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This Article Full Text Full Text (PDF) All Versions of this Article: jnnp.2007.117507v1 79/7/813    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this link to a friend Similar articles in this journal Similar articles in PubMed Add article to my folders Download to citation manager Request Permissions Google Scholar Articles by Tommasi, G Articles by Pollak, P PubMed PubMed Citation Articles by Tommasi, G Articles by Pollak, P

Pyramidal tract side effects induced by deep brain stimulation of the subthalamic nucleus

¹ Department of Neurology, University Hospital, Joseph Fourier University, Grenoble, France
² INSERM U318, Joseph Fourier University, Grenoble, France
³ Magnetic Resonance Imaging Unit, University Hospital, Joseph Fourier University, Grenoble, France
⁴ Department of Neurosurgery, University Hospital, Joseph Fourier University, Grenoble, France

Correspondence to:
Dr P Pollak, Department of Neurology, University of Grenoble, 38043 Grenoble, Cedex 9, France; pierre.pollak{at}ujf-grenoble.fr

Methods: 14 patients bilaterally implanted with tetrapolar electrodes were assessed. For each side separately, the threshold of adverse effects induced by monopolar stimulation delivered by the chronically used contact was detected. The voltage was progressively increased until the patient experienced discomfort. All the PTSEs induced at 130 Hz (high-frequency stimulation (HFS)) and 2 or 3 Hz (low-frequency stimulation (LFS)) were videotaped. By superimposing the preoperative and postoperative MR images, the minimum distance (R) from the centre of the used contact to the medial border of the PT were measured.

Results: The progressive increase in voltage at HFS induced tonic motor contractions, mainly located in the face, in 27/28 electrodes. LFS induced synchronous rhythmic myoclonus in the same territory. PTSEs induced at threshold voltage by HFS were observed in the upper face at 13/28 electrodes (bilaterally in six cases) and in the contralateral lower face at five electrodes. A positive correlation was found between the stimulus intensity capable of eliciting motor contractions at HFS and R.

Conclusions: HFS of the STN preferentially activates the corticobulbar tract over the corticospinal tract. Therefore, cranial motor contractions need to be looked for during electrical parameter setting. The positive correlation between the electrical intensity threshold for PTSEs and R reflects the need for millimetre accuracy in electrode positioning.