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Vol. 88, No. 4, 2010
Issue release date: July 2010
Free Access
Stereotact Funct Neurosurg 2010;88:224–233
(DOI:10.1159/000314357)

Patient-Specific Model-Based Investigation of Speech Intelligibility and Movement during Deep Brain Stimulation

Åström M.a · Tripoliti E.c · Hariz M.I.b, c · Zrinzo L.U.c · Martinez-Torres I.c · Limousin P.c · Wårdell K.a
aDepartment of Biomedical Engineering, Linköping University, Linköping, and bDepartment of Neurosurgery, University Hospital, Umeå, Sweden; cInstitute of Neurology, University College, London, UK
email Corresponding Author

Abstract

Background/Aims: Deep brain stimulation (DBS) is widely used to treat motor symptoms in patients with advanced Parkinson’s disease. The aim of this study was to investigate the anatomical aspects of the electric field in relation to effects on speech and movement during DBS in the subthalamic nucleus. Methods: Patient-specific finite element models of DBS were developed for simulation of the electric field in 10 patients. In each patient, speech intelligibility and movement were assessed during 2 electrical settings, i.e. 4 V (high) and 2 V (low). The electric field was simulated for each electrical setting. Results: Movement was improved in all patients for both high and low electrical settings. In general, high-amplitude stimulation was more consistent in improving the motor scores than low-amplitude stimulation. In 6 cases, speech intelligibility was impaired during high-amplitude electrical settings. Stimulation of part of the fasciculus cerebellothalamicus from electrodes positioned medial and/or posterior to the center of the subthalamic nucleus was recognized as a possible cause of the stimulation-induced dysarthria. Conclusion: Special attention to stimulation-induced speech impairments should be taken in cases when active electrodes are positioned medial and/or posterior to the center of the subthalamic nucleus.


 goto top of outline Key Words

  • Deep brain stimulation
  • Dysarthria
  • Speech intelligibility
  • Parkinson’s disease
  • Electric field
  • Fasciculus cerebellothalamicus

 goto top of outline Abstract

Background/Aims: Deep brain stimulation (DBS) is widely used to treat motor symptoms in patients with advanced Parkinson’s disease. The aim of this study was to investigate the anatomical aspects of the electric field in relation to effects on speech and movement during DBS in the subthalamic nucleus. Methods: Patient-specific finite element models of DBS were developed for simulation of the electric field in 10 patients. In each patient, speech intelligibility and movement were assessed during 2 electrical settings, i.e. 4 V (high) and 2 V (low). The electric field was simulated for each electrical setting. Results: Movement was improved in all patients for both high and low electrical settings. In general, high-amplitude stimulation was more consistent in improving the motor scores than low-amplitude stimulation. In 6 cases, speech intelligibility was impaired during high-amplitude electrical settings. Stimulation of part of the fasciculus cerebellothalamicus from electrodes positioned medial and/or posterior to the center of the subthalamic nucleus was recognized as a possible cause of the stimulation-induced dysarthria. Conclusion: Special attention to stimulation-induced speech impairments should be taken in cases when active electrodes are positioned medial and/or posterior to the center of the subthalamic nucleus.

