The treatment of Parkinson's disease with deep brain stimulation: current issues

Intraoperative DBS targeting of the globus pallidus internus by using motor evoked potentials

OBJECTIVES

Target localization for deep brain stimulation (DBS) is a crucial step that influences the clinical benefit of the DBS procedure together with the reduction of side effects. In this work, we address the feasibility of DBS target localization in the globus pallidus internus (GPi) aided by intraoperative motor evoked potentials (MEP) with emphasis on the reduction of capsular side effects.

MATERIAL AND METHODS

Micro-macroelectrode recordings were performed intraoperatively on 20 patients that underwent DBS treatment of the GPi (GPi-DBS). MEP were elicited intraoperatively by microelectrode stimulation during stereotactic DBS surgery. We studied the relationship between MEP thresholds and the internal capsule (IC) proximity.

RESULTS

We found a significant correlation between intraoperative MEP thresholds and IC proximity.

CONCLUSIONS

We provide further evidence of the role of MEPs for DBS target localization in the GPi, which extends and confirms the usefulness of MEPs as previously reported by DBS target localization studies dealing with the subthalamic and thalamic nuclei. Our approach is advantageous in that it provides criteria to determine the DBS target without the need to rely on a patient's response while avoiding capsular effects.

Concept for intrathecal delivery of brain recording and stimulation device

Neurological disorders are common, yet many neurological diseases don't have efficacious treatments. The protected nature of the brain both anatomically and physiologically through the blood brain barrier (BBB) make it exceptionally hard to access. Recent advancements in interventional approaches, like the Stentrode™, have opened the possibility of using the cerebral vasculature as a highway for minimally invasive therapeutic delivery to the brain. Despite the immense success that the Stentrode™ has faced recently, it is limited to major cerebral vasculature and exists outside the BBB, making drug eluting configurations largely ineffective. The present study seeks to identify a separate anatomical pathway for therapeutic delivery to the deep brain using the ventricular system. The intrathecal route, in which drug pumps and spinal cord stimulators are delivered through a lumbar puncture, is a well-established route for delivering therapies to the spinal cord as high as C1. The present study identifies an extension of this anatomical pathway through the foramen of Magendie and into the brains ventricular system. To test this pathway, a narrow self-expanding electrical recording device was manufactured and its potential to navigate the ventricular system was assessed on human anatomical brain samples. While the results of this paper are largely preliminary and a substantial amount of safety and efficacy data is needed, this paper identifies an important anatomical pathway for delivery of therapeutic and diagnostics tools to the brain that is minimally invasive, can access limbic structures, and is within the BBB.

A Novel and Selective Dopamine Transporter Inhibitor, (S)-MK-26, Promotes Hippocampal Synaptic Plasticity and Restores Effort-Related Motivational Dysfunctions

Dopamine (DA), the most abundant human brain catecholaminergic neurotransmitter, modulates key behavioral and neurological processes in young and senescent brains, including motricity, sleep, attention, emotion, learning and memory, and social and reward-seeking behaviors. The DA transporter (DAT) regulates transsynaptic DA levels, influencing all these processes. Compounds targeting DAT (e.g., cocaine and amphetamines) were historically used to shape mood and cognition, but these substances typically lead to severe negative side effects (tolerance, abuse, addiction, and dependence). DA/DAT signaling dysfunctions are associated with neuropsychiatric and progressive brain disorders, including Parkinson’s and Alzheimer diseases, drug addiction and dementia, resulting in devastating personal and familial concerns and high socioeconomic costs worldwide. The development of low-side-effect, new/selective medicaments with reduced abuse-liability and which ameliorate DA/DAT-related dysfunctions is therefore crucial in the fields of medicine and healthcare. Using the rat as experimental animal model, the present work describes the synthesis and pharmacological profile of (S)-MK-26, a new modafinil analogue with markedly improved potency and selectivity for DAT over parent drug. Ex vivo electrophysiology revealed significantly augmented hippocampal long-term synaptic potentiation upon acute, intraperitoneally delivered (S)-MK-26 treatment, whereas in vivo experiments in the hole-board test showed only lesser effects on reference memory performance in aged rats. However, in effort-related FR5/chow and PROG/chow feeding choice experiments, (S)-MK-26 treatment reversed the depression-like behavior induced by the dopamine-depleting drug tetrabenazine (TBZ) and increased the selection of high-effort alternatives. Moreover, in in vivo microdialysis experiments, (S)-MK-26 significantly increased extracellular DA levels in the prefrontal cortex and in nucleus accumbens core and shell. These studies highlight (S)-MK-26 as a potent enhancer of transsynaptic DA and promoter of synaptic plasticity, with predominant beneficial effects on effort-related behaviors, thus proposing therapeutic potentials for (S)-MK-26 in the treatment of low-effort exertion and motivational dysfunctions characteristic of depression and aging-related disorders.

