Affiliations: Department of Speech and Hearing Sciences, The George Washington University, Washington, DC, USA | Language Section, Voice, Speech and Language Branch, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, USA | Fischell Department of Bioengineering, University of Maryland, College Park, MD, USA | Voice Treatment Center, Medical Faculty Associates, The George Washington University Medical Center, Washington, DC, USA | Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA | University of Kansas Medical Center, Kansas City, KS, USA | Department of Neurological Sciences, Rush University Medical Center, Chicago, IL, USA
Note:  Correspondence to: Geralyn M. Schulz, Ph.D., Associate Dean for Research, Columbian College of Arts and Sciences, 801 22nd St., NW, Phillips Hall, Room 213, Washington, DC 20052, USA. E-mail: [email protected]
Abstract: Deep brain stimulation (DBS) of the subthalamic nucleus improves the motor symptoms of Parkinson's disease, but may produce a worsening of speech and language performance at rates and amplitudes typically selected in clinical practice. The possibility that these dissociated effects might be modulated by selective stimulation of left and right STN has never been systematically investigated. To address this issue, we analyzed motor, speech and language functions of 12 patients implanted with bilateral stimulators configured for optimal motor responses. Behavioral responses were quantified under four stimulator conditions: bilateral DBS, right-only DBS, left-only DBS and no DBS. Under bilateral and left-only DBS conditions, our results exhibited a significant improvement in motor symptoms but worsening of speech and language. These findings contribute to the growing body of literature demonstrating that bilateral STN DBS compromises speech and language function and suggests that these negative effects may be principally due to left-sided stimulation. These findings may have practical clinical consequences, suggesting that clinicians might optimize motor, speech and language functions by carefully adjusting left- and right-sided stimulation parameters.
Keywords: Parkinson's disease, deep brain stimulation, speech, language, lateralization