Objective: In Parkinson’s disease (PD), recognition of speech deviations often follows clinical diagnosis. But what if speech is a prodromal biomarker in PD? The study examines if speech movements of patients with isolated REM sleep behavior disorder (iRBD) differ from patients with PD.

Background: Patients with iRBD have an increased risk of developing PD in the future. Speech production is a sensitive domain that can provide early information about motor control. Previous acoustic studies have shown that articulatory deficits [1] and a reduced pitch range can be found in patients with iRBD [2].

Method: Data were collected from 66 age and sex-matched subjects: healthy control speakers (n=22), patients with iRBD (n=22), and patients with PD (n=22). Patients with PD were assessed in medication-OFF condition after cessation of dopaminergic drugs for at least 12 hours.

All participants were recorded with an electromagnetic articulograph (AG 501) to capture tongue and lip movements. Ten different target words, such as Mila or Lina, embedded in a carrier sentence were produced by the speakers in three different conditions. The target syllables contain peripheral vowels of German /i,e,a,o,u/ flanked by alveolar and labial consonants. In total 1980 items went into the analysis (66 speaker x 10 words x 3 conditions).  Kinematic tongue and lip measures (durations, amplitudes, peak velocities) were calculated. In addition, the motor status of all subjects were determined using the motor part of the UPDRS (part III) [3].

Results: Preliminary results indicate that both, patients with iRBD and with PD need more time to achieve the articulatory target of the tongue body compared to healthy controls. Interestingly, when looking at maximal velocities, tongue body movements are faster in patients with iRBD compared to controls. Patients with PD show overall increased movement durations and slower velocities of the tongue tip and the lip which is not presentin iRBD.

Conclusion: In iRBD only the tongue body is affected, whereas in PD the whole tongue is affected which might indicate an evolution towards dysarthria from the dorsal to ventral parts of the tongue. Patients with iRBD seem to compensate for longer movements with faster maximal velocities. Affected tongue movements in iRBD patients might indicate articulatory distortion as early signs of hypokinetic dysarthria (e.g., imprecise consonants, articulated with the tongue tip [4]).

References: [1] Rusz, J., Hlavnička, J., Tykalová, T., Bušková, J., Ulmanová, O., Růžička, E., & Šonka, K. (2016). Quantitative assessment of motor speech abnormalities in idiopathic rapid eye movement sleep behaviour disorder. Sleep medicine, 19, 141-147.
[2] Rusz, J., Hlavnička, J., Novotný, M., Tykalová, T., Pelletier, A., Montplaisir, J., … & Šonka, K. (2021). Speech Biomarkers in Rapid Eye Movement Sleep Behavior Disorder and Parkinson Disease. Annals of Neurology, 90, 62-75.
[3] Fahn, S., & Elton, R. L. (1987). UPDRS program members. Unified Parkinsons disease rating scale. Recent developments in Parkinson’s disease, 2, 153-163.
[4] Duffy, Joseph R. (2019). Motor Speech Disorders: Substrates, Differential Diagnosis, and Management, 4th ed. Edinburgh: Elsevier.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/affected-tongue-movements-in-idiopathic-rem-sleep-behavior-disorder/