Metabolic Imaging of Deep Brain Stimulation in Meige Syndrome

Objectives

The subthalamic nucleus (STN) has been shown to be a safe and effective deep brain stimulation (DBS) surgical target for the treatment of Meige syndrome. The aim of this study was to compare changes in brain metabolism before and 6 months after STN-DBS surgery.

Methods

Twenty-five patients with primary Meige syndrome underwent motor function assessment, including the Burke–Fahn–Marsden Dystonia Rating Scale movement (BFMDRS-M) and disability subscale (BFMDRS-D) and positron emission tomography with an 18[F]-fluorodeoxyglucose scan before and 6 months after STN-DBS surgery. For the voxelwise metabolic change assessment, the p-value was controlled for multiple comparisons using the familywise error rate.

Results

There was a significant decrease in BFMDRS-M scores 6 months after STN-DBS, from 10.02 ± 3.99 to 4.00 ± 2.69 (p < 0.001). The BFMDRS-D scores also decreased significantly from 4.52 ± 2.90 to 0.64 ± 1.29 (p < 0.001). In the left hemisphere, hypermetabolism was found in the occipital lobe, superior parietal gyrus, postcentral gyrus and thalamus. In the right hemisphere, hypermetabolism was found in the lentiform nucleus, precuneus and precentral gyrus in patients with Meige syndrome receiving DBS. In addition, the bilateral inferior temporal gyrus and middle frontal gyrus exhibited glucose hypermetabolism.

Conclusion

Our findings indicate that STN-DBS has a significant effect on metabolic level in the brain, which may be an important mechanism for the treatment of Meige syndrome using STN-DBS.

Therapeutic potentials of human microfluidic encapsulated conjunctival mesenchymal stem cells on the rat model of Parkinson's disease

BACKGROUND AND AIM

Parkinson's disease (PD) is a progressive neurodegenerative disorder caused by the destruction of the dopaminergic neurons in the nigrostriatal pathway, leading to motor-behavioral complications. Cell therapy has been proposed as a promising approach for PD treatment using various cellular sources. Despite a few disadvantages mesenchymal stem cells (MSCs) represent, they have more auspicious effects for PD cell therapy. The present study aimed to evaluate a new source of MSCs isolated from human Conjunctiva (CJ-MSCs) impact on PD complications for the first time.

MATERIALS AND METHODS

Parkinson's was induced by stereotactic injection of 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle (MFB). An apomorphine-induced rotation test was used to confirm the model establishment. After PD model confirmation, green fluorescent protein (GFP) labeled CJ-MSCs and induced CJ-MSCs (microfluidic encapsulated and non-capsulated) were transplanted into the rats' right striatum. Then Rotation, Rotarod, and Open-field tests were performed to evaluate the behavioral assessment. Additionally, the immunohistochemistry technique was used for identifying tyrosine hydroxylase (TH).

RESULTS

According to the obtained data, the cell transplantation caused a reduction in the rats' rotation number and improved locomotion compared to the control group. The previous results were also more pronounced in induced and microfluidic encapsulated cells compared to other cells. Rats recipient CJ-MSCs also have represented more TH-expressed GFP-labeled cell numbers in the striatum than the control group.

CONCLUSION

It can be concluded that CJ-MSCs therapy can have protective effects against PD complications and nerve induction of cells due to their ability to express dopamine. On the other hand, CJ-MSCs microencapsulating leads to enhance even more protective effect of CJ-MSCs. However, confirmation of this hypothesis requires further studies and investigation of these cells' possible mechanisms of action.

A technology evaluation of CVT-301 (Inbrija): an inhalable therapy for treatment of Parkinson's disease

Introduction: The most widely used pharmacological treatment for Parkinson's disease is levodopa, the precursor for dopamine formation in the brain. Over time, the effectiveness of levodopa declines, and patients experience motor fluctuations, or OFF periods. A levodopa formulation administered via a capsule-based oral inhaler provides a new delivery mechanism for levodopa that provides rapid relief of OFF periods.Areas covered: CVT-301 is a dry powder formulation designed to supply levodopa to the systemic circulation via pulmonary absorption. The technology, pharmacokinetics, efficacy, and safety data of this formulation are presented.Expert opinion: Oral inhalation is a novel method of administration for levodopa that bypasses the gastrointestinal tract, allowing levodopa to enter the systemic circulation rapidly and more reliably than oral medications. Gastrointestinal dysfunction, a common feature of Parkinson's disease, can lead to impaired absorption of oral medications. Pulmonary delivery rapidly elevates levodopa plasma concentrations to provide relief of OFF periods for patients receiving oral levodopa.

