Objective: To assess the relationship between along-1-year stimulation voltage(V)/frequency(F) adjustments and speech intelligibility (SI) in PD patients treated with STN-DBS.

Background: Low V/F stimulation improves SI in PD patients treated with STN-DBS [1-3]. This benefit could be transient [3], but there are no studies about STN-DBS settings (pulse width (pw), V, and F) and SI along the course of treatment with this therapy.

Method: Eight idiopathic PD patients treated with STN-DBS and Levodopa (L-dopa) were studied (4 men: 63 ± 6 years old at the time of study enrollment (y-old), 11 ± 4 years with PD diagnosis (y-PD), 3.5 ± 2 Duffy´s Dysarthria Scale [4] score pre-surgery in off-L-dopa state (DDS-pre), and 4.3 ± 1 at 1 year post-surgery in off-L-dopa state (DDS-post), and 4 women: 63 ± 10 y-old, 9.3 ± 2 y-PD, 4.3 ± 3 DDS-pre, and 3.8 ± 3 DDS-post). Each patient was visited at home at 3, 6, 9, and 12 months post-STN-DBS surgery (mps) and was audio-recorded in OFF-L-dopa/ON-STN-DBS state, performing a spontaneous speech task. Corresponding STN-DBS settings data was taken from neurology’s medical records (NMR). At follow-up, the patients’ neurologist changed STN-DBS settings to improve motor signs evidenced during the examination. Grade of intelligibility (GI) and % of correctly identified words (%CIW), 2 SI measures, were rated blindly by 3 pairs of non-familiar listeners (1 pair per patient) from patients´ audio recordings.

Results: Every listener pair had no significative (NS) intra or inter-listener differences in SI rates (p>.05). NMRs showed that during follow-up, pw was constant (60 or 70 µs), V was low (≤ 2.9 V) or high (≥ 3 V), and F was low (60-90 Hz) or mid (100-139 Hz). At 6mps, significative positive correlations were found between F and SI with low voltage (l-V) at right (R-elec) (%CIW:R=.96, p <.0001; GI:R=.89, p<.01) and left electrode (L-elec) (%CIW:R=.61, p<.05), and at 12mps with l-V at R-elec only (%CIW:R=.73, p<.05; GI:R=.75, p<.05). Significative negative correlations were found between F and GI with h-V at R-elec (R=-.67, p<.01) and L-elec (R=-.52, p<.05). At 3 and 9mps we found NS correlations between F and SI measures independently on V level, which partially agrees with previous research.

Conclusion: Our data suggest that stimulation F and V could modulate SI differently depending on the treatment time.

References: [1] Abeyesekera A, Adams S, Mancinelli C, Knowles T, Gilmore G, Delrobaei M, Jog M. Effects of Deep Brain Stimulation of the Subthalamic Nucleus Settings on Voice Quality, Intensity, and Prosody in Parkinson’s Disease: Preliminary Evidence for Speech Optimization. Can J Neurol Sci. 2019 May;46(3):287-94.
[2] Grover T, Georgiev D, Kalliola R, Mahlknecht P, Zachaira A, Candelario J, et al. Effect of Low versus High Frequency Subthalamic Deep Brain Stimulation on Speech Intelligibility and Verbal Fluency in Parkinson’s Disease: A Double-Blind Study. J Parkinsons Dis. 2019;9(1):141-51.
[3] Tripoliti E, Zrinzo L, Martínez-Torres I, Tisch S, Frost E, Borrell E, et al. Effects of Contact Location and Voltage Amplitude on Speech and Movement in Bilateral Subthalamic Nucleus Deep Brain Stimulation. Mov Disord. 2008 Dec;23(16):2377-83.
[4] Duffy JR. Motor speech disorders. Substrates, differential diagnosis, and management. 2nd ed. Philadelphia: Elsevier Health Sciences;2005

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-one-year-follow-up-study-of-effects-of-voltage-frequency-subthalamic-nucleus-deep-brain-stimulation-stn-dbs-adjustments-on-speech-intelligibility-in-parkinsons-disease-pd/