The Impact of Deep-Brain Stimulation on Speech Comprehensibility and Swallowing in Patients with Idiopathic Parkinson's Disease

Abstract

Objective: This is a pilot study designed to assess speech and swallowing characteristics of participants with idiopathic Parkinson’s disease (IPD) before deep brain stimulation surgery of the subthalamic nucleus (DBS-STN), after the DBS-STN surgery, and at follow up evaluation sessions. Method: A within participant, single-subject experimental A-B-A-A design was used to measure changes in the dependent variables for each participant. The primary dependent variables were intelligibility scores of words and sentences, vowel space area (VSA), vocal sound pressure level (dB SPL) of sustained vowels, single words, and contextual speech, Multidimensional voice program (MDVP) analysis of phonatory stability of sustained vowel phonation, lip pressure, tongue tip to alveolar ridge pressure, maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), and diadochokinetic rate. The secondary dependent variables were: duration of sustained vowel phonation, Visual analog scales (VAS) for communicative difficulties and swallowing difficulties, the EAT-10 swallowing questionnaire, and the qualitative narrative of life with IPD before and after the DBS-STN surgery. Results: DBS-01 had significant declines of intelligibility with individual words, but did not have statistically significant changes for complete sentences. The VSA declined over the course of the study. The MDVP analyses indicated general declines in phonatory stability, but not significantly. There was a statistically significant increase in dB SPL for sustained vowel phonation, but there were overall declines in loudness for connected speech. The duration of sustained vowel phonation increased and the DDK rate varied across the experiment. Left lip and tongue pressures had overall declines, but right and center lip pressures increased. The VAS for communicative difficulties revealed worsening of symptoms. The VAS and the EAT-10 questionnaire for swallowing difficulties both recorded worsening of symptoms after surgery, and symptom improvements later on. The timed swallow test did not show any meaningful impairment in drinking or eating. DBS-02 had statistically significant gains of intelligibility with individual words after the DBS-STN surgery, but had statistically significantly declines later on. The changes in the intelligibility of complete sentences were not significant. The VSA contracted after the surgery, but it increased afterwards. The MDVP analyses indicated an overall significant increase of phonatory stability. The dB SPL had a statistically significant increase for sustained vowel phonation, but the connected speech loudness had mixed results. The duration of sustained vowel phonation increased after surgery, but then declined later on. The DDK rate varied across the experiment. Lip and tongue pressures had overall increases. The VAS for