Effects of varying subthalamic nucleus stimulation on apraxia of lid opening in Parkinson's disease

Blepharospasm Secondary to Deep Brain Stimulation of the Subthalamic Nucleus in Parkinson Disease: Clinical Characteristics and Management Outcomes

BACKGROUND

Deep brain stimulation of the subthalamic nucleus (STN-DBS) is an effective treatment for patients with motor symptoms of Parkinson disease but can be complicated by disabling blepharospasm and apraxia of eyelid opening (ALO). Currently, there is no clear consensus on optimal management, and addressing these issues is further hindered by systemic morbidity and resistance to treatments. We aim to describe the different phenotypes of these eyelid movement disorders, to report our management approach and patient responses to treatment.

METHODS

A retrospective case series of all patients with blepharospasm/ALO secondary to STN-DBS that were treated at a tertiary center between 2011 and 2020. Data collected included date of Parkinson diagnosis, date of DBS surgery, date of development of blepharospasm/ALO symptoms, STN-DBS stimulation settings, and treatment given. Patients' symptoms before and after treatment were measured using the blepharospasm disability index and Jankovic Rating Scale.

RESULTS

Five patients were identified with eyelid movement disorders secondary to STN-DBS. All patients had moderate-to-severe symptoms at presentation. Four patients received periocular botulinum toxin injections. Three patients underwent surgery in the form of frontalis suspension or direct brow lift with or without upper lid blepharoplasty. All reported an improvement in symptoms following treatment.

CONCLUSIONS

A multimodality, patient-specific approach is required in the treatment of blepharospasm/ALO secondary to STN-DBS. Botulinum toxin injections can be effective, but patients may require surgery if toxin treatment alone becomes ineffective. Tailoring treatment to individual needs can result in a measurable improvement in symptoms.

Validating a Portable Device for Blinking Analyses through Laboratory Neurophysiological Techniques

Blinking analysis contributes to the understanding of physiological mechanisms in healthy subjects as well as the pathophysiological mechanisms of neurological diseases. To date, blinking is assessed by various neurophysiological techniques, including electromyographic (EMG) recordings and optoelectronic motion analysis. We recorded eye-blink kinematics with a new portable device, the EyeStat (Generation 3, blinktbi, Inc., Charleston, SC, USA), and compared the measurements with data obtained using traditional laboratory-based techniques. Sixteen healthy adults underwent voluntary, spontaneous, and reflex blinking recordings using the EyeStat device and the SMART motion analysis system (BTS, Milan, Italy). During the blinking recordings, the EMG activity was recorded from the orbicularis oculi muscles using surface electrodes. The blinking data were analyzed through dedicated software and evaluated with repeated-measure analyses of variance. The Pearson’s product-moment correlation coefficient served to assess possible associations between the EyeStat device, the SMART motion system, and the EMG data. We found that the EMG data collected during the EyeStat and SMART system recordings did not differ. The blinking data recorded with the EyeStat showed a linear relationship with the results obtained with the SMART system (r ranging from 0.85 to 0.57; p ranging from <0.001 to 0.02). These results demonstrate a high accuracy and reliability of a blinking analysis through this portable device, compared with standard techniques. EyeStat may make it easier to record blinking in research activities and in daily clinical practice, thus allowing large-scale studies in healthy subjects and patients with neurological diseases in an outpatient clinic setting.

Development of Quality of Life Questionnaire for Patients with Parkinson's Disease Undergoing STN-DBS

In device-aided therapy (DAT) for Parkinson’s disease (PD), factors such as device-related adverse effects, psychological and lifestyle changes, and specific disease progression can affect the quality of life (QoL) of patients with advanced PD. However, there is no existing QoL scale that includes the effects of therapeutic devices. From a semi-structured interview with patients with PD undergoing deep brain stimulation (DBS), we extracted the content of utterances that were thought to affect the QoL and created a draft questionnaire consisting of 113 items. This questionnaire was administered to 54 other patients undergoing DBS, whose data were examined for reliability and validity by factor analysis, and finally, a 24-item PD QoL questionnaire for patients on DAT (PDQ-DAT) was developed. Presently, the PDQ-DAT is the only scale that can assess the QoL of patients on DAT, including the influence treatment devices have on them. In the future, it might be used to help in shared decision-making in medicine by incorporating the patient’s sense of burden and values in the selection of treatment methods.

