Use of transcranial magnetic stimulation of the brain in stroke rehabilitation

Transcutaneous Vagus Nerve Stimulation Combined with Robotic Rehabilitation Improves Upper Limb Function after Stroke

The efficacy of standard rehabilitative therapy for improving upper limb functions after stroke is limited; thus, alternative strategies are needed. Vagus nerve stimulation (VNS) paired with rehabilitation is a promising approach, but the invasiveness of this technique limits its clinical application. Recently, a noninvasive method to stimulate vagus nerve has been developed. The aim of the present study was to explore whether noninvasive VNS combined with robotic rehabilitation can enhance upper limb functionality in chronic stroke. Safety and efficacy of this combination have been assessed within a proof-of-principle, double-blind, semirandomized, sham-controlled trial. Fourteen patients with either ischemic or haemorrhagic chronic stroke were randomized to robot-assisted therapy associated with real or sham VNS, delivered for 10 working days. Efficacy was evaluated by change in upper extremity Fugl–Meyer score. After intervention, there were no adverse events and Fugl–Meyer scores were significantly better in the real group compared to the sham group. Our pilot study confirms that VNS is feasible in stroke patients and can produce a slight clinical improvement in association to robotic rehabilitation. Compared to traditional stimulation, noninvasive VNS seems to be safer and more tolerable. Further studies are needed to confirm the efficacy of this innovative approach.

Transcranial Magnetic Stimulation with the Maximum Voluntary Muscle Contraction Facilitates Motor Neuron Excitability and Muscle Force

Three trials of transcranial magnetic stimulation (TMS) during the maximum voluntary muscle contraction (MVC) were repeated at 15-minute intervals for 1 hour to examine the effects on motor evoked potentials (MEPs) in the digital muscles and pinching muscle force before and after 4 high-intensity TMSs (test 1 condition) or sham TMS (test 2 condition) with MVC. Under the placebo condition, real TMS with MVC was administered only before and 1 hour after the sham TMS with MVC. Magnetic stimulation at the foramen magnum level (FMS) with MVC was performed by the same protocol as that for the test 2 condition. As a result, MEP sizes in the digital muscles significantly increased after TMS with MVC under test conditions compared with the placebo conditions (P < 0.05). Pinching muscle force was significantly larger 45 minutes and 1 hour after TMS with MVC under the test conditions than under the placebo condition (P < 0.05). FMS significantly decreased MEP amplitudes 60 minutes after the sham TMS with MVC (P < 0.005). The present results suggest that intermittently repeated TMS with MVC facilitates motor neuron excitabilities and muscle force. However, further studies are needed to confirm the effects of TMS with MVC and its mechanism.

Effect of repetitive transcranial magnetic stimulation on patients with brain injury and Dysphagia

OBJECTIVE

To investigate the effect of repetitive transcranial magnetic stimulation (rTMS) on recovery of the swallowing function in patients with a brain injury.

METHOD

Patients with a brain injury and dysphagia were enrolled. Patients were randomly assigned to sham, and low and high frequency stimulation groups. We performed rTMS at 100% of motor evoked potential (MEP) threshold and a 5 Hz frequency for 10 seconds and then repeated this every minute in the high frequency group. In the low frequency group, magnetic stimulation was conducted at 100% of MEP threshold and a 1 Hz frequency. The sham group was treated using the same parameters as the high frequency group, but the coil was rotated 90° to create a stimulus noise. The treatment period was 2 weeks (5 days per week, 20 minutes per session). We evaluated the Functional Dysphagia Scale (FDS) and the Penetration Aspiration Scale (PAS) with a videofluoroscopic swallowing study before and after rTMS.

RESULTS

Thirty patients were enrolled, and mean patient age was 68.2 years. FDS and PAS scores improved significantly in the low frequency group after rTMS, and American Speech-Language Hearing Association National Outcomes Measurements System Swallowing Scale scores improved in the sham and low frequency groups. FDS and PAS scores improved significantly in the low frequency group compared to those in the other groups.

CONCLUSION

We demonstrated that low frequency rTMS facilitated the recovery of swallowing function in patients with a brain injury, suggesting that rTMS is a useful modality to recover swallowing function.

The corticospinal system and transcranial magnetic stimulation in stroke

During the last decades, transcranial magnetic stimulation (TMS) has been used as a noninvasive method to investigate motor cortical reorganization and neuroplasticity in humans after stroke. An increasing number of studies in the field of motor control have used TMS to gain an understanding of the different aspects of stroke cortical physiology and motor recovery. This review addresses the effects of corticospinal tract (CST) lesions in humans and nonhuman primates on the functional organization of the motor system. We review information on the physiological mechanisms by which the CST contributes to normal motor control and to central nervous system reorganization following stroke when the CST is injured as measured using TMS. Insight into these physiological mechanisms has led to the development of scientifically sound interventional proposals in the field of neurorehabilitation.

Modifying motor learning through gating and homeostatic metaplasticity

Synaptic plasticity in the motor cortex is involved at least in some forms of motor learning. Recent evidence showed that the extent of practice-dependent plasticity in the motor cortex can be purposefully enhanced by experimental manipulation. One way of improving motor learning is to transiently increase the excitability of the motor cortex during motor learning. This can be achieved by weakening the excitability of intracortical inhibitory circuits concurrently with practice. This principle is being referred to as "gating." Another strategy to boost learning is to decrease the threshold for induction of synaptic plasticity by lowering neuronal activity in the motor cortex before practice. This approach invokes homeostatic metaplasticity. Here we highlight how transcranial brain stimulation can exploit gating and homeostatic metaplasticity to enhance motor learning in healthy subjects and in patients after stroke.