title: The Feasibility of Using Acoustic Markers of Speech for Optimizing Patient Outcomes during Randomized Amplitude Variation in Deep Brain Stimulation: A Proof of Principle Methods Study.
abstract: BACKGROUND
  Deep brain stimulation (DBS) is an effective treatment for reducing symptoms of tremor. A common and typically subjectively determined adverse effect of DBS is dysarthria. Current assessment protocols are driven by the qualitative judgments of treating clinicians and lack the sensitivity and objectivity required to optimize patient outcomes where multiple stimulation parameters are trialed.
  
  
  OBJECTIVE
  To examine the effect of DBS on speech in patients receiving stimulation to the posterior sub-thalamic area (PSA) via randomized manipulation of amplitude parameters.
  
  
  METHODS
  Six patients diagnosed with tremor receiving treatment via DBS of the PSA were assessed in a double-blinded, within-subjects experimental protocol. Amplitude (i.e., voltage or current) was randomly adjusted across 10 settings, while speech samples (e.g., sustained vowel, counting to 10) were recorded to identify the patient-specific settings required for optimal therapeutic benefit (reduced tremor) with minimal adverse effects (altered speech). Speech production between stimulation parameters was quantified using acoustic analysis.
  
  
  RESULTS
  Speech changed as a response to DBS but those changes were not uniform across patients nor were they generally in line with changes in amplitude with the exception of reduced vocal control and increased mean silence length in two patients. Speech outcomes did not correlate with changes in tremor.
  
  
  CONCLUSIONS
  Intra-individual changes in speech were detected as a response to modified amplitude; however, no clear pattern was observed across patients as a group. The use of objective acoustic measures allows for quantification of speech changes during DBS optimization protocols, even when those changes are subtle and potentially difficult to detect perceptually.
authors.affiliation: The Bionics Institute of Australia , Melbourne, VIC , Australia ; Speech Neuroscience Unit, The University of Melbourne , Melbourne, VIC , Australia ; Department of Neurodegeneration, Hertie Institute for Clinical Brain Research, University of Tübingen , Tübingen , Germany ; Department of Audiology and Speech Pathology, The University of Melbourne , Melbourne, VIC , Australia.
authors.forename: Adam P
authors.initials: AP
authors.lastname: Vogel
authors.affiliation: The Bionics Institute of Australia , Melbourne, VIC , Australia ; Department of Medical Bionics, The University of Melbourne , Melbourne, VIC , Australia.
authors.forename: Hugh J
authors.initials: HJ
authors.lastname: McDermott
authors.affiliation: The Bionics Institute of Australia , Melbourne, VIC , Australia ; Department of Medical Bionics, The University of Melbourne , Melbourne, VIC , Australia.
authors.forename: Thushara
authors.initials: T
authors.lastname: Perera
authors.affiliation: Department of Neurology, St Vincent's Hospital , Melbourne, VIC , Australia.
authors.forename: Mary
authors.initials: M
authors.lastname: Jones
authors.affiliation: Department of Neurology, St Vincent's Hospital , Melbourne, VIC , Australia.
authors.forename: Richard
authors.initials: R
authors.lastname: Peppard
authors.affiliation: The Bionics Institute of Australia , Melbourne, VIC , Australia ; Department of Medical Bionics, The University of Melbourne , Melbourne, VIC , Australia.
authors.forename: Colette M
authors.initials: CM
authors.lastname: McKay
keywords: acoustic analysis; brain stimulation; dysarthria; optimization; side effects; speech