Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 59, Num. 5, 2011, pp. 669-673

Neurology India, Vol. 59, No. 5, September-October, 2011, pp. 669-673

Original Article

Pilot study on a fast postoperative programming approach to subthalamic nucleus stimulation in Parkinson's disease

Peng Li¹, Boyong Mao¹, Huifang Shang², Alain Kaelin-Lang³, Wei Wang¹

¹ Department of Neurosurgery, West China Hospital of Sichuan University, Chengdu, Sichuan Province, China
² Department of Neurology, West China Hospital of Sichuan University, Chengdu, Sichuan Province, China
³ Department of Neurology, Inselsptial, Bern University, Bern, Switzerland
Correspondence Address: Wei Wang, Department of Neurosurgery, West China Hospital of Sichuan University, 610041 Chengdu, Sichuan Province, China, wcnslp@163.com

Date of Submission: 01-Jun-2011
Date of Decision: 29-Jun-2011
Date of Acceptance: 26-Jul-2011

Code Number: ni11208

PMID: 22019648

DOI: 10.4103/0028-3886.86538

Abstract

Keywords: Deep brain stimulation, Parkinson's disease, subthalamic nucleus

Introduction

Deep brain stimulation (DBS) is currently a standard surgical treatment for patients with advanced Parkinson's disease (PD). ^[1],[2],[3] Aside from accurately placed electrodes, an optimal outcome from DBS critically depends on the quality of postoperative management. ^[4],[5],[6] However, postoperative programming is both complex and time consuming because of the mass combinations of pulse width, frequency and voltage within the recommended charge density limitation. ^[7] To date, there are no adequate prospective studies comparing the best time points and methods for initial DBS programming. To optimize programming efficiency in the early postoperative phase, a standardized fast postoperative programming protocol was developed in order to rapidly identify the best parameters for each patient. To the best of our knowledge, this work is the first to use and test a fast standardized screening method in the early postoperative phase to shorten the time needed for programming. This protocol is described along with the results of a preliminary study in a cohort of PD patients.

Materials and Methods

Between 2009 and 2010, 12 patients with idiopathic PD who underwent implantation of electrodes for subthalamic nucleus (STN) DBS were subjected to the standardized fast-screening programming method at our center (Group II). Serving as the control group (Group I) was 12 patients treated with traditional programming method during the same study period. The criteria for undergoing DBS included : d0 isease duration more than 5 years, age less 75 years, significant disabling dyskinesia and motor fluctuation or serious side effect with medication, more than 30% reduction of Unified Parkinson's Disease Rating Scale III (UPDRS) motor score with a challenge dose of Madopar, request for operation by the patients, and H-Y scale less than stage V. The implanted leads were Model 3389 (Medtronic, Minneapolis, MN), and the pulse generators were Kinetra (Medtronic) for bilateral implantation and Soletra (Medtronic) for unilateral implantation. The characteristics of the patients in each group are detailed in [Table - 1].

Programming for all the 24 patients was carried out by the same certified physician at least 12 hours after the last medication for PD had been taken. Motor scores on the UPDRS were assessed by an independent physician for all the patients before programming with medication and stimulation "off."

Patients in Group I were treated with the traditional programming protocol [Figure - 1] introduced by Volkmann, ^[8] whereas patients in Group II were treated with the fast programming approach [Figure - 2]. In the fast programming protocol, the initial parameters were set to monopolar, 60 ms, and 130 Hz. The voltage was slowly increased to 2.0 V using the autoincrease function of the programmer (Model 8840, Medtronic). Starting with the lowest contact of the electrode, the four contacts were tested with the same parameters to analyze the beneficial effects (improvement of rigidity, tremor and the limbs motor ability) and side effects of each contact. Then different effects of the four contacts were compared, and the best contact was determined. The voltage was adjusted to obtain the best effect without inducing side effects using the best contact. The contact screening method for the contralateral side was the same as for the ipsilateral side. In those patients who showed serious side effects, either the voltage was decreased, or the bipolar stimulation mode was chosen.