Copyright © 2010 S. Karger AG, Basel


 goto top of outline References
  1. Limousin P, Krack P, Pollak P, Benazzouz A, Ardouin C, Hoffmann D, Benabid AL: Electrical stimulation of the subthalamic nucleus in advanced Parkinson’s disease. N Engl J Med 1998;339:1105–1111.
  2. Krack P, Batir A, Van Blercom N, Chabardes S, Fraix V, Ardouin C, Koudsie A, Limousin PD, Benazzouz A, LeBas JF, Benabid AL, Pollak P: Five-year follow-up of bilateral stimulation of the subthalamic nucleus in advanced Parkinson’s disease. N Engl J Med 2003;349:1925–1934.
  3. Moro E, Scerrati M, Romito LM, Roselli R, Tonali P, Albanese A: Chronic subthalamic nucleus stimulation reduces medication requirements in Parkinson’s disease. Neurology 1999;53:85–90.
  4. Schulz GM, Grant MK: Effects of speech therapy and pharmacologic and surgical treatments on voice and speech in Parkinson’s disease: a review of the literature. J Commun Disord 2000;33:59–88.
  5. Ramig LO, Dromey C: Aerodynamic mechanisms underlying treatment-related changes in vocal intensity in patients with Parkinson disease. J Speech Hear Res 1996;39:798–807.
  6. Ho AK, Iansek R, Marigliani C, Bradshaw JL, Gates S: Speech impairment in a large sample of patients with Parkinson’s disease. Behav Neurol 1998;11:131–137.
  7. Logemann JA, Fisher HB, Boshes B, Blonsky ER: Frequency and cooccurrence of vocal tract dysfunctions in the speech of a large sample of Parkinson patients. J Speech Hear Disord 1978;43:47–57.
  8. Darley FL, Aronson AE, Brown JR: Clusters of deviant speech dimensions in the dysarthrias. J Speech Hear Res 1969;12:462–496.
  9. Darley FL, Aronson AE, Brown JR: Differential diagnostic patterns of dysarthria. J Speech Hear Res 1969;12:246–269.
  10. Rousseaux M, Krystkowiak P, Kozlowski O, Ozsancak C, Blond S, Destee A: Effects of subthalamic nucleus stimulation on parkinsonian dysarthria and speech intelligibility. J Neurol 2004;251:327–334.
  11. Romito LM, Scerrati M, Contarino MF, Iacoangeli M, Bentivoglio AR, Albanese A: Bilateral high frequency subthalamic stimulation in Parkinson’s disease: long-term neurological follow-up. J Neurosurg Sci 2003;47:119–128.
  12. Rodriguez-Oroz MC, Obeso JA, Lang AE, Houeto JL, Pollak P, Rehncrona S, Kulisevsky J, Albanese A, Volkmann J, Hariz MI, Quinn NP, Speelman JD, Guridi J, Zamarbide I, Gironell A, Molet J, Pascual-Sedano B, Pidoux B, Bonnet AM, Agid Y, Xie J, Benabid AL, Lozano AM, Saint-Cyr J, Romito L, Contarino MF, Scerrati M, Fraix V, Van Blercom N: Bilateral deep brain stimulation in Parkinson’s disease: a multicentre study with 4 years follow-up. Brain 2005;128:2240–2249.
  13. Törnqvist AL, Schalen L, Rehncrona S: Effects of different electrical parameter settings on the intelligibility of speech in patients with Parkinson’s disease treated with subthalamic deep brain stimulation. Mov Disord 2005;20:416–423.
  14. Guehl D, Cuny E, Benazzouz A, Rougier A, Tison F, Machado S, Grabot D, Gross C, Bioulac B, Burbaud P: Side-effects of subthalamic stimulation in Parkinson’s disease: clinical evolution and predictive factors. Eur J Neurol 2006;13:963–971.
  15. Klostermann F, Ehlen F, Vesper J, Nubel K, Gross M, Marzinzik F, Curio G, Sappok T: Effects of subthalamic deep brain stimulation on dysarthrophonia in Parkinson’s disease. J Neurol Neurosurg Psychiatry 2008;79:522–529.
  16. Piboolnurak P, Lang AE, Lozano AM, Miyasaki JM, Saint-Cyr JA, Poon YY, Hutchison WD, Dostrovsky JO, Moro E: Levodopa response in long-term bilateral subthalamic stimulation for Parkinson’s disease. Mov Disord 2007;22:990–997.
  17. Farrell A, Theodoros D, Ward E, Hall B, Silburn P: Effects of neurosurgical management of Parkinson’s disease on speech characteristics and oromotor function. J Speech Lang Hear Res 2005;48:5–20.