Measuring General Expectations of Advanced Stage Treatment Outcomes in Parkinson's Disease

BACKGROUND

Recent research suggests that a significant number of those who receive advanced treatments for Parkinson's disease (PD) do not report improvements for some symptoms, which may relate to their pre-treatment expectations. It is important that expectations of treatment are measured and discussed prior to advanced treatment.

OBJECTIVE

The primary aim of this study was to develop a measure of treatment expectations of two advanced-stage treatments in PD, deep brain stimulation (DBS), and Levodopa/Carbidopa Intestinal Gel (LCIG). A secondary aim was to explore potential predictors of treatment expectations.

METHODS

The questionnaire-based measure was developed by researchers in conjunction with a highly experienced clinician, and evaluated treatment expectations in 189 people aged 46-91 years (M = 71.35, SD = 8.73; 61% male) with idiopathic PD.

RESULTS

The overall measure demonstrated excellent internal consistency (α= 0.96). Exploratory factor analysis suggested the scale was unidimensional for both DBS and LCIG. Participant expectations of the two treatments differed significantly, with expectations being higher for DBS. Perceived symptom severity was the strongest predictor of treatment expectations.

CONCLUSION

This scale has potential to inform clinicians about client expectations prior to advanced stage therapy for PD, with a view to the management of these expectations. Further evaluation of the scale is required across different treatment contexts.

On demand therapy for Parkinson's disease patients: Opportunities and choices

Levodopa is the most effective symptomatic treatment for Parkinson's disease (PD), but a major treatment challenge is that over time, many patients experience periods of return of PD symptoms intermittently through the day, known as OFF periods. OFF periods typically manifest as a return of motor symptoms but can also involve non-motor symptoms and these periods can disrupt good control despite optimization of the oral levodopa regimen. OFF periods emerge in large measure due to a shortening of the duration of clinical benefit from oral levodopa, thought to be related to a progressive loss of dopamine neurons and their ability to store and release levodopa-derived dopamine over many hours. The problem is further compounded by impaired absorption of oral levodopa due to gastroparesis and other factors limiting its uptake in the small intestine, including competition for uptake by meals and their protein content. On-demand therapies are now available for the treatment of OFF episodes in PD and are administered intermittently, on an as-needed basis, on top of the patient's maintenance medication regimen. To be useful, an on-demand medication should take effect more rapidly and reliably than oral levodopa. Options for on-demand therapy for OFF periods have recently increased with the approval of levodopa inhalation powder and sublingual apomorphine as alternatives to the older option of subcutaneous apomorphine injection, each of which avoids the gastrointestinal tract and its potential for absorption delay. On-demand therapy is now available for patients experiencing episodic or intermittent need for rapid and reliable onset of benefit. On-demand therapy may also provide an alternative to more invasive treatment such as infusion of levodopa/carbidopa intestinal gel and for patients whose OFF episodes are not controlled despite deep brain stimulation.

The management of risk and investment in cell therapy process development: a case study for neurodegenerative disease

Cell-based therapies must achieve clinical efficacy and safety with reproducible and cost-effective manufacturing. This study addresses process development issues using the exemplar of a human pluripotent stem cell-based dopaminergic neuron cell therapy product. Early identification and correction of risks to product safety and the manufacturing process reduces the expensive and time-consuming bridging studies later in development. A New Product Introduction map was used to determine the developmental requirements specific to the product. Systematic Risk Analysis is exemplified here. Expected current value-based prioritization guides decisions about the sequence of process studies and whether and if an early abandonment of further research is appropriate. The application of the three tools enabled prioritization of the development studies.

Beyond Emotions: Oscillations of the Amygdala and Their Implications for Electrical Neuromodulation

The amygdala is a structure involved in emotions, fear, learning and memory and is highly interconnected with other brain regions, for example the motor cortex and the basal ganglia that are often targets of treatments involving electrical stimulation. Deep brain stimulation of the basal ganglia is successfully used to treat movement disorders, but can carry along non-motor side effects. The origin of these non-motor side effects is not fully understood yet, but might be altered oscillatory communication between specific motor areas and the amygdala. Oscillations in various frequency bands have been detected in the amygdala during cognitive and emotional tasks, which can couple with oscillations in cortical regions or the hippocampus. However, data on oscillatory coupling between the amygdala and motor areas are still lacking. This review provides a summary of oscillation frequencies measured in the amygdala and their possible functional relevance in different species, followed by evidence for connectivity between the amygdala and motor areas, such as the basal ganglia and the motor cortex. We hypothesize that the amygdala could communicate with motor areas through coherence of low frequency bands in the theta-alpha range. Furthermore, we discuss a potential role of the amygdala in therapeutic approaches based on electrical stimulation.