Apraxia of Lid Opening in Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease-Frequency, Risk Factors and Response to Treatment

Background

New-onset apraxia of lid opening (ALO) is reported to occur in Parkinson's disease (PD) patients following Deep Brain Stimulation (DBS). There are only few systematic studies on this uncommon disorder of eyelid movements.

Objectives

We aimed to examine the frequency, temporal evolution, predisposing factors and response to treatment, of new-onset ALO in PD patients who underwent bilateral subthalamic nucleus (STN) DBS.

Methods

We retrospectively reviewed the data of patients who underwent STN DBS at our centre between 1999 and 2017, with a minimum of 2 years of follow up after surgery.

Results

New-onset ALO was seen in 17 (9.1%) of the 187 patients after an average of 16.9 months (Range - 6-36 months). Comparison of the groups with and without ALO revealed that ALO occurred more often in older patients, both at the onset of PD symptoms and at surgery and in those with non-tremor dominant subtypes of PD and freezing of gait at baseline. The extent of levodopa dose reduction after surgery and the pre-operative severity of motor symptoms were not risk factors. Response to adjustments of dopaminergic medications and stimulation parameters was ill-sustained or nil. Botulinum toxin therapy resulted in satisfactory improvement in the majority.

Conclusions

New-onset ALO is an uncommon phenomenon that manifests months after STN DBS. Development of ALO is likely to be due to the effects of chronic stimulation of basal ganglia-thalamo-cortical or brain stem circuits controlling lid movements in susceptible patients. Botulinum toxin therapy offers relatively better relief of symptoms than other strategies.

Apraxia of eyelid opening might be critical for levodopa-carbidopa intestinal gel treatment

Apraxia of eyelid opening (AEO) has been associated with levodopa. It has also been linked to impaired function of the frontal lobe, with the dopaminergic neuron projected to the frontal lobe. However, dopaminergic treatment for AEO is still controversial. Here we describe two patients with both Parkinson's disease (PD) and AEO, who responded differently to a continuous intrajejunal levodopa-carbidopa intestinal gel (LCIG) infusion. One of the patients manifested a deterioration of AEO after LCIG infusion, and off-periods were shortened by the decrease in the severity of dyskinesia. After discontinuing the use of LCIG, there was an improvement in the patient's ability to open her eyelids. The other patient had AEO prior to LCIG treatment, and this treatment spontaneously elevated her eyelids. These two PD patients raised the concern as to whether AEO may be a critical symptom for the indication of LCIG treatment. The different responses to LCIG might have been due to the fluctuation in brain dopamine levels during LCIG treatment.

Stimulation-Induced Dyskinesia After Subthalamic Nucleus Deep Brain Stimulation in Patients With Meige Syndrome

OBJECTIVES

Deep brain stimulation of the subthalamic nucleus (STN-DBS) is increasingly used to treat Meige syndrome (MS) and markedly improves symptoms. Stimulation-induced dyskinesia (SID), which adversely affects surgical outcomes and patient satisfaction, may, however, occur in some patients. This study attempts to explore possible causes of SID.

MATERIALS AND METHODS

Retrospectively collected clinical data on 32 patients who underwent STN-DBS between October 2016 and April 2019 were analyzed. Clinical outcomes were assessed pre- and post-surgery, using the Burke-Fahn-Marsden dystonia rating scale (BFMDRS). Patients were divided into a dyskinesia group and a non-dyskinesia group, according to whether or not they experienced persistent SID during follow-up. The coordinates of the active contacts were calculated from post-operative computerized tomography or magnetic resonance imaging, using the inter-commissural line as a reference. At final follow-up, the main stimulatory parameters for further study included pulse width, voltage, and frequency.

RESULTS

At final follow-up (mean = 16.3 ± 7.2 months), MS patients had improved BFMDRS total scores compared with pre-surgical scores (mean improvement = 79.0%, p < 0.0001). The mean improvement in BFMDRS total scores in the dyskinesia (n = 10) and non-dyskinesia (n = 22) groups were 81.6 ± 8.8% and 77.9 ± 14.2%, respectively. The mean minimum voltage to induce dyskinesia was 1.7 ± 0.3 V. The programmed parameters of both groups were similar. When compared with the non-dyskinesia group, active stimulatory contact coordinates in the dyskinesia group were inferior (mean left side: z = -2.3 ± 1.7 mm vs. z = -1.2 ± 1.5 mm; p = 0.0282; mean right side: z = -2.7 ± 1.9 mm vs. z = -2.3 ± 1.7 mm; p = 0.0256). The x and y coordinates were similar.

