Control of post-stroke movement disorders using chronic motor cortex stimulation

Movement Disorders Following Cerebrovascular Lesions: Etiology, Treatment Options and Prognosis

Post-stroke movement disorders are uncommon, but comprise an important part of secondary movement disorders. These exert variable and heterogeneous clinical courses according to the stroke lesion and its temporal relationships. Moreover, the predominant stroke symptoms hinder a proper diagnosis in clinical practice. This article describes the etiology, treatment options and prognosis of post-stroke movement disorders.

Use of cortical stimulation in neuropathic pain, tinnitus, depression, and movement disorders

Medical treatment must strike a balance between benefit and risk. As the field of neuromodulation develops, decreased invasiveness, in combination with maintenance of efficacy, has become a goal. We provide a review of the history of cortical stimulation from its origins to the current state. The first part discusses neuropathic pain and the nonpharmacological treatment options used. The second part covers transitions to tinnitus, believed by many to be another deafferentation disorder, its classification, and treatment. The third part focuses on major depression. The fourth section concludes with the discussion of the use of cortical stimulation in movement disorders. Each part discusses the development of the field, describes the current care protocols, and suggests future avenues for research needed to advance neuromodulation.

Motor cortex stimulation in Parkinson's disease

Motor Cortex Stimulation (MCS) is less efficacious than Deep Brain Stimulation (DBS) in Parkinson's disease. However, it might be proposed to patients excluded from DBS or unresponsive to DBS. Ten patients with advanced PD underwent unilateral MCS contralaterally to the worst clinical side. A plate electrode was positioned over the motor cortex in the epidural space through single burr hole after identification of the area with neuronavigation and neurophysiological tests. Clinical assessment was performed by total UPDRS, UPDRS III total, UPDRS III-items 27–31, UPDRS IV, and UPDRS II before implantation in off-medication and on-medication states and after surgery at 1, 3, 6, 12, 18, 24, and 36 months in on-medication/on-stimulation and off-medication/on-stimulation states. We assessed changes of quality of life, throughout the Parkinson's disease quality of life scale (PDQoL-39), and the dose of anti-Parkinson's disease medications, throughout the Ldopa equivalent daily dose (LEDD). During off-medication state, we observed moderate and transitory reduction of total UPDRS and UPDRS total scores and significant and long-lasting improvement in UPDRS III items 27–31 score for axial symptoms. There was marked reduction of UPDRS IV score and LEDD. PDQL-39 improvement was also significant. No important complications and adverse events occurred.

Improved dexterity after chronic electrical stimulation of the motor cortex for central pain: a special relevance for thalamic syndrome

OBJECTIVES

To demonstrate that motor cortex stimulation (MCS) could improve motor function in patients with neuropathic pain.

METHODS

In this prospective clinical study of 38 patients referred for MCS as treatment for their neuropathic pain, we collected any declaration of improvement in motor performance that could be attributed to MCS.

RESULTS

Ten patients (26%) declared a benefit in their motor function. Eight presented objective evidence of recovered dexterity for rapid alternating movements. A minor proportion had improvement in dystonic posture (n = 2), but none had detectable increased motor strength or tonus changes. Overall, 73% of the patients with limb ataxia declared a benefit after MCS. In 6 out of 10 patients (60%), the anatomic lesion responsible for pain was restricted to the lateral aspect of the thalamus. All of them had either clinical or electrophysiological evidence of lemniscal dysfunction (proprioceptive ataxia). No correlation was found between the scores of pain relief and the modification of motor status. The correlation between thalamic lesions and benefits in motor performance was significant (Fisher's exact test, two-tailed, p = 0.0017).

CONCLUSIONS

Up to 26% of patients estimated that MCS improved their motor outcome through recovered dexterity and in cases of lateral thalamic lesions.

