Therapeutic Use of Non-invasive Brain Stimulation in Dystonia

Applications of Transcranial Magnetic Stimulation for Understanding and Treating Dystonia

Transcranial magnetic stimulation (TMS)-based studies have led to an advanced understanding of the pathophysiology of dystonia. This narrative review summarizes the TMS data contributed to the literature so far. Many studies have shown that increased motor cortex excitability, excessive sensorimotor plasticity, and abnormal sensorimotor integration are the core pathophysiological substrates for dystonia. However, an increasing body of evidence supports a more widespread network dysfunction involving many other brain regions. Repetitive TMS pulses (rTMS) in dystonia have therapeutic potential as they can induce local and network-wide effects through modulation of excitability and plasticity. The bulk of rTMS studies has targeted the premotor cortex with some promising results in focal hand dystonia. Some studies have targeted the cerebellum for cervical dystonia and the anterior cingulate cortex for blepharospasm. We believe that therapeutic potential could be leveraged better when rTMS is implemented in conjunction with standard-of-care pharmacological treatments. However, due to several limitations in the studies conducted to date, including small samples, heterogeneous populations, variability in the target sites, and inconsistencies in the study design and control arm, it is hard to draw a definite conclusion. Further studies are warranted to determine optimal targets and protocols yielding the most beneficial outcomes that will translate into meaningful clinical changes.

Transcranial Magnetic Stimulation in the Treatment of Neurological Diseases

Transcranial Magnetic Stimulation (TMS) has widespread use in research and clinical application. For psychiatric applications, such as depression or OCD, repetitive TMS protocols (rTMS) are an established and globally applied treatment option. While promising, rTMS is not yet as common in treating neurological diseases, except for neurorehabilitation after (motor) stroke and neuropathic pain treatment. This may soon change. New clinical studies testing the potential of rTMS in various other neurological conditions appear at a rapid pace. This can prove challenging for both practitioners and clinical researchers. Although most of these neurological applications have not yet received the same level of scientific/empirical scrutiny as motor stroke and neuropathic pain, the results are encouraging, opening new doors for TMS in neurology. We here review the latest clinical evidence for rTMS in pioneering neurological applications including movement disorders, Alzheimer's disease/mild cognitive impairment, epilepsy, multiple sclerosis, and disorders of consciousness.

Rehabilitation in movement disorders: From basic mechanisms to clinical strategies

Movement disorders encompass a variety of conditions affecting the nervous system at multiple levels. The pathologic processes underlying movement disorders alter the normal neural functions and could lead to aberrant neuroplastic changes and to clinical phenomenology that is not expressed only through mere motor symptoms. Given this complexity, the responsiveness to pharmacologic and surgical therapies is often disappointing. Growing evidence supports the efficacy of neurorehabilitation for the treatment of movement disorders. Specific form of training involving both goal-based practice and aerobic training could drive and modulate neuroplasticity in order to restore the circuitries dysfunctions and to achieve behavioral gains. This chapter provides an overview of the alterations expressed in some movement disorders in terms of clinical signs and symptoms and plasticity, and suggests which ones and why tailored rehabilitation strategies should be adopted for the management of the different movement disorders.

Experimental Protocol to Test Explicit Motor Learning–Cerebellar Theta Burst Stimulation

Implicit and explicit motor learning processes work interactively in everyday life to promote the creation of highly automatized motor behaviors. The cerebellum is crucial for motor sequence learning and adaptation, as it contributes to the error correction and to sensorimotor integration of on-going actions. A non-invasive cerebellar stimulation has been demonstrated to modulate implicit motor learning and adaptation. The present study aimed to explore the potential role of cerebellar theta burst stimulation (TBS) in modulating explicit motor learning and adaptation, in healthy subjects. Cerebellar TBS will be applied immediately before the learning phase of a computerized task based on a modified Serial Reaction Time Task (SRTT) paradigm. Here, we present a study protocol aimed at evaluating the behavioral effects of continuous (cTBS), intermittent TBS (iTBS), or sham Theta Burst Stimulation (TBS) on four different conditions: learning, adaptation, delayed recall and re-adaptation of SRTT. We are confident to find modulation of SRTT performance induced by cerebellar TBS, in particular, processing acceleration and reduction of error in all the conditions induced by cerebellar iTBS, as already known for implicit processes. On the other hand, we expect that cerebellar cTBS could induce opposite effects. Results from this protocol are supposed to advance the knowledge about the role of non-invasive cerebellar modulation in neurorehabilitation, providing clinicians with useful data for further exploiting this technique in different clinical conditions.

