Objective: We conducted a 2-year prospective study of PD patients treated with subthalamic nucleus deep brain stimulation (STN-DBS) to elucidate the predictive factors of deterioration in speech function.

Background: Speech disorders are one of the most common adverse effects following STN-DBS in PD patients. However, it still remains difficult to predict the deterioration of speech disorders.

Methods: Twenty-five PD patients (age, 65.0 ± 8.8 years; disease duration, 11.8 ± 4.1 years) were assessed before and up to 2 years after STN implantation. All patients received the cognitive examinations using Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), verbal fluency, Stroop color-word test (SCWT), digit span, and line-orientation before operation. The speech samples used for the speech assessments were a reading task of a standard passage (The North Wind and the Sun) in Japanese, and short conversations. We used the perceptual scale (Assessment of Motor Speech for Dysarthria) which comprised analogous variables developed by Darley et al. Speech function was evaluated in the on-stimulation condition and then 30 min after stimulation was stopped. Patients who experienced worsening in scores of speech intelligibility or speech naturalness ≥1 were classified as “Deteriorated (Det) group”. The remaining subjects were classified as “Stable (St) group”. Motor function (UPDRS III and IV) was also assessed simultaneously.

Results: Both speech intelligibility and speech naturalness in the on-stimulation condition gradually worsened over time after surgery (p < 0.001) despite improvement in motor fluctuation (UPDRS III, p=0.419; IV, p < 0.001). Twenty-five patients were divided into two groups: Det group (n = 16) and St group (n = 9). Regarding the clinical backgrounds at baseline, Det group had significantly worse frontal lobe function compared with St group (SCWT part2, Det = 35.1 ± 14.1s, St = 24.4 ± 6.1s, p = 0.045; and digit span test, Det = 10.8 ± 2.6, St = 14.5 ± 3.2, p = 0.011). Although the parameters of electrical stimulation gradually increased over time, there were no significant differences between groups.

Conclusions: Our results suggest that preoperative frontal lobe dysfunction may predict postoperative speech deterioration within 2 years.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/predictor-for-speech-deterioration-following-stn-dbs-in-pd-patients/