CONCLUSION

STN-DBS is an effective intervention for MS, providing marked improvements in clinical symptoms; SID may, however occur in the subsequent programming control process. Comparing patients with/without dyskinesia, the active contacts were located closer to the inferior part of the STN in patients with dyskinesia, which may provide an explanation for the dyskinesia.

Apraxia of eyelid opening secondary to possible progressive supranuclear palsy: a case report

Apraxia of eyelid opening (AEO) is a disabling syndrome characterized by inability to open the eyes at will, and patients occasionally attempt to open their eyes by contracting the frontalis muscles and touching their eye lids with their fingers. The exact pathophysiological mechanisms underlying this syndrome remain unknown. Previous reports suggest that AEO is often associated with blepharospasm and is occasionally seen in patients with Parkinson's disease or other movement disorders. These reports suggest that AEO may be caused by lesions at the basal ganglia. In this report, we show a video of typical AEO.

Parkinsonism and subthalamic deep brain stimulation dysregulate behavioral motivation in a rodent model

BACKGROUND

Apathy and impulsivity constitute opposite poles of a behavioral motivation spectrum often disrupted by both the symptoms and therapies for Parkinson's Disease (PD). Upwards of 70% of PD patients experience symptoms of apathy, frequently unresolved or worsened by deep brain stimulation (DBS) of the subthalamic nucleus (STN). Worse, more than half of patients receiving DBS for PD experience new-onset impulse control disorders of varying severity following therapy initiation. While these symptoms and side-effects have been widely reported in clinical studies, they are largely unexplored in animal models.

METHODS

We applied high-frequency DBS in a 6-OHDA hemiparkinsonian rat model. We trained rats on a series of go/stop and go/no-go behavioral paradigms and examined how parkinsonism and DBS modulated task responses.

RESULTS

STN DBS in healthy rodents drove impulsive behavior in the form of stop and no-go task failure, impulsive reward seeking, and noninstructed task attempts. While trained rats without DBS only tended to fail stop and no-go cues very shortly after the cue, DBS led to failures at significantly later time points. Hemiparkinsonism slowed response times and reduced response rates, not alleviated by effective DBS.

INTERPRETATIONS

PD interrupts neural signaling responsible for healthy action selection, not restored by DBS. PD may be associated with a dearth of action commands, manifesting as apathy. Conversely, effective DBS may bias the system toward the impulsive end of the behavioral motivation spectrum without restoring behaviorally reasonable actions, mis-weighting reward-based action selection and manifesting as impulsivity, aided by DBS interfering with stop signaling.

Treatment options for postural instability and gait difficulties in Parkinson's disease

Introduction: Gait and balance disorders in Parkinson's disease (PD) represent a major therapeutic challenge as frequent falls and freezing of gait impair quality of life and predict mortality. Limited dopaminergic therapy responses implicate non-dopaminergic mechanisms calling for alternative therapies.Areas covered: The authors provide a review that encompasses pathophysiological changes involved in axial motor impairments in PD, pharmacological approaches, exercise, and physical therapy, improving physical activity levels, invasive and non-invasive neurostimulation, cueing interventions and wearable technology, and cognitive interventions.Expert opinion: There are many promising therapies available that, to a variable degree, affect gait and balance disorders in PD. However, not one therapy is the 'silver bullet' that provides full relief and ultimately meaningfully improves the patient's quality of life. Sedentariness, apathy, and emergence of frailty in advancing PD, especially in the setting of medical comorbidities, are perhaps the biggest threats to experience sustained benefits with any of the available therapeutic options and therefore need to be aggressively treated as early as possible. Multimodal or combination therapies may provide complementary benefits to manage axial motor features in PD, but selection of treatment modalities should be tailored to the individual patient's needs.

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).

Dystonia and Parkinson's disease: What is the relationship?

