Long-Term Effect of Repetitive Transcranial Magnetic Stimulation on Parkinson’s Disease Patients with Different Severity of Hypokinetic Dysarthria

Abstract

The prevalence of Parkinson’s disease (PD), severe neurodegenerative disorder, has steadily increased. Among the symptoms of PD is hypokinetic dysarthria (HD), a motor speech disorder, characterised by respiratory, articulatory, prosodic and phonatory impairments. It has been demonstrated that both motor and non-motor symptoms of PD can be improved using the repetitive Transcranial Magnetic Stimulation (rTMS). This study analyses acoustic speech characteristics of 19 participants diagnosed with PD before (one pre-stimulus) and after (four poststimulus) evaluation sessions of rTMS treatment. The participants were divided into two groups – receiving either rTMS or sham stimulation (1:1 randomization). Based on the prestimulus subresults of the Test 3F, participants were stratified into two cohorts, according to their possible HD severity level. Speech recordings were also taken during each evaluation session. The outcome of the follow-up acoustic analysis resulted in 16 parameters for each of those sessions. Their evaluation demonstrated the dependence of the effect of rTMS treatment on the severity level. The actively stimulated group of the first cohort showed consistent improvement in articulation and prosody (sham did not) while the actively stimulated group of the second stratified cohort showed consistent improvement in phonation (sham did not). The study provides early preliminary insights into the benefits of rTMS for the alleviation of HD manifestations (symptomatic treatment of PD). In addition, it provides new insights into the possible relationship between the effectiveness of rTMS and the degree of severity in HD.