Acoustic Voice Modifications in Individuals with Parkinson Disease Submitted to Deep Brain Stimulation

Introduction  Subthalamic nucleus deep brain stimulation (STN-DBS) improves motor function in individuals with Parkinson disease (PD). The evidence about the effects of STN-DBS on the voice is still inconclusive. Objective  To verify the effect of STN-DBS on the voice of Brazilian individuals with PD. Methods  Sixteen participants were evaluated on the Unified Parkinson Disease Rating Scale-Part III, and by the measurement of the acoustic modifications in on and off conditions of stimulation. Results  The motor symptoms showed significant improvement with STN-DBS on. Regarding the acoustic measures of the voice, only the maximum fundamental frequency (fhi) showed a statistical difference between on- and off-conditions, with reduction in off-condition. Conclusion  Changes in computerized acoustic measures are more valuable when interpreted in conjunction with changes in other measures. The single finding in fhi suggests that DBS-STN increases vocal instability. The interpretation of this result should be done carefully, since it may not be of great value if other measures that also indicate instability are not significantly different.

Perspectives on the Earlier Use of Deep Brain Stimulation for Parkinson Disease from a Qualitative Study of U.S. Clinicians

BACKGROUND

In November 2015, the U.S. Food and Drug Administration (FDA) approved the use of deep brain stimulation (DBS) therapy in people with Parkinson's disease (PD) "of at least four years duration and with a recent onset of motor complications, or motor complications of longer-standing duration that are not adequately controlled with medication." Although the full implications of this more recent approval are yet to be determined, to date, there are no strict criteria defining appropriate earlier use of DBS. As such, confusion remains regarding the actual meaning of early DBS initiation. To better inform responsive policy, we sought the perspectives of movement disorder neurologists and neurosurgeons regarding the earlier use of DBS. Insights from these clinicians are key to developing appropriate clinical guidelines and determining how early is too early. The objective of this study is to explore attitudes among clinicians toward the earlier use of DBS for PD.

METHODS

Twelve Michigan-based clinicians were interviewed both about DBS referral/use processes and their perspectives regarding the earlier use of DBS in PD. We used a structured interview with closed- and open-ended questions. All interviews were transcribed verbatim and analyzed using a mixed-method approach.

RESULTS

We found that most clinicians considered earlier use not solely to be time dependent but instead determined by patient symptoms. Only 16.8% were aware of the FDA's recent indication of early use of DBS, with 25% of our respondents being unsure as to whether it should be seen as an early treatment modality. On average, neurologists suggested DBS as the next treatment option, after medications have been exhausted, typically 6 years after diagnosis.

CONCLUSIONS

There remain wide variations in terms of clinicians' parameters for referrals and timing of DBS. Larger studies are needed to support or refute our findings.

A Non-Invasive Medical Device for Parkinson's Patients with Episodes of Freezing of Gait

A critical symptom of Parkinson’s disease (PD) is the occurrence of Freezing of Gait (FOG), an episodic disorder that causes frequent falls and consequential injuries in PD patients. There are various auditory, visual, tactile, and other types of stimulation interventions that can be used to induce PD patients to escape FOG episodes. In this article, we describe a low cost wearable system for non-invasive gait monitoring and external delivery of superficial vibratory stimulation to the lower extremities triggered by FOG episodes. The intended purpose is to reduce the duration of the FOG episode, thus allowing prompt resumption of gait to prevent major injuries. The system, based on an Android mobile application, uses a tri-axial accelerometer device for gait data acquisition. Gathered data is processed via a discrete wavelet transform-based algorithm that precisely detects FOG episodes in real time. Detection activates external vibratory stimulation of the legs to reduce FOG time. The integration of detection and stimulation in one low cost device is the chief novel contribution of this work. We present analyses of sensitivity, specificity and effectiveness of the proposed system to validate its usefulness.

