Effect of deep brain stimulation on amplitude and frequency characteristics of rest tremor in Parkinson’s disease

Abstract

The effect of chronic high frequency deep brain stimulation (DBS) on rest tremor was investigated in subjects with Parkinson's disease (PD). Eight PD subjects with high amplitude tremor (Group 1) and eight PD subjects with low amplitude tremor (Group 2, used as a reference group) were examined by a clinical neurologist and tested with a velocity laser to quantify time and frequency domain characteristics of tremor. Possible rebound effects in rest tremor when DBS was stopped for 60 min were also explored. Participants received DBS of the internal globus pallidus (GPi) (n = 7), the subthalamic nucleus (STN) (n = 6) or the ventrointermediate nucleus of the thalamus (Vim) (n = 3). Tremor was recorded with a velocity laser under two conditions of DBS (on-off) and two conditions of medication (L-Dopa on-off). Correlations between clinical and experimental results for tremor amplitude was 0.70 with no medication and no stimulation. In Group 1, DBS decreased tremor amplitude but also increased spectral concentration and median frequency significantly. Under medication, the changes in tremor with and without stimulation were not statistically significant (Group 1). When stimulation was stopped for 60 min, a rebound in tremor amplitude was observed and median frequency remained stable in Group 1. None of the comparisons examined produced significant effects in Group 2. Taken together, these results suggest that beyond its effect on tremor amplitude DBS acted also on tremor frequency and did not modify tremor characteristics in subjects with low amplitude tremor.

Discrimination and Characterization of Parkinsonian Rest Tremors by Analyzing Long-Term Correlations and Multifractal Signatures

“…PD is characterized by the progressive loss of dopaminergic neurons in the substantia nigra of the midbrain. The most evident symptoms associated with PD are tremors, bradykinesia, rigidity, and postural instability, while in more advanced stages of the disease other factors might be present such as different types of cognitive impairments (e.g., dementia) and changes in behavior and/or emotional states [3,14]. The causes of PD are, however, still largely unknown.…”

“…Deep brain stimulation (DBS) [26,27,32] is neurosurgical procedure that involves a surgical intervention to implant electrodes in brain areas suitable for receiving electrical impulses. DBS proved to be effective in the treatment of PD and other diseases, such as obsessive-compulsive disorders [4].In this paper, we study 48 signals recorded from 12 subjects affected by PD [3]. Tremor signals are recorder by means of a velocity laser targeted to their index finger.…”

“…For each subject, signal recording is performed in four different settings, given by the combination of the use of DBS and L-DOPA medication. The original experiment [3,35] was performed on a larger set of 16 subjects. However, not all subjects were recorded in the four aforementioned conditions.…”

“…We develop two main low-dimensional, feature-based representations (FBRs) of such signals, which are obtained by considering (i) the LTC and multifractal properties and (ii) the power spectra. The power spectra are principally used for comparison purposes, since they have been already analyzed in detail by Beuter et al [3]. The FBRs are initially utilized for the purpose of characterizing the subjects under different test settings.…”

Virial Theorem and Non-Equilibrium Canonical-Dissipative Distributions Characterizing Parkinson Tremor

“…We will examine publicly available data (Physionet) from six Parkinson patients who will be referred to as G2, V4, V5, S6, S7, and S8. 50,51 The average age of these subjects was 57.2 years (SD 9.8 years). All subjects were receiving chronic deep brain stimulation 52 as a remedy for Parkinson's disease symptoms such as Parkinsonian hand tremor.…”