An exploration of the application of non-invasive cerebellar stimulation in the neurorehabilitation of dysphagia after stroke

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Swallowing problems (dysphagia) after stroke represent a major clinical problem for the NHS, with over 40,000 patients annually suffering from dysphagia with consequent aspiration/pneumonia. This leads to longer hospital stays, increased demands on feeding resources, higher admissions to care homes and poorer survival, costing the NHS an estimated £400 million a year. Traditionally, speech and language therapists have used dietary modifications and bedside strategies to rehabilitate swallowing albeit with little evidence base for benefit. And while tube feeding can improve nutrition, there is no evidence that the risk of (food) aspiration is reduced. With the incidence of stroke projected to increase over the next 20 years, the problem of dysphagia is likely to grow, so a better understanding of how swallowing recovery can be manipulated would of clear benefit to human health and disease. Previous work from our group has looked at the factors that might make for successful recovery from dysphagia in stroke patients, and some of this work led to development of a pharyngeal stimulation therapy via a swallowing catheter that is now undergoing phase III clinical trials. Unfortunately, many patients cannot participate in such trials because their stroke has resulted in either impaired sensation in the mouth/throat or because they cannot comply with catheter placement. Moreover, about a third of dysphagic stroke patients don't seem to respond to this sensory intervention. There is therefore a need to explore alternative strategies to improve control of swallowing in this group of patients.In this proposal we will explore the effectiveness of a new and exciting approach, non-invasive cerebellar stimulation, to enhance motor plasticity in the swallowing cortex after stroke. This approach has mainly been examined in animals where direct cerebellar stimulation has showed enhancement of limb motor responses and enhanced motor recovery after artificial stroke in rats. By comparison, we have shown that the human cerebellum is strongly activated during the act of swallowing and when stimulated with magnetic pulses over the back of the head can strongly improve the cortex to swallowing muscles pathway in humans. More recently we have identified the most relevant frequency of magnetic stimulation of the cerebellum (10Hz) that can produce longer term improvements in the human swallowing motor system. We therefore believe that the potential for cerebellar stimulation in improving swallowing is much greater than other methods.Our plans are to look at this new approach through three studies that each build on the other. First we will use a "virtual lesion" technique to suppress the swallowing areas of the brain before applying the cerebellar stimulation in health participants to see if stimulation either side of the cerebellum can restore the swallowing regions to normal. We will then test out stimulation of best cerebellar side/site in dysphagic stroke patients to see if we can improve swallowing in the period immediately after stimulation (1 hour). Assuming this works, we will then run a small dose ranging study of cerebellar stimulation in dysphagic stroke patients to see which recipe of stimulation (how many days and how many times per day) produces the greatest long term changes in swallowing (beyond 1 hour, to 2 weeks). If there is an optimal/best recipe for this, we expect this will then lead on to future larger scale studies of the cerebellar stimulation in dysphagic stroke with the anticipation that this will eventually become a treatment option for these distressed and debilitated victims of stroke.