Modulation of brain activity by electrical stimulation and external cues to treat Parkinson's disease symptoms
Summary
Despite being one of the most common and best studied neurological disorders, Parkinson's disease symptoms remain difficult to treat. Pharmacological therapy has proven to be very effective to ameliorate parkinsonian symptoms, and remains the most common treatment method to this day. But because its positive effects decline over time and it can cause some serious side effect, some patients need to resort to other treatment methods. High frequency electrical stimulation of components of the basal ganglia or thalamus, called deep brain stimulation, has become increasingly popular over the last years to help patients with severe Parkinson's disease. But also noninvasive treatments can be effective, as certain external cues can improve gait patterns of patients. In this review, the effectiveness of these treatment methods are investigated and compared to each other. We found that both deep brain stimulation and external cues can be helpful to patients, but they affect different parts of the neuronal network involved in Parkinson’s disease and therefore have a different effect on the parkinsonian symptoms. Deep brain stimulation generally affects a wide variety of symptoms, but has less effect on gait patterns, which are strongly affected by external cues. External cues may therefore be a beneficial addition to deep brain stimulation. However, it may be more effective to simulate the effect of an external cue with electrical stimulation. We will give suggestions for areas in the brain that may be effective targets for electrical stimulation, and give an overview of targets that have already been tested. We believe that modulation of several of these targets by electrical stimulation will be more effective than standard methods. The most effective treatment method is likely to be highly patient-specific, but with more brain areas available as potential targets for electrical stimulation, the treatment of parkinsonian symptoms may ultimately become more effective.