  18. D’Alatri L, Paludetti G, Contarino MF, Galla S, Marchese MR, Bentivoglio AR: Effects of bilateral subthalamic nucleus stimulation and medication on parkinsonian speech impairment. J Voice 2008;22:365–372.
  19. Gentil M, Pinto S, Pollak P, Benabid AL: Effect of bilateral stimulation of the subthalamic nucleus on parkinsonian dysarthria. Brain Lang 2003;85:190–196.
  20. Pinto S, Gentil M, Fraix V, Benabid AL, Pollak P: Bilateral subthalamic stimulation effects on oral force control in Parkinson’s disease. J Neurol 2003;250:179–187.
  21. Dromey C, Kumar R, Lang AE, Lozano AM: An investigation of the effects of subthalamic nucleus stimulation on acoustic measures of voice. Mov Disord 2000;15:1132–1138.
  22. Gentil M, Garcia-Ruiz P, Pollak P, Benabid AL: Effect of stimulation of the subthalamic nucleus on oral control of patients with parkinsonism. J Neurol Neurosurg Psychiatry 1999;67:329–333.
  23. Tripoliti E, Zrinzo L, Martinez-Torres I, Tisch S, Frost E, Borrell E, Hariz MI, Limousin P: Effects of contact location and voltage amplitude on speech and movement in bilateral subthalamic nucleus deep brain stimulation. Mov Disord 2008;23:2377–2383.
  24. Åstrom M, Zrinzo LU, Tisch S, Tripoliti E, Hariz MI, Wårdell K: Method for patient-specific finite element modeling and simulation of deep brain stimulation. Med Biol Eng Comput 2009;47:21–28.
  25. Hariz MI, Krack P, Melvill R, Jorgensen JV, Hamel W, Hirabayashi H, Lenders M, Wesslen N, Tengvar M, Yousry TA: A quick and universal method for stereotactic visualization of the subthalamic nucleus before and after implantation of deep brain stimulation electrodes. Stereotact Funct Neurosurg 2003;80:96–101.
  26. Yorkston KM, Beukelman DR: Communication efficiency of dysarthric speakers as measured by sentence intelligibility and speaking rate. J Speech Hear Disord 1981;46:296–301.
  27. Andreuccetti D, Fossi R, Petrucci C: Dielectric properties of body tissue. Italian National Research Council, Institute for Applied Physics, Florence, Italy. 2005. http://niremf.ifac.cnr.it/tissprop/.
  28. Åström M, Zrinzo LU, Tisch S, Tripoliti E, Hariz MI, Wårdell K: Method for patient-specific finite element modeling and simulation of deep brain stimulation. Med Biol Eng Comput 2009;47:21–28.
  29. Butson CR, McIntyre CC: Differences among implanted pulse generator waveforms cause variations in the neural response to deep brain stimulation. Clin Neurophysiol 2007;118:1889–1894.
  30. Cheng DK: Field and Wave Electromagnetics. Reading, Addison-Wesley Publishing Company Inc, 1989.
  31. Gallay MN, Jeanmonod D, Liu J, Morel A: Human pallidothalamic and cerebellothalamic tracts: anatomical basis for functional stereotactic neurosurgery. Brain Struct Funct 2008;212:443–463.
  32. Morel A: Stereotactic Atlas of the Human Thalamus and Basal Ganglia. New York, Informa Healthcare, 2007.
  33. Krack P, Fraix V, Mendes A, Benabid AL, Pollak P: Postoperative management of subthalamic nucleus stimulation for Parkinson’s disease. Mov Disord 2002;17(suppl 3):S188–S197.
  34. Pinto S, Gentil M, Krack P, Sauleau P, Fraix V, Benabid AL, Pollak P: Changes induced by levodopa and subthalamic nucleus stimulation on parkinsonian speech. Mov Disord 2005;20:1507–1515.
  35. Deuschl G, Herzog J, Kleiner-Fisman G, Kubu C, Lozano AM, Lyons KE, Rodriguez-Oroz MC, Tamma F, Troster AI, Vitek JL, Volkmann J, Voon V: Deep brain stimulation: postoperative issues. Mov Disord 2006;21(suppl 14):S219–S237.
  36. Tripoliti E, Limousin P, Tisch S, Borrell E, Hariz M: Speech in Parkinson’s disease following subthalamic nucleus deep brain stimulation: preliminary results. J Med Speech Lang Pathol 2006;14:309–315.

