First-in-human demonstration of floating EMG sensors and stimulators wirelessly powered and operated by volume conduction.

BACKGROUND: Recently we reported the design and evaluation of floating semi-implantable devices that receive power from and bidirectionally communicate with an external system using coupling by volume conduction. The approach, of which the semi-implantable devices are proof-of-concept prototypes, may overcome some limitations presented by existing neuroprostheses, especially those related to implant size and deployment, as the implants avoid bulky components and can be developed as threadlike devices. Here, it is reported the first-in-human acute demonstration of these devices for electromyography (EMG) sensing and electrical stimulation. METHODS: A proof-of-concept device, consisting of implantable thin-film electrodes and a nonimplantable miniature electronic circuit connected to them, was deployed in the upper or lower limb of six healthy participants. Two external electrodes were strapped around the limb and were connected to the external system which delivered high frequency current bursts. Within these bursts, 13 commands were modulated to communicate with the implant. RESULTS: Four devices were deployed in the biceps brachii and the gastrocnemius medialis muscles, and the external system was able to power and communicate with them. Limitations regarding insertion and communication speed are reported. Sensing and stimulation parameters were configured from the external system. In one participant, electrical stimulation and EMG acquisition assays were performed, demonstrating the feasibility of the approach to power and communicate with the floating device. CONCLUSIONS: This is the first-in-human demonstration of EMG sensors and electrical stimulators powered and operated by volume conduction. These proof-of-concept devices can be miniaturized using current microelectronic technologies, enabling fully implantable networked neuroprosthetics.

Is Lyapunov exponent a reliable metric to detect dynamic stability in Parkinson's disease?

Idiopathic Parkinson's disease (PD) is the second most common neurodegenerative disorder worldwide. It affects the nervous system, causing motor and non-motor symptomatology. However, its clinical diagnosis remains dependent on the expertise of clinicians, as perceptual clinical scales are often used. Gait stability is one of the most relevant motor signs in PD. Nonetheless, it is usually not reported or quantified, possibly due to its unclear meaning and the high variability of metrics used in the literature. This work aims to identify a reliable and objective indicator that clinicians can use to assess patients in realistic contexts. We focused on the Largest Lyapunov Exponent (LLE), being the most common metric used in previous research works to quantify gait stability. The short and long-term LLEs were calculated in a group of 34 healthy and 42 participants diagnosed with PD. The long-term LLE extracted from the chest, right arm and right foot sensors showed statistical differences between subjects with PD and healthy control (HC) subjects, showing that the HC subjects are more stable than PD patients, whereas the short-term LLE showed the opposite results. Further investigation is required to clarify the reliability of this metric to detect and rate gait stability in people affected with PD.Clinical Relevance- This study is the first step towards the identification of an objective methodology to assess gait stability in clinical settings. Achieving this goal will contribute to improve the understanding and support the diagnosis of gait disorders that cause gait stability problems.

COVID19-associated new-onset movement disorders: a follow-up study.

BACKGROUND: Neurological symptoms are common manifestation in acute COVID-19. This includes hyper- and hypokinetic movement disorders. Data on their outcome, however, is limited. METHODS: Cases with new-onset COVID-19-associated movement disorders were identified by searching the literature. Authors were contacted for outcome data which were reviewed and analyzed. RESULTS: Movement disorders began 12.6 days on average after the initial onset of COVID-19. 92% of patients required hospital admission (mean duration 23 days). In a fraction of patients (6 of 27; 22%; 4 males/2 females, mean age 66.8 years) the movement disorder (ataxia, myoclonus, tremor, parkinsonism) was still present after a follow-up period of 7.5 ± 3 weeks. Severe COVID-19 in general and development of encephalopathy were risk factors, albeit not strong predictors, for the persistence. CONCLUSIONS: The prognosis of new-onset COVID-19-associated movement disorder appears to be generally good. The majority recovered without residual symptoms within several weeks or months. Permanent cases may be due to unmasking of a previous subclinical movement disorder or due to vascular/demyelinating damage. Given the relatively low response rate of one third only and the heterogeneity of mechanisms firm conclusions on the (long-term) outome cannot, however, be drawn.

Classification of Kinematic and Electromyographic Signals Associated with Pathological Tremor Using Machine and Deep Learning.

