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Chapter 40 - Noninvasive brain stimulation in neurorehabilitation
Handbook of Clinical Neurology
Introduction
Stroke is the major cause of long-term disability worldwide (Kolominsky-Rabas et al., 2001) and recovery of motor function is often incomplete (Roger et al., 2011). Six months after the ictal event, two-thirds of stroke survivors are unable to carry out independently activities of daily living with their paretic hand to the extent they could before (Kolominsky-Rabas et al., 2001), and only a few are able to return to their previous job (Lai et al., 2002).
Patients with motor deficits resulting from stroke must confront the need to generate compensatory strategies or to relearn the motor programs utilized to accomplish a particular goal before the lesion (Frey et al., 2011, Pomeroy et al., 2011, Sathian et al., 2011). From a behavioral point of view, there are different ways to accomplish the same goal in neurorehabilitation (e.g., grasp a glass of water). One possibility is to implement a motor strategy different from that utilized before the stroke (i.e., compensation) (Levin et al., 2009). An alternative way is to relearn to perform the task in the same way it was done before the lesion. Clearly, both processes are likely to involve fundamentally different pathophysiological mechanisms, even when the goals and outcomes are the same. Different motor training strategies have been tested in neurorehabilitation of motor function. Examples include constraint-induced movement therapy, bilateral arm training, mirror therapy, randomized training schedules, robotic-based approaches, virtual reality, electromyogram-triggered stimulation, action observation, motor imagery, and brain–computer interfaces between others (Cauraugh and Kim, 2003, Wittenberg et al., 2003, Bolton et al., 2004, Deutsch et al., 2004, Luft et al., 2004, Krakauer, 2006, Sharma et al., 2006, Birbaumer and Cohen, 2007, Ertelt et al., 2007, Page et al., 2007, Buch et al., 2008, Buch et al., 2012, Celnik et al., 2008, Cramer, 2008b, Cheeran et al., 2009a, Lo et al., 2009, Dimyan and Cohen, 2011). Noninvasive somatosensory (Conforto et al., 2007, Conforto et al., 2010), transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) (Hallett, 2000, Kaelin-Lang et al., 2002, Nitsche et al., 2008, Wassermann et al., 2008, Sandrini et al., 2011, Tanaka et al., 2011, Brunoni et al., 2012) have been proposed as adjuvant ways to improve the beneficial effects of training protocols on functional recovery.
In this chapter, we discuss the use of noninvasive brain stimulation (NIBS) in the setting of stroke rehabilitation. Interest in NIBS developed after the observation of long-term effects on cortical excitability that occur after repeated stimulation (Huang et al., 2005, Fitzgerald et al., 2006, Nitsche et al., 2008). Depending on the stimulation parameters, motor cortical excitability can be reduced (inhibition) by means of low-frequency repetitive TMS (rTMS), continuous theta-burst stimulation (cTBS), and cathodal tDCS, or enhanced (facilitation) by means of high-frequency rTMS, intermittent theta-burst stimulation (iTBS), and anodal stimulation. There is evidence that links the effects of these NIBS techniques to long-term potentiation (LTP)-like and long-term depression (LTD)-like mechanisms (Cooke and Bliss, 2006, Thickbroom, 2007, Wagner et al., 2007, Ziemann et al., 2008, Fritsch et al., 2010). After stroke, NIBS has been studied as a tool to modulate cortical excitability in the affected and intact hemispheres, predominantly with the goal of correcting hypothesized imbalances in interhemispheric interactions (Kinsbourne, 1974, Hummel and Cohen, 2006).
Section snippets
Poststroke reorganization
The magnitude and type of motor impairments that follow stroke are influenced by multiple factors such as lesion site, size, and time after stroke (Rossini et al., 2003, Ward and Cohen, 2004, Frey et al., 2011, Pomeroy et al., 2011, Sathian et al., 2011).
Recovery of motor function after the first few days poststroke is likely related to the resolution of edema as well as to reperfusion of the ischemic penumbra through collateral circulation (Furlan et al., 1996). At later stages after stroke,
Physiological mechanisms of reorganization
It is possible to study physiological features of cortical organization after stroke using TMS. Paired-pulse TMS delivered through the same magnetic coil over M1, where a suprathreshold test stimulus (TS) is preceded by a subthreshold or suprathreshold conditioning stimulus (CS), can be used to gain insight into the relative contribution of local inhibitory and excitatory inputs to M1 pyramidal tract cells (Reis et al., 2008). Interstimulus intervals of approximately 1–5 ms cause attenuation of
Noninvasive brain stimulation in neurorehabilitation
Based on the hypothesis of abnormal interhemispheric inhibitory interactions after stroke, two strategies have been proposed to ameliorate paretic hand function: (1) to downregulate excitability of contralesional M1, and (2) to upregulate excitability of ipsilesional M1 (Hummel and Cohen, 2006, Webster et al., 2006) (Fig. 40.1). Depending on the stimulus type and stimulation parameters, NIBS can facilitate cortical excitability in the ipsilesional M1 through direct stimulation of this region or
Conclusion
In summary, there is an increasing body of literature on possible beneficial effects of modulation of cortical excitability in the ipsilesional or contralesional M1s, or a combination of both on motor function. These effects have so far been stronger when NIBS is applied in close relationship with motor training (Takeuchi et al., 2008, Takeuchi et al., 2009, Chang et al., 2010, Koganemaru et al., 2010, Lindenberg et al., 2010b, Lindenberg et al., 2012b, Bolognini et al., 2011, Avenanti et al.,
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