    External Resources

  37. Plaha P, Ben-Shlomo Y, Patel NK, Gill SS: Stimulation of the caudal zona incerta is superior to stimulation of the subthalamic nucleus in improving contralateral parkinsonism. Brain 2006;129:1732–1747.
  38. Velasco F, Jimenez F, Perez ML, Carrillo-Ruiz JD, Velasco AL, Ceballos J, Velasco M: Electrical stimulation of the prelemniscal radiation in the treatment of Parkinson’s disease: an old target revised with new techniques. Neurosurgery 2001;49:293–306.
  39. Santens P, De Letter M, Van Borsel J, De Reuck J, Caemaert J: Lateralized effects of subthalamic nucleus stimulation on different aspects of speech in Parkinson’s disease. Brain Lang 2003;87:253–258.
  40. Wang E, Verhagen Metman L, Bakay R, Arzbaecher J, Bernard B: The effect of unilateral electrostimulation of the subthalamic nucleus on respiratory/phonatory subsystems of speech production in Parkinson’s disease – A preliminary report. Clin Linguist Phon 2003;17:283–289.
  41. Wang EQ, Metman LV, Bakay RA, Arzbaecher J, Bernard B, Corcos DM: Hemisphere-specific effects of subthalamic nucleus deep brain stimulation on speaking rate and articulatory accuracy of syllable repetitions in Parkinson’s disease. J Med Speech Lang Pathol 2006;14:323–334.

 goto top of outline Author Contacts

Mattias Åström, MSc
Department of Biomedical Engineering
Linköping University
SE–58185 Linköping (Sweden)
Tel. +46 736 290 978, E-Mail matas@imt.liu.se


 goto top of outline Article Information

Conflict of Interest: Marwan Hariz and Ludvic Zrinzo occasionally received travel expenses from Medtronic to lecture at meetings.

Received: October 1, 2009
Accepted after revision: March 4, 2010
Published online: May 12, 2010
Number of Print Pages : 10
Number of Figures : 5, Number of Tables : 2, Number of References : 41


 goto top of outline Publication Details

Stereotactic and Functional Neurosurgery

Vol. 88, No. 4, Year 2010 (Cover Date: July 2010)

Journal Editor: Roberts D.W. (Lebanon, N.H.)
ISSN: 1011-6125 (Print), eISSN: 1423-0372 (Online)

For additional information: http://www.karger.com/SFN


Copyright / Drug Dosage / Disclaimer

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in goverment regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

Abstract

Background/Aims: Deep brain stimulation (DBS) is widely used to treat motor symptoms in patients with advanced Parkinson’s disease. The aim of this study was to investigate the anatomical aspects of the electric field in relation to effects on speech and movement during DBS in the subthalamic nucleus. Methods: Patient-specific finite element models of DBS were developed for simulation of the electric field in 10 patients. In each patient, speech intelligibility and movement were assessed during 2 electrical settings, i.e. 4 V (high) and 2 V (low). The electric field was simulated for each electrical setting. Results: Movement was improved in all patients for both high and low electrical settings. In general, high-amplitude stimulation was more consistent in improving the motor scores than low-amplitude stimulation. In 6 cases, speech intelligibility was impaired during high-amplitude electrical settings. Stimulation of part of the fasciculus cerebellothalamicus from electrodes positioned medial and/or posterior to the center of the subthalamic nucleus was recognized as a possible cause of the stimulation-induced dysarthria. Conclusion: Special attention to stimulation-induced speech impairments should be taken in cases when active electrodes are positioned medial and/or posterior to the center of the subthalamic nucleus.