Dystonia and Parkinson's disease are closely linked disorders sharing many pathophysiological overlaps. Dystonia can be seen in 30% or more of the patients suffering with PD and sometimes can precede the overt parkinsonism. The response of early dystonia to the introduction of dopamine replacement therapy (levodopa, dopamine agonists) is variable; dystonia commonly occurs in PD patients following levodopa initiation. Similarly, parkinsonism is commonly seen in patients with mutations in various DYT genes including those involved in the dopamine synthesis pathway. Pharmacological blockade of dopamine receptors can cause both tardive dystonia and parkinsonism and these movement disorders syndromes can occur in many other neurodegenerative, genetic, toxic and metabolic diseases. Pallidotomy in the past and currently deep brain stimulation largely involving the GPi are effective treatment options for both dystonia and parkinsonism. However, the physiological mechanisms underlying the response of these two different movement disorder syndromes are poorly understood. Interestingly, DBS for PD can cause dystonia such as blepharospasm and bilateral pallidal DBS for dystonia can result in features of parkinsonism. Advances in our understanding of these responses may provide better explanations for the relationship between dystonia and Parkinson's disease.

Subthalamic Nucleus Deep Brain Stimulation in Parkinson's Disease: The Effect of Varying Stimulation Parameters

Subthalamic Nucleus Deep Brain Stimulation (STN DBS) is a well-established and effective treatment modality for selected patients with Parkinson's disease (PD). Since its advent, systematic exploration of the effect of stimulation parameters including the stimulation intensity, frequency, and pulse width have been carried out to establish optimal therapeutic ranges. This review examines published data on these stimulation parameters in terms of efficacy of treatment and adverse effects. Altering stimulation intensity is the mainstay of titration in DBS programming via alterations in voltage or current settings, and is characterised by a lower efficacy threshold and a higher side effect threshold which define the therapeutic window. In addition, much work has been done in exploring the effects of frequency modulation, which may help patients with gait freezing and other axial symptoms. However, there is a paucity of data on the use of ultra-short pulse width settings which are now possible with technological advances. We also discuss current evidence for the use of novel programming techniques including directional and adaptive stimulation, and highlight areas for future research.

Eyelid Dysfunction in Neurodegenerative, Neurogenetic, and Neurometabolic Disease

Eye movement abnormalities are among the earliest clinical manifestations of inherited and acquired neurodegenerative diseases and play an integral role in their diagnosis. Eyelid movement is neuroanatomically linked to eye movement, and thus eyelid dysfunction can also be a distinguishing feature of neurodegenerative disease and complements eye movement abnormalities in helping us to understand their pathophysiology. In this review, we summarize the various eyelid abnormalities that can occur in neurodegenerative, neurogenetic, and neurometabolic diseases. We discuss eyelid disorders, such as ptosis, eyelid retraction, abnormal spontaneous and reflexive blinking, blepharospasm, and eyelid apraxia in the context of the neuroanatomic pathways that are affected. We also review the literature regarding the prevalence of eyelid abnormalities in different neurologic diseases as well as treatment strategies (Table 1).

Delayed Onset Eye Opening Apraxia due to Progression of Brain Atrophy following Subthalamic Nucleus Deep Brain Stimulation: A Case Report

Eye opening apraxia (EOA) has been described in literature as a complication of deep brain stimulation (DBS), especially after electrode implantation in the subthalamic nucleus (STN). EOA can be either worsened or alleviated by DBS depending on the etiology. Herein, we report a rare case where the progression of brain atrophy may have contributed to the delayed onset of EOA. The patient, a 73-year-old woman, had previously undergone bilateral STN-DBS for advanced Parkinson’s disease (PD), which was performed by another DBS team, at the age of 68 years. She initially experienced a dramatic improvement in her motor symptoms, with no adverse events. However, she had difficulty in opening her right eye 3 years after the DBS surgery. Imaging studies showed that the brain atrophy had progressed over the past 5 years, and that the DBS electrodes were implanted through the far anterior entry points. We considered that the relative movement of the DBS might have been caused by the progression of the brain atrophy to the posterior limb of the internal capsule (IC) where the corticobulbar tract exists, and this was enhanced by the lower implantation angle. The present case illustrates the importance of the DBS insertion angle considering the a+ trophic effect and the follow-up imaging studies after DBS.

