Quantitative DigitoGraphy: a Comprehensive Real-Time Remote Monitoring System for Parkinson's Disease

People with Parkinson's disease (PWP) face critical challenges, including lack of access to neurological care, inadequate measurement and communication of motor symptoms, and suboptimal medication management and compliance. We have developed QDG-Care: a comprehensive connected care platform for Parkinson's disease (PD) that delivers validated, quantitative metrics of all motor signs in PD in real time, monitors the effects of adjusting therapy and medication adherence and is accessible in the electronic health record. In this article, we describe the design and engineering of all components of QDG-Care, including the development and utility of the QDG Mobility and Tremor Severity Scores. We present the preliminary results and insights from the first at-home trial using QDG-Care. QDG technology has enormous potential to improve access to, equity of, and quality of care for PWP, and improve compliance with complex time-critical medication regimens. It will enable rapid "Go-NoGo" decisions for new therapeutics by providing high-resolution data that require fewer participants at lower cost and allow more diverse recruitment.

The digital signature of emergent tremor in Parkinson's disease

Background

Emergent tremor in Parkinson's disease (PD) can occur during sustained postures or movement that is different from action tremor. Tremor can contaminate the clinical rating of bradykinesia during finger tapping. Currently, there is no reliable way of isolating emergent tremor and measuring the cardinal motor symptoms based on voluntary movements only.

Objective

Investigate whether emergent tremor during repetitive alternating finger tapping (RAFT) on a quantitative digitography (QDG) device can be reliably identified and distinguished from voluntary tapping.

Methods

Ninety-six individuals with PD and forty-two healthy controls performed a thirty-second QDG-RAFT task and the Movement Disorders Society - Unified Parkinson's Disease Rating Scale Part III (MDS-UPDRS III). Visual identification of tremor during QDG-RAFT was labelled by an experienced movement disorders specialist. Two methods of identifying tremor were investigated: 1) physiologically-informed temporal thresholds 2) XGBoost model using temporal and amplitude features of tapping.

Results

The XGBoost model showed high accuracy for identifying tremor (area under the precision-recall curve of 0.981) and outperformed temporal-based thresholds. Percent time duration of classifier-identified tremor showed significant correlations with MDS-UPDRS III tremor subscores (r = 0.50, P < 0.0001). There was a significant change in QDG metrics for bradykinesia, rigidity and arrhythmicity after tremor strikes were excluded (p < 0.01).

Conclusions

Emergent tremor during QDG-RAFT has a unique digital signature and the duration of tremor correlated with the MDS-UPDRS III tremor items. When involuntary tremor strikes were excluded, the QDG metrics of bradykinesia and rigidity were significantly worse, demonstrating the importance of distinguishing tremor from voluntary movement when rating bradykinesia.

Proceedings of the 10th annual deep brain stimulation think tank: Advances in cutting edge technologies, artificial intelligence, neuromodulation, neuroethics, interventional psychiatry, and women in neuromodulation

The deep brain stimulation (DBS) Think Tank X was held on August 17-19, 2022 in Orlando FL. The session organizers and moderators were all women with the theme women in neuromodulation. Dr. Helen Mayberg from Mt. Sinai, NY was the keynote speaker. She discussed milestones and her experiences in developing depression DBS. The DBS Think Tank was founded in 2012 and provides an open platform where clinicians, engineers and researchers (from industry and academia) can freely discuss current and emerging DBS technologies as well as the logistical and ethical issues facing the field. The consensus among the DBS Think Tank X speakers was that DBS has continued to expand in scope however several indications have reached the "trough of disillusionment." DBS for depression was considered as "re-emerging" and approaching a slope of enlightenment. DBS for depression will soon re-enter clinical trials. The group estimated that globally more than 244,000 DBS devices have been implanted for neurological and neuropsychiatric disorders. This year's meeting was focused on advances in the following areas: neuromodulation in Europe, Asia, and Australia; cutting-edge technologies, closed loop DBS, DBS tele-health, neuroethics, lesion therapy, interventional psychiatry, and adaptive DBS.

Quantitative Digitography Measures Motor Symptoms and Disease Progression in Parkinson’s Disease

Background:

Assessment of motor signs in Parkinson’s disease (PD) requires an in-person examination. However, 50% of people with PD do not have access to a neurologist. Wearable sensors can provide remote measures of some motor signs but require continuous monitoring for several days. A major unmet need is reliable metrics of all cardinal motor signs, including rigidity, from a simple short active task that can be performed remotely or in the clinic.

Objective:

Investigate whether thirty seconds of repetitive alternating finger tapping (RAFT) on a portable quantitative digitography (QDG) device, which measures amplitude and timing, produces reliable metrics of all cardinal motor signs in PD.

Methods:

Ninety-six individuals with PD and forty-two healthy controls performed a thirty-second QDG-RAFT task and clinical motor assessment. Eighteen individuals were followed longitudinally with repeated assessments for an average of three years and up to six years.

Results:

QDG-RAFT metrics showed differences between PD and controls and provided correlated metrics for total motor disability (MDS-UPDRS III) and for rigidity, bradykinesia, tremor, gait impairment, and freezing of gait (FOG). Additionally, QDG-RAFT tracked disease progression over several years off therapy and showed differences between akinetic-rigid and tremor-dominant phenotypes, as well as people with and without FOG.