 goto top of outline Author Contacts

Mattias Åström, MSc
Department of Biomedical Engineering
Linköping University
SE–58185 Linköping (Sweden)
Tel. +46 736 290 978, E-Mail matas@imt.liu.se


 goto top of outline Article Information

Conflict of Interest: Marwan Hariz and Ludvic Zrinzo occasionally received travel expenses from Medtronic to lecture at meetings.

Received: October 1, 2009
Accepted after revision: March 4, 2010
Published online: May 12, 2010
Number of Print Pages : 10
Number of Figures : 5, Number of Tables : 2, Number of References : 41


 goto top of outline Publication Details

Stereotactic and Functional Neurosurgery

Vol. 88, No. 4, Year 2010 (Cover Date: July 2010)

Journal Editor: Roberts D.W. (Lebanon, N.H.)
ISSN: 1011-6125 (Print), eISSN: 1423-0372 (Online)

For additional information: http://www.karger.com/SFN


Copyright / Drug Dosage

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in goverment regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

References

  1. Limousin P, Krack P, Pollak P, Benazzouz A, Ardouin C, Hoffmann D, Benabid AL: Electrical stimulation of the subthalamic nucleus in advanced Parkinson’s disease. N Engl J Med 1998;339:1105–1111.
  2. Krack P, Batir A, Van Blercom N, Chabardes S, Fraix V, Ardouin C, Koudsie A, Limousin PD, Benazzouz A, LeBas JF, Benabid AL, Pollak P: Five-year follow-up of bilateral stimulation of the subthalamic nucleus in advanced Parkinson’s disease. N Engl J Med 2003;349:1925–1934.
  3. Moro E, Scerrati M, Romito LM, Roselli R, Tonali P, Albanese A: Chronic subthalamic nucleus stimulation reduces medication requirements in Parkinson’s disease. Neurology 1999;53:85–90.
  4. Schulz GM, Grant MK: Effects of speech therapy and pharmacologic and surgical treatments on voice and speech in Parkinson’s disease: a review of the literature. J Commun Disord 2000;33:59–88.
  5. Ramig LO, Dromey C: Aerodynamic mechanisms underlying treatment-related changes in vocal intensity in patients with Parkinson disease. J Speech Hear Res 1996;39:798–807.
  6. Ho AK, Iansek R, Marigliani C, Bradshaw JL, Gates S: Speech impairment in a large sample of patients with Parkinson’s disease. Behav Neurol 1998;11:131–137.
  7. Logemann JA, Fisher HB, Boshes B, Blonsky ER: Frequency and cooccurrence of vocal tract dysfunctions in the speech of a large sample of Parkinson patients. J Speech Hear Disord 1978;43:47–57.
  8. Darley FL, Aronson AE, Brown JR: Clusters of deviant speech dimensions in the dysarthrias. J Speech Hear Res 1969;12:462–496.
  9. Darley FL, Aronson AE, Brown JR: Differential diagnostic patterns of dysarthria. J Speech Hear Res 1969;12:246–269.
  10. Rousseaux M, Krystkowiak P, Kozlowski O, Ozsancak C, Blond S, Destee A: Effects of subthalamic nucleus stimulation on parkinsonian dysarthria and speech intelligibility. J Neurol 2004;251:327–334.
  11. Romito LM, Scerrati M, Contarino MF, Iacoangeli M, Bentivoglio AR, Albanese A: Bilateral high frequency subthalamic stimulation in Parkinson’s disease: long-term neurological follow-up. J Neurosurg Sci 2003;47:119–128.
  12. Rodriguez-Oroz MC, Obeso JA, Lang AE, Houeto JL, Pollak P, Rehncrona S, Kulisevsky J, Albanese A, Volkmann J, Hariz MI, Quinn NP, Speelman JD, Guridi J, Zamarbide I, Gironell A, Molet J, Pascual-Sedano B, Pidoux B, Bonnet AM, Agid Y, Xie J, Benabid AL, Lozano AM, Saint-Cyr J, Romito L, Contarino MF, Scerrati M, Fraix V, Van Blercom N: Bilateral deep brain stimulation in Parkinson’s disease: a multicentre study with 4 years follow-up. Brain 2005;128:2240–2249.
  13. Törnqvist AL, Schalen L, Rehncrona S: Effects of different electrical parameter settings on the intelligibility of speech in patients with Parkinson’s disease treated with subthalamic deep brain stimulation. Mov Disord 2005;20:416–423.
  14. Guehl D, Cuny E, Benazzouz A, Rougier A, Tison F, Machado S, Grabot D, Gross C, Bioulac B, Burbaud P: Side-effects of subthalamic stimulation in Parkinson’s disease: clinical evolution and predictive factors. Eur J Neurol 2006;13:963–971.
  15. Klostermann F, Ehlen F, Vesper J, Nubel K, Gross M, Marzinzik F, Curio G, Sappok T: Effects of subthalamic deep brain stimulation on dysarthrophonia in Parkinson’s disease. J Neurol Neurosurg Psychiatry 2008;79:522–529.