Differentiation of adult human mesenchymal stem cells into dopaminergic neurons

The striatal dopamine (DA) deficiency is known as the main cause of the clinical picture of Parkinson’s disease (PD). The disease is a progressive degeneration of dopaminergic neurons in the striatum. The treatment of PD is based on compensation for the brain’s supply of DA lost by drug therapy, deep brain stimulation, surgery, gene and cell therapies. Clinical studies have focused on the utility of stem cell-based therapies in PD. Embryonic and mesenchymal stem cells (MSCs) are widely used. Recently, human adipose derived stem cells (hADSCs) have been considered as a suitable source of tissue for this purpose. In this project, hADSCs differentiated into dopaminergic neurons and the specificity of the cell preparations was examined. Human adipose tissues were collected from healthy volunteers undergoing liposuction and hADSCs were isolated by collagenase-based enzymatic method. Flow cytometry was performed using the surface cluster of differentiation (CD) markers to confirm the cell typical properties. Then hADSCs were differentiated to dopaminergic neurons in neurobasal medium in the presence of differentiation factors and confirmed by immunocytochemistry via neuronal and dopaminergic markers. The isolated hADSCs were cultured and identified by the expression of MSCs surface markers including CD90, and CD44. These cells did not express hematopoietic surface markers such as CD45 and CD14. Differentiated cells express neuronal marker NeuN and dopaminergic marker tyrosine hydroxylase (TH). It is concluded that hADSCs can be easily taken from the patient’s own body and differentiated into dopaminergic cells having a lower risk of transplant rejection.

Safety and efficacy of levodopa-carbidopa intestinal gel: results from an open-label extension study in Japanese, Korean and Taiwanese patients with advanced Parkinson's disease

Objectives:

Levodopa-carbidopa intestinal gel (LCIG) was developed to reduce motor complications in Parkinson’s disease (PD) caused by pulsatile levodopa plasma concentrations following oral levodopa administration. Dyskinesia and ‘wearing off’ symptoms can vary between Asian and Caucasian patients with PD, thus highlighting the importance of assessing the effectiveness of LCIG in an Asian population. Efficacy and safety of LCIG were previously assessed in a 12-week open-label study; we report the efficacy and safety of at least 52 weeks of LCIG treatment in Japanese, Taiwanese, and Korean patients with advanced PD in the ongoing extension study.

Methods:

In this interim analysis of a phase III, open-label, multicenter extension study in Japan, South Korea, and Taiwan [ClinicalTrials.gov identifier: NCT02082249/JapiCTI-142482], the mean change from baseline to final visit in ‘off’ time, as reported in the PD symptom diary, was normalized to a 16-h waking day. Changes in Parkinson’s Disease Questionnaire-39 (PDQ-39) summary index and domains scores were also analyzed. Adverse events (AEs) were recorded.

Results:

Of the 28 patients enrolled (21 Japanese, 3 Taiwanese, 4 Korean), 27 completed at least 52 total weeks of treatment, and 25 patients were continuing in the study at data cutoff. The mean [standard deviation (SD)] ‘off’ time was significantly reduced by 4.6 (3.1) h/day (p < 0.001, n = 28). Patients experienced significant improvements in quality of life, as recorded by the mean change from baseline in PDQ-39 summary index (p < 0.001). All patients had at least one AE; three patients (11%) discontinued due to an AE. There were two deaths (sepsis and drowning), both of which the investigator considered unrelated to LCIG treatment.

Conclusions:

These data suggest that LCIG treatment is efficacious, safe, and well tolerated in Japanese, Taiwanese, and Korean patients with advanced PD, thus confirming the consistency of LCIG treatment in patients with advanced PD.

Selection of the Optimal Algorithm for Real-Time Estimation of Beta Band Power during DBS Surgeries in Patients with Parkinson's Disease

Deep Brain Stimulation (DBS) is a surgical procedure for the treatment of motor disorders in patients with Parkinson's Disease (PD). DBS involves the application of controlled electrical stimuli to a given brain structure. The implantation of the electrodes for DBS is performed by a minimally invasive stereotactic surgery where neuroimaging and microelectrode recordings (MER) are used to locate the target brain structure. The Subthalamic Nucleus (STN) is often chosen for the implantation of stimulation electrodes in DBS therapy. During the surgery, an intraoperative validation is performed to locate the dorsolateral region of STN. Patients with PD reveal a high power in the β band (frequencies between 13 Hz and 35 Hz) in MER signal, mainly in the dorsolateral region of STN. In this work, different power spectrum density methods were analyzed with the aim of selecting one that minimizes the calculation time to be used in real time during DBS surgery. In particular, the results of three nonparametric and one parametric methods were compared, each with different sets of parameters. It was concluded that the optimum method to perform the real-time spectral estimation of beta band from MER signal is Welch with Hamming windows of 1.5 seconds and 50% overlap.