Conclusions:

QDG is a reliable technology, which could be used in the clinic or remotely. This could improve access to care, allow complex remote disease management based on data received in real time, and accurate monitoring of disease progression over time in PD. QDG-RAFT also provides the comprehensive motor metrics needed for therapeutic trials.

Concurrent stimulation and sensing in bi-directional brain interfaces: a multi-site translational experience

OBJECTIVE

To provide a design analysis and guidance framework for the implementation of concurrent stimulation and sensing during adaptive deep brain stimulation (aDBS) with particular emphasis on artifact mitigations.

APPROACH

We defined a general architecture of feedback-enabled devices, identified key components in the signal chain which might result in unwanted artifacts and proposed methods that might ultimately enable improved aDBS therapies. We gathered data from research subjects chronically-implanted with an investigational aDBS system, Summit RC+S, to characterize and explore artifact mitigations arising from concurrent stimulation and sensing. We then used a prototype investigational implantable device, DyNeuMo, and a bench-setup that accounts for tissue-electrode properties, to confirm our observations and verify mitigations. The strategies to reduce transient stimulation artifacts and improve performance during aDBS were confirmed in a chronic implant using updated configuration settings.

MAIN RESULTS

We derived and validated a "checklist" of configuration settings to improve system performance and areas for future device improvement. Key considerations for the configuration include 1) active instead of passive recharge, 2) sense-channel blanking in the amplifier, 3) high-pass filter settings, 4) tissue-electrode impedance mismatch management, 5) time-frequency trade-offs in the classifier, 6) algorithm blanking and transition rate limits. Without proper channel configuration, the aDBS algorithm was susceptible to limit-cycles of oscillating stimulation independent of physiological state. By applying the checklist, we could optimize each block's performance characteristics within the overall system. With system-level optimization, a 'fast' aDBS prototype algorithm was demonstrated to be feasible without reentrant loops, and with noise performance suitable for subcortical brain circuits.

SIGNIFICANCE

We present a framework to study sources and propose mitigations of artifacts in devices that provide chronic aDBS. This work highlights the trade-offs in performance as novel sensing devices translate to the clinic. Finding the appropriate balance of constraints is imperative for successful translation of aDBS therapies.

Assessing inertial measurement unit locations for freezing of gait detection and patient preference

Background

Freezing of gait, a common symptom of Parkinson’s disease, presents as sporadic episodes in which an individual’s feet suddenly feel stuck to the ground. Inertial measurement units (IMUs) promise to enable at-home monitoring and personalization of therapy, but there is a lack of consensus on the number and location of IMUs for detecting freezing of gait. The purpose of this study was to assess IMU sets in the context of both freezing of gait detection performance and patient preference.

Methods

Sixteen people with Parkinson’s disease were surveyed about sensor preferences. Raw IMU data from seven people with Parkinson’s disease, wearing up to eleven sensors, were used to train convolutional neural networks to detect freezing of gait. Models trained with data from different sensor sets were assessed for technical performance; a best technical set and minimal IMU set were identified. Clinical utility was assessed by comparing model- and human-rater-determined percent time freezing and number of freezing events.

Results

The best technical set consisted of three IMUs (lumbar and both ankles, AUROC = 0.83), all of which were rated highly wearable. The minimal IMU set consisted of a single ankle IMU (AUROC = 0.80). Correlations between these models and human raters were good to excellent for percent time freezing (ICC = 0.93, 0.89) and number of freezing events (ICC = 0.95, 0.86) for the best technical set and minimal IMU set, respectively.

Conclusions

Several IMU sets consisting of three IMUs or fewer were highly rated for both technical performance and wearability, and more IMUs did not necessarily perform better in FOG detection. We openly share our data and software to further the development and adoption of a general, open-source model that uses raw signals and a standard sensor set for at-home monitoring of freezing of gait.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12984-022-00992-x.

A validated measure of rigidity in Parkinson's disease using alternating finger tapping on an engineered keyboard

INTRODUCTION

Reliable and accurate measures of rigidity have remained elusive in remote assessments of Parkinson's disease (PD). This has severely limited the utility of telemedicine in the care and treatment of people with PD. It has also had a large negative impact on the scope of available outcomes, and on the costs, of multicenter clinical trials in PD. The goal of this study was to determine if quantitative measures from an engineered keyboard were sensitive and related to clinical measures of rigidity.

METHODS

Sixteen participants with idiopathic PD, off antiparkinsonian medications, and eleven age-matched control participants performed a 30 second repetitive alternating finger tapping task on an engineered keyboard and were assessed with the Unified Parkinson's Disease Rating Scale - motor (UPDRS-III).

RESULTS

The speed of the key release was significantly slower in the PD compared to control cohorts (p < 0.0001). In the PD cohort key release speed correlated with the lateralized upper extremity UPDRS III rigidity score (r = - 0.58, p < 0.0001), but not with the lateralized upper extremity tremor score (r = - 0.14, p = 0.43).

CONCLUSIONS

This validated measure of rigidity complements our previous validation of temporal metrics of the repetitive alternating finger tapping task with the UPDRS III, bradykinesia and with the ability to quantify tremor, arrhythmicity and freezing episodes, and suggests that 30 seconds of alternating finger tapping on a portable engineered keyboard could transform the treatment of PD with telemedicine and the precision of multicenter clinical trials.

