Graph Theory on Brain Cortical Sources in Parkinson's Disease: The Analysis of 'Small World' Organization from EEG.

Fabrizio Vecchio,Maria Cotelli,Francesca Alù,Paolo Maria Rossini,Francesca Miraglia,Francesca Pistoia,Elda Judica,Alessandro Orticoni,Chiara Pappalettera

doi:10.3390/s21217266

Abstract

Parkinson’s disease (PD) is the second most common neurodegenerative disease in the elderly population. Similarly to other neurodegenerative diseases, the early diagnosis of PD is quite difficult. The current pilot study aimed to explore the differences in brain connectivity between PD and NOrmal eLDerly (Nold) subjects to evaluate whether connectivity analysis may speed up and support early diagnosis. A total of 26 resting state EEGs were analyzed from 13 PD patients and 13 age-matched Nold subjects, applying to cortical reconstructions the graph theory analyses, a mathematical representation of brain architecture. Results showed that PD patients presented a more ordered structure at slow-frequency EEG rhythms (lower value of SW) than Nold subjects, particularly in the theta band, whereas in the high-frequency alpha, PD patients presented more random organization (higher SW) than Nold subjects. The current results suggest that PD could globally modulate the cortical connectivity of the brain, modifying the functional network organization and resulting in motor and non-motor signs. Future studies could validate whether such an approach, based on a low-cost and non-invasive technique, could be useful for early diagnosis, for the follow-up of PD progression, as well as for evaluating pharmacological and neurorehabilitation treatments.

Highlights

Parkinson’s disease (PD) is a slowly progressive movement condition and one of the most common neurodegenerative disorders, affecting worldwide approximately 1–2%individuals older than 60 years old
It is well established that α-Synuclein, linked genetically and neuropathologically to PD, is one of the main components of Lewy body deposits in the substantia nigra, leading to dopaminergic dysfunction in the basal ganglia, the diagnosis of PD is still based on the clinical history and the physical examination of the patient [1,2]
As PD is caused by the prominent death of dopaminergic neurons in the substantia nigra pars compacta, and several neuroimaging studies suggest that striatal dopamine reduction causes disorders affecting brain circuits governed and orchestrated by the basal ganglia, various mathematical approaches have been applied in order to identify and visualize abnormal connectivity in brain networks in PD [61,62,63,64]

Summary

Introduction

Parkinson’s disease (PD) is a slowly progressive movement condition and one of the most common neurodegenerative disorders, affecting worldwide approximately 1–2%individuals older than 60 years old. The clinical manifestations of PD are predominantly characterized by motor symptoms, such as bradykinesia, resting tremor, gait disturbance, rigidity and postural instability [4,5,6]. Non-tremor dominant (nTD), the latter mainly characterized by postural instability, gait difficulty and akinetic–rigid syndrome [7,8]. Most PD patients may suffer from non-motor-symptoms such as autonomic dysfunction, hyposmia, sleep disorders, cognitive impairments or psychiatric disturbances [9,10]. These symptoms lead to serious disability and poor quality of life among patients. The presence of both cardinal motor dysfunction (i.e., akinesia, rigidity, postural instability and resting tremor) and response to levodopa supports the diagnosis of PD [3,11,12,13]

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