Coordinated Reset Deep Brain Stimulation of Subthalamic Nucleus Produces Long-Lasting, Dose-Dependent Motor Improvements in the 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine Non-Human Primate Model of Parkinsonism

BACKGROUND

Novel deep brain stimulation (DBS) paradigms are being explored in an effort to further optimize therapeutic outcome for patients with Parkinson's disease (PD). One approach, termed 'Coordinated Reset' (CR) DBS, was developed to target pathological oscillatory network activity. with desynchronizing effects and associated therapeutic benefit hypothesized to endure beyond cessation of stimulus delivery.

OBJECTIVE

To characterize the acute and carry-over effects of low-intensity CR DBS versus traditional DBS (tDBS) in the region of the subthalamic nucleus (STN).

METHODS

A within-subject, block treatment design involving the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) non-human primate model of parkinsonism was used. Each treatment block consisted of five days of daily DBS delivery followed by a one week minimum post-treatment observation window. Motor behavior was quantified using a modified rating scale for both animals combined with an objective, upper-extremity reach task in one animal.

RESULTS

Both animals demonstrated significant motor improvements during acute tDBS; however, within-session and post-treatment carry-over was limited. Acute motor improvements were also observed in response to low-intensity CR DBS; however, both within- and between-session therapeutic carry-over enhanced progressively following each daily treatment. Moreover, in contrast to tDBS, five consecutive days of CR DBS treatment yielded carry-over benefits that persisted for up to two weeks without additional intervention. Notably, the magnitude and time-course of CR DBS' effects on each animal varied with daily dose-duration, pointing to possible interaction effects involving baseline parkinsonian severity.

CONCLUSION

Our results support the therapeutic promise of CR DBS for PD, including its potential to induce carryover while reducing both side effect risk and hardware power consumption.

Anti-kindling Induced by Two-Stage Coordinated Reset Stimulation with Weak Onset Intensity

Abnormal neuronal synchrony plays an important role in a number of brain diseases. To specifically counteract abnormal neuronal synchrony by desynchronization, Coordinated Reset (CR) stimulation, a spatiotemporally patterned stimulation technique, was designed with computational means. In neuronal networks with spike timing–dependent plasticity CR stimulation causes a decrease of synaptic weights and finally anti-kindling, i.e., unlearning of abnormally strong synaptic connectivity and abnormal neuronal synchrony. Long-lasting desynchronizing aftereffects of CR stimulation have been verified in pre-clinical and clinical proof of concept studies. In general, for different neuromodulation approaches, both invasive and non-invasive, it is desirable to enable effective stimulation at reduced stimulation intensities, thereby avoiding side effects. For the first time, we here present a two-stage CR stimulation protocol, where two qualitatively different types of CR stimulation are delivered one after another, and the first stage comes at a particularly weak stimulation intensity. Numerical simulations show that a two-stage CR stimulation can induce the same degree of anti-kindling as a single-stage CR stimulation with intermediate stimulation intensity. This stimulation approach might be clinically beneficial in patients suffering from brain diseases characterized by abnormal neuronal synchrony where a first treatment stage should be performed at particularly weak stimulation intensities in order to avoid side effects. This might, e.g., be relevant in the context of acoustic CR stimulation in tinnitus patients with hyperacusis or in the case of electrical deep brain CR stimulation with sub-optimally positioned leads or side effects caused by stimulation of the target itself. We discuss how to apply our method in first in man and proof of concept studies.

Deep brain stimulation exacerbates hypokinetic dysarthria in a rat model of Parkinson's disease

