title: Effects of contact location and voltage amplitude on speech and movement in bilateral subthalamic nucleus deep brain stimulation.
abstract: Subthalamic nucleus deep brain stimulation (STN-DBS) is particularly effective in improving limb symptoms in Parkinson's disease. However, speech shows a variable response. Contact site and amplitude of stimulation have been suggested as possible factors influencing speech. In this double blind study, we assessed 14 patients post bilateral STN-DBS, without medication. Six conditions were studied in random order as follows: stimulation inside the STN at low voltage (2 V) and at high voltage (4 V); above the STN at 2 V and at 4 V, at usual clinical parameters, and off-stimulation. The site of stimulation was defined on the postoperative stereotactic MRI data. Speech protocol consisted of the assessment of intelligibility of the dysarthric speech, maximum sustained phonation, and a 1-minute monologue. Movement was assessed using the UPDRS-III. Stimulation at 4 V significantly reduced the speech intelligibility (P = 0.004) independently from the site of stimulation. Stimulation at 4 V significantly improved the motor function. Stimulation inside the nucleus was significantly more effective than outside the nucleus (P = 0.0006). The significant improvement in movement coupled with significant deterioration in speech intelligibility when patients are stimulated inside the nucleus at high voltage indicates a critical role for electrical stimulation parameters in speech motor control.
authors.affiliation: Unit of Functional Neurosurgery, Sobell Department, Institute of Neurology, London, United Kingdom. e.tripoliti@ion.ucl.ac.uk
authors.forename: Elina
authors.initials: E
authors.lastname: Tripoliti
authors.forename: Ludvic
authors.initials: L
authors.lastname: Zrinzo
authors.forename: Irene
authors.initials: I
authors.lastname: Martinez-Torres
authors.forename: Stephen
authors.initials: S
authors.lastname: Tisch
authors.forename: Eleanor
authors.initials: E
authors.lastname: Frost
authors.forename: Ellie
authors.initials: E
authors.lastname: Borrell
authors.forename: Marwan I
authors.initials: MI
authors.lastname: Hariz
authors.forename: Patricia
authors.initials: P
authors.lastname: Limousin
mesh_terms: D000162:Acoustics; D000368:Aged; D000704:Analysis of Variance; D000911:Antibodies, Monoclonal; D000077552:Basiliximab; D055592:Biophysical Phenomena; D046690:Deep Brain Stimulation / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D009460:Neurologic Examination; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000503:physiopathology* / Q000628:therapy; D011993:Recombinant Fusion Proteins; D012720:Severity of Illness Index; D013060:Speech / Q000502:physiology*; D020531:Subthalamic Nucleus / Q000502:physiology*
chemical_list: D000911:Antibodies, Monoclonal; D011993:Recombinant Fusion Proteins; D000077552:Basiliximab