GPi neuronal responses to passive movement of the contralateral limbs in 22 patients with primary dystonia undergoing microelectrode recording for placement of deep brain stimulator leads. We plotted coordinates of cells responding to limb movement in a common space. We observed distinct representations of leg and arm movement localized to the dorsal and ventral part of the posterior GPi, respectively. Comparing patients with generalized dystonia versus patients with segmental craniocervical dystonia, there was no difference in the volumes or separations of leg and arm related territories. In contrast to parkinsonism, only a small minority of units were responsive to movement across multiple joints. Abnormally increased directional selectivity was found in units responding to dystonic limbs compared with nondystonic limbs. Some affected GPi neurons therefore appear to have altered proprioceptive tuning for movement direction. There is an apparent preservation of GPi somatotopic organization in dystonia in comparison with prior studies of GPi somatotopic organization in non-human primates and humans with Parkinson's disease.

Pallidal stimulation for dystonia in pantothenate kinase-associated neurodegeneration

Patients with generalized dystonia secondary to pantothenate kinase-associated neurodegeneration are traditionally treated palliatively with medical therapy. Therapeutic advances include stereotactic basal ganglia ablative techniques and, more recently, pallidal deep-brain stimulation. We report the course of dystonia in a teenage male. Bilateral microelectrode-guided pallidal deep-brain stimulators were placed while the patient was awake. Three parasagittal microelectrodes were inserted simultaneously. Two anterior microelectrodes were relatively quiet. The posterior electrode demonstrated a pattern of frequent bursts with high-frequency activity. The stimulator was therefore placed in the posterior location, which resulted in symptomatic improvement. Pallidal deep-brain stimulation appears to create a functional correction that may alter globus pallidus internus inhibitory output to the motor thalamus. The prominent, noisy bursting patterns observed in the globus pallidus internus suggests that high-frequency stimulation may improve signs of dystonia by normalizing thalamic discharge patterns.

Globus pallidus deep brain stimulators for a case of severe neuroleptic-related dystonia and dyskinesia

We report a 45 year old man with neuroleptic-induced dyskinesia for whom deep brain stimulators (DBS) were implanted in the globus pallidus internus (GPi). We describe a significant improvement in his symptoms. Lastly, we review briefly the success of deep brain stimulation to date, and discuss the clinical implications for individuals who develop movement disorders during neuroleptic use.

Pearls in patient selection for deep brain stimulation

BACKGROUND

Deep brain stimulation (DBS) has emerged as an important treatment for medication refractory movement and neuropsychiatric disorders. General neurologists and even general practitioners may be called upon to screen potential candidates for DBS. The patient selection process plays an important role in this procedure.

REVIEW SUMMARY

In this article, we discuss "pearls" for the clinician who may be called upon to identify appropriate candidates for DBS. Additionally, we will discuss the important points that should be considered when referring patients for surgical intervention.

CONCLUSION

Diagnosis, response to levodopa, cognitive status, psychiatric status, access to care, and patient expectations are all essential elements of the patient selection process for DBS. These areas must be adequately addressed prior to any surgical procedure.

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.

First case of X-linked dystonia-parkinsonism (“Lubag”) to demonstrate a response to bilateral pallidal stimulation

"Lubag" or X-linked dystonia-parkinsonism (XDP) is a genetic syndrome afflicting Filipino men. Intracranial surgical procedures for Lubag have been unsuccessful. We report a 45-year-old Filipino male with genetically confirmed XDP who underwent bilateral pallidal deep brain stimulation (DBS) surgery. The patient started to exhibit improvement on initial programming, most notably of his severe jaw-opening dystonia. At 1-year follow-up, his Burke-Fahn-Marsden dystonia score and motor Unified Parkinson's Disease Rating Scale score were improved by 71% and 62%, respectively, with the stimulators on compared to stimulators off state. Bilateral pallidal DBS may be a viable option for Lubag patients with medically refractory symptoms.

Surgery for other movement disorders: dystonia, tics

PURPOSE OF REVIEW

Various movement disorders are now treated with stereotactic procedures, particularly deep brain stimulation. We review the neurosurgical treatment of dystonias and tics, focusing mainly on the surgical aspects and outcome of deep brain stimulation.

