Microelectrode recording revealing a somatotopic body map in the subthalamic nucleus in humans with Parkinson disease

2004 ◽  
Vol 100 (4) ◽  
pp. 611-618 ◽  
Author(s):  
Pantaleo Romanelli ◽  
Gary Heit ◽  
Bruce C. Hill ◽  
Alli Kraus ◽  
Trevor Hastie ◽  
...  
Keyword(s):  
Basal Ganglia ◽  
Parkinson Disease ◽  
Subthalamic Nucleus ◽  
Anterior Commissure ◽  
Optimal Placement ◽  
Posterior Commissure ◽  
Content Type ◽  
Somatotopic Organization ◽  
Body Map ◽  
Fine Print

Object. The subthalamic nucleus (STN) is a key structure for motor control through the basal ganglia. The aim of this study was to show that the STN in patients with Parkinson disease (PD) has a somatotopic organization similar to that in nonhuman primates. Methods. A functional map of the STN was obtained using electrophysiological microrecording during placement of deep brain stimulation (DBS) electrodes in patients with PD. Magnetic resonance imaging was combined with ventriculography and intraoperative x-ray film to assess the position of the electrodes and the STN units, which were activated by limb movements to map the sensorimotor region of the STN. Each activated cell was located relative to the anterior commissure—posterior commissure line. Three-dimensional coordinates of the cells were analyzed statistically to determine whether those cells activated by movements of the arm and leg were segregated spatially. Three hundred seventy-nine microelectrode tracks were created during placement of 71 DBS electrodes in 44 consecutive patients. Somatosensory driving was found in 288 tracks. The authors identified and localized 1213 movement-related cells and recorded responses from 29 orofacial cells, 480 arm-related cells, 558 leg-related cells, and 146 cells responsive to both arm and leg movements. Leg-related cells were localized in medial (p < 0.0001) and ventral (p < 0.0004) positions and tended to be situated anteriorly (p = 0.063) relative to arm-related cells. Conclusions. Evidence of somatotopic organization in the STN in patients with PD supports the current theory of highly segregated loops integrating cortex—basal ganglia connections. These loops are preserved in chronic degenerative diseases such as PD, but may subserve a distorted body map. This finding also supports the relevance of microelectrode mapping in the optimal placement of DBS electrodes along the subthalamic homunculus.

Determining the position and size of the subthalamic nucleus based on magnetic resonance imaging results in patients with advanced Parkinson disease

2004 ◽  
Vol 100 (3) ◽  
pp. 541-546 ◽  
Author(s):  
Erich O. Richter ◽  
Tasnuva Hoque ◽  
William Halliday ◽  
Andres M. Lozano ◽  
Jean A. Saint-Cyr
Keyword(s):  
Magnetic Resonance ◽  
Parkinson Disease ◽  
Subthalamic Nucleus ◽  
Anterior Commissure ◽  
Mr Images ◽  
Posterior Commissure ◽  
Content Type ◽  
Imaging Results ◽  
Fine Print ◽  
Brain Atlases

Object. The subthalamic nucleus (STN) is a target in surgery for Parkinson disease, but its location according to brain atlases compared with its position on an individual patient's magnetic resonance (MR) images is incompletely understood. In this study both the size and location of the STN based on MR images were compared with those on the Talairach and Tournoux, and Schaltenbrand and Wahren atlases. Methods. The position of the STN relative to the midcommissural point was evaluated on 18 T2-weighted MR images (2-mm slices). Of 35 evaluable STNs, the most anterior, posterior, medial, and lateral borders were determined from axial images, dorsal and ventral borders from coronal images. These methods were validated using histological measurements in one case in which a postmortem examination was performed. The mean length of the anterior commissure—posterior commissure was 25.8 mm. Subthalamic nucleus borders derived from MR imaging were highly variable: anterior, 4.1 to −3.7 mm relative to the midcommissural point; posterior, 4.2 to 10 mm behind the midcommissural point; medial, 7.9 to 12.1 mm from the midline; lateral, 12.3 to 15.4 mm from the midline; dorsal, 0.2 to 4.2 mm below the intercommissural plane; and ventral, 5.7 to 9.9 mm below the intercommissural plane. The position of the anterior border on MR images was more posterior, and the medial border more lateral, than its position in the brain atlases. The STN was smaller on MR images compared with its size in atlases in the anteroposterior (mean 5.9 mm), mediolateral (3.7 mm), and dorsoventral (5 mm) dimensions. Conclusions. The size and position of the STN are highly variable, appearing to be smaller and situated more posterior and lateral on MR images than in atlases. Care must be taken in relying on coordinates relative to the commissures for targeting of the STN.

