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Effects of Reimplantation

Mathieu Anheim, MD; Alina Batir, MD; Valérie Fraix, MD; Madjid Silem, MD; Stéphan Chabardès, MD; Eric Seigneuret, MD; Paul Krack, MD; Alim-Louis Benabid, MD, PhD; Pierre Pollak, MD

Arch Neurol. 2008;65(5):612-616.

Background  The misplacement of electrodes is a possible explanation for suboptimal response to bilateral subthalamic nucleus (STN) stimulation in patients with Parkinson disease.

Objective  To evaluate whether reimplantation of electrodes in the STN can produce improvement in patients with poor results from surgery and with suspected electrode misplacement based on imaging findings.

Design  Prospective follow-up study.

Setting  Academic research.

Patients  A 1-year postoperative study was undertaken in 7 consecutive patients with Parkinson disease who, despite bilateral STN stimulation, experienced persistent motor disability and who were operated on for reimplantation a median of 16.9 months later.

Main Outcome Measures  The primary outcome was measured as the change in the Unified Parkinson Disease Rating Scale (UPDRS) motor score 1 year after reimplantation. The secondary outcome was measured as the extent of pharmacologic and electrical treatments required and the threshold at which the first stimulation-induced adverse effect appeared. The distances between the electrode contacts used for chronic stimulation and the STN theoretical effective target, defined as the mean position of the clinically efficient contact from 193 previously implanted electrodes, were compared.

Results  Except for a single patient, all patients displayed improvement following reimplantation. Under off-medication (ie, the patient is taking no medication) condition, STN stimulation improved the basal state UPDRS motor score by 26.7% before reimplantation and by 59.4% at 1 year after reimplantation. The median off-medication Schwab and England score improved from 51% to 76%. The median levodopa equivalent daily dose was reduced from 1202 mg to 534 mg. The stimulation varibles changed from a mean of 2.6 V/73.0 µs/163.0 Hz to 2.8 V/60. 0 µs/ 140.0 Hz. The mean threshold of the first stimulation-induced adverse effect increased from 2.6 to 4.4 V. The mean distance between the contacts used for chronic stimulation and the theoretical effective target decreased from 5.4 to 2.0 mm. This distance correlated inversely with the percentage improvement in theUPDRS motor score.

Conclusion  Patients demonstrating poor response to STN stimulation as a result of electrode misplacement can benefit from reimplantation in the STN closer to the theoretical target.

Author Affiliations: Departments of Neurology (Drs Anheim, Batir, Fraix, Silem, Krack, and Pollak) and Neurosurgery (Drs Chabardès, Seigneuret, and Benabid), University Hospital A. Michallon, and Department of Clinical and Biologic Neurosciences, Joseph Fourier University, and Institut National de la Santé et de la Récherche Médicale Unité 318 (Drs Fraix, Chabardès, Seigneuret, Krack, Benabid, and Pollak), Grenoble; and Department of Neurology, University Hospital, Strasbourg (Dr Anheim), France.

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