The turning and barrier course reveals gait parameters for detecting freezing of gait and measuring the efficacy of deep brain stimulation

Freezing of gait (FOG) is a devastating motor symptom of Parkinson’s disease that leads to falls, reduced mobility, and decreased quality of life. Reliably eliciting FOG has been difficult in the clinical setting, which has limited discovery of pathophysiology and/or documentation of the efficacy of treatments, such as different frequencies of subthalamic deep brain stimulation (STN DBS). In this study we validated an instrumented gait task, the turning and barrier course (TBC), with the international standard FOG questionnaire question 3 (FOG-Q3, r = 0.74, p < 0.001). The TBC is easily assembled and mimics real-life environments that elicit FOG. People with Parkinson’s disease who experience FOG (freezers) spent more time freezing during the TBC compared to during forward walking (p = 0.007). Freezers also exhibited greater arrhythmicity during non-freezing gait when performing the TBC compared to forward walking (p = 0.006); this difference in gait arrhythmicity between tasks was not detected in non-freezers or controls. Freezers’ non-freezing gait was more arrhythmic than that of non-freezers or controls during all walking tasks (p < 0.05). A logistic regression model determined that a combination of gait arrhythmicity, stride time, shank angular range, and asymmetry had the greatest probability of classifying a step as FOG (area under receiver operating characteristic curve = 0.754). Freezers’ percent time freezing and non-freezing gait arrhythmicity decreased, and their shank angular velocity increased in the TBC during both 60 Hz and 140 Hz STN DBS (p < 0.05) to non-freezer values. The TBC is a standardized tool for eliciting FOG and demonstrating the efficacy of 60 Hz and 140 Hz STN DBS for gait impairment and FOG. The TBC revealed gait parameters that differentiated freezers from non-freezers and best predicted FOG; these may serve as relevant control variables for closed loop neurostimulation for FOG in Parkinson’s disease.

Biophysical basis of subthalamic local field potentials recorded from deep brain stimulation electrodes

Clinical deep brain stimulation (DBS) technology is evolving to enable chronic recording of local field potentials (LFPs) that represent electrophysiological biomarkers of the underlying disease state. However, little is known about the biophysical basis of LFPs, or how the patient's unique brain anatomy and electrode placement impact the recordings. Therefore, we developed a patient-specific computational framework to analyze LFP recordings within a clinical DBS context. We selected a subject with Parkinson's disease implanted with a Medtronic Activa PC+S DBS system and reconstructed their subthalamic nucleus (STN) and DBS electrode location using medical imaging data. The patient-specific STN volume was populated with 235,280 multicompartment STN neuron models, providing a neuron density consistent with histological measurements. Each neuron received time-varying synaptic inputs and generated transmembrane currents that gave rise to the LFP signal recorded at DBS electrode contacts residing in a finite element volume conductor model. We then used the model to study the role of synchronous beta-band inputs to the STN neurons on the recorded power spectrum. Three bipolar pairs of simultaneous clinical LFP recordings were used in combination with an optimization algorithm to customize the neural activity parameters in the model to the patient. The optimized model predicted a 2.4-mm radius of beta-synchronous neurons located in the dorsolateral STN. These theoretical results enable biophysical dissection of the LFP signal at the cellular level with direct comparison to the clinical recordings, and the model system provides a scientific platform to help guide the design of DBS technology focused on the use of subthalamic beta activity in closed-loop algorithms. NEW & NOTEWORTHY The analysis of deep brain stimulation of local field potential (LFP) data is rapidly expanding from scientific curiosity to the basis for clinical biomarkers capable of improving the therapeutic efficacy of stimulation. With this growing clinical importance comes a growing need to understand the underlying electrophysiological fundamentals of the signals and the factors contributing to their modulation. Our model reconstructs the clinical LFP from first principles and highlights the importance of patient-specific factors in dictating the signals recorded.

Subthalamic neural entropy is a feature of freezing of gait in freely moving people with Parkinson's disease

The goal of this study was to investigate subthalamic (STN) neural features of Freezers and Non-Freezers with Parkinson's disease (PD), while freely walking without freezing of gait (FOG) and during periods of FOG, which were better elicited during a novel turning and barrier gait task than during forward walking.

METHODS

Synchronous STN local field potentials (LFPs), shank angular velocities, and ground reaction forces were measured in fourteen PD subjects (eight Freezers) off medication, OFF deep brain stimulation (DBS), using an investigative, implanted, sensing neurostimulator (Activa® PC+S, Medtronic, Inc.). Tasks included standing still, instrumented forward walking, stepping in place on dual forceplates, and instrumented walking through a turning and barrier course.

RESULTS

During locomotion without FOG, Freezers showed lower beta (13-30Hz) power (P=0.036) and greater beta Sample Entropy (P=0.032), than Non-Freezers, as well as greater gait asymmetry and arrhythmicity (P<0.05 for both). No differences in alpha/beta power and/or entropy were evident at rest. During periods of FOG, Freezers showed greater alpha (8-12Hz) Sample Entropy (P<0.001) than during walking without FOG.

CONCLUSIONS

A novel turning and barrier course was superior to FW in eliciting FOG. Greater unpredictability in subthalamic beta rhythms was evident during stepping without freezing episodes in Freezers compared to Non-Freezers, whereas greater unpredictability in alpha rhythms was evident in Freezers during FOG. Non-linear analysis of dynamic neural signals during gait in freely moving people with PD may yield greater insight into the pathophysiology of FOG; whether the increases in STN entropy are causative or compensatory remains to be determined. Some beta LFP power may be useful for rhythmic, symmetric gait and DBS parameters, which completely attenuate STN beta power may worsen rather than improve FOG.