Peripheral Electrical Stimulation (PES) of afferent pathways has received increased interest as a solution to reduce pathological tremors with minimal side effects. Closed-loop PES systems might present some advantages in reducing tremors, but further developments are required in order to reliably detect pathological tremors to accurately enable the stimulation only if a tremor is present. This study explores different machine learning (K-Nearest Neighbors, Random Forest and Support Vector Machines) and deep learning (Long Short-Term Memory neural networks) models in order to provide a binary (Tremor; No Tremor) classification of kinematic (angle displacement) and electromyography (EMG) signals recorded from patients diagnosed with essential tremors and healthy subjects. Three types of signal sequences without any feature extraction were used as inputs for the classifiers: kinematics (wrist flexion-extension angle), raw EMG and EMG envelopes from wrist flexor and extensor muscles. All the models showed high classification scores (Tremor vs. No Tremor) for the different input data modalities, ranging from 0.8 to 0.99 for the f1 score. The LSTM models achieved 0.98 f1 scores for the classification of raw EMG signals, showing high potential to detect tremors without any processed features or preliminary information. These models may be explored in real-time closed-loop PES strategies to detect tremors and enable stimulation with minimal signal processing steps.

Prediction of Pathological Tremor Signals Using Long Short-Term Memory Neural Networks.

Previous implementations of closed-loop peripheral electrical stimulation (PES) strategies have provided evidence about the effect of the stimulation timing on tremor reduction. However, these strategies have used traditional signal processing techniques that only consider phase prediction and might not model the non-stationary behavior of tremor. Here, we tested the use of long short-term memory (LSTM) neural networks to predict tremor signals using kinematic data recorded from Essential Tremor (ET) patients. A dataset comprising wrist flexion-extension data from 12 ET patients was pre-processed to feed the predictors. A total of 180 models resulting from the combination of network (neurons and layers of the LSTM networks, length of the input sequence and prediction horizon) and training parameters (learning rate) were trained, validated and tested. Predicted tremor signals using LSTM-based models presented high correlation values (from 0.709 to 0.998) with the expected values, with a phase delay between the predicted and real signals below 15 ms, which corresponds approximately to 7.5% of a tremor cycle. The prediction horizon was the parameter with a higher impact on the prediction performance. The proposed LSTM-based models were capable of predicting both phase and amplitude of tremor signals outperforming results from previous studies (32--56% decreased phase prediction error compared to the out-of-phase method), which might provide a more robust PES-based closed-loop control applied to PES-based tremor reduction.

Tract-specific damage at spinal cord level in pure hereditary spastic paraplegia type 4: a diffusion tensor imaging study.

BACKGROUND: SPG4 is a subtype of hereditary spastic paraplegia (HSP), an upper motor neuron disorder characterized by axonal degeneration of the corticospinal tracts and the fasciculus gracilis. The few neuroimaging studies that have focused on the spinal cord in HSP are based mainly on the analysis of structural characteristics. METHODS: We assessed diffusion-related characteristics of the spinal cord using diffusion tensor imaging (DTI), as well as structural and shape-related properties in 12 SPG4 patients and 14 controls. We used linear mixed effects models up to T3 in order to analyze the global effects of 'group' and 'clinical data' on structural and diffusion data. For DTI, we carried out a region of interest (ROI) analysis in native space for the whole spinal cord, the anterior and lateral funiculi, and the dorsal columns. We also performed a voxelwise analysis of the spinal cord to study local diffusion-related changes. RESULTS: A reduced cross-sectional area was observed in the cervical region of SPG4 patients, with significant anteroposterior flattening. DTI analyses revealed significantly decreased fractional anisotropy (FA) and increased radial diffusivity at all the cervical and thoracic levels, particularly in the lateral funiculi and dorsal columns. The FA changes in SPG4 patients were significantly related to disease severity, measured as the Spastic Paraplegia Rating Scale score. CONCLUSIONS: Our results in SPG4 indicate tract-specific axonal damage at the level of the cervical and thoracic spinal cord. This finding is correlated with the degree of motor disability.

Corticospinal tract and motor cortex degeneration in pure hereditary spastic paraparesis type 4 (SPG4).