UPDRS motor score with medication "off" and stimulation "on" was assessed when the stimulation parameters were set for all the 24 patients. The time needed for programming was measured from the beginning of programming to the end when the last parameters were set. The results are presented as means ± SD. The change in UPDRS scores with stimulation off and stimulation on, and the programming time required were compared using a Student's 't' test [Table - 1]. P<0.05 was considered significant.

Results

The stimulation parameters and motor scores of the two groups are detailed in [Table - 1]. All 12 patients in Group I were subjected to monopolar stimulation. In Group II, 11 patients were exposed to monopolar stimulation, but one patient was subjected to tripolar stimulation for best clinical outcome. The monopolar stimulation caused the patient to experience contralateral limb spasm, possibly due to unsatisfactory electrode implantation. However, the postoperative control of the electrode location was not available because of her refusal to MRI or CT scanning. Tripolar stimulation was set with the two best contacts as cathodes and the adjacent lower contact as the anode. No significant difference in the average amplitude, pulse width or frequency between the two groups was observed at the end of the programming session [Table - 1]. The mean motor scores for "off medication" and "on stimulation" were significantly lower for both groups than scores when both DBS and medication were "off" (paired t-test, P<0.05, [Table - 1]. The mean time required for the programming of patients in Group II was significantly shorter than that of Group I (P<0.05). Intelligibility of speech deteriorated slightly in three patients in Group I and two patients in Group II with the stimulator on. No other stimulation-related side effects were observed.

Discussion

Early postoperative phase after STN-DBS is probably the most difficult period for both the patients and physicians. Ongoing dopaminergic drug reductions, microlesion effects, and possible postoperative complications make the identification of the best stimulation parameters difficult for PD patients with implanted DBS electrodes. The widely used basic programming algorithm can help determine the threshold for beneficial effects and side effects of each electrode contact, as well as aid in defining the optimal stimulation parameters. ^[8],[9],[10] However, this time-consuming method is usually performed during drug withdrawal, so the long period needed for programming may be associated with patient fatigue and discomfort. ^[11] This study demonstrates that the time needed for initial programming can be markedly reduced without losing clinical efficacy by employing a fast postoperative programming protocol. During programming, all of the contacts on each electrode were tested using the same parameters.

The evaluation of beneficial motor effects with DBS is partially subjective, ^[10] so the effects of stimulation may be influenced by both the examiner's expectations and the patient's post-operative state. Therefore, a fast comparison of different contacts with the same parameter can reduce the interval time between two different comparisons. This may help both the patient and the physician make more accurate judgments. The initial stimulation protocol partially relieved the Parkinsonian syndrome in 11 out of 12 patients without intolerable side effects. If the location of the electrodes is not optimal, the bipolar or tripolar mode can be selected to minimize side effects. ^[12],[13] The new fast programming can also provide a reference for parameter selection by setting the contact with serious side effects as the anode and the contacts with more beneficial effects as the cathode according to the test results.

The time required for postoperative programming can last hours. ^[9],[11] Development of fast programming method helped to reduce the programming time to less than 1 hour without losing clinical efficacy with respected to the previous reports. ^{[3],[14],[15],[16]} Although other groups have developed fast postoperative programming models, ^[10],[17] their methods of tracking the optimal parameters remained the same as the basic programming approach introduced by Volkmann. ^[8] The fast tracking method introduced in this study may be the first with significant changes to the basic method. However, while our simplified procedure provided a fast way to screen for the best contact, we did not obtain complete information of all contacts. Nonetheless, this method may be particularly well-suited for patients who cannot tolerate long duration tests in the "off medication" conditions in the early postoperative phase. Considering the small cohort in this study, however, further studies with larger patient groups are required. Our initial success also indicates that such large scale studies are clearly warranted.

In conclusion the fast programming protocol reported in this study can help identify the optimal stimulation parameters more quickly, and so markedly reduce the time required for programming of DBS stimulus parameters. This greatly benefits patients in the postoperative state. The fast programming method does not replace a more detailed approach, but it does allow for timely and efficient stimulation in the early postoperative phase to reduce patient discomfort.

References

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