Effect of bilateral subthalamic electrical stimulation in Parkinson's disease

What Is "Advanced" Parkinson's Disease? Defining What Determines Medicare Coverage for Deep Brain Stimulation in the USA

BACKGROUND

The National Coverage Determination (NCD) by the Centers for Medicare and Medicaid Services (CMS) for deep brain stimulation requires that a patient have "advanced idiopathic Parkinson's disease (PD) as determined by Hoehn and Yahr (HY) stage or the Unified Parkinson's Disease Rating Scale part III motor subscale (UPDRS III)." How to apply the HY or UPDRS III scales to define "advanced" PD is unclear.

SUMMARY

There is an ongoing recovery audit by the CMS of deep brain stimulation cases that were covered by Medicare but are deemed not to have met the NCD requirements and therefore not to have been medically necessary. Whether a hospital is asked to refund Medicare often hinges upon whether medical documentation supports the diagnosis of advanced PD. However, neither the HY nor the UPDRS III scales use "advanced" to define or describe stages of PD. The NCD has an accompanying National Coverage Analysis that reviews the studies that inform the NCD. These studies use "advanced" as well as the HY and UPDRS III scales. This review identifies how the HY and UPDRS III scales were used to categorize advanced PD in the studies that were cited in the National Coverage Analysis.

KEY MESSAGES

In the studies used for the NCD for deep brain stimulation for PD, an HY score ≥3 or a UPDRS III score ≥30 was used to describe patient cohorts considered to have advanced PD.

Early-morning OFF in Parkinson's disease: A systematic literature review and current therapeutics

OBJECTIVE

Early morning OFF (EMO) is one of the first motor complications to manifest and frequently signals the onset of additional motor complications in Parkinson's Disease (PD). Although EOM are frequently observed in patients with PD and many caregivers must help with their motor inability, the treatment is still unsatisfactory. The majority of research that has been conducted on the wearing-off state of patients with PD has focused on daytime symptoms; evening and early morning symptoms have received much less attention.This study aimed to review the clinical perspectives of current therapies for EMO.

MATERIALS AND METHODS

We reviewed the searching relevant publications from the key words such as morning off. A total of 456 publications were identified and we reviewed 21 clinical trials as well as other relevant clinical studies and reviews.

RESULTS

EMO are frequently disregarded or undervalued, which could have resulted in unintentional risks, inadequate management, and an increased burden of care. Oral medication is still the primary medical intervention for EMO. However, new developments in non-oral medications and advanced formulations aim to reduce the delay in experiencing the benefits of oral levodopa due to gastrointestinal problems.

CONCLUSIONS

The current therapies for EMO could be helpful in selecting a limited practical treatment. Advancements in non-oral medications and oral formulations hold promise for improving efficacy in EMO.

Criteria for deep-brain stimulation in Parkinson’s disease: review and analysis

Deep-brain stimulation is currently the most effective surgical treatment for advanced Parkinson's disease. The relevant targets to date are the subthalamic nucleus and the globus pallidus internus, although the thalamus (ventralis intermedius nucleus) is preferred in tremor-dominant, aged Parkinson's disease patients. Long-term benefit in cardinal parkinsonian signs, motor fluctuations and dyskinesia has been reported in 5-year follow-up studies of subthalamic nucleus deep-brain stimulation. However, some psychiatric consequences have raised important issues and emphasized the need for an experienced deep-brain stimulation surgical team. This team should be multidisciplinary and involve movement disorder neurologists, neurosurgeons, neuropsychologists and psychiatrists. The recent observation that deep-brain stimulation of the pedunculopontine nucleus improves axial signs, possibly even in those less responsive to levodopa, brings new hope to the management of advanced Parkinson's disease.

A positive correlation between fractional white matter volume and the response of Parkinson disease patients to subthalamic stimulation

BACKGROUND

Since optimal patient selection is essential for the success of subthalamic nucleus (STN) stimulation, the identification of reliable outcome predictors is important. The purpose of this study was to identify new imaging characteristics sufficiently reliable to predict treatment results.

METHOD

Using preoperative magnetic resonance imaging studies of 21 Parkinson disease (PD) patients treated by STN stimulation, we performed whole brain-based analysis of voxel-based morphometry (VBM) data. Intracranial structures segmented into the gray matter fraction (GMF), white matter fraction (WMF), and cerebrospinal fluid fraction (CSFF) were subjected to univariate and multivariate analysis of the correlation between fractional volumes and postoperative improvement rates using the Unified PD Rating Scale (UPDRS).

FINDINGS

At 3 months after surgery, the WMF was significantly correlated with improvement rated on the total UPDRS (p = 0.006), UPDRS part II (activities of daily living; p = 0.008), UPDRS part III (motor; p = 0.005). In contrast, there was no significant correlation between the effect of STN stimulation and GMF or the effect of stimulation and CSFF. The WMF also showed a significant correlation with postoperative scores in the "on" drug and "on" stimulation state (total UPDRS, p = 0.027; UPDRS part II, p = 0.019; UPDRS part III, p = 0.034).