Long-term detection of Parkinsonian tremor activity from subthalamic nucleus local field potentials

Current deep brain stimulation paradigms deliver continuous stimulation to deep brain structures to ameliorate the symptoms of Parkinson's disease. This continuous stimulation has undesirable side effects and decreases the lifespan of the unit's battery, necessitating earlier replacement. A closed-loop deep brain stimulator that uses brain signals to determine when to deliver stimulation based on the occurrence of symptoms could potentially address these drawbacks of current technology. Attempts to detect Parkinsonian tremor using brain signals recorded during the implantation procedure have been successful. However, the ability of these methods to accurately detect tremor over extended periods of time is unknown. Here we use local field potentials recorded during a deep brain stimulation clinical follow-up visit 1 month after initial programming to build a tremor detection algorithm and use this algorithm to detect tremor in subsequent visits up to 8 months later. Using this method, we detected the occurrence of tremor with accuracies between 68-93%. These results demonstrate the potential of tremor detection methods for efficacious closed-loop deep brain stimulation over extended periods of time.

Proceedings of the Second Annual Deep Brain Stimulation Think Tank: What's in the Pipeline

The proceedings of the 2nd Annual Deep Brain Stimulation Think Tank summarize the most contemporary clinical, electrophysiological, and computational work on DBS for the treatment of neurological and neuropsychiatric disease and represent the insights of a unique multidisciplinary ensemble of expert neurologists, neurosurgeons, neuropsychologists, psychiatrists, scientists, engineers and members of industry. Presentations and discussions covered a broad range of topics, including advocacy for DBS, improving clinical outcomes, innovations in computational models of DBS, understanding of the neurophysiology of Parkinson's disease (PD) and Tourette syndrome (TS) and evolving sensor and device technologies.

Arrhythmokinesis is evident during unimanual not bimanual finger tapping in Parkinson's disease

BACKGROUND

Arrhythmokinesis, the variability in repetitive movements, is a fundamental feature of Parkinson's disease (PD). We hypothesized that unimanual repetitive alternating finger tapping (AFT) would reveal more arrhythmokinesis compared to bimanual single finger alternating hand tapping (SFT), in PD.

METHODS

The variability of inter-strike interval (CVISI) and of amplitude (CVAMP) during AFT and SFT were measured on an engineered, MRI-compatible keyboard in sixteen PD subjects off medication and in twenty-four age-matched controls.

RESULTS

The CVISI and CVAMP of the more affected (MA) and less affected (LA) sides in PD subjects were greater during AFT than SFT (P < 0.05). However, there was no difference between AFT and SFT for controls. Both CVISI and CVAMP were greater in the MA and LA hands of PD subjects versus controls during AFT (P < 0.01). The CVISI and CVAMP of the MA, but not the LA hand, were greater in PDs versus controls during SFT (P < 0.05). Also, AFT, but not SFT, detected a difference between the MA and LA hands of PDs (P < 0.01).

CONCLUSIONS

Unimanual, repetitive alternating finger tapping brings out more arrhythmokinesis compared to bimanual, single finger tapping in PDs but not in controls. Arrhythmokinesis during unimanual, alternating finger tapping captured a significant difference between both the MA and LA hands of PD subjects and controls, whereas that during a bimanual, single finger tapping task only distinguished between the MA hand and controls. Arrhythmokinesis underlies freezing of gait and may also underlie the freezing behavior documented in fine motor control if studied using a unimanual alternating finger tapping task.

Resting beta hypersynchrony in secondary dystonia and its suppression during pallidal deep brain stimulation in DYT3+ Lubag dystonia

OBJECTIVES

1) To characterize patterns of globus pallidus interna neural synchrony in patients with secondary dystonia; 2) to determine whether neural hypersynchrony in the globus pallidus externa (GPe) and interna (GPi) is attenuated during high frequency deep brain stimulation (HF DBS) in a patient with DYT3+ dystonia and in a patient with secondary dystonia due to childhood encephalitis.

MATERIALS AND METHODS

We recorded local field potentials from the DBS lead in the GPi of four patients (seven hemispheres) with secondary dystonia and from one patient (two hemispheres) with primary DYT3+ dystonia. In two patients, we also recorded pallidal local field potentials during the administration of 10 sec epochs of HF DBS.

RESULTS

Power spectral densities during rest demonstrated visible peaks in the beta band in seven out of nine cases. In DYT3+ dystonia, power in the alpha and beta bands, but not theta band, was attenuated during HF DBS in the GPe and in GPi, and attenuation was most prominent in the high beta band. This patient demonstrated an early and maintained improvement in dystonia. There was no beta peak and the power spectrum was not attenuated during HF DBS in a patient with secondary dystonia due to childhood encephalitis.

CONCLUSIONS

These results suggest that beta hypersynchrony, demonstrated now in both primary and secondary dystonia, may play a pathophysiological role in pathological hyperkinesis. Further investigation is needed in a larger cohort of well-characterized primary and secondary dystonia patients.