The Ties That Bind: Aberrant Plasticity and Networks Dysfunction in Movement Disorders-Implications for Rehabilitation

Background: Movement disorders encompass various conditions affecting the nervous system. The pathological processes underlying movement disorders lead to aberrant synaptic plastic changes, which in turn alter the functioning of large-scale brain networks. Therefore, clinical phenomenology does not only entail motor symptoms but also cognitive and motivational disturbances. The result is the disruption of motor learning and motor behavior. Due to this complexity, the responsiveness to standard therapies could be disappointing. Specific forms of rehabilitation entailing goal-based practice, aerobic training, and the use of noninvasive brain stimulation techniques could "restore" neuroplasticity at motor-cognitive circuitries, leading to clinical gains. This is probably associated with modulations occurring at both molecular (synaptic) and circuitry levels (networks). Several gaps remain in our understanding of the relationships among plasticity and neural networks and how neurorehabilitation could promote clinical gains is still unclear. Purposes: In this review, we outline first the networks involved in motor learning and behavior and analyze which mechanisms link the pathological synaptic plastic changes with these networks' disruption in movement disorders. Therefore, we provide theoretical and practical bases to be applied for treatment in rehabilitation.

[Issues of diagnostic and therapeutic use of transcranial magnetic stimulation in patients with writing cramp]

OBJECTIVE

To study diagnostic and therapeutic values of transcranial magnetic stimulation (TMS) in writing cramp (WC).

MATERIAL AND METHODS

Twelve right-handed patients with WC were enrolled in the study. All patients underwent low-frequency repetitive TMS (rTMS) of the premotor cortex of contralateral to affected hand hemisphere. The clinical efficacy was assessed using the Writer's Cramp Rating Scale (WCRS) and the Medical Outcomes Study-Short Form (MOS-SF-36). Before and after last rTMS session, motor mapping of Abductor pollicis brevis muscle (APB) was performed using navigated TMS (nTMS). Localization, area, and amplitude-weighted area of the APB muscle cortical representations were compared with the healthy controls. After the rTMS course, the dynamics of the studied parameters was assessed.

RESULTS

Ten sessions of low-frequency rTMS of premotor cortex reduced the severity of WS clinical symptoms with a duration of effect of at least 1 month (p<0.05). There was no statistically significant difference between the area and the weighted area of cortical muscle representations between patients and healthy controls or in patients before and after rTMS. When assessing the localization of cortical muscle representations, two trends were noted: in 4 patients, the localization remained stable, with a shift in the center of gravity of less than 4 mm; in the other 8 patients, a shift in the center of mass of more than 5 mm was noted. No significant correlation between the stability of the cortical muscle representations (the magnitude of the shift in the center of gravity) and the improvement on the WCRS were found.

CONCLUSION

The low-frequency rTMS of the premotor cortex of the contralateral to affected hand hemisphere can be used as an adjuvant therapy for WC. The TMS-motor mapping study did not show its diagnostic value.

Altered sensory system activity and connectivity patterns in adductor spasmodic dysphonia

Adductor-type spasmodic dysphonia (ADSD) manifests in effortful speech temporarily relievable by botulinum neurotoxin type A (BoNT-A). Previously, abnormal structure, phonation-related and resting-state sensorimotor abnormalities as well as peripheral tactile thresholds in ADSD were described. This study aimed at assessing abnormal central tactile processing patterns, their spatial relation with dysfunctional resting-state connectivity, and their BoNT-A responsiveness. Functional MRI in 14/12 ADSD patients before/under BoNT-A effect and 15 controls was performed (i) during automatized tactile stimulus application to face/hand, and (ii) at rest. Between-group differential stimulation-induced activation and resting-state connectivity (regional homogeneity, connectivity strength within selected sensory(motor) networks), as well as within-patient BoNT-A effects on these differences were investigated. Contralateral-to-stimulation overactivity in ADSD before BoNT-A involved primary and secondary somatosensory representations, along with abnormalities in higher-order parietal, insular, temporal or premotor cortices. Dysphonic impairment in ADSD positively associated with left-hemispheric temporal activity. Connectivity was increased within right premotor (sensorimotor network), left primary auditory cortex (auditory network), and regionally reduced at the temporoparietal junction. Activation/connectivity before/after BoNT-A within-patients did not significantly differ. Abnormal ADSD central somatosensory processing supports its significance as common pathophysiologic focal dystonia trait. Abnormal temporal cortex tactile processing and resting-state connectivity might hint at abnormal cross-modal sensory interactions.