Voltage adjustment improves rigidity and tremor in Parkinson's disease patients receiving deep brain stimulation

Deep brain stimulation of the subthalamic nucleus is recognized as the most effective treatment for moderate and advanced Parkinson's disease. Programming of the stimulation parameters is important for maintaining the efficacy of deep brain stimulation. Voltage is considered to be the most effective programming parameter. The present study is a retrospective analysis of six patients with Parkinson's disease (four men and two women, aged 37–65 years), who underwent bilateral deep brain stimulation of the subthalamic nucleus at the First Affiliated Hospital of Sun Yat-sen University, China, and who subsequently adjusted only the stimulation voltage. We evaluated motor symptom severity using the Unified Parkinson's Disease Rating Scale Part III, symptom progression using the Hoehn and Yahr scale, and the levodopa equivalent daily dose, before surgery and 1 and 2 years after surgery. The 2-year follow-up results show that rigidity and tremor improved, and clinical symptoms were reduced, while pulse width was maintained at 60 μs and frequency at 130 Hz. Voltage adjustment alone is particularly suitable for patients who cannot tolerate multiparameter program adjustment. Levodopa equivalent daily dose was markedly reduced 1 and 2 years after surgery compared with baseline. Our results confirm that rigidity, tremor and bradykinesia can be best alleviated by voltage adjustment. The trial was registered at ClinicalTrials.gov (identifier: NCT01934881).

Intraoperative Localization of the Subthalamic Nucleus Using Long-Latency Somatosensory Evoked Potentials

BACKGROUND

Target localization for deep brain stimulation (DBS) is a challenging step that determines not only the correct placement of stimulation electrodes, but also influences the success of the DBS procedure as reflected in the desired clinical outcome of a patient.

OBJECTIVE

We report on the feasibility of DBS target localization in the subthalamic nucleus (STN) by long-latency somatosensory evoked potentials (LL-SSEPs) (>40 msec) in Parkinson's disease (PD) patients.

METHODS

Micro-macroelectrode recordings were performed intraoperatively on seven PD patients (eight STN hemispheres) who underwent DBS treatment. LL-SSEPs were elicited by ipsi- and contralateral median nerve stimulation to the wrist.

RESULTS

Four distinctive LL-SSEP components were elicited ("LL-complex" consisting of P80, N100, P140, and N200). The P80 appeared as the most visible and reliable intraoperative component. Localization of the "LL-complex" within the target was approved with typical microelectrode firing activity patterns, atlas visualization of recording electrodes, and postoperative CT-based visualization of final DBS electrodes.

CONCLUSIONS

LL-SSEPs represent a promising approach for DBS target localization in the STN, provided deeper understanding on their anesthesia effect is obtained. This approach is advantageous in that it does not require the patient's participation in an intraoperative setting.

Vocalic transitions as markers of speech acoustic changes with STN-DBS in Parkinson's Disease

PURPOSE

Deep Brain Stimulation of the subthalamic nucleus (STN-DBS) effectively treats cardinal symptoms of idiopathic Parkinson's disease (PD) that cannot be satisfactorily managed with medication. Research is equivocal regarding speech changes associated with STN-DBS. This study investigated the impact of STN-DBS on vocalic transitions and the relationship to intelligibility.

METHODS

Eight Quebec-French speakers with PD and eight healthy controls participated. The slope of the second formant frequency (F2 slope) for glides was obtained. Locus equations (LEs) were calculated to capture vocalic transitions in consonant-vowel sequences. A visual analog scale was used to obtain judgments of intelligibility. Measures for the PD group were obtained both On and Off stimulation.

RESULTS

F2 slopes and LEs differed among groups, but there were no systematic differences for On versus Off STN-DBS. On an individual level, participants with PD exhibited heterogeneous changes with DBS stimulation. Intelligibility was significantly correlated with F2 slope.

CONCLUSION

F2 slope appears to be sensitive to articulatory impairment in PD and could be used in clinical settings to distinguish these speakers from healthy controls. However, acoustic metrics failed to identify systematic change with STN-DBS. The heterogeneity of results, as well as the clinical relevance of acoustic metrics are discussed.

Human subthalamic nucleus - Automatic auditory change detection as a basis for action selection

The subthalamic nucleus (STN) shapes motor behavior and is important for the initiation and termination of movements. Here we ask whether the STN takes aggregated sensory information into account, in order to exert this function. To this end, local field potentials (LFP) were recorded in eight patients suffering from Parkinson's disease and receiving deep-brain stimulation of the STN bilaterally. Bipolar recordings were obtained postoperatively from the externalized electrode leads. Patients were passively exposed to trains of auditory stimuli containing global deviants, local deviants or combined global/local deviants. The surface event-related potentials of the Parkinson's patients as well as those of 19 age-matched healthy controls were characterized by a mismatch negativity (MMN) that was most pronounced for the global/local double deviants and less prominent for the other deviant conditions. The left and right STN LFPs similarly were modulated by stimulus deviance starting at about 100ms post-stimulus onset. The MMN has been viewed as an index of an automatic auditory change detection system, more recently phrased in terms of predictive coding theory, which prepares the organism for attention shifts and for action. The LFP-data from the STN clearly demonstrate that the STN receives information on stimulus deviance, possibly as a means to bias the system to interrupt ongoing and to allow alternative actions.