Motor cortex stimulation for pain and movement disorders

Since initial reports in the early 1990s, stimulation of the M1 region of the cortex (MCS) has been used to treat chronic refractory pain conditions and a variety of movement disorders. A Medline search of literature between 1991 and 2007 revealed 512 cases using MCS. Although most of these relate to the treatment of pain (422), 84 of them involve movement disorders. More recently, several studies have specifically looked at treating Parkinson's disease (PD) with MCS. We report here several of our own cases using MCS to treat poststroke and non-poststroke pain syndromes and movement disorders (n = 8), PD (n = 4), ET (n = 2), and cortico-basal degeneration (n = 1). We also cover the essential history of this procedure and our current research using computational modeling to understand further the underlying mechanisms of MCS.

Repetitive transcranial magnetic stimulation (rTMS): insights into the treatment of Parkinson’s disease by cortical stimulation

Repetitive transcranial magnetic stimulation (rTMS) is a potent tool that can be used to modify activity of targeted cortical areas. Significant clinical effects have been obtained in patients with Parkinson's disease (PD) by stimulating different cortical regions with rTMS at inhibitory (low) or excitatory (high) frequency. These effects were thought to result from plastic changes in motor cortical networks. Actually cortical dysfunction has been documented in PD by neuroimaging and neurophysiologic studies showing either hypo- or hyper-activation of various brain areas. In addition, cortical excitability studies using transcranial magnetic stimulation disclosed significant alterations in intracortical facilitatory or inhibitory processes according to the resting state or to phases of movement preparation or execution. These observations clearly support the therapeutic potential of cortical neuromodulation in PD. Motor cortex stimulation could impact on any station within the cortico-basal ganglia-thalamo-cortical loops that are involved in motor control, providing alleviation of parkinsonian symptoms. Depending on the target, cortical stimulation might improve motor performance or other symptoms associated with PD, like depression. Clinical application of rTMS to treat PD patients is limited by the short duration of the effects beyond the time of stimulation, even if long-lasting improvements have been observed after repeated rTMS sessions. In any case, the place of cortical stimulation in the therapeutic management of PD patients remains to be determined, as an alternative or a complementary technique to deep brain stimulation. The rTMS technique could be used to better define the targets and the parameters of stimulation subsequently applied in chronic epidural stimulation.

Stimulation du cortex moteur, Parkinson et dystonie : que nous enseigne la stimulation magnétique transcrânienne? revue de la littérature

INTRODUCTION

Over the last few years, deep brain stimulation techniques, with targets such as the subthalamic nucleus or the pallidum, have bee found to be beneficial in the treatment of Parkinson's disease and dystonia. Conversely, therapeutic strategies of cortical stimulation have not yet been validated in these diseases, although they are known to be associated with various cortical dysfunctions. Transcranial magnetic stimulation (TMS) is a valuable tool for non-invasive study of the role played by the motor cortex in the pathophysiology of movement disorders, in particular by assessing various cortical excitability determinants using single or paired pulse paradigms. In addition, repetitive TMS (rTMS) trains can be used to study the effects of transient activity changes of a targeted cortical area.

BACKGROUND

Studies with TMS revealed significant motor cortex excitability changes, particularly regarding intracortical inhibitory pathways, both in Parkinson's disease and in dystonia, and these changes can be distinguished owing to the resting state or to the phases of movement preparation or execution. However, more specific correlation between electrophysiological features and clinical symptoms remains to be established. In addition, the stimulation of various cortical targets by rTMS protocols applied at low or high frequencies have induced some clear clinical effects.

PERSPECTIVES

The TMS effects are and will remain applied in movement disorders to better understand the role played by the motor cortex, to assess various types of treatment and appraise the therapeutic potential of cortical stimulation.

CONCLUSION

TMS provides evidence for motor cortex dysfunction in Parkinson's disease or dystonia. Moreover, rTMS results have opened new perspectives for therapeutic strategies of implanted cortical stimulation. By these both aspects, TMS techniques show their usefulness in the assessment of movement disorders.