Long term follow-up study of non-invasive brain stimulation (NBS) (rTMS and tDCS) in Parkinson’s disease (PD). Strong age-dependency in the effect of NBS

The Effects of Non-Invasive Brain Stimulation on Quantitative EEG in Patients With Parkinson's Disease: A Systematic Scoping Review

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by motor and non-motor symptoms, aside from alterations in the electroencephalogram (EEG) already registered. Non-invasive brain stimulation (NIBS) techniques have been suggested as an alternative rehabilitative therapy, but the neurophysiological changes associated with these techniques are still unclear. We aimed to identify the nature and extent of research evidence on the effects of NIBS techniques in the cortical activity measured by EEG in patients with PD. A systematic scoping review was configured by gathering evidence on the following bases: PubMed (MEDLINE), PsycINFO, ScienceDirect, Web of Science, and cumulative index to nursing & allied health (CINAHL). We included clinical trials with patients with PD treated with NIBS and evaluated by EEG pre-intervention and post-intervention. We used the criteria of Downs and Black to evaluate the quality of the studies. Repetitive transcranial magnetic stimulation (TMS), transcranial electrical stimulation (tES), electrical vestibular stimulation, and binaural beats (BBs) are non-invasive stimulation techniques used to treat cognitive and motor impairment in PD. This systematic scoping review found that the current evidence suggests that NIBS could change quantitative EEG in patients with PD. However, considering that the quality of the studies varied from poor to excellent, the low number of studies, variability in NIBS intervention, and quantitative EEG measures, we are not yet able to use the EEG outcomes to predict the cognitive and motor treatment response after brain stimulation. Based on our findings, we recommend additional research efforts to validate EEG as a biomarker in non-invasive brain stimulation trials in PD.

Cerebellar tDCS as Therapy for Cerebellar Ataxias

In recent years, a growing body of literature has investigated the use of non-invasive brain stimulation (NIBS) techniques to influence cerebellar activity and the effects of cerebellar stimulation on other brain regions through its multiple complex projections. From the early 1990s, with the discovery of the so-called cerebellar inhibition (CBI), several studies have focused their attention on the use of cerebellar NIBS as treatment for different motor disorders. Cerebellar ataxias (CAs) represent the prototypical clinical manifestation of cerebellar alterations, but other movement disorders, such as Parkinson's disease, essential tremor, and dystonia have also been associated with alterations of networks which include the cerebellum, or of the cerebellum itself. Cerebellar transcranial direct current stimulation (ctDCS) could indeed represent an economical, non-invasive therapeutic tool with minimal side effects, thus improving the clinical management of patients and their quality of life. Studies show that ctDCS is effective as a therapeutic option for motor symptoms in patients with CAs, and especially in those with less severe forms, suggesting that ctDCS efficacy could result from augmented neuronal compensation, which itself relies on preserved cerebellar volume. Evidence for the efficacy of ctDCS is less conclusive for the other aforementioned motor disorders, although preliminary results are promising. Future studies should adopt more rigorous methods (e.g., larger sample sizes, double blinding, better characterization of the sample, reliable biomarkers), in order to allow the scientific community to derive higher-quality evidence on the efficacy of ctDCS as a therapeutic option for motor disorders.

Consensus Paper: Novel Directions and Next Steps of Non-invasive Brain Stimulation of the Cerebellum in Health and Disease

The cerebellum is involved in multiple closed-loops circuitry which connect the cerebellar modules with the motor cortex, prefrontal, temporal, and parietal cortical areas, and contribute to motor control, cognitive processes, emotional processing, and behavior. Among them, the cerebello-thalamo-cortical pathway represents the anatomical substratum of cerebellum-motor cortex inhibition (CBI). However, the cerebellum is also connected with basal ganglia by disynaptic pathways, and cerebellar involvement in disorders commonly associated with basal ganglia dysfunction (e.g., Parkinson's disease and dystonia) has been suggested. Lately, cerebellar activity has been targeted by non-invasive brain stimulation (NIBS) techniques including transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) to indirectly affect and tune dysfunctional circuitry in the brain. Although the results are promising, several questions remain still unsolved. Here, a panel of experts from different specialties (neurophysiology, neurology, neurosurgery, neuropsychology) reviews the current results on cerebellar NIBS with the aim to derive the future steps and directions needed. We discuss the effects of TMS in the field of cerebellar neurophysiology, the potentials of cerebellar tDCS, the role of animal models in cerebellar NIBS applications, and the possible application of cerebellar NIBS in motor learning, stroke recovery, speech and language functions, neuropsychiatric and movement disorders.