Motor symptoms of Parkinson's disease (PD) follow the degeneration of dopaminergic neurons in the substantia nigra pars compacta. Deep brain stimulation (DBS) treats some parkinsonian symptoms, such as tremor, rigidity, and bradykinesia, but may worsen certain medial motor symptoms, including hypokinetic dysarthria. The mechanisms by which DBS exacerbates dysarthria while improving other symptoms are unclear and difficult to study in human patients. This study proposes an animal model of DBS-exacerbated dysarthria. We use the unilateral, 6-hydroxydopamine (6-OHDA) rat model of PD to test the hypothesis that DBS exacerbates quantifiable aspects of vocalization. Mating calls were recorded from sexually experienced male rats under healthy and parkinsonian conditions and during DBS of the subthalamic nucleus. Relative to healthy rats, parkinsonian animals made fewer calls with shorter and less complex vocalizations. In the parkinsonian rats, putatively therapeutic DBS further reduced call frequency, duration, and complexity. The individual utterances of parkinsonian rats spanned a greater bandwidth than those of healthy rats, potentially reducing the effectiveness of the vocal signal. This utterance bandwidth was further increased by DBS. We propose that the parkinsonism-associated changes in call frequency, duration, complexity, and dynamic range combine to constitute a rat analog of parkinsonian dysarthria. Because DBS exacerbates the parkinsonism-associated changes in each of these metrics, the subthalamic stimulated 6-OHDA rat is a good model of DBS-induced hypokinetic dysarthria in PD. This model will help researchers examine how DBS alleviates many motor symptoms of PD while exacerbating parkinsonian speech deficits that can greatly diminish patient quality of life.

Fabrication and initial testing of the μDBS: a novel Deep Brain Stimulation electrode with thousands of individually controllable contacts

High frequency electrical stimulation of deep brain structures such as the subthalamic nucleus in Parkinson's disease or thalamus for essential tremor is used clinically to reduce symptom severity. Deep brain stimulation activates neurons in specific brain structures and connection pathways, overriding aberrant neural activity associated with symptoms. While optimal deep brain stimulation might activate a particular neural structure precisely, existing deep brain stimulation can only generate roughly-spherical regions of activation that do not overlap with any target anatomy. Additionally, side effects linked to stimulation may be the result of limited control over placement of stimulation and its subsequent spread out of optimal target boundaries. We propose a novel lead with thousands of individually controllable contacts capable of asymmetric stimulation profiles. Here we outline the design motivation, manufacturing process, and initial testing of this new electrode design, placing it on track for further directional stimulation studies.

An age-related shift of resting-state functional connectivity of the subthalamic nucleus: a potential mechanism for compensating motor performance decline in older adults

Healthy aging is associated with decline in basic motor functioning and higher motor control. Here, we investigated age-related differences in the brain-wide functional connectivity (FC) pattern of the subthalamic nucleus (STN), which plays an important role in motor response control. As earlier studies revealed functional coupling between STN and basal ganglia, which both are known to influence the conservativeness of motor responses on a superordinate level, we tested the hypothesis that STN FC with the striatum becomes dysbalanced with age. To this end, we performed a seed-based resting-state analysis of fMRI data from 361 healthy adults (mean age: 41.8, age range: 18-85) using bilateral STN as the seed region of interest. Age was included as a covariate to identify regions showing age-related changes of FC with the STN seed. The analysis revealed positive FC of the STN with several previously described subcortical and cortical regions like the anterior cingulate and sensorimotor cortex, as well as not-yet reported regions including central and posterior insula. With increasing age, we observed reduced positive FC with caudate nucleus, thalamus, and insula as well as increased positive FC with sensorimotor cortex and putamen. Furthermore, an age-related reduction of negative FC was found with precuneus and posterior cingulate cortex. We suggest that this reduced de-coupling of brain areas involved in self-relevant but motor-unrelated cognitive processing (i.e. precuneus and posterior cingulate cortex) from the STN motor network may represent a potential mechanism behind the age-dependent decline in motor performance. At the same time, older adults appear to compensate for this decline by releasing superordinate motor control areas, in particular caudate nucleus and insula, from STN interference while increasing STN-mediated response control over lower level motor areas like sensorimotor cortex and putamen.

Postoperative management of deep brain stimulation in Parkinson's disease

Deep brain stimulation has become an established treatment for advanced Parkinson's disease. Its postoperative management is a delicate phase, dedicated to finding the optimal balance between stimulation and dopaminergic treatment. Postoperative management can be divided into an acute phase, aimed at the selection of the best stimulation contact, and a stabilization phase, aimed at the progressive adjustment of stimulation parameters and medications. A good knowledge of the electrophysiological anatomy of the target and surrounding structures, of the potential consequences of dopaminergic treatment modifications, and of the time course and interactions between stimulation and medication effects is mandatory for optimal outcome. This chapter focuses on the main strategies for the acute and chronic management of stimulation parameters and medication in the three main nuclei targeted in Parkinson's disease, namely the subthalamic nucleus, the ventral intermediate thalamic nucleus, and the internal part of the globus pallidus.