Objective: SPG4 is an autosomal dominant pure form of hereditary spastic paraplegia (HSP) caused by mutations in the SPAST gene. HSP is considered an upper motor neuron disorder characterized by progressive retrograde degeneration, or "dying-back" phenomenon, of the corticospinal tract's longest axons. Neuroimaging studies mainly focus on white matter changes and, although previous studies reported cortical thinning in complicated HSP forms, cortical changes remain unclear in SPG4 patients. This work aimed to compare changes in white matter microstructure and cortical thickness between 12 SPG4 patients and 22 healthy age-matched controls. We also explore whether white matter alterations are related to cortical thickness and their correlation with clinical symptoms. Methods: we used fixel-based analysis, an advanced diffusion-weighted imaging technique, and probabilistic tractography of the corticospinal tracts. We also analyzed cortical morphometry using whole-brain surface-based and atlas-based methods in sensorimotor areas. Results: SPG4 patients showed bilateral involvement in the corticospinal tracts; this was more intense in the distal portion than in the upper segments and was associated with the degree of clinical impairment. We found a significant correlation between disease severity and fiber density and cross-section of the corticospinal tracts. Furthermore, corticospinal tract changes were significantly correlated with bilateral cortical thinning in the precentral gyrus in SPG4 patients. Conclusions: Our data point to axonal damage of the corticospinal motor neurons in SPG4 patients might be related to cortical thinning in motor regions.

Present and Future of Parkinson's Disease in Spain: PARKINSON-2030 Delphi Project.

Parkinson's disease (PD) is a chronic progressive and irreversible disease and the second most common neurodegenerative disease worldwide. In Spain, it affects around 120.000-150.000 individuals, and its prevalence is estimated to increase in the future. PD has a great impact on patients' and caregivers' lives and also entails a substantial socioeconomic burden. The aim of the present study was to examine the current situation and the 10-year PD forecast for Spain in order to optimize and design future management strategies. This study was performed using the modified Delphi method to try to obtain a consensus among a panel of movement disorders experts. According to the panel, future PD management will improve diagnostic capacity and follow-up, it will include multidisciplinary teams, and innovative treatments will be developed. The expansion of new technologies and studies on biomarkers will have an impact on future PD management, leading to more accurate diagnoses, prognoses, and individualized therapies. However, the socio-economic impact of the disease will continue to be significant by 2030, especially for patients in advanced stages. This study highlighted the unmet needs in diagnosis and treatment and how crucial it is to establish recommendations for future diagnostic and therapeutic management of PD.

Thalamic atrophy in patients with pure hereditary spastic paraplegia type 4.

SPG4 is an autosomal dominant pure form of hereditary spastic paraplegia (HSP) caused by mutations in the SPAST gene. HSP is considered an upper motor neuron disorder characterized by progressive spasticity and weakness of the lower limbs caused by degeneration of the corticospinal tract. In other neurodegenerative motor disorders, the thalamus and basal ganglia are affected, with a considerable impact on disease progression. However, only a few works have studied these brain structures in HSP, mainly in complex forms of this disease. Our research aims to detect potential alterations in the volume and shape of the thalamus and various basal ganglia structures by comparing 12 patients with pure HSP and 18 healthy controls. We used two neuroimaging procedures: automated segmentation of the subcortical structures (thalamus, hippocampus, caudate nucleus, globus pallidus, and putamen) in native space and shape analysis of the structures. We found a significant reduction in thalamic volume bilaterally, as well as an inward deformation, mainly in the sensory-motor thalamic regions in patients with pure HSP and a mutation in SPG4. We also observed a significant negative correlation between the shape of the thalamus and clinical scores (the Spastic Paraplegia Rating Scale score and disease duration). Moreover, we found a 'Group × Age' interaction that was closely related to the severity of the disease. No differences in volume or in shape were found in the remaining subcortical structures studied. Our results suggest that changes in structure of the thalamus could be an imaging biomarker of disease progression in pHSP.

Neurological complications of COVID-19 in hospitalized patients: The registry of a neurology department in the first wave of the pandemic.