Multisite non-invasive brain stimulation in Parkinson's disease: A scoping review

BACKGROUND:

Parkinson’s disease (PD) is a progressive neurodegenerative disorder, characterized by cardinal motor symptoms in addition to cognitive impairment. New insights concerning multisite non-invasive brain stimulation effects have been gained, which can now be used to develop innovative treatment approaches.

OBJECTIVE:

Map the researchs involving multisite non-invasive brain stimulation in PD, synthesize the available evidence and discuss future directions.

METHODS:

The databases PubMed, PsycINFO, CINAHL, LILACS and The Cochrane Library were searched from inception until April 2020, without restrictions on the date of publication or the language in which it was published. The reviewers worked in pairs and sequentially evaluated the titles, abstracts and then the full text of all publications identified as potentially relevant.

RESULTS:

Twelve articles met the inclusion criteria. The target brain regions included mainly the combination of a motor and a frontal area, such as stimulation of the primary motor córtex associated with the dorsolateral prefrontal cortex. Most of the trials showed that this modality was only more effective for the motor component, or for the cognitive and/or non-motor, separately.

CONCLUSIONS:

Despite the results being encouraging for the use of the multisite aproach, the indication for PD management should be carried out with caution and deserves scientific deepening.

Motor Cortex Stimulation Reversed Hypernociception, Increased Serotonin in Raphe Neurons, and Caused Inhibition of Spinal Astrocytes in a Parkinson's Disease Rat Model

Persistent pain is a prevalent symptom of Parkinson’s disease (PD), which is related to the loss of monoamines and neuroinflammation. Motor cortex stimulation (MCS) inhibits persistent pain by activating the descending analgesic pathways; however, its effectiveness in the control of PD-induced pain remains unclear. Here, we evaluated the analgesic efficacy of MCS together with serotonergic and spinal glial modulation in an experimental PD (ePD) rat model. Wistar rats with unilateral striatal 6-OHDA and MCS were assessed for behavioral immobility and nociceptive responses. The immunoreactivity of dopamine in the substantia nigra and serotonin in the nucleus raphe magnus (NRM) and the neuronal, astrocytic, and microglial activation in the dorsal horn of the spinal cord were evaluated. MCS, without interfering with dopamine loss, reversed ePD-induced immobility and hypernociception. This response was accompanied by an exacerbated increase in serotonin in the NRM and a decrease in neuronal and astrocytic hyperactivation in the spinal cord, without inhibiting ePD-induced microglial hypertrophy and hyperplasia. Taken together, MCS induces analgesia in the ePD model, while restores the descending serotonergic pathway with consequent inhibition of spinal neurons and astrocytes, showing the role of MCS in PD-induced pain control.

Non-invasive brain stimulation for Parkinson's disease: Clinical evidence, latest concepts and future goals: A systematic review

Parkinson's disease (PD) is becoming a major public-health issue in an aging population. Available approaches to treat advanced PD still have limitations; new therapies are needed. The non-invasive brain stimulation (NIBS) may offer a complementary approach to treat advanced PD by personalized stimulation. Although NIBS is not as effective as the gold-standard levodopa, recent randomized controlled trials show promising outcomes in the treatment of PD symptoms. Nevertheless, only a few NIBS-stimulation paradigms have shown to improve PD's symptoms. Current clinical recommendations based on the level of evidence are reported in Table 1 through Table 3. Furthermore, novel technological advances hold promise and may soon enable the non-invasive stimulation of deeper brain structures for longer periods.

