Local Field Potentials in Deep Brain Stimulation for Parkinson's Disease: Assessment of the Effects of the Intervention and Relation with Inertial Signals

Parkinson disease (PD) is a neurodegenerative disorder characterized by a progressive loss of dopaminergic neurons in the basal ganglia, and specifically in the substantia nigra. The main motor symptoms are tremor, bradykinesia, rigidity, postural instability, dyskinesia and dystonia. Non-motor symptoms are also common, including neuropsychiatric issues, speech and swallowing problems, and sleep disturbances. Clinical assessment for PD is based on rating scales such as the MDS-UPDRS scale. Since clinical rating scales are subject to the interpretation of the examiner, the use of wearable inertial sensors (WS) to quantitatively assess patient motor performance is becoming more common. Nowadays both pharmacological and surgical treatments are used to contain PD symptoms. The assumption of Levodopa medication represents the most common pharmacological treatment, while Deep Brain Stimulation (DBS) is a common surgical intervention. Innovative DBS systems allow the recording of low frequency brain signals called Local Field Potentials (LFPs), which represent the synchronous activity of large populations of neurons. The main goal of this thesis is to assess how motor performance of PD patients change in different conditions of medication and stimulation, by analyzing data recorded using both WS and the implanted neurostimulator. LFPs recorded in real-life conditions have been evaluated to see how their trend changes in different time intervals after the DBS surgery, and to assess whether LFPs behavior is affected by Levodopa intake during the day. In particular, the trend of LFP power recorded during the first month after DBS surgery was evaluated. Moreover, motor parameters extracted from inertial sensors were analyzed to compare motor performance before and after the DBS surgery. Finally, motor impairment was assessed by comparing the MDS-UPDRS clinical rating scores in the different conditions included in the clinical protocol, before and after the DBS surgery.