Making Sense of Vagus Nerve Stimulation for Stroke.

Implantable vagus nerve stimulation, paired with high-dose occupational therapy, has been shown to be effective in improving upper limb function among patients with stroke and received regulatory approval from the US Food and Drug Administration and the Centers for Medicare & Medicaid Services. Combining nonsurgical and surgical approaches of vagus nerve stimulation in recent meta-analyses has resulted in misleading reports on the efficacy of each type of stimulation among patients with stroke. This article aims to clarify the confusion surrounding implantable vagus nerve stimulation as a poststroke treatment option, highlighting the importance of distinguishing between transcutaneous auricular vagus nerve stimulation and implantable vagus nerve stimulation. Recent meta-analyses on vagus nerve stimulation have inappropriately combined studies of fundamentally different interventions, outcome measures, and participant selection, which do not conform to methodological best practices and, hence, cannot be used to deduce the relative efficacy of the different types of vagus nerve stimulation for stroke rehabilitation. Health care providers, patients, and insurers should rely on appropriately designed research to guide well-informed decisions.

Mixed effectiveness of rTMS and retraining in the treatment of focal hand dystonia.

UNLABELLED: Though the pathophysiology of dystonia remains uncertain, two primary factors implicated in the development of dystonic symptoms are excessive cortical excitability and impaired sensorimotor processing. The aim of this study was to determine the functional efficacy of an intervention combining repetitive transcranial magnetic stimulation (rTMS) and sensorimotor retraining. A randomized, single-subject, multiple baseline design with crossover was used to examine participants with focal hand dystonia (FHD) (n = 9). INTERVENTION: 5 days rTMS + sensorimotor retraining (SMR) vs. Five days rTMS + control therapy (CTL) (which included stretching and massage). The rTMS was applied to the premotor cortex at 1 Hz at 80% resting motor threshold for 1200 pulses. For sensorimotor retraining, a subset of the Learning-based Sensorimotor Training program was followed. Each session in both groups consisted of rTMS followed immediately by 30 min of the therapy intervention (SMR or CTL). Contrary to our hypothesis, group analyses revealed no additional benefit from the SMR training vs. CTL. When analyzed across group however, there was significant improvement from the first baseline assessment in several measures, including tests of sensory ability and self-rated changes. The patient rated improvements were accompanied by a moderate effect size suggesting clinical meaningfulness. These results provide encouragement for further investigation of rTMS in FHD with a need to optimize a secondary intervention and determine likely responders vs. non-responders.

Neural substrates for motor imagery in severe hemiparesis.

BACKGROUND: The beneficial effects of imagined movements on motor learning and performance suggest that motor imagery is functionally close to preparatory and executive motor processes. OBJECTIVE: The purpose of this study was to examine the cortical processes associated with imagery of movement of the wrist in subjects with severe hemiparesis. METHODS: During fMRI, subjects with stroke performed alternating blocks of imagining wrist-tracking movements with the hemiparetic hand, active wrist-tracking movements with the unaffected hand, and resting. Control subjects performed the same tasks using an assigned hand. Cortical activation in the primary motor (M1), primary sensory (S1), supplementary motor area (SMA), and pre-SMA regions was determined through a laterality index of active voxels and signal intensity. Ability to imagine was assessed with an Imagery Rating Scale. RESULTS: All subjects displayed primarily contralateral control during the track condition. Healthy subjects demonstrated contralateral control in all areas during the imagine condition, whereas subjects with stroke displayed primarily contralateral activation in S1 but ipsilateral in M1 and SMA. The percentage change in signal intensity was greater in the ipsilateral hemisphere in subjects with stroke than in the ipsilateral hemisphere in healthy subjects during the imagine condition. Additionally, subjects with self-reported low ability to imagine displayed no difference in activation compared to those with high imagery ability. CONCLUSIONS: These findings are consistent with other works demonstrating primarily ipsilateral control of the hemiparetic hand in subjects with functional movement and lay the groundwork for further investigation into the ability of mental imagery to affect functionally relevant cortical control in subjects recovering from stroke.

Electrical stimulation driving functional improvements and cortical changes in subjects with stroke.

It has been proposed that somatosensory stimulation in the form of electromyographically triggered neuromuscular electrical stimulation (NMES) to the peripheral nerve can influence functional measures of motor performance in subjects with stroke and can additionally produce changes in cortical excitability. Using a controlled, double-blind design, we studied the effects of intensive (60 h/3 weeks) treatment at home with NMES compared with a sham treatment, applied to the extensor muscles of the hemiplegic forearm to facilitate hand opening in 16 chronic stroke subjects. We investigated improvement in functional use of the hand and change in cortical activation as measured by functional magnetic resonance imaging (fMRI). Following treatment, subjects improved on measures of grasp and release of objects (Box and Block Test and Jebsen Taylor Hand Function Test [JTHFT]: small objects, stacking, heavy cans), isometric finger extension strength, and self-rated Motor Activity Log (MAL): Amount of Use and How Well score. The sham subjects did not improve on any grasp and release measure or self-rated scale, but did improve on isometric finger extension strength. Importantly, however, following crossover, these subjects improved further in the measure of strength, grasp and release (Box and Block [JTHFT]: page turning), and self-rated MAL: Amount of Use score and How Well score. Using fMRI and a finger-tracking task, an index of cortical intensity in the ipsilateral somatosensory cortex increased significantly from pre-test to post-test following treatment. Cortical activation, as measured by voxel count, did not change. These findings suggest that NMES may have an important role in stimulating cortical sensory areas allowing for improved motor function.

Neuromuscular electrical stimulation in stroke rehabilitation.

We briefly review the literature related to the use of neuromuscular electrical stimulation (ES) in promoting recovery from stroke. ES can be used to facilitate motor learning in ankle dorsiflexion and wrist extension. It also has been shown to be beneficial in reducing shoulder subluxation but inconsistent in reducing shoulder pain. The mechanism of benefit of ES is unknown, but increased synaptic effectiveness has been suggested.