The effects of spaced transcranial Direct Current Stimulation combined with conventional dysphagia therapy in Parkinson's disease: A case report

Parkinson's disease (PD) is a neurodegenerative disease of the central nervous system that is characterized by a set of motor and non-motor symptoms. Impaired swallowing or dysphagia is one relatively common motor symptom in patients with PD. We investigated whether neuroplasticity induction by spaced transcranial Direct Current Stimulation (tDCS) combined with conventional swallowing therapy leads to long-lasting effects on swallowing ability in patients with PD. We present a case of a 61-year-old male PD patient with dysphagia. Conventional Swallowing Therapy (CDT) combined with tDCS (bilateral anodal, 1 mA, 20 min, 10 online sessions, twice daily with a 20 min interval in between for five days over two weeks) was applied over the pharyngeal motor cortex. Our findings suggest that anodal tDCS combined with CDT is feasible, safe, and well-tolerated, and leads to a clinically relevant improvement of swallowing functions.

The effect of repetitive transcranial magnetic stimulation for insomnia: a systematic review and meta-analysis

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) might be a promising technique in treating insomnia. A comprehensive meta-analysis of the available literature is conducted to offer evidence.

OBJECTIVE

To evaluate the efficacy and safety of rTMS for insomnia, either as monotherapy or as a complementary strategy.

METHODS

CENTRAL, PubMed, EMBASE, PsycINFO, CINAHL, PEDro, CBM, CNKI, WANFANG, and VIP were searched from earliest record to August 2019. Randomized control trials (RCTs) published in English and Chinese examining effects of rTMS on patients with insomnia were included. Two authors independently completed the article selection, data extraction and rating. Physiotherapy Evidence Database (PEDro) scale was used to assess the methodological quality of the included studies. The RevMan software was used for meta-analysis. The quality of the evidence was assessed by Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

RESULTS

A total of 36 trials from 28 eligible studies were included, involving a total of 2357 adult participants (mean age, 48.80 years; 45.33% males). Compared with sham rTMS, rTMS was associated with improved PSQI total score (SMD -2.31, 95% CI -2.95 to -1.66; Z = 7.01, P < 0.00001) and scores of seven subscales. Compared to other treatment, rTMS as an adjunct to other treatment was associated with improved PSQI total score (SMD -1.44, 95% CI -2.00 to -0.88; Z = 5.01, P < 0.00001), and may have effects on scores of seven subscales. Compared with other treatment, rTMS was associated with improved Pittsburgh sleep quality index (PSQI) total score (SMD -0.63, 95% CI -1.22 to -0.04; Z = 2.08, P = 0.04), and may have a better score in sleep latency, sleep disturbance and hypnotic using of seven subscales. In the three pair of comparisons, the results for polysomnography (PSG) outcomes were varied. In general, rTMS may improve sleep quality through increasing slow wave and rapid eye movement (REM) sleep. The rTMS group was more prone to headache than the sham or blank control group (RR 1.71, 95% CI 1.03 to 2.85; Z = 2.07, P = 0.04). No severe adverse events were reported. Reporting biases and low and very low grade of some evidences should be considered when interpreting the results of this meta-analysis.

CONCLUSIONS

Our findings indicate that rTMS may be a safe and effective option for insomnia. Further international, multicenter, high-quality RCTs with more objective, quality of life related and follow-up assessments are needed.

Destroyed non-dopaminergic pathways in the early stage of Parkinson's disease assessed by posturography

BACKGROUND

The early stage of Parkinson's disease (PD) (Hoehn-Yahr (HY) I-II stages) is characterized by a negative pull test, which clinically excludes postural instability. Previous studies with dynamic posturography detected balance disturbances even at the onset of the disease but the age dependency or prediction of dyskinesia with dynamic posturography are not known.

OBJECTIVE/HYPOTHESIS

We hypothesized that the postural instability evoked by dynamic posturography was part of the early stage of PD. Furthermore, we studied how we can provoke dyskinesia.

METHODS

Postural instability with static and dynamic posturography (passing balls with different weights around the body) was studied in 45 patients with PD in their HY I, II stages. They were compared with 35 age-matched healthy controls. Eighteen patients with dyskinesia were involved in the study. Fourteen patients were followed for two years.