Improved efficacy of temporally non-regular deep brain stimulation in Parkinson's disease

High frequency deep brain stimulation is an effective therapy for motor symptoms in Parkinson's disease. However, the relative clinical efficacy of regular versus non-regular temporal patterns of stimulation in Parkinson's disease remains unclear. To determine the temporal characteristics of non-regular temporal patterns of stimulation important for the treatment of Parkinson's disease, we compared the efficacy of temporally regular stimulation with four non-regular patterns of stimulation in subjects with Parkinson's disease using an alternating finger tapping task. The patterns of stimulation were also evaluated in a biophysical model of the parkinsonian basal ganglia that exhibited prominent oscillatory activity in the beta frequency range. The temporal patterns of stimulation differentially improved motor task performance. Three of the non-regular patterns of stimulation improved performance of the finger tapping task more than temporally regular stimulation. In the computational model all patterns of deep brain stimulation suppressed beta band oscillatory activity, and the degree of suppression was strongly correlated with the clinical efficacy across stimulation patterns. The three non-regular patterns of stimulation that improved motor performance over regular stimulation also suppressed beta band oscillatory activity in the computational model more effectively than regular stimulation. These data demonstrate that the temporal pattern of stimulation is an important consideration for the clinical efficacy of deep brain stimulation in Parkinson's disease. Furthermore, non-regular patterns of stimulation may ameliorate motor symptoms and suppress pathological rhythmic activity in the basal ganglia more effectively than regular stimulation. Therefore, non-regular patterns of deep brain stimulation may have useful clinical and experimental applications.

High frequency deep brain stimulation attenuates subthalamic and cortical rhythms in Parkinson's disease

Parkinson's disease (PD) is marked by excessive synchronous activity in the beta (8–35 Hz) band throughout the cortico-basal ganglia network. The optimal location of high frequency deep brain stimulation (HF DBS) within the subthalamic nucleus (STN) region and the location of maximal beta hypersynchrony are currently matters of debate. Additionally, the effect of STN HF DBS on neural synchrony in functionally connected regions of motor cortex is unknown and is of great interest. Scalp EEG studies demonstrated that stimulation of the STN can activate motor cortex antidromically, but the spatial specificity of this effect has not been examined. The present study examined the effect of STN HF DBS on neural synchrony within the cortico-basal ganglia network in patients with PD. We measured local field potentials dorsal to and within the STN of PD patients, and additionally in the motor cortex in a subset of these patients. We used diffusion tensor imaging (DTI) to guide the placement of subdural cortical surface electrodes over the DTI-identified origin of the hyperdirect pathway (HDP) between motor cortex and the STN. The results demonstrated that local beta power was attenuated during HF DBS both dorsal to and within the STN. The degree of attenuation was monotonic with increased DBS voltages in both locations, but this voltage-dependent effect was greater in the central STN than dorsal to the STN (p < 0.05). Cortical signals over the estimated origin of the HDP also demonstrated attenuation of beta hypersynchrony during DBS dorsal to or within STN, whereas signals from non-specific regions of motor cortex were not attenuated. The spatially-specific suppression of beta synchrony in the motor cortex support the hypothesis that DBS may treat Parkinsonism by reducing excessive synchrony in the functionally connected sensorimotor network.

Maximal subthalamic beta hypersynchrony of the local field potential in Parkinson's disease is located in the central region of the nucleus

A pathological marker of Parkinson's disease is the existence of abnormal synchrony of neuronal activity within the beta frequency range (13-35 Hz) in the subthalamic nucleus (STN). Recent studies examining the topography of this rhythm have located beta hypersynchrony in the most dorsal part of the STN. In contrast, this study of the topography of the local field potential beta oscillations in 18 STNs with a 1 mm spatial resolution revealed that the point of maximal beta hypersynchrony was located at 53 ± 24% of the trajectory span from the dorsal to the ventral borders of the STN (corresponding to a 3.0 ± 1.6 mm depth for a 5.9 ± 0.75 mm STN span). This suggests that maximal beta hypersynchrony is located in the central region of the nucleus and that further investigation should be done before using STN spectral profiles as an indicator for guiding placement of deep brain stimulation leads.

Effect of medication and STN-DBS on postural control in subjects with Parkinson's disease

AIMS AND OBJECTIVES

To assess the effect of disease severity, dopaminergic medication (med) and STN-DBS on postural stability in Parkinson's disease (PD).

METHODS

Postural sway in quiet stance, and the Unified Parkinson's Disease Rating Scale (motor) (UPDRS III) were evaluated in 129 subjects in the off-med state. A subgroup of 28 subjects was studied on-med and after STN-DBS. Postural sway was measured using center of pressure (CoP) root mean square displacement (RMS(CoP)) and mean velocity (V(CoP)) in the anterior-posterior (AP) and medial-lateral (ML) directions.

RESULTS

All CoP parameters were larger in moderate/advanced subjects vs controls (P < 0.001) and early subjects. Only RMS(CoP)ML was larger in early subjects vs controls (P < 0.05). Med, DBS and DBS + med decreased UPDRS III compared to off-med (P < 0.001). RMS(CoP)ML and V(CoP)ML were larger on-med vs off-med and vs DBS (P < 0.001). Compared to controls and PD subjects with normal CoP sway off-med, med increased all CoP parameters (P < 0.01) but DBS returned V(CoP)ML to normal values. For 'abnormal' PD subjects, STN-DBS improved the excessive V(CoP) in ML compared to off and on-med pre-DBS (P < 0.05).

CONCLUSIONS

Postural sway in quiet stance increased with disease severity. Only ML CoP displacement was abnormal in early stage PD, and this may be a compensatory mechanism. Medication increased ML postural sway. In 'normal' PD subjects, STN-DBS reversed medication induced postural instability. Subjects with abnormal balance in quiet stance did not benefit from medication or DBS, except for improvement in ML CoP velocity from DBS. This may serve to reduce postural instability and falling.