Different outcomes of phonemic verbal fluency in Parkinson's disease patients with subthalamic nucleus deep brain stimulation

Subthalamic nucleus deep brain stimulation (STN-DBS) is a surgical technique to treat motor symptoms in patients with Parkinson's disease (PD). Studies have shown that STN-DBS may cause a decline in verbal fluency performance. We aimed to verify the effects of STN-DBS on the performance of phonemic verbal fluency in Brazilian PD patients. Sixteen participants were evaluated on the Unified Parkinson's Disease Rating Scale - Part III and for phonemic fluency ("FAS" version) in the conditions of on- and off-stimulation. We identified two different patterns of phonemic verbal fluency outcomes. The results indicate that there may be no expected pattern of effect of bilateral STN-DBS in the phonemic fluency, and patients may present with different outcomes for some reason not well understood.

Are Patients Ready for "EARLYSTIM"? Attitudes towards Deep Brain Stimulation among Female and Male Patients with Moderately Advanced Parkinson's Disease

Objective. To explore, in female and male patients with medically treated, moderately advanced Parkinson's disease (PD), their knowledge and reasoning about Deep Brain Stimulation (DBS). Methods. 23 patients with PD (10 women), aged 46–70, were interviewed at a mean of 8 years after diagnosis, with open-ended questions concerning their reflections and considerations about DBS. The interviews were transcribed verbatim and analysed according to the difference and similarity technique in Grounded Theory. Results. From the patients' narratives, the core category “Processing DBS: balancing symptoms, fears and hopes” was established. The patients were knowledgeable about DBS and expressed cautious and well considered attitudes towards its outcome but did not consider themselves ill enough to undergo DBS. They were aware of its potential side-effects. They considered DBS as the last option when oral medication is no longer sufficient. There was no difference between men and women in their reasoning and attitudes towards DBS. Conclusion. This study suggests that knowledge about the pros and cons of DBS exists among PD patients and that they have a cautious attitude towards DBS. Our patients did not seem to endorse an earlier implementation of DBS, and they considered that it should be the last resort when really needed.

Neurotrophin signalling: novel insights into mechanisms and pathophysiology

Neurotrophins, such as brain-derived neurotrophic factor (BDNF), are prominent regulators of neuronal survival, growth and differentiation during development. While trophic factors are viewed as well-understood but not innovative molecules, there are many lines of evidence indicating that BDNF plays an important role in the pathophysiology of many neurodegenerative disorders, depression, anxiety and other psychiatric disorders. In particular, lower levels of BDNF are associated with the aetiology of Alzheimer's and Huntington's diseases. A major challenge is to explain how neurotrophins are able to induce plasticity, improve learning and memory and prevent age-dependent cognitive decline through receptor signalling. This article will review the mechanism of action of neurotrophins and how BDNF/tropomyosin receptor kinase B (TrkB) receptor signaling can dictate trophic responses and change brain plasticity through activity-dependent stimulation. Alternative approaches for modulating BDNF/TrkB signalling to deliver relevant clinical outcomes in neurodegenerative and neuropsychiatric disorders will also be described.

Deep Brain Stimulation Frequency of the Subthalamic Nucleus Affects Phonemic and Action Fluency in Parkinson's Disease

Introduction. Deep brain stimulation of the subthalamic nucleus (STN-DBS) in Parkinson's disease (PD) has been linked to a decline in verbal fluency. The decline can be attributed to surgical effects, but the relative contributions of the stimulation parameters are not well understood. This study aimed to investigate the impact of the frequency of STN-DBS on the performance of verbal fluency tasks in patients with PD. Methods. Twenty individuals with PD who received bilateral STN-DBS were evaluated. Their performances of verbal fluency tasks (semantic, phonemic, action, and unconstrained fluencies) upon receiving low-frequency (60 Hz) and high-frequency (130 Hz) STN-DBS were assessed. Results. The performances of phonemic and action fluencies were significantly different between low- and high-frequency STN-DBS. Patients showed a decrease in these verbal fluencies for high-frequency STN-DBS. Conclusion. Low-frequency STN-DBS may be less harmful to the verbal fluency of PD patients.