Non-invasive brain stimulation and kinesiotherapy for treatment of focal dystonia: Instrumental analysis of three cases

Dystonia is a disabling movement disorder characterized by co-contraction of antagonist and agonist muscles, leading to abnormal sustained postures and impaired motor control. Cervical Dystonia (CD) and Hand Focal Dystonia (HFD) have been the most common forms of focal dystonia (FD). Do Non-Invasive Brain Neuromodulation (NIBS) such as Transcranial Direct Current Stimulation (tDCS) and repetitive Transcranial Magnetic Stimulation (rTMS) modulate the excitability of the connections between the motor cortical areas and may represent a therapeutic alternative for focal dystonia? Herein, we reported three cases of focal dystonia, two of them with cervical dystonia (CD) and one with hand focal dystonia (HFD), treated with NIBS combined to kinesiotherapy. The patients were daily submitted to 15 sessions of NIBS combined simultaneously with kinesiotherapy. CD patients were treated with tDCS (2 mA, 20 min, over the primary motor cortex), and HFD patient with rTMS (1 Hz, 1200 pulses, 80% of resting motor threshold, over the premotor cortex). For the CD patient's assessment, the Modified Toronto Scale for Cervical Dystonia Assessment (MTS), quiet balance test, and visual postural assessment were applied to observe the therapeutic effects. Quality handwriting analysis, tremor acceleration amplitudes, and the Wrinter's Cramp Rating Scale (WCRS) were used to assess the NIBS effect on HFD symptoms. Patients were evaluated before (pretest), immediately after (posttest), and three months after treatment (retention). NIBS associated with kinesiotherapy produced a long-term improvement of dystonia symptoms in all three patients. rTMS and tDCS associated with kinesiotherapy showed to be useful and safe to relief the dystonia symptoms in individuals with different types of focal dystonia with distinct functional disorders. SIGNIFICANCE: The combined use of these intervention strategies seems to optimize and anticipate satisfactory clinical results in these neurological conditions, characterized by its difficult clinical management.

Medical and Surgical Treatments for Dystonia

The dystonias are a large and heterogenous group of disorders characterized by excessive muscle contractions leading to abnormal postures and/or repetitive movements. Their clinical manifestations vary widely, and there are many potential causes. Despite the heterogeneity, helpful treatments are available for the vast majority of patients. Symptom-based therapies include oral medications, botulinum toxins, and surgical interventions. For some subtypes of dystonia, specific mechanism-based treatments are available. Advances in understanding the biological basis for many types of dystonia have led to numerous recent clinical trials, so additional treatments are likely to become available in the very near future.

[Diagnostic and therapeutic issues of using transcranial magnetic stimulation in patients with writer's cramp]

AIM

To assess diagnostic and therapeutic values of transcranial magnetic stimulation (TMS) in patients with writer's cramp (WC).

MATERIAL AND METHODS

Twelve right-handed patients with WC were enrolled in the study. All patients underwent low-frequency repetitive TMS (rTMS) over the premotor cortex of the hemisphere contralateral to the affected hand. The clinical efficacy was assessed using the Writer's Cramp Rating Scale (WCRS) and the Medical Outcomes Study-Short Form (MOS-SF-36). Before and after the last rTMS session, motor mapping of abductor pollicis brevis muscle (APB) was performed using navigated TMS (nTMS). Localization, area, and amplitude-weighted area of the APB muscle cortical representations were compared with the healthy controls. The dynamics of the mentioned above parameters after the rTMS course was assessed.

RESULTS

Ten sessions of low-frequency rTMS over premotor cortex reduced the severity of WC clinical symptoms, with a duration of effect of at least 1 month (p<0.05). There was no significant difference between the area and the weighted area of cortical muscle representations between patients and healthy controls or in patients before and after rTMS. When assessing the localization of cortical muscle representations, two trends were noted: in 4 patients, the localization remained stable, with a shift in the center of gravity of less than 4 mm; in the other 8 patients, a shift in the center of gravity of more than 5 mm was noted. No significant correlations between the stability of the cortical muscle representations (the magnitude of the shift in the center of gravity) and the improvement on the WCRS scale were found.

CONCLUSION

The low-frequency rTMS over the premotor cortex of the hemisphere contralateral to the affected hand can be used as an adjuvant therapy for WC. The TMS-motor mapping study did not show its diagnostic value.

Lasting Effects of Low-Frequency Repetitive Transcranial Magnetic Stimulation in Writer's Cramp: A Case Report

The treatment of writer’s cramp (W’sC) is essentially based on the use of botulinum toxin. However, additional treatments are sometime required to prolong the effects of the toxin, compensate for its progressive loss of efficacy in some subjects, and re-educate handwriting (e.g., rehabilitation strategies). Low-frequency repetitive transcranial magnetic stimulation (rTMS) has been employed to improve W’sC, but with short-lasting and controversial outcomes. We report on the effects of a long-lasting low-frequency rTMS paradigm on W’sC symptoms. A 25-year-old male with a diagnosis of simple W’sC was enrolled in the study. He underwent an objective assessment using the Writer’s Cramp Rating Scale (WCRS) and the 1-min writing test. Further, we recorded muscle activation of the upper limb during handwriting using an EMG wireless system. The patient was provided with 1,200 biphasic magnetic pulses delivered at 1 Hz over the left premotor cortex (PMC), 15 times scheduled every 2 days, thus covering a period of 5 weeks, followed by 10 days of rest. This block of stimulations was practiced other four times, for a period of 6 months. The patient showed a gradual clinical improvement with the progression of the treatments. W’sC symptoms totally disappeared and all the clinical scores showed a significant improvement after rTMS completion. Such improvement lasted up to 1 year after the end of the treatment. Moreover, we detected a long-lasting improvement in sensorimotor plasticity as measured by a paired associative stimulation protocol. Our case suggests that the long-lasting application of 1 Hz rTMS to PMC is a safe and potentially valuable tool to improve W’sC symptoms enduringly, probably by reverting maladaptive plasticity mechanisms within the sensory-motor areas of the hemisphere contralateral to the dystonic hand.