Movement-related neurons of the subthalamic nucleus in patients with Parkinson disease

2002 ◽  
Vol 97 (5) ◽  
pp. 1167-1172 ◽  
Author(s):  
Aviva Abosch ◽  
William D. Hutchison ◽  
Jean A. Saint-Cyr ◽  
Jonathan O. Dostrovsky ◽  
Andres M. Lozano
Keyword(s):  
Receptive Field ◽  
Parkinson Disease ◽  
Subthalamic Nucleus ◽  
Receptive Fields ◽  
Median Number ◽  
Content Type ◽  
Pooled Data ◽  
Somatotopic Organization ◽  
Fine Print ◽  
Deep Brain

Object. The subthalamic nucleus (STN) is a target in the surgical treatment of Parkinson disease (PD). Little is known about the neurons within the human STN that modulate movement. The authors' goal was to examine the distribution of movement-related neurons within the STN of humans by using microelectrode recording to identify neuronal receptive fields. Methods. Data were retrospectively collected from microelectrode recordings that had been obtained in 38 patients with PD during surgery for placement of STN deep brain stimulation electrodes. The recordings had been obtained in awake, nonsedated patients. Antiparkinsonian medications were withheld the night before surgery. Neuronal discharges were amplified, filtered, and displayed on an oscilloscope and fed to an audio monitor. The receptive fields were identified by the presence of reproducible, audible changes in the firing rate that were time-locked to the movement of specific joint(s). The median number of electrode tracks per patient was six (range two–nine). The receptive fields were identified in 278 (55%) of 510 STN neurons studied. One hundred one tracks yielded receptive field data. Fourteen percent of 64 cells tested positive for face receptive fields, 32% of 687 cells tested positive for upper-extremity receptive fields, and 21% of 242 cells tested positive for lower-extremity receptive fields. Sixty-eight cells (24%) demonstrated multiple-joint receptive fields. Ninety-three cells (65%) with movement-related receptive fields were located in the dorsal half of the STN, and 96.8% of these were located in the rostral two thirds of the STN. Analysis of receptive field locations from pooled data and along individual electrode tracks failed to reveal a consistent somatotopic organization. Conclusions. Data from this study demonstrate a regional compartmentalization of neurons with movement-related receptive fields within the STN, supporting the existence of specific motor territories within the STN in patients suffering from PD.

Localization of clinically effective stimulating electrodes in the human subthalamic nucleus on magnetic resonance imaging

2002 ◽  
Vol 97 (5) ◽  
pp. 1152-1166 ◽  
Author(s):  
Jean A. Saint-Cyr ◽  
Tasnuva Hoque ◽  
Luiz C. M. Pereira ◽  
Jonathan O. Dostrovsky ◽  
William D. Hutchison ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Mr Imaging ◽  
Subthalamic Nucleus ◽  
Anterior Commissure ◽  
Zona Incerta ◽  
Neurosurgical Procedures ◽  
Posterior Commissure ◽  
Content Type ◽  
Neurophysiological Data ◽  
Fine Print

Object. The authors sought to determine the location of deep brain stimulation (DBS) electrodes that were most effective in treating Parkinson disease (PD). Methods. Fifty-four DBS electrodes were localized in and adjacent to the subthalamic nucleus (STN) postoperatively by using magnetic resonance (MR) imaging in a series of 29 patients in whom electrodes were implanted for the treatment of medically refractory PD, and for whom quantitative clinical assessments were available both pre- and postoperatively. A novel MR imaging sequence was developed that optimized visualization of the STN. The coordinates of the tips of these electrodes were calculated three dimensionally and the results were normalized and corrected for individual differences by using intraoperative neurophysiological data (mean 5.13 mm caudal to the midcommissural point [MCP], 8.46 mm inferior to the anterior commissure—posterior commissure [AC—PC], and 10.2 mm lateral to the midline). Despite reported concerns about distortion on the MR image, reconstructions provided consistent data for the localization of electrodes. The neurosurgical procedures used, which were guided by combined neuroimaging and neurophysiological methods, resulted in the consistent placement of DBS electrodes in the subthalamus and mesencephalon such that the electrode contacts passed through the STN and dorsally adjacent fields of Forel (FF) and zona incerta (ZI). The mean location of the clinically effective contacts was in the anterodorsal STN (mean 1.62 mm posterior to the MCP, 2.47 mm inferior to the AC—PC, and 11.72 mm lateral to the midline). Clinically effective stimulation was most commonly directed at the anterodorsal STN, with the current spreading into the dorsally adjacent FF and ZI. Conclusions. The anatomical localization of clinically effective electrode contacts provided in this study yields useful information for the postoperative programming of DBS electrodes.