Development and Antiparkinsonian Activity of VU0418506, a Selective Positive Allosteric Modulator of Metabotropic Glutamate Receptor 4 Homomers without Activity at mGlu2/4 Heteromers

Metabotropic glutamate receptor 4 (mGlu4) is emerging as a potential therapeutic target for numerous central nervous system indications, including Parkinson's disease (PD). As the glutamate binding sites among the eight mGlu receptors are highly conserved, modulation of receptor activity via allosteric sites within the receptor transmembrane domains using positive and negative allosteric modulators (PAMs and NAMs, respectively) has become a common strategy. We and others have used PAMs targeting mGlu4 to show that potentiation of receptor signaling induces antiparkinsonian activity in a variety of PD animal models, including haloperidol-induced catalepsy and 6-hydroxydopamine-induced lesion. Recently, mGlu4 has been reported to form heteromeric complexes with other mGlu receptor subtypes, such as mGlu2, and the resulting heteromer exhibits a distinct pharmacological profile in response to allosteric modulators. For example, some mGlu4 PAMs do not appear to potentiate glutamate activity when mGlu2 and mGlu4 are coexpressed, whereas other compounds potentiate mGlu4 responses regardless of mGlu2 coexpression. We report here the discovery and characterization of VU0418506, a novel mGlu4 PAM with activity in rodent PD models. Using pharmacological approaches and Complemented Donor-Acceptor resonance energy transfer (CODA-RET) technology, we find that VU0418506 does not potentiate agonist-induced activity when mGlu2 and mGlu4 are heterodimerized, suggesting that the antiparkinsonian action of mGlu4 PAMs can be induced by compounds without activity at mGlu2/4 heteromers.

Disease-Toxicant Interactions in Parkinson's Disease Neuropathology

Human disease commonly manifests as a result of complex genetic and environmental interactions. In the case of neurodegenerative diseases, such as Parkinson's disease (PD), understanding how environmental exposures collude with genetic polymorphisms in the central nervous system to cause dysfunction is critical in order to develop better treatment strategies, therapies, and a more cohesive paradigm for future research. The intersection of genetics and the environment in disease etiology is particularly relevant in the context of their shared pathophysiological mechanisms. This review offers an integrated view of disease-toxicant interactions in PD. Particular attention is dedicated to how mutations in the genes SNCA, parkin, leucine-rich repeat kinase 2 (LRRK2) and DJ-1, as well as dysfunction of the ubiquitin proteasome system, may contribute to PD and how exposure to heavy metals, pesticides and illicit drugs may further the consequences of these mutations to exacerbate PD and PD-like disorders. Although the toxic effects induced by exposure to these environmental factors may not be the primary causes of PD, their mechanisms of action are critical for our current understanding of the neuropathologies driving PD. Elucidating how environment and genetics collude to cause pathogenesis of PD will facilitate the development of more effective treatments for the disease. Additionally, we discuss the neuroprotection exerted by estrogen and other compounds that may prevent PD and provide an overview of current treatment strategies and therapies.

Effect of levodopa-carbidopa intestinal gel on resting tremors in patients with advanced Parkinson's disease

Resting tremors occur in more than 70% of patients with advanced Parkinson’s disease (PD). PD patients with resting tremors are typically treated with oral dopaminergic therapy or non-dopaminergic agents. However, treatment response with these medications is inconsistent and often unsatisfactory. Levodopa-carbidopa intestinal gel (LCIG, also known in the United States as carbidopa-levodopa enteral suspension (CLES)), administered continuously by a portable pump via a percutaneous endoscopic gastrojejunostomy (PEG-J) tube, significantly improves motor complications in patients with advanced PD. This was a post hoc analysis of a large phase 3, 12-month, open-label study evaluating long-term safety and efficacy of LCIG via PEG-J tube (NCT00335153). Unified Parkinson’s Disease Rating Scale Part III Question 20 total scores at baseline, measuring resting tremors, were used to stratify patients into three subgroups (none, mild, or significant baseline resting tremors). Out of 354 enrolled patients, 286 had baseline and post-PEG-J assessments of resting tremors and were included in this analysis. At baseline the majority of patients (69%) had no resting tremors, whereas 13% had mild resting tremors, and 18% had significant resting tremors. A complete resolution in resting tremors after 12 months of LCIG treatment was reported for 78% and 70% of patients with mild and significant baseline resting tremors, respectively. Improvements in motor complications and quality of life occurred regardless of degree of baseline resting tremors. LCIG may provide more consistent and sustained improvements in resting tremors that were not well-controlled with optimized oral medication among patients with advanced PD.