RESULTS

The pathway and velocity of the movement assessed by static and the dynamic posturography were significantly higher in the group >65 years than that of age-matched healthy controls, while the group ≤65 years showed a significant increment only in the antero-posterior sway during dynamic posturography. The imbalance of patients with dyskinesia was significantly (p < 0.05) provoked by dynamic posturography compared to patients with PD without dyskinesia. The results were independent of age.

CONCLUSION

Postural instability is part of the early symptoms of PD. Non-dopaminergic pathways may be involved in the early stage of PD.

Oscillations in cortico-basal ganglia circuits: implications for Parkinson’s disease and other neurologic and psychiatric conditions

Cortico-basal ganglia circuits are thought to play a crucial role in the selection and control of motor behaviors and have also been implicated in the processing of motivational content and in higher cognitive functions. During the last two decades, electrophysiological recordings in basal ganglia circuits have shown that several disease conditions are associated with specific changes in the temporal patterns of neuronal activity. In particular, synchronized oscillations have been a frequent finding suggesting that excessive synchronization of neuronal activity may be a pathophysiological mechanism involved in a wide range of neurologic and psychiatric conditions. We here review the experimental support for this hypothesis primarily in relation to Parkinson’s disease but also in relation to dystonia, essential tremor, epilepsy, and psychosis/schizophrenia.

High frequency repetitive transcranial magnetic stimulation improves neuronal activity without affecting astrocytes and microglia density

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive neuromodulation technique capable of producing changes in the electrical potential of neurons. Currently, the application of rTMS in clinical practice and as a neurophysiological tool is increasing. However, the exact cellular mechanisms underlying rTMS-based therapies are not completely clear. Additionally, glial cells have been studied less. Our aim was to investigate the effect of three days of high-frequency rTMS on neuronal metabolism and neuronal activation, in addition to its effect on glial cells. For this purpose, we performed histochemistry and immunohistochemistry procedures: the histochemistry of cytochrome oxidase (COx) to assess neuronal metabolic activity, and the immunohistochemistry of c-Fos (marker of neuronal activity), GFAP (marker of astrocytic reactivity), and Iba1 (selective marker of reactive microglia). Our results showed enhanced metabolic activity after rTMS in the retrosplenial and parietal cortex and CA1 and CA3 subfields of the hippocampus. Moreover, higher c-Fos activity was found in the agranular retrosplenial cortex. Finally, we did not find changes between groups in the induction of astrocyte and microglia reactivity in any of the immunostained regions. In conclusion, we can assume that three days of high-frequency rTMS applied in healthy rats does not alter astroglia reactivity or inflammatory responses, such as microglia proliferation. Because we have shown an upregulation of neuronal metabolic activity in many limbic brain structures, in addition to higher c-Fos levels in the nearest cortical area to the rTMS, our work provides novel insight into the effectiveness and safety of rTMS as a brain modulation therapy.

Transcranial direct current stimulation enhances theory of mind in Parkinson's disease patients with mild cognitive impairment: a randomized, double-blind, sham-controlled study

Background

Parkinson’s Disease (PD) with mild cognitive impairment (MCI) (PD-MCI) represents one of the most dreaded complications for patients with PD and is associated with a higher risk of developing dementia. Although transcranial direct current stimulation (tDCS) has been demonstrated to improve motor and non-motor symptoms in PD, to date, no study has investigated the effects of tDCS on Theory of Mind (ToM), i.e., the ability to understand and predict other people’s behaviours, in PD-MCI.

Methods

In this randomized, double-blind, sham-controlled study, we applied active tDCS over the medial frontal cortex (MFC) to modulate ToM performance in twenty patients with PD-MCI. Twenty matched healthy controls (HC) were also enrolled and were asked to perform the ToM task without receiving tDCS.

Results

In the patients with PD-MCI, i) ToM performance was worse than that in the HC, ii) ToM abilities were poorer in those with fronto-executive difficulties, and iii) tDCS over the MFC led to significant shortening of latency for ToM tasks.

Conclusions

We show for the first time that active tDCS over the MFC enhances ToM in patients with PD-MCI, and suggest that non-invasive brain stimulation could be used to ameliorate ToM deficits observed in these patients.