RECENT FINDINGS

Pallidal stimulation is nowadays the mainstay surgical treatment for patients with dystonia, particularly generalized dystonia. Various well designed recent clinical trials support the efficacy of the procedure. Improvements of 40-80% have been reported in primary generalized, segmental and cervical dystonia. For secondary dystonia, a similar outcome has been described in patients with tardive dystonia and pantothenate kinase-associated neurodegeneration. In patients with Tourette's syndrome, the results of the first trials with thalamic and pallidal deep brain stimulation have been very promising. Improvements of 70-90% in the frequency of tics have been reported with surgery in both targets.

SUMMARY

Deep brain stimulation has become an established therapy for dystonia and is currently being used to treat Tourette's syndrome. With accumulation of experience, clinical features that are more responsive to surgery and the best surgical candidates will be revealed. This will likely improve even further the outcome of surgery for the treatment of these disorders.

A simple indicator of nonstationarity of firing rate in spike trains

The assessment of stationarity of firing rate in neural spike trains is important but is often performed only visually. Facing the growing amount of neural data generated by multi-electrode recording, there is a need for an automatic method to identify and disqualify spike trains with highly nonstationary firing rates. In this report, we propose a simple test of nonstationarity, associated with an indicator quantifying the degree of nonstationary in a spike train. This method is compared to the Mann-Kendall test of trend detection and the Runs test on simulated and real spike trains.

Neuronal firing rates and patterns in the globus pallidus internus of patients with cervical dystonia differ from those with Parkinson's disease

Cervical dystonia (CD) is a movement disorder that involves involuntary turning and twisting of the neck caused by abnormal muscle contraction. Deep brain stimulation (DBS) in the globus pallidus internus (GPi) is used to treat both CD and the motor symptoms of Parkinson's disease (PD). It has been suggested that the differing motor symptoms in CD and PD may arise from a decreased GPi output in CD and elevation of output in PD. To test this hypothesis, extracellular recordings of GPi neuronal activity were obtained during stereotactic surgery for the implantation of DBS electrodes in seven idiopathic CD and 14 PD patients. The mean GPi neuronal firing rate recorded from CD patients was lower than that in PD patients (P < 0.001; means +/- SE: 71.4 +/- 2.2 and 91.7 +/- 3.0 Hz, respectively). Furthermore, GPi neurons fired in a more irregular pattern consisting of more frequent and longer pauses in CD compared with PD patients. When comparisons were done based on locations of recordings, these differences in firing rates and patterns were limited to the ventral portion of the GPi. In contrast, no difference in firing rate or pattern was observed in the globus pallidus externus between the two groups. These findings suggest that alterations in both firing rate and firing pattern may underlie the differing motor symptoms associated with these two movement disorders.

Lower stimulation frequency can enhance tolerability and efficacy of pallidal deep brain stimulation for dystonia

We report the case of a patient with medically refractory primary dystonia who was treated with bilateral pallidal deep brain stimulation. Stimulation at 130 Hz or higher, by means of the more ventral contacts generated capsular side effects, which made their use impractical. Consequently, the patient was treated for 9 months at 130 to 185 Hz, by means of the more dorsal contacts, achieving modest results. By reducing the stimulation frequency to 80 Hz, we were able to activate the ventral contacts without inducing side effects. Within days, the patient experienced a dramatic improvement in function that has persisted for 1 year. A further reduction in stimulation frequency to 60 Hz resulted in a worsening of his symptoms. We conclude that chronic stimulation at frequencies of <100 Hz may be efficacious in dystonia and may enhance the tolerability of stimulation by means of contacts that are positioned posteroventrally within the internal globus pallidus, nearer the internal capsule.

Deep brain stimulation for treatment of cervical dystonia

Pallidal deep brain stimulation is an efficient treatment option in those patients with cervical dystonia who do not benefit from conservative treatment including local botulinum toxin injections. Given the fact that other surgical treatment options such as selective peripheral denervation are available, it may be considered third-line treatment in most instances. Chronic bilateral pallidal stimulation improves dystonic posture and movements, pain caused by dystonia and disability related to dystonia. Preliminary data on longterm follow-up confirm its beneficial effect in the majority of patients. Given the frequency of cervical dystonia, pallidal deep brain stimulation will play a major role in the future.