Optimizing accuracy in magnetic resonance imaging—guided stereotaxis: a technique with validation based on the anterior commissure—posterior commissure line

1999 ◽  
Vol 90 (1) ◽  
pp. 94-100 ◽  
Author(s):  
Charles G. diPierro ◽  
Paul C. Francel ◽  
Theodore R. Jackson ◽  
Toshifumi Kamiryo ◽  
Edward R. Laws
Keyword(s):  
Basal Ganglia ◽  
Magnetic Resonance ◽  
Mr Imaging ◽  
Anterior Commissure ◽  
Geometric Distortion ◽  
Posterior Commissure ◽  
Midsagittal Plane ◽  
Content Type ◽  
Tomography Scanning ◽  
Fine Print

Object. Some of the earliest successful frame-based stereotactic interventions directed toward the thalamus and basal ganglia depended on identifying the anterior commissure (AC) and posterior commissure (PC) in a sagittal ventriculogram and defining the intercommissural line that connects them in the midsagittal plane. The AC—PC line became the essential landmark for the localization of neuroanatomical targets in the basal ganglia and diencephalon and for relating them to stereotactic atlases.Stereotactic/functional neurosurgery has come to rely increasingly on magnetic resonance (MR) imaging guidance, and methods for accurately determining the AC—PC line on MR imaging are being developed. The goal of the present article is to present the authors' technique.Methods. The technique described uses MR sequences that minimize geometric distortion and registration error, thereby maximizing accuracy in AC—PC line determinations from axially displayed MR data. The technique is based on the authors' experience with the Leksell G-frame but can be generalized to other MR imaging—based stereotactic systems.This methodology has been used in a series of 62 stereotactic procedures in 47 adults (55 pallidotomies and seven thalamotomies) with preliminary results that compare favorably with results reported when using microelectrode recordings. The measurements of the AC—PC line reported here also compare favorably with those based on ventriculography and computerized tomography scanning.Conclusions. The methodology reported here is critical in maintaining the accuracy and utility of MR imaging as its role in modern stereotaxy expands. Accurate parameters such as these aid in ensuring the safety, efficacy, and reproducibility of MR-guided stereotactic procedures.

Bilateral stimulation of the subthalamic nucleus in patients with Parkinson disease: a study of efficacy and safety

2002 ◽  
Vol 96 (4) ◽  
pp. 666-672 ◽  
Author(s):  
Tanya Simuni ◽  
Jurg L. Jaggi ◽  
Heather Mulholland ◽  
Howard I. Hurtig ◽  
Amy Colcher ◽  
...  
Keyword(s):  
Deep Brain Stimulation ◽  
Parkinson Disease ◽  
Subthalamic Nucleus ◽  
Brain Stimulation ◽  
Bilateral Stimulation ◽  
Content Type ◽  
Preoperative Status ◽  
Fine Print ◽  
Deep Brain ◽  
Stimulation Of

Object. Palliative neurosurgery has reemerged as a valid therapy for patients with advanced Parkinson disease (PD) that is complicated by severe motor fluctuations. Despite great enthusiasm for long-term deep brain stimulation (DBS) of the subthalamic nucleus (STN), existing reports on this treatment are limited. The present study was designed to investigate the safety and efficacy of bilateral stimulation of the STN for the treatment of PD. Methods. In 12 patients with severe PD, electrodes were stereotactically implanted into the STN with the assistance of electrophysiological conformation of the target location. All patients were evaluated preoperatively during both medication-off and -on conditions, as well as postoperatively at 3, 6, and 12 months during medication-on and -off states and stimulation-on and -off conditions. Tests included assessments based on the Unified Parkinson's Disease Rating Scale (UPDRS) and timed motor tests. The stimulation effect was significant in patients who were in the medication-off state, resulting in a 47% improvement in the UPDRS Part III (Motor Examination) score at 12 months, compared with preoperative status. The benefit was stable for the duration of the follow-up period. Stimulation produced no additional benefit during the medication-on state, however, when compared with patient preoperative status. Significant improvements were made in reducing dyskinesias, fluctuations, and duration of off periods. Conclusions. This study demonstrates that DBS of the STN is an effective treatment for patients with advanced, medication-refractory PD. Deep brain stimulation of the STN produced robust improvements in motor performance in these severely disabled patients while they were in the medication-off state. Serious adverse events were common in this cohort; however, only two patients suffered permanent sequelae.