Inclusion and exclusion criteria for DBS in dystonia

When considering a patient with dystonia for deep brain stimulation (DBS) surgery several factors need to be considered. Level B evidence has shown that all motor features and associated pain in primary generalized and segmental dystonia are potentially responsive to globus pallidus internus (GPi) DBS. However, improvements in clinical series of ≥ 90% may reflect methods that need improvement, and larger prospective studies are needed to address these factors. Nevertheless, to date the selection criteria for DBS-specifically in terms of patient features (severity and nature of symptoms, age, time of evolution, or any other demographic or disease aspects)--have not been assessed in a systematic fashion. In general, dystonia patients are not considered for DBS unless medical therapies have been previously and extensively tested. The vast majority of reported patients have had DBS surgery when the disease was provoking important disability, with loss of independence and impaired quality of life. There does not appear to be an upper age limit or a minimum age limit, although there are no published data regarding the outcome of GPi DBS for dystonia in children younger than 7 years of age. There is currently no enough evidence to prove that subjects with primary--generalized dystonia who undergo DBS at an early age and sooner rather than later after disease onset may gain more benefit from DBS than those undergoing DBS after the development of fixed skeletal deformities. There is no enough evidence to refuse or support consideration of DBS in patients with previous ablative procedures.

Repetitive stepping in place identifies and measures freezing episodes in subjects with Parkinson's disease

Freezing of gait (FOG) in Parkinson's disease (PD) is challenging to measure. We asked whether a repetitive stepping in place (SIP) task on force plates could identify freezing episodes (FEs) in PD subjects, self-classified as "freezers", using the validated FOG questionnaire (FOG-Q) and whether a computerized algorithm could provide automatic detection of FEs during SIP. Thirty PD subjects and nine age-matched controls completed the SIP task. PD subjects were assessed using the Unified Parkinson's Disease Rating motor Scale (UPDRS-III) and the FOG-Q. The identification of "freezers" using the SIP task correlated with the FOG-Q (r=0.80, P<0.001). The specificity and sensitivity of identifying freezers using the SIP task reached 93% and 87%. The number and duration of FEs detected by the algorithm correlated with visual inspection (r=0.97, r=0.998, P<0.001). Freezers had larger SIP asymmetry compared to controls (P=0.02) and non-freezers (P=0.03) as well as larger arhythmicity (P=0.003 and P<0.001, respectively). UPDRS subscores were higher in freezers compared to non-freezers (P<0.05). These results suggest that the SIP task is a useful tool to detect freezing in PD and is correlated with FOG-Q. SIP cycle asymmetry and stride time variability were worse in freezers, similar to that shown in FOG studies. Detection of the number and duration of FEs using a computerized algorithm correlated with independent visual inspection of records.

Quantitative lateralized measures of bradykinesia at different stages of Parkinson's disease: the role of the less affected side

The onset of motor abnormalities in Parkinson's disease (PD) is usually unilateral. However, current therapeutic trials do not analyze separately the performance of the more affected (MA) and less affected (LA) limbs. From a cohort of 85 subjects at different stages of PD, we asked whether the relationship between bradykinesia and disease severity was similar on both limbs and if the MA side remained more bradykinetic than the LA side in advanced PD. MA and LA limb determination was made from the history of the side first affected. Twenty-one age-matched subjects were used as controls. The velocities of finger and arm movements on both sides were inversely correlated with disease severity (P < 0.03). The slope of the decline in wrist movement velocity was steeper on the LA side (P = 0.029). When the regression lines were extrapolated to the y-axis (UPDRS III = 0) the performance of the LA side was not different from that of controls (P = 0.954 and P = 0.829 for finger and arm movements, respectively), whereas that of the MA side was slower (P = 0.019 and P = 0.016), suggesting that at the theoretical state of no disease the LA side would reflect less or no contralateral nigral pathology. With increasing disease severity, there was less difference between MA and LA sides in both finger and arm bradykinesia (P < 0.004). These findings highlight the value of analyzing separately the MA and LA sides in subjects with PD, especially for clinical trials of potential disease modifying agents in early stages of disease.

Testing objective measures of motor impairment in early Parkinson's disease: Feasibility study of an at-home testing device

We tested the feasibility of a computer based at-home testing device (AHTD) in early-stage, unmedicated Parkinson's disease (PD) patients over 6 months. We measured compliance, technical reliability, and patient satisfaction to weekly assessments of tremor, small and large muscle bradykinesia, speech, reaction/movement times, and complex motor control. relative to the UPDRS motor score. The AHTD is a 6.5'' x 10'' computerized assessment battery. Data are stored on a USB memory stick and sent by internet to a central data repository as encrypted data packets. Although not designed or powered to measure change, the study collected data to observe patterns relative to UPDRS motor scores. Fifty-two PD patients enrolled, and 50 completed the 6 month trial, 48 remaining without medication. Patients complied with 90.6% of weekly 30-minute assessments, and 98.5% of data packets were successfully transmitted and decrypted. On a 100-point scale, patient satisfaction with the program at study end was 87.2 (range: 80-100). UPDRS motor scores significantly worsened over 6 months, and trends for worsening over time occurred for alternating finger taps (P = 0.08), tremor (P = 0.06) and speech (P = 0.11). Change in tremor was a significant predictor of change in UPDRS (P = 0.047) and was detected in the first month of the study. This new computer-based technology offers a feasible format for assessing PD-related impairment from home. The high patient compliance and satisfaction suggest the feasibility of its incorporation into larger clinical trials, especially when travel is difficult and early changes or frequent data collection are considered important to document.

