Objective: To evaluate the long-term effects of bilateral STN-DBS on speech in advanced Parkinson’s disease (PD) patients.

Background: Bilateral STN-DBS is an effective treatment in advanced PD. However, the effects of STN-DBS on speech are still debated particularly regarding the long-term follow-up.

Method: This observational study included consecutive PD patients treated with bilateral STN-DBS. All available demographic variables, neuroimaging data, and clinical characteristics were collected. Each patient was evaluated before surgery in the off-medication and on-medication conditions through a neurological evaluation (UPDRS part III score and subscores) and a perceptual-acoustic analysis of speech. Each patient has been reevaluated in the long-term postoperative assessment in different stimulation and drug conditions (on-stimulation/off-medication; off-stimulation/off-medication; on-stimulation/on-medication). Primary outcome was the percentage change of speech intelligibility obtained by comparing postoperative on-stimulation/off-medication condition with preoperative off-medication condition. Based on the presence/absence of postoperative worsening of speech intelligibility, patients were divided into two groups (“stable” vs “worsened”) that were compared to find significant differences in demographic, clinical and speech variables.

Results: 25 PD patients treated with bilateral STN-DBS with a five years follow-up were included. In the long-term, speech intelligibility did not worsen if compared with preoperative values. Bilateral STN-DBS led to a significant improvement of speech intelligibility (p<0.005) in the postoperative assessment by comparing the on-stimulation/off-medication and off-stimulation/off-medication conditions. In the “worsened” group (n=9) a greater severity of PD motor symptoms before surgery was found together with postoperative lower intensity of spontaneous speech and sustained phonation; higher shimmer of sustained phonation; and worse speech intelligibility.

Conclusion: These results highlight the possible beneficial long-term effects of STN-DBS on speech intelligibility. Moreover, a better understanding of PD characteristics associated with long-term speech worsening after STN-DBS may allow to obtain a greater prognostic accuracy and to employ, if necessary, early speech interventions.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/long-term-effects-of-bilateral-stn-dbs-on-speech-in-parkinsons-disease-patients/