Lack of agreement between direct magnetic resonance imaging and statistical determination of a subthalamic target: the role of electrophysiological guidance

2002 ◽  
Vol 97 (3) ◽  
pp. 591-597 ◽  
Author(s):  
Emmanuel Cuny ◽  
Dominique Guehl ◽  
Pierre Burbaud ◽  
Christian Gross ◽  
Vincent Dousset ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Mr Imaging ◽  
Functional Response ◽  
Anterior Commissure ◽  
Surgical Techniques ◽  
High Frequency Stimulation ◽  
Mr Images ◽  
Posterior Commissure ◽  
Content Type ◽  
Fine Print

Object. The goal of this study was to determine the most suitable procedure(s) to localize the optimal site for high-frequency stimulation of the subthalamic nucleus (STN) for the treatment of advanced Parkinson disease. Methods. Stereotactic coordinates of the STN were determined in 14 patients by using three different methods: direct identification of the STN on coronal and axial T2-weighted magnetic resonance (MR) images and indirect targeting in which the STN coordinates are referred to the anterior commissure—posterior commissure (AC—PC) line, which, itself, is determined either by using stereotactic ventriculography or reconstruction from three-dimensional (3D) MR images. During the surgical procedure, electrode implantation was guided by single-unit microrecordings on multiple parallel trajectories and by clinical assessment of stimulations. The site where the optimal functional response was obtained was considered to be the best target. Computerized tomography scanning was performed 3 days later and the scans were combined with preoperative 3D MR images to transfer the position of the best target to the same system of stereotactic coordinates. An algorithm was designed to convert individual stereotactic coordinates into an all-purpose PC-referenced system for comparing the respective accuracy of each method of targeting, according to the position of the best target. Conclusions. The target that is directly identified by MR imaging is more remote (mainly in the lateral axis) from the site of the optimal functional response than targets obtained using other procedures, and the variability of this method in the lateral and superoinferior axes is greater. In contrast, the target defined by 3D MR imaging is closest to the target of optimal functional response and the variability of this method is the least great. Thus, 3D reconstruction adjusted to the AC—PC line is the most accurate technique for STN targeting, whereas direct visualization of the STN on MR images is the least effective. Electrophysiological guidance makes it possible to correct the inherent inaccuracy of the imaging and surgical techniques and is not designed to modify the initial targeting.

Effect of subthalamic nucleus stimulation on obsessive—compulsive disorder in a patient with Parkinson disease

2004 ◽  
Vol 100 (6) ◽  
pp. 1084-1086 ◽  
Author(s):  
Denys Fontaine ◽  
Vianney Mattei ◽  
Michel Borg ◽  
Daniel von Langsdorff ◽  
Marie-Noelle Magnie ◽  
...  
Keyword(s):  
Parkinson Disease ◽  
Obsessive Compulsive Disorder ◽  
Subthalamic Nucleus ◽  
Obsessive Compulsive ◽  
Content Type ◽  
Motor Disability ◽  
Compulsive Disorder ◽  
Subthalamic Nucleus Stimulation ◽  
Scale Scores ◽  
Fine Print

✓ The authors report on a patient with Parkinson disease (PD) and severe obsessive—compulsive disorder (OCD), in whom bilateral stimulation of the subthalamic nucleus (STN) was used to treat both PD and OCD symptoms. This 49-year-old man had displayed symptoms of PD for 13 years. Progressively, his motor disability became severe despite optimal medical treatment. In parallel, he suffered severe OCD for 16 years, with obsessions of accumulation and compulsions of gathering and rubbing that lasted more than 8 hours per day. Bilateral high-frequency STN stimulation was performed to treat motor disability. After surgery (at 1-year follow up), motor and OCD symptoms were dramatically improved. The pre- and postoperative Yale—Brown Obsessive—Compulsive Scale scores were 32 and 1, respectively. No additional antiparkinsonian drugs were administered. This case and other recent reports indicate that OCD symptoms can be improved by deep brain stimulation, a finding that opens new perspectives in the surgical treatment of severe and medically intractable OCD.

