Abstract
To investigate the effects of l-dopa (Levodopa) and cZi-DBS (deep brain stimulation in caudal zona incerta) on spontaneous speech intelligibility in patients with PD (Parkinson's disease). Spontaneous utterances were extracted from anechoic recordings from 11 patients with PD preoperatively (off and on l-dopa medication) and 6 and 12months post bilateral cZi-DBS operation (off and on stimulation, with simultaneous l-dopa medication). Background noise with an amplitude corresponding to a clinical setting was added to the recordings. Intelligibility was assessed through a transcription task performed by 41 listeners in a randomized and blinded procedure. A group-level worsening in spontaneous speech intelligibility was observed on cZi stimulation compared to off 6months postoperatively (8 adverse, 1 positive, 2 no change). Twelve months postoperatively, adverse effects of cZi-DBS were not frequently observed (2 positive, 3 adverse, 6 no change). l-dopa administered preoperatively as part of the evaluation for DBS operation provided the overall best treatment outcome (1 adverse, 4 positive, 6 no change). cZi-DBS was shown to have smaller negative effects when evaluated from spontaneous speech compared to speech effects reported previously. The previously reported reduction in word-level intelligibility 12months postoperatively was not transferred to spontaneous speech for most patients. Reduced intelligibility due to cZi stimulation was much more prominent 6months postoperatively than at 12months.
Highlights
Parkinson’s disease (PD) may affect patients’ clarity of speech in a way that is traditionally classified as hypokinetic dysarthria, affecting patients’ speech motor control and phonatory functioning
In the last two decades, DBS has become an established alternative method for the treatment of advanced PD. It is associated with minimal morbidity and is effective for PD patients that have ceased to respond L-dopa (Levodopa) treatment (Breit et al 2004)
Patients had been selected on clinical grounds for bilateral DBS surgery in the caudal part of the zona incerta (cZi) based on the assessment of overall motor function; no consideration was taken with regard to speech status
Summary
Parkinson’s disease (PD) may affect patients’ clarity of speech in a way that is traditionally classified as hypokinetic dysarthria, affecting patients’ speech motor control and phonatory functioning. In the last two decades, DBS (deep brain stimulation) has become an established alternative method for the treatment of advanced PD. It is associated with minimal morbidity and is effective for PD patients that have ceased to respond L-dopa (Levodopa) treatment (Breit et al 2004). For STN-DBS, occurrences of reduction in speech quality have been reported as a result of stimulation (Krause et al 2004; Rodriguez-Oroz et al 2005; To€rnqvist et al 2005; Fasano et al 2010; Sidtis et al 2012; Eklund et al 2014).
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