Motor and Perceptual Recovery in Adult Patients with Mild Intellectual Disability

Introduction

The relationship between intellectual disability (ID) and hand motor coordination and speed-accuracy, as well as the effect of aging on fine motor performance in patients with ID, has been previously investigated. However, only a few data are available on the impact of the nonpharmacological interventions in adult patients with long-term hand motor deficit.

Methods

Fifty adults with mild ID were enrolled. A group of thirty patients underwent a two-month intensive ergotherapic treatment that included hand motor rehabilitation and visual-perceptual treatment (group A); twenty patients performing conventional motor rehabilitation alone (group B) served as a control group. Data on attention, perceptual abilities, hand dexterity, and functional independence were collected by a blind operator, both at entry and at the end of the study.

Results

After the interventions, group A showed significantly better performance than group B in all measures related to hand movement from both sides and to independence in activities of daily living.

Discussion

Multimodal integrated interventions targeting visual-perceptual abilities and motor skills are an effective neurorehabilitative approach in adult patients with mild ID. Motor learning and memory-mediated mechanisms of neural plasticity might underlie the observed recovery, suggesting the presence of plastic adaptive changes even in the adult brain with ID.

Motor and Perceptual Recovery in Adult Patients with Mild Intellectual Disability

INTRODUCTION

The relationship between intellectual disability (ID) and hand motor coordination and speed-accuracy, as well as the effect of aging on fine motor performance in patients with ID, has been previously investigated. However, only a few data are available on the impact of the nonpharmacological interventions in adult patients with long-term hand motor deficit.

METHODS

Fifty adults with mild ID were enrolled. A group of thirty patients underwent a two-month intensive ergotherapic treatment that included hand motor rehabilitation and visual-perceptual treatment (group A); twenty patients performing conventional motor rehabilitation alone (group B) served as a control group. Data on attention, perceptual abilities, hand dexterity, and functional independence were collected by a blind operator, both at entry and at the end of the study.

RESULTS

After the interventions, group A showed significantly better performance than group B in all measures related to hand movement from both sides and to independence in activities of daily living.

DISCUSSION

Multimodal integrated interventions targeting visual-perceptual abilities and motor skills are an effective neurorehabilitative approach in adult patients with mild ID. Motor learning and memory-mediated mechanisms of neural plasticity might underlie the observed recovery, suggesting the presence of plastic adaptive changes even in the adult brain with ID.

The Anatomical Basis for Dystonia: The Motor Network Model

Background

The dystonias include a clinically and etiologically very diverse group of disorders. There are both degenerative and non-degenerative subtypes resulting from genetic or acquired causes. Traditionally, all dystonias have been viewed as disorders of the basal ganglia. However, there has been increasing appreciation for involvement of other brain regions including the cerebellum, thalamus, midbrain, and cortex. Much of the early evidence for these other brain regions has come from studies of animals, but multiple recent studies have been done with humans, in an effort to confirm or refute involvement of these other regions. The purpose of this article is to review the new evidence from animals and humans regarding the motor network model, and to address the issues important to translational neuroscience.

Methods

The English literature was reviewed for articles relating to the neuroanatomical basis for various types of dystonia in both animals and humans.

Results

There is evidence from both animals and humans that multiple brain regions play an important role in various types of dystonia. The most direct evidence for specific brain regions comes from animal studies using pharmacological, lesion, or genetic methods. In these studies, experimental manipulations of specific brain regions provide direct evidence for involvement of the basal ganglia, cerebellum, thalamus and other regions. Additional evidence also comes from human studies using neuropathological, neuroimaging, non-invasive brain stimulation, and surgical interventions. In these studies, the evidence is less conclusive, because discriminating the regions that cause dystonia from those that reflect secondary responses to abnormal movements is more challenging.

Discussion

Overall, the evidence from both animals and humans suggests that different regions may play important roles in different subtypes of dystonia. The evidence so far provides strong support for the motor network model. There are obvious challenges, but also advantages, of attempting to translate knowledge gained from animals into a more complete understanding of human dystonia and novel therapeutic strategies.