Subthalamic nucleus stimulation for Parkinson disease: benefits observed in levodopa-intolerant patients

2001 ◽  
Vol 95 (2) ◽  
pp. 213-221 ◽  
Author(s):  
Yoichi Katayama ◽  
Masahiko Kasai ◽  
Hideki Oshima ◽  
Chikashi Fukaya ◽  
Takamitsu Yamamoto ◽  
...  
Keyword(s):  
Parkinson Disease ◽  
Subthalamic Nucleus ◽  
Large Dose ◽  
Daily Activity ◽  
Daily Activities ◽  
Content Type ◽  
Percentage Time ◽  
Group I ◽  
Group Ii ◽  
Fine Print

Object. A blinded evaluation of the effects of subthalamic nucleus (STN) stimulation was performed in levodopaintolerant patients with Parkinson disease (PD). These patients (Group I, seven patients) were moderately or severely disabled (Hoehn and Yahr Stages III–V during the off period), but were receiving only a small dose of medication (levodopa-equivalent dose [LED] 0–400 mg/day) because they suffered unbearable side effects. The results were analyzed in comparison with those obtained in patients with advanced PD (Group II, seven patients) who were severely disabled (Hoehn and Yahr Stages IV and V during the off period), but were treated with a large dose of medication (500–990 mg/day). Methods. The patients were evaluated twice at 6 to 8 months after surgery. To determine the actual benefits afforded by STN stimulation to their overall daily activities, the patients were maintained on their medication regimen with optimal doses and schedules. Stimulation was turned off overnight for at least 12 hours. It was turned on in the morning (or remained turned off), and each patient's best and worst scores on the Unified Parkinson's Disease Rating Scale during waking daytime activity were recorded as on- and off-period scores, respectively. The order of assessment with respect to whether stimulation was occurring was determined randomly. The STN stimulation markedly improved daily activity and total motor scores in Group I patients. The percentage time of immobility (Hoehn and Yahr Stages IV and V) became 0% in patients who were intermittently immobile while not receiving stimulation. Improvements were demonstrated in tremor, rigidity, akinesia, and gait subscores. The STN stimulation produced less marked but still noticeable improvements in the daily activity and total motor scores in Group II patients. The percentage time of immobility as well as the LED was reduced in patients who displayed intermittent immobility with pronounced motor fluctuations while not receiving stimulation. Improvements were demonstrated in tremor, rigidity, and dyskinesia subscores in these patients. In contrast, STN stimulation did not improve the overall daily activities at all in patients who had become unresponsive to a tolerable dose of levodopa and were continuously immobile, even though these patients' tremor and rigidity subscores were still improved by stimulation. Conclusions. Consistent with earlier findings, the great benefit of STN stimulation in levodopa-intolerant patients is that STN stimulation can reduce the level of required levodopa medication. This suggests that STN stimulation could be a therapeutic option for patients with less-advanced PD by allowing levodopa medication to be maintained at as low a dose as possible, and to prevent adverse reactions to the continued use of large-dose levodopa.

Gamma knife subthalamotomy for Parkinson disease: the subthalamic nucleus as a new radiosurgical target

2002 ◽  
Vol 97 ◽  
pp. 592-599 ◽  
Author(s):  
Marcus F. Keep ◽  
Lois Mastrofrancesco ◽  
Daniel Erdman ◽  
Brent Murphy ◽  
Lynn S. Ashby
Keyword(s):  
Mr Imaging ◽  
Parkinson Disease ◽  
Subthalamic Nucleus ◽  
Gamma Knife ◽  
Gamma Knife Radiosurgery ◽  
Single Shot ◽  
Content Type ◽  
The Right ◽  
End Stage ◽  
Fine Print