CONCLUSIONS

Our data indicate that patients with a larger white matter volume benefited from STN stimulation whereas the volume of other brain structures was not correlated with its effect. We posit that preserved connectivity between components of the basal ganglia-thalamocortical circuit may be required for the effectiveness of electrical stimulation. VBM may represent a powerful tool to predict the response of patients with advanced PD to STN stimulation.

Subthalamic nucleus stimulation affects subjective emotional experience in Parkinson's disease patients

A number of studies have reported impaired facial emotion recognition following subthalamic nucleus (STN) stimulation in Parkinson's disease (PD), and have related these changes to a limbic dysfunction induced by STN stimulation. The present study examined the effect of STN stimulation in PD patients on a specific component of emotion, namely the subjective experience of emotion. Thirteen post-operative PD patients, 13 pre-operative PD patients matched on clinical and neuropsychological characteristics, and 16 controls matched on age and education, were administered a validated battery of film excerpts known to primarily induce specific emotional feelings (anger, happiness, sadness, fear, disgust, and neutral), and self-rated the intensity of their emotional feelings on a discrete emotions questionnaire. The post-operative group showed a significant lower level of differentiation between the target feeling (i.e., the more likely to be reported) and non-target feelings for the film excerpts intended to induce "sadness" and "fear" respectively, as compared with the pre-operative and healthy control groups. Moreover, the post-operative group reported significantly less intense feelings of fear, anxiety and disgust for the excerpt intended to induce "fear" as compared with the pre-operative and the control groups, while no significant difference was observed between the pre-operative and control groups. Finally, the post-operative group reported significantly less intense feelings of sadness and anxiety during the excerpt intended to induce "sadness" as compared to the control group, although the differences between the pre- and post-operative groups and between the pre-operative and the control groups did not reach significance. Our study suggests that STN stimulation affects the subjective experience of emotion, thus providing a preliminary account of the modulation induced by STN stimulation of a distributed neuronal network underlying the subjective experience of emotion, although the exact contribution of the STN within such network remains to be specified.

Fast-track programming and rehabilitation model: a novel approach to postoperative deep brain stimulation patient care

OBJECTIVE

To propose a new model of integrated, multidisciplinary postoperative care of the patients with deep brain stimulation (DBS).

DESIGN

Observational cohort study with follow-up at 3 months and 1 year.

SETTING

Academic medical center movement disorder clinic.

PARTICIPANTS

Seventy-three consecutive patients with medically refractory Parkinson's disease underwent bilateral DBS. Patients were then transferred directly to an inpatient rehabilitation facility.

INTERVENTION

DBS and inpatient programming and rehabilitation. Simultaneous programming and rehabilitation was carried out by a multidisciplinary team.

MAIN OUTCOME MEASURES

The FIM instrument, Unified Parkinson Disease Rating Scale (UPDRS), and levodopa dosage.

RESULTS

The average rehabilitation stay was 17.3 days, with a mean of 6.2 stimulator adjustments during that time. FIM scores improved from 62.1 (admission) to 98.5 (discharge), an average improvement of 36.4 (58.6%). Average UPDRS scores improved from 52.5 (preoperative off) and 30.1 (preoperative on) to 20.4 (3mo postoperative on-medication, on-stimulation), a 32.2% improvement from the preoperative on score. Levodopa dosages decreased by an average of 48.3% (all P<.001).

CONCLUSIONS

We describe our fast-track protocol, which allows for rapid DBS programming and tapering of Parkinson's medications. It also provides for treatment of concomitant medical and psychologic problems and optimized physical performance.

Deep brain stimulation for Parkinson's disease

Indications for the treatment of Parkinson's disease (PD) with deep brain stimulation (DBS) are severe, therapy refractory tremor and complications of long-term levodopa uptake. Since its first application DBS has become a standard therapy for these patients. Theoretically, the ventrolateral part of the internal pallidum (GPI) or the subthalamic nucleus (STN) are suitable targets in order to treat all cardinal symptoms of patients in an advanced stage of PD stereotactically. Although clinical efficacy of both GPI or STN stimulation is obviously comparable, it has become widely accepted to prefer STN over GPI DBS. If PD-associated, medically intractable tremor is the most disabling symptom, stimulation of the ventrolateral motor thalamus can be an alternative. Anatomical targets for DBS are small and located in critical brain areas. Furthermore, this type of surgery is highly elective. As a consequence, high resolution multiplanar imaging and adequate treatment planning software are indispensable prerequisites for DBS surgery. Currently, commercially available impulse generators deliver a permanent high frequency periodic pulse train stimulation that interacts rather unspecifically with the firing pattern of both normal and pathological neurons. Prospectively, the development of more specific stimulation paradigms may help to improve the efficacy of this treatment modality.