The STN beta-band profile in Parkinson's disease is stationary and shows prolonged attenuation after deep brain stimulation

Producing accurate movements may rely on the functional independence of sensorimotor circuits within basal ganglia nuclei. In parkinsonism there is abnormal synchrony of electrical activity within these circuits that results in a loss of independence across motor channels. Local field potential (LFP) recordings reflect the summation of local electrical fields and an increase in LFP power reflects increased synchrony in local neuronal networks. We recorded LFPs from the subthalamic nucleus (STN) deep brain stimulation (DBS) lead in the operating room in 22 cases from 16 subjects with Parkinson's disease (PD) who were off medication. There was elevated LFP power at beta frequencies (13-35 Hz) at rest. The LFP spectral profile was consistent across several periods of rest that were separated by movement and/or DBS, and appeared to be a relatively stationary phenomenon. The spectral profile and frequencies of the beta-band peak(s) varied among subjects but were similar between the right and left STNs within certain individuals. These results suggest that the LFP spectrum at rest may characterize a "signature" rhythm for an individual with PD. Beta-band power was attenuated after intra-operative STN DBS (p<0.05). The attenuation lasted for 10 s after short periods (30 s) and for up to 50 s after longer periods (5 min) of DBS. The finding that longer periods of DBS attenuated beta power for a longer time suggests that there may be long-acting functional changes to networks in the STN in PD after chronic DBS.

Practice Parameter: Treatment of Parkinson disease with motor fluctuations and dyskinesia (an evidence-based review): [RETIRED]

Objective: To make evidence-based treatment recommendations for the medical and surgical treatment of patients with Parkinson disease (PD) with levodopa-induced motor fluctuations and dyskinesia. To that end, five questions were addressed. 1. Which medications reduce off time? 2. What is the relative efficacy of medications in reducing off time? 3. Which medications reduce dyskinesia? 4. Does deep brain stimulation (DBS) of the subthalamic nucleus (STN), globus pallidus interna (GPi), or ventral intermediate (VIM) nucleus of the thalamus reduce off time, dyskinesia, and antiparkinsonian medication usage and improve motor function? 5. Which factors predict improvement after DBS?

Methods: A 10-member committee including movement disorder specialists and general neurologists evaluated the available evidence based on a structured literature review including MEDLINE, EMBASE, and Ovid databases from 1965 through June 2004.

Results, Conclusions, and Recommendations: 1. Entacapone and rasagiline should be offered to reduce off time (Level A). Pergolide, pramipexole, ropinirole, and tolcapone should be considered to reduce off time (Level B). Apomorphine, cabergoline, and selegiline may be considered to reduce off time (Level C). 2. The available evidence does not establish superiority of one medicine over another in reducing off time (Level B). Sustained release carbidopa/levodopa and bromocriptine may be disregarded to reduce off time (Level C). 3. Amantadine may be considered to reduce dyskinesia (Level C). 4. Deep brain stimulation of the STN may be considered to improve motor function and reduce off time, dyskinesia, and medication usage (Level C). There is insufficient evidence to support or refute the efficacy of DBS of the GPi or VIM nucleus of the thalamus in reducing off time, dyskinesia, or medication usage, or to improve motor function. 5. Preoperative response to levodopa predicts better outcome after DBS of the STN (Level B).

The North American Survey of Placement and Adjustment Strategies for Deep Brain Stimulation

BACKGROUND

Deep brain stimulation (DBS) is gaining wide acceptance as treatment for Parkinson's disease (PD), essential tremor, and dystonia.

METHODS

A 40-item questionnaire commissioned by the DBS Study Group was sent to 46 centers that had performed at least 25 DBS implantations. These centers were identified through the DBS Study Group, other professional societies, and with the assistance of the Medtronic Corporation. The results were then tabulated and descriptive analyses were performed.

RESULTS

Thirty-six of 47 centers (77%) responded, they had implanted 4,553 patients. The timing for bilaterally implanted patients varied, as 13 sites almost always implanted simultaneously whereas 14 sites almost never implanted simultaneously. Stereotactic frames included Leksell (n = 19), CRW (n = 15) and Compass (n = 2). Post-placement imaging was routinely performed by almost all centers and included MRI (n = 23), CT (n = 4), CT/MRI variably (n = 5), and ventriculography (n = 1). Two centers used more than one electrode per side. The 34 centers that used a single electrode averaged 2.3 +/- 1.4 passes per electrode (range: 1-18 passes). Most centers used macro-stimulation to confirm placement by assessing the intra-operative clinical response (n = 34), and to assess for adverse events (n = 26) at high voltages, averaging 6.7 +/- 2.3 V (range: 4-10). The initial activation averaged 18 +/- 12 days after electrode placement (average range: 11 +/- 10 to 28 +/- 18 days, absolute range: 1-90 days). Most sites had several programmers; however, the primary programmers were neurology staff (n = 15), the neurologist (n = 13), neurosurgery staff (n = 6), the neurosurgeon (n = 2), or a physiatrist (n = 1). Twelve centers automatically reduced PD medications on the day of initial activation, 9 centers reduced them variably, and 16 centers initially did not reduce them. Eventually, 80.4% of patients were reported to have some dose reduction, and 47.1% had a greater than 50% reduction of PD medications.