  16. Piboolnurak P, Lang AE, Lozano AM, Miyasaki JM, Saint-Cyr JA, Poon YY, Hutchison WD, Dostrovsky JO, Moro E: Levodopa response in long-term bilateral subthalamic stimulation for Parkinson’s disease. Mov Disord 2007;22:990–997.
  17. Farrell A, Theodoros D, Ward E, Hall B, Silburn P: Effects of neurosurgical management of Parkinson’s disease on speech characteristics and oromotor function. J Speech Lang Hear Res 2005;48:5–20.
  18. D’Alatri L, Paludetti G, Contarino MF, Galla S, Marchese MR, Bentivoglio AR: Effects of bilateral subthalamic nucleus stimulation and medication on parkinsonian speech impairment. J Voice 2008;22:365–372.
  19. Gentil M, Pinto S, Pollak P, Benabid AL: Effect of bilateral stimulation of the subthalamic nucleus on parkinsonian dysarthria. Brain Lang 2003;85:190–196.
  20. Pinto S, Gentil M, Fraix V, Benabid AL, Pollak P: Bilateral subthalamic stimulation effects on oral force control in Parkinson’s disease. J Neurol 2003;250:179–187.
  21. Dromey C, Kumar R, Lang AE, Lozano AM: An investigation of the effects of subthalamic nucleus stimulation on acoustic measures of voice. Mov Disord 2000;15:1132–1138.
  22. Gentil M, Garcia-Ruiz P, Pollak P, Benabid AL: Effect of stimulation of the subthalamic nucleus on oral control of patients with parkinsonism. J Neurol Neurosurg Psychiatry 1999;67:329–333.
  23. Tripoliti E, Zrinzo L, Martinez-Torres I, Tisch S, Frost E, Borrell E, Hariz MI, Limousin P: Effects of contact location and voltage amplitude on speech and movement in bilateral subthalamic nucleus deep brain stimulation. Mov Disord 2008;23:2377–2383.
  24. Åstrom M, Zrinzo LU, Tisch S, Tripoliti E, Hariz MI, Wårdell K: Method for patient-specific finite element modeling and simulation of deep brain stimulation. Med Biol Eng Comput 2009;47:21–28.
  25. Hariz MI, Krack P, Melvill R, Jorgensen JV, Hamel W, Hirabayashi H, Lenders M, Wesslen N, Tengvar M, Yousry TA: A quick and universal method for stereotactic visualization of the subthalamic nucleus before and after implantation of deep brain stimulation electrodes. Stereotact Funct Neurosurg 2003;80:96–101.
  26. Yorkston KM, Beukelman DR: Communication efficiency of dysarthric speakers as measured by sentence intelligibility and speaking rate. J Speech Hear Disord 1981;46:296–301.
  27. Andreuccetti D, Fossi R, Petrucci C: Dielectric properties of body tissue. Italian National Research Council, Institute for Applied Physics, Florence, Italy. 2005. http://niremf.ifac.cnr.it/tissprop/.
  28. Åström M, Zrinzo LU, Tisch S, Tripoliti E, Hariz MI, Wårdell K: Method for patient-specific finite element modeling and simulation of deep brain stimulation. Med Biol Eng Comput 2009;47:21–28.
  29. Butson CR, McIntyre CC: Differences among implanted pulse generator waveforms cause variations in the neural response to deep brain stimulation. Clin Neurophysiol 2007;118:1889–1894.
  30. Cheng DK: Field and Wave Electromagnetics. Reading, Addison-Wesley Publishing Company Inc, 1989.
  31. Gallay MN, Jeanmonod D, Liu J, Morel A: Human pallidothalamic and cerebellothalamic tracts: anatomical basis for functional stereotactic neurosurgery. Brain Struct Funct 2008;212:443–463.
  32. Morel A: Stereotactic Atlas of the Human Thalamus and Basal Ganglia. New York, Informa Healthcare, 2007.
  33. Krack P, Fraix V, Mendes A, Benabid AL, Pollak P: Postoperative management of subthalamic nucleus stimulation for Parkinson’s disease. Mov Disord 2002;17(suppl 3):S188–S197.
  34. Pinto S, Gentil M, Krack P, Sauleau P, Fraix V, Benabid AL, Pollak P: Changes induced by levodopa and subthalamic nucleus stimulation on parkinsonian speech. Mov Disord 2005;20:1507–1515.
  35. Deuschl G, Herzog J, Kleiner-Fisman G, Kubu C, Lozano AM, Lyons KE, Rodriguez-Oroz MC, Tamma F, Troster AI, Vitek JL, Volkmann J, Voon V: Deep brain stimulation: postoperative issues. Mov Disord 2006;21(suppl 14):S219–S237.
  36. Tripoliti E, Limousin P, Tisch S, Borrell E, Hariz M: Speech in Parkinson’s disease following subthalamic nucleus deep brain stimulation: preliminary results. J Med Speech Lang Pathol 2006;14:309–315.