OBJECTIVE: To describe the spectrum of neurological complications observed in a hospital-based cohort of COVID-19 patients who required a neurological assessment. METHODS: We conducted an observational, monocentric, prospective study of patients with a COVID-19 diagnosis hospitalized during the 3-month period of the first wave of the COVID-19 pandemic in a tertiary hospital in Madrid (Spain). We describe the neurological diagnoses that arose after the onset of COVID-19 symptoms. These diagnoses could be divided into different groups. RESULTS: Only 71 (2.6%) of 2750 hospitalized patients suffered at least one neurological complication (77 different neurological diagnoses in total) during the timeframe of the study. The most common diagnoses were neuromuscular disorders (33.7%), cerebrovascular diseases (CVDs) (27.3%), acute encephalopathy (19.4%), seizures (7.8%), and miscellanea (11.6%) comprising hiccups, myoclonic tremor, Horner syndrome and transverse myelitis. CVDs and encephalopathy were common in the early phase of the COVID-19 pandemic compared to neuromuscular disorders, which usually appeared later on (p = 0.005). Cerebrospinal fluid severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) polymerase chain reaction was negative in 15/15 samples. The mortality was higher in the CVD group (38.1% vs. 8.9%; p = 0.05). CONCLUSIONS: The prevalence of neurological complications is low in patients hospitalized for COVID-19. Different mechanisms appear to be involved in these complications, and there was no evidence of direct invasion of the nervous system in our cohort. Some of the neurological complications can be classified into early and late neurological complications of COVID-19, as they occurred at different times following the onset of COVID-19 symptoms.

Intramuscular Stimulation of Muscle Afferents Attains Prolonged Tremor Reduction in Essential Tremor Patients.

This study proposes and clinically tests intramuscular electrical stimulation below motor threshold to achieve prolonged reduction of wrist flexion/extension tremor in Essential Tremor (ET) patients. The developed system consisted of an intramuscular thin-film electrode structure that included both stimulation and electromyography (EMG) recording electrodes, and a control algorithm for the timing of intramuscular stimulation based on EMG (closed-loop stimulation). Data were recorded from nine ET patients with wrist flexion/extension tremor recruited from the Gregorio Marañón Hospital (Madrid, Spain). Patients participated in two experimental sessions comprising: 1) sensory stimulation of wrist flexors/extensors via thin-film multichannel intramuscular electrodes; and 2) surface stimulation of the nerves innervating the same target muscles. For each session, four of these patients underwent random 60-s trials of two stimulation strategies for each target muscle: 1) selective and adaptive timely stimulation (SATS) - based on EMG of the antagonist muscle; and 2) continuous stimulation (CON) of target muscles. Two patients underwent SATS stimulation trials alone while the other three underwent CON stimulation trials alone in each session. Kinematics of wrist, elbow, and shoulder, together with clinical scales, were used to assess tremor before, right after, and 24 h after each session. Intramuscular SATS achieved, on average, 32% acute (during stimulation) tremor reduction on each trial, while continuous stimulation augmented tremorgenic activity. Furthermore, tremor reduction was significantly higher using intramuscular than surface stimulation. Prolonged reduction of tremor amplitude (24 h after the experiment) was observed in four patients. These results showed acute and prolonged (24 h) tremor reduction using a minimally invasive neurostimulation technology based on SATS of primary sensory afferents of wrist muscles. This strategy might open the possibility of an alternative therapeutic approach for ET patients.

Genetic variation in APOE, GRN, and TP53 are phenotype modifiers in frontotemporal dementia.

Frontotemporal dementia (FTD) is a clinical, genetic, and pathologic heterogeneous group of neurodegenerative diseases. In this study, we investigated the role of APOƐ4, rs5848 in GRN, and rs1042522 in TP53 gene as disease risk factors and/or phenotype modifiers in 440 FTD patients, including 175 C9orf72 expansion carriers. We found that the C9orf72 expansion carriers showing an earlier age at onset (p < 0.001). Among the clinical groups, the FTD-MND (motoneuron disease) showed the lowest survival (hazard ratio [HR] = 4.12), and the progressive nonfluent aphasia group showed the highest onset age (p = 0.03). In our cohort, the rs1042522 in TP53 was associated with disease onset (p = 0.02) and survival (HR = 1.73) and rs5848 GRN with a significantly shorter survival in CC homozygous patients (HR = 1.98). The frequency of APOƐ4 carriers was significantly increased in the C9orf72 noncarriers (p = 0.022). Although validation of our findings is necessary, our results suggest that TP53, GRN, and APOE genes may act as phenotype modifiers in FTD and should be considered in future clinical trials.

Erratum: Pagonabarraga, J.; et al. A Spanish Consensus on the Use of Safinamide for Parkinson's Disease in Clinical Practice. Brain Sci. 2020, 10, 176.