✓ The authors present the neuroimaging, treatment planning, and radiosurgical technique for the first reported case of unilateral radiosurgical subthalamotomy, which was performed to control motor symptoms associated with advanced Parkinson disease (PD) in a patient who had undergone previous contralateral radiofrequency (RF) pallidotomy. A 73-year-old woman with end-stage PD had undergone RF pallidotomy of the right globus pallidus with resolution of symptoms. Two years following this procedure, due to the natural progression of her disease, she suffered recurrent motor fluctuations, dyskinesia, and worsening bradykinesia of the right side. Her Parkinson's Disease Disability Rating (PDDR) score was 28. Computerized tomography and magnetic resonance (MR) imaging were used to localize the left subthalamic nucleus (STN). The patient underwent gamma knife radiosurgery—a single shot of 120 Gy was administered using the 4-mm collimator helmet. The patient was evaluated up to 42 months after the procedure. The dyskinesia became minimal. Right-sided motor control improved as did her balance. At 3 months after treatment MR imaging demonstrated the radiosurgical lesion in the left STN. At 3.5 years postradiosurgery, she experienced minimal focal (oral) dyskinesia, no bradykinesia or rigidity, and her PDDR score was 11. Radiosurgery of the STN in this case was safe and effective. The STN is a readily localized anatomical target with neuroimaging. Radiosurgery avoids the risks of open procedures.

Long-term follow up of bilateral deep brain stimulation of the subthalamic nucleus in patients with advanced Parkinson disease

2003 ◽  
Vol 99 (3) ◽  
pp. 489-495 ◽  
Author(s):  
Galit Kleiner-Fisman ◽  
David N. Fisman ◽  
Elspeth Sime ◽  
Jean A. Saint-Cyr ◽  
Andres M. Lozano ◽  
...  
Keyword(s):  
Deep Brain Stimulation ◽  
Parkinson Disease ◽  
Subthalamic Nucleus ◽  
Brain Stimulation ◽  
Content Type ◽  
Over Time ◽  
Fine Print ◽  
Deep Brain

Object. The use of deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been associated with a marked initial improvement in individuals with advanced Parkinson disease (PD). Few data are available on the long-term outcomes of this procedure, however, or whether the initial benefits are sustained over time. The authors present the long-term results of a cohort of 25 individuals who underwent bilateral DBS of the STN between 1996 and 2001 and were followed up for 1 year or longer after implantation of the stimulator. Methods. Patients were evaluated at baseline and repeatedly after surgery by using the Unified Parkinson's Disease Rating Scale (UPDRS); the scale was applied to patients during periods in which antiparkinsonian medications were effective and periods when their effects had worn off. Postoperative UPDRS total scores and subscores, dyskinesia scores, and drug dosages were compared with baseline values, and changes in the patients' postoperative scores were evaluated to assess the possibility that the effect of DBS diminished over time. In this cohort the median duration of follow-up review was 24 months (range 12–52 months). The combined (ADL and motor) total UPDRS score during the medication-off period improved after 1 year, decreasing by 42% relative to baseline (95% confidence interval [CI 35–50%], p < 0.001) and the motor score decreased by 48% (95% CI 42–55%, p < 0.001). These gains did diminish over time, although a sustained clinical benefit remained at the time of the last evaluation (41% improvement over baseline, 95% CI 31–50%; p < 0.001). Axial subscores at the time of the last evaluation showed only a trend toward improvement (p = 0.08), in contrast to scores for total tremor (p < 0.001), rigidity (p < 0.001), and bradykinesia (p = 0.003), for which highly significant differences from baseline were still present at the time of the last evaluation. Medication requirements diminished substantially, with total medication doses reduced by 38% (95% CI 27–48%, p < 0.001) at 1 year and 36% (95% CI 25–48%, p < 0.001) at the time of the last evaluation; this decrease may have accounted, at least in part, for the significant decrease of 46.4% (95% CI 20.2–72.5%, p = 0.007) in dyskinesia scores obtained by patients during the medication-on period. No preoperative demographic variable, such as the patient's age at the time of disease onset, age at surgery, sex, duration of disease before surgery, preoperative drug dosage, or preoperative severity of dyskinesia, was predictive of long-term outcome. The only predictor of a better outcome was the patient's preoperative response to levodopa. Conclusions. In this group of patients with advanced PD who underwent bilateral DBS of the STN, sustained improvement in motor function was present a mean of 2 years after the procedure, and sustained reductions in drug requirements were also achieved. Improvements in tremor, rigidity, and bradykinesia were more marked and better sustained over time than improvements in axial symptoms. A good preoperative response to levodopa predicted a good response to surgery.

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