Abstract Background Deep brain stimulation (DBS) is a viable surgical treatment method for Parkinson’s disease (PD). It has positive effects on the classical motor symptoms, but effects on speech and voice are not equally beneficial. The speech disorder related to PD is hypokinetic dysarthria, with impaired articulatory precision as a prominent symptom. Studies have shown effects on different aspects of speech due to DBS of the subthalamic nucleus (STN) but the effects of stimulation of the caudal zona incerta (cZi) are less explored. Aims The aim of the current study was to investigate the effect of STN-DBS and cZi-DBS on perceptually measured articulatory precision in PD patients. Method Read speech productions were collected from 19 DBS-treated PD patients, ten STN and nine cZi. The recordings were made before surgery and 12 months postoperatively with stimulator on and off. Levodopa medication was always on. From the reading passage, three-syllable words were selected and isolated. Articulatory precision of the words was rated in two different assessments; an overall rating of articulatory precision and an identification of occurring misarticulations. Results The results from the perceptual assessment showed a decrease in articulatory precision after surgery for both groups. The decrease was significant for the cZi group, but not for the STN group. There was no significant difference between the groups. The frequency of observed misarticulations increased as an effect of DBS for both patient groups, with significant increase for the STN group but not for the cZi group. There was no significant difference between the groups. The most commonly observed misarticulation categories were stop-plosive reduced in quality, fricative realized as other fricative and stop-plosive realized as fricative . Conclusions The results obtained in the current study show that STN-DBS and cZi-DBS may have adverse effects on articulatory precision in PD patients. Keywords Articulatory precision, Parkinson’s disease, DBS, STN, cZi

Bakgrund: Deep Brain Stimulation (DBS) i nucleus subthalamicus (STN) och i kaudala zona incerta (cZi) har visat positiva effekter på motoriska symtom (rörelseförmåga och balans) vid Parkinsons sjukdom. Efter DBS har dock negativa taleffekter noterats, inklusive nedsatt artikulatorisk precision och stabilitet. Nedsatt artikulatorisk precisionoch stabilitet påverkar klusilproduktionen mest vilket kan resultera i att klusilexplosionen uteblir eller att multipla explosioner uppstår. Mål: Att undersöka artikulatorisk precision och stabilitet vid klusilexplosionen efter DBS i STN respektive cZi. Metod: I studien deltog 19 patienter varav 9 deltagare stimulerats i STN och 10 deltagare i cZi. Talinspelningar gjordes innan operation och ett år efter operation med DBSstimulering på och av. Klusilerna i talmaterialet delades in i tre kategorier, de med en klusilexplosion, de med två eller flera klusilexplosioner samt de utan klusilexplosion. Hypotesprövning gjordes gällande fördelningen av klusiler med multipla explosioner samt klusiler utan explosion mellan och inom patientgrupperna samt inom respektive klusil. Resultat: Multipla explosioner ökade hos cZi-patienterna och minskade hos STNpatienterna. Klusiler som saknade explosion ökade hos STN-patienterna medan de minskade hos cZi-patienterna. För båda patientgrupperna ökade multipla explosioner och klusiler utan explosion då stimuleringen var på jämfört med av. Skillnaderna mellan och inom grupperna var inte signifikanta. Slutsats: Artikulatorisk precision och stabilitet påverkades efter DBS i form av bristande stabilitet, för kort slutningsrörelse och felaktig koordination av slutningsrörelsen. Detta resulterade i multipla explosioner och uteblivna explosioner med olika effekter för elektrodlokalisationerna. / Background: Deep Brain Stimulation (DBS) in Subthalamicus Nucleus (STN) and Caudala zona incerta (cZi) have shown positive effects on motor symptoms in Parkinson‘s disease. Negative effects on speech after DBS has been noted including reduced articulatory precision. Reduced articulatory precision and stability affects the production of stop consonants and as a result, loss of burst or multiple burst can occur. Aim: To investigate articulatory precision and stability regarding the burst in stop consonants after DBS of STN or cZi. Method: The study included 19 patients with 9 patients stimulated in STN and 10 patientsin cZi. Speech recordings were made before surgery and one year after with stimulation ON and OFF. The stop consonants were divided into three categories, those with one burst, those with two or more bursts (multiple burst) and those with loss of burst. Hypothesis testing was done on the categorization of the stop consonants in and between the groups and between the stop consonants types. Results: Multiple burst increased in the cZi group and decreased in the STN group. Stop consonants with loss of burst increased in the STN group but decreased in the cZi group. For both groups multiple burst and stop consonants with loss of burst increased with stimulation on. The differences between and within the groups were not significant. Conclusion: Articulatory precision and stability were affected by DBS with decreased stability, shortened occlusion and incorrect coordination. As a result multiple burst and loss of burst occurred in both groups. / Speech, voice and swallowing outcomes after deep brain stimulation of the zona incerta and the pedunculopontine nucleus in Parkinson’s disease: Comparsion with stimulation of the subthalamic nucleus