A Neuroprosthesis for Tremor Management

Abstract

Tremor is the most common movement disorder, affecting 15 % of people over 50 years old according to some estimates. It appears due to a number of syndromes, being essential tremor and Parkinson's disease the most prevalent among them. None of these conditions is fully understood. Tremor is currently treated through drugs or neurosurgery, but unfortunately, it is not managed e ectively in 25 % of the patients. Therefore, it constitutes a major cause of loss of independence and quality of life. Various alternative approaches for tremor management are reported in the literature. Among them, those devices that rely on the application of forces to the tremulous segments show a considerable potential. A number of prototypes that exploit this principle are available, spanning xed devices and orthoses. However, none of them has fu lfilled user's expectation for continuous use during daily living. This thesis presents the development and validation of a neuroprosthesis for tremor management. A neuroprosthesis is a system that restores or compensates for a neurological function that is lost. In this case, the neuroprosthesis aims at compensating the functional disability caused by the tremor. To this end, it applies forces to the tremulous limb through the control of muscle contraction, which is modulated according to the characteristics of the tremor. The concept design envisions the device as a textile that is worn on the a ected limb, thus meeting the usability requirements de ned by the patients. The development of the neuroprosthesis comprised the following tasks:

1. The development of a concept design of the neuroprosthesis, which incorporates state of the art knowledge on tremor, and user's needs. 2. The design and validation of a cognitive interface that parameterizes the tremor in functional contexts. This interface provides the information that the neuroprosthesis uses for tremor suppression. Two versions are developed: a multimodal interface that integrates the recordings of the whole neuromusculoskeletal system, and an interface incorporating only wearable movement sensors. The latter is intended for the functional validation of the neuroprosthesis, while the former is a proof of concept of an optimal interface for this type of applications.3. The development of a novel approach for tremor suppression through transcutaneous neurostimulation. The approach relies on the modulation of muscle cocontraction as a means of attenuating the tremor without the need of conventional actuators. The experimental validation here provided demonstrates the feasibility and interest of the approach.

In parallel with the validation of the neuroprosthesis, I performed a detailed study on the physiology of motoneurons in tremor, given the lack of a complete description of its behavior. The outcome of this study contributes to the interpretation of the results obtained with the neuroprosthesis, and opens new research lines, both related to alternative interventions and basic neuroscience. In summary, the results here presented demonstrate that tremor may be accurately parameterized while the patient performs functional activities, and that this information may be exploited to drive a neuroprosthesis for tremor management. Furthermore, the novel approach for tremor suppression presented in this dissertation constitutes a potential approach for treating upper limb tremor, either alone, or as a complement to pharmacotherapy. These results encourage the validation of the neuroprosthesis in a large cohort of patients, in order to enable its translation to the market.