CONCLUSIONS

Strategies regarding DBS placement and adjustment vary in North America.

The Functional Organization of the Sensorimotor Region of the Subthalamic Nucleus

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is viewed by many as the ultimate therapy targeting severe advanced stages of Parkinson's disease (PD). A fundamental constituent of the mechanisms underlying the therapeutic effects of DBS is clearly the functional organization of the STN; however, there is limited understanding of the organization of this structure in humans. Data from primates suggest that different domains can be identified in the STN, including a sensorimotor area with a segregated body map, as well as nonmotor areas. Recent clinical studies have used microelectrode recording to investigate the presence of a body map in the sensorimotor STN of PD patients. This paper will review and compare experimental and clinical data regarding the functional organization of the STN and discuss the clinical implications for PD patients undergoing STN DBS.

Surgical therapy for dystonia

Surgical treatments for dystonia have been available since the early 20th century, but have improved in their efficacy to adversity ratio through a combination of technologic advances and better understanding of the role of the basal ganglia in dystonia. The word "dystonia" describes a phenotype of involuntary movement that may manifest from a variety of conditions. Dystonia may affect only certain regions of the body or may be generalized. It appears to be critical to determine whether the etiology underlying the dystonia is "primary" (ie, occurring from a genetic or idiopathic origin) or "secondary" (ie, occurring as a result of structural, metabolic, or neurodegenerative disorders). Secondary dystonias are far more common than primary dystonias. Primary dystonias respond well to pallidotomy or deep brain stimulation of the internal segment of the globus pallidum, whereas secondary dystonias appear to respond partially at best. Limited historic and current data suggest that the thalamus may be a promising target for the treatment of secondary dystonias, but more careful, prospective, randomized studies are needed. Combinations of bilateral targets are possible with the current technology of DBS, but not widely used due to surgical morbidity and expense. This article reviews the surgical treatment of dystonia from past to present, with a focus on separating the outcomes for primary versus secondary and generalized versus cervical dystonia.

Parkinson's Disease: Surgical Options

Surgical therapy for Parkinson's disease (PD) has been a treatment option for over 100 years. Advances in the knowledge of basal ganglia physiology and in techniques of stereotactic neurosurgery and neuroimaging have allowed more accurate placement of lesions or "brain pacemakers" in the sensorimotor regions of target nuclei. This, in turn, has led to improved efficacy with fewer complications than in the past. Currently, bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) or the internal segment of the globus pallidus (GPi) is the preferred option (and is approved by the US Food and Drug Administration) for the surgical treatment of PD. The most important predictors for outcome for DBS for PD are patient selection and electrode location. Patients should have a documented preoperative improvement from dopaminergic medication of at least 30% in the patient's Unified Parkinson's Disease Rating Scale motor disability scores. A levodopa challenge may be needed to document the best "on" state. Dementia or active cognitive decline must be excluded. Active psychiatric disease should be treated preoperatively. Patients should be motivated, with good support systems, and committed to the postoperative management of DBS therapy. Deep brain stimulation should be considered when the patient begins to experience dyskinesia and on-off fluctuations despite optimal medical therapy. Deep brain stimulation is not a good option at the final stages of the disease because of the increased incidence of dementia and severe comorbidity. The DBS electrode should be placed in the sensorimotor region of the GPi or STN. Subthalamic nucleus and GPi DBS can improve all motor aspects of PD, as well as predictable "on" time, without dyskinesia or fluctuations. On average, STN DBS results in a greater reduction of dopaminergic medication compared with GPi DBS. Because of the smaller size of the target region, the pulse generator battery life is longer with STN then with GPi DBS. Deep brain stimulation programming is a skill that is readily learned and may be required of all neurologists in the future. Emerging surgical therapies are restorative, and they aim to replace or regenerate degenerating dopaminergic neurons. These include embryonic mesencephalic tissue transplantation, human embryonic stem cell transplantation, and gene-derived methods of intracerebral implantation of growth factors and dopamine- producing cell lines. It will be important to determine whether DBS, if performed before the onset of motor response complications to medical therapy, may prevent this stage of disease altogether or delay it for a significant period of time. The same question applies to the future with restorative therapy.

The cerebrospinal fluid production rate is reduced in dementia of the Alzheimer's type

OBJECTIVE

To evaluate the production rate of CSF in patients with differing disease states.

METHODS

The authors measured the production rate of CSF in three groups of patients: five patients with PD below age 60 (aged 51 +/- 4 years, mean +/- SD), nine with PD over age 60 (aged 69 +/- 6 years, mean +/- SD), and seven with dementia of the Alzheimer's type (AD) (aged 72 +/- 9 years, mean +/- SD). This method, based on the Masserman technique, employs ventricular rather than a lumbar access to the CSF space. Furthermore, the volume of CSF removed during the procedure is only 3 mL rather than 10 mL.

RESULTS

These measurements indicate that the mean rate of CSF production in patients with PD under age 60 was 0.47 +/- 0.13 mL/minute, in patients with PD aged 60 or older the mean rate was 0.40 +/- 0.12 mL/minute, and in patients with AD the mean rate was 0.20 +/- 0.06 mL/minute.

CONCLUSION

These results indicate that the rate of CSF production in patients with PD is normal, and that the rate of CSF production in patients with AD is markedly reduced.