    External Resources

  37. Plaha P, Ben-Shlomo Y, Patel NK, Gill SS: Stimulation of the caudal zona incerta is superior to stimulation of the subthalamic nucleus in improving contralateral parkinsonism. Brain 2006;129:1732–1747.
  38. Velasco F, Jimenez F, Perez ML, Carrillo-Ruiz JD, Velasco AL, Ceballos J, Velasco M: Electrical stimulation of the prelemniscal radiation in the treatment of Parkinson’s disease: an old target revised with new techniques. Neurosurgery 2001;49:293–306.
  39. Santens P, De Letter M, Van Borsel J, De Reuck J, Caemaert J: Lateralized effects of subthalamic nucleus stimulation on different aspects of speech in Parkinson’s disease. Brain Lang 2003;87:253–258.
  40. Wang E, Verhagen Metman L, Bakay R, Arzbaecher J, Bernard B: The effect of unilateral electrostimulation of the subthalamic nucleus on respiratory/phonatory subsystems of speech production in Parkinson’s disease – A preliminary report. Clin Linguist Phon 2003;17:283–289.
  41. Wang EQ, Metman LV, Bakay RA, Arzbaecher J, Bernard B, Corcos DM: Hemisphere-specific effects of subthalamic nucleus deep brain stimulation on speaking rate and articulatory accuracy of syllable repetitions in Parkinson’s disease. J Med Speech Lang Pathol 2006;14:323–334.