We would like to submit the following erratum to our recently published paper [...].

Un Servicio de Neurología de un hospital terciario en la pandemia COVID-19 / A neurology department at a tertiary-level hospital during the COVID-19 pandemic

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Pretarsal blepharospasm: Clinical and electromyographic characteristics.

OBJECTIVE: To describe the clinical and electromyographic characteristics of blepharospasm caused by selective involvement of the pars pretarsalis of the orbicularis oculi muscle. METHODS: Clinical assessment and simultaneous electromyographic recordings from levator palpebrae superioris and pars orbitaria and pretarsalis of orbicularis oculi muscles were performed in patients with blepharospasm and primary failure to botulinum toxin injections. Patients with selective abnormal electromyographic activity of the pars pretarsalis of the orbicularis oculi muscle were identified and treated with selective pretarsal injections of botulinum toxin. RESULTS: We found 24 patients with pretarsal blepharospasm confirmed by the electromyographic assessment. All of them were functionally blind. Three clinical-electromyographic patterns were identified: (a) Impairment of eyelid opening; (b) Increased blinking; (c) Spasms of eye closure combined with varying degrees of excessive blinking and impairment of eye-opening. Pretarsal injections of botulinum toxin induced a significant improvement in all patients and 50 % regained normal or near-normal vision. The clinical improvement was sustained after repeated pretarsal injections. CONCLUSIONS: Pretarsal blepharospasm can be suspected on clinical grounds and it can be confirmed by electromyographic recordings. SIGNIFICANCE: Recognition of this type of blepharospasm is important because of its excellent response to botulinum toxin injections applied into the pretarsal part of the orbicularis oculi muscle.

A Spanish Consensus on the Use of Safinamide for Parkinson's Disease in Clinical Practice.

Safinamide is an approved drug for the treatment of fluctuations in Parkinson's disease (PD). Scarce data are available on its use in clinical practice. A group of Spanish movement disorders specialists was convened to review the use of safinamide across different clinical scenarios that may guide neurologists in clinical practice. Eight specialists with recognized expertise in PD management elaborated the statements based on available evidence in the literature and on their clinical experience. The RAND/UCLA method was carried, with final conclusions accepted after a 2-round modified Delphi process. Higher level of agreement between panellists was reached for the following statements. Safinamide significantly improves mean daily ON time without troublesome dyskinesias [corrected]. Adjunctive treatment with safinamide is associated with motor improvements in patients with mid-to-late PD. The efficacy of safinamide on motor fluctuations is maintained at long-term, with no increase over time in dyskinesias severity. The clinical benefits of safinamide on pain and depression remain unclear. Safinamide presents a similar incidence of adverse events compared with placebo. The efficacy and safety of safinamide shown in the pivotal clinical trials are reproduced in clinical practice, with improvement of parkinsonian symptoms, decrease of daily OFF time, control of dyskinesias at the long term, and good tolerability and safety.

Role for ATXN1, ATXN2, and HTT intermediate repeats in frontotemporal dementia and Alzheimer's disease.

We analyzed the frequency of intermediate alleles (IAs) in the ATXN1, ATXN2, and HTT genes in several neurodegenerative diseases. The study included 1126 patients with Alzheimer's disease (AD), 440 patients with frontotemporal dementia (FTD), and 610 patients with Parkinson's disease. In all cohorts, we genotyped ATXN1 and ATXN2 CAG repeats. In addition, in the FTD cohort, we determined the number of HTT CAG repeats. The frequency of HTT IAs was higher in patients with FTD (6.9%) versus controls (2.9%) and in the C9orf72 expansion noncarriers (7.2%) versus controls (2.9%), although the difference was nonsignificant after correction for multiple testing. Compared with controls, progressive nonfluent aphasia (PNFA) groups showed a significantly higher frequency of HTT IAs (13.6% vs. 2.9% controls). For the ATXN2 gene, we observed an increase in IA frequency in AD cases (AD 4.1% vs. controls 1.8%) and in the behavioral FTD group (4.8% vs. 1.8%). For the ATXN1 gene, we found a significant increase of IAs in patients with PNFA (18.6%) versus controls (6.7%). In conclusion, our work suggests that the HTT and ATXN1 IAS may contribute to PNFA pathogenesis and point to a link between ATXN2 IAS and AD.