An Exploration of the Application of Non-invasive Cerebellar Stimulation in the Neurorehabilitation of Dysphagia After Stroke

Detailed Summary

The study is designed to explore the effectiveness of non-invasive cerebellar stimulation to enhance motor plasticity in the cortex after stroke. The investigators have shown that the human cerebellum is strongly activated during the act of swallowing and when stimulated with single TMS pulses can strongly facilitate the corticobulbar projection to the pharynx in humans. More recently the investigators have identified the most relevant frequency of stimulation of the cerebellum that can produce longer term excitation in the human swallowing motor system. The investigators therefore believe that the potential for cerebellar stimulation in improving swallowing is much greater than other methods for two reasons. Firstly, previous work has shown that unlike successful recovery of hand/arm function which relies on restoring activity in the stroke hemisphere, recovery of swallowing function relies on increased excitability in intact projections from the non-stroke hemisphere. The investigators believe that methods that can enhance these undamaged pathways have a greater chance of inducing recovery in the human swallowing system in unilateral stroke. Additionally cerebellar stimulation produces very high levels of corticobulbar excitation it may also have the advantage of improving dysphagia in posterior fossa strokes. Second, the human cerebellum is relatively easy to target and stimulate and has reduced risk of inducing unwanted effects (such as seizures) which as a consequence makes cerebellar stimulation a more pragmatic method for delivering therapeutic neurorehabilitation to dysphagic stroke patients compared to other more complex/riskier methods. A final factor is that the investigators have developed a "virtual lesion" model of swallowing dysfunction in healthy volunteers which can be reversed quite successfully with other neuro-stimulation protocols. The investigators can therefore use this model to test the effectiveness of cerebellar stimulation protocols (ipsilateral and contralateral cerebellar sites) before choosing the most effective side to apply stimulation in a proof of principle trial/study in a small group of sub-acute dysphagic patients. The hypotheses are that cerebellar TMS will: i. Reverse the brain inhibition and behavioural dysfunction following a virtual lesion model of disrupted swallowing in healthy brain (phase 1); ii. Reduce the degree of aspiration in acute dysphagia after a stroke (phase 2).

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