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Abstract
Objective: Subthalamic nucleus deep brain stimulation (STN-DBS) is an effective treatment for advanced Parkinson disease (PD). Following STN-DBS, speech intelligibility can deteriorate, limiting its beneficial effect. Here we prospectively examined the short- and long-term speech response to STN-DBS in a consecutive series of patients to identify clinical and surgical factors associated with speech change.
Methods: Thirty-two consecutive patients were assessed before surgery, then 1 month, 6 months, and 1 year after STN-DBS in 4 conditions on- and off-medication with on- and off-stimulation using established and validated speech and movement scales. Fifteen of these patients were followed up for 3 years. A control group of 12 patients with PD were followed up for 1 year.
Results: Within the surgical group, speech intelligibility significantly deteriorated by an average of 14.2% ± 20.15% off-medication and 16.9% ± 21.8% on-medication 1 year after STN-DBS. The medical group deteriorated by 3.6% ± 5.5% and 4.5% ± 8.8%, respectively. Seven patients showed speech amelioration after surgery. Loudness increased significantly in all tasks with stimulation. A less severe preoperative on-medication motor score was associated with a more favorable speech response to STN-DBS after 1 year. Medially located electrodes on the left STN were associated with a significantly higher risk of speech deterioration than electrodes within the nucleus. There was a strong relationship between high voltage in the left electrode and poor speech outcome at 1 year.
Conclusion: The effect of STN-DBS on speech is variable and multifactorial, with most patients exhibiting decline of speech intelligibility. Both medical and surgical issues contribute to deterioration of speech in STN-DBS patients.
Classification of evidence: This study provides Class III evidence that STN-DBS for PD results in deterioration in speech intelligibility in all combinations of medication and stimulation states at 1 month, 6 months, and 1 year compared to baseline and to control subjects treated with best medical therapy.
Footnotes
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Study funding: Supported by the Parkinson's Disease Society UK (grant 4070), Parkinson's Appeal, Brain Research Trust, Medtronic, and the NIH (R01-NS40902). This work was undertaken at UCLH/UCL, which received a proportion of funding from the UK Department of Health's NIHR Biomedical Research Centres funding scheme.
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- CI
- confidence interval
- LEDD
- levodopa equivalent daily dose
- LTAS
- long-term average spectrum
- PD
- Parkinson disease
- SPL
- sound pressure level
- STN-DBS
- subthalamic nucleus deep brain stimulation
- UPDRS-III
- Unified Parkinson's Disease Rating Scale
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Supplemental data at www.neurology.org
- Received December 14, 2009.
- Accepted September 3, 2010.
- Copyright © 2010 by AAN Enterprises, Inc.
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