Subthalamic nucleus neurones in slices from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned mice show irregular, dopamine-reversible firing pattern changes, but without synchronous activity

The loss of dopamine in idiopathic or animal models of Parkinson's disease induces synchronized low-frequency oscillatory burst-firing in subthalamic nucleus neurones. We sought to establish whether these firing patterns observed in vivo were preserved in slices taken from dopamine-depleted animals, thus establishing a role for the isolated subthalamic-globus pallidus complex in generating the pathological activity. Mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) showed significant reductions of over 90% in levels of dopamine as measured in striatum by high pressure liquid chromatography. Likewise, significant reductions in tyrosine hydroxylase immunostaining within the striatum (>90%) and tyrosine hydroxylase positive cell numbers (65%) in substantia nigra were observed. Compared with slices from intact mice, neurones in slices from MPTP-lesioned mice fired significantly more slowly (mean rate of 4.2 Hz, cf. 7.2 Hz in control) and more irregularly (mean coefficient of variation of inter-spike interval of 94.4%, cf. 37.9% in control). Application of ionotropic glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 2-amino-5-phosphonopentanoic acid (AP5) and the GABA(A) receptor antagonist picrotoxin caused no change in firing pattern. Bath application of dopamine significantly increased cell firing rate and regularized the pattern of activity in cells from slices from both MPTP-treated and control animals. Although the absolute change was more modest in control slices, the maximum dopamine effect in the two groups was comparable. Indeed, when taking into account the basal firing rate, no differences in the sensitivity to dopamine were observed between these two cohorts. Furthermore, pairs of subthalamic nucleus cells showed no correlated activity in slices from either control (21 pairs) or MPTP-treated animals (20 pairs). These results indicate that the isolated but interconnected subthalamic-globus pallidus network is not itself sufficient to generate the aberrant firing patterns in dopamine-depleted animals. More likely, inputs from other regions, such as the cortex, are needed to generate pathological oscillatory activity.

Dopamine transporter imaging and the effects of deep brain stimulation in patients with Parkinson’s disease

PURPOSE

Single-photon emission computed tomography (SPECT) with [123I]FP-CIT is a marker for loss of presynaptic dopamine transporters in the striatum in Parkinson's disease (PD). We used [123I]FP-CIT SPECT in order to evaluate binding to the dopamine transporter before and after neurosurgical treatment with bilateral stimulation in the subthalamic nucleus (STN).

METHODS

Thirty-five patients with levodopa-responsive PD were examined with [123I]FP-CIT SPECT pre-operatively (baseline scan: mean 3 months before surgery), and 3 and 12 months after surgery.

RESULTS

Pre-operatively, all patients already had substantial signs of severe nigrostriatal neuronal loss as determined from the [123I]FP-CIT SPECT scans. One year after surgery the specific [123I]FP-CIT binding to the striatum was significantly reduced by 10.3% compared with the pre-operative baseline scan. The mean time span from the baseline scan before surgery to the follow-up scan 1 year after surgery was 16.2 months. Hence, the rate of reduction equals a mean annual reduction of 7.7%. A comparable control group of patients with PD who did not undergo surgery was also examined longitudinally. In this group the specific binding of [123I]FP-CIT was reduced by 6.7% per year.

CONCLUSION

The specific binding of [123I]FP-CIT was reduced equally in the STN-stimulated patients and a group of non-operated PD patients with advanced disease. Our study does not support the notion that electrode implantation and STN stimulation exert a neuroprotective effect by themselves.

Subthalamic nucleus deep brain stimulation: summary and meta-analysis of outcomes

Subthalamic nucleus (STN) deep brain stimulation (DBS) is currently the most common therapeutic surgical procedure for patients with Parkinson's disease (PD) who have failed medical management. However, a recent summary of clinical evidence on the effectiveness of STN DBS is lacking. We report the results of such a systematic review and meta-analysis. A comprehensive review of the literature using Medline and Ovid databases from 1993 until 2004 was conducted. Estimates of change in absolute Unified Parkinson's Disease Rating Scale (UPDRS) scores after surgery were generated using random-effects models. Sources of heterogeneity were explored with meta-regression models, and the possibility of publication bias was evaluated. Patient demographics, reduction in medication requirements, change in dyskinesia, daily offs, quality of life, and a ratio of postoperative improvement from stimulation compared to preoperative improvement by medication from each study were tabulated and average scores were calculated. Adverse effects from each study were summarized. Thirty-seven cohorts were included in the review. Twenty-two studies with estimates of standard errors were included in the meta-analysis. The estimated decreases in absolute UPDRS II (activities of daily living) and III (motor) scores after surgery in the stimulation ON/medication off state compared to preoperative medication off state were 13.35 (95% CI: 10.85-15.85; 50%) and 27.55 (95% CI: 24.23-30.87; 52%), respectively. Average reduction in L-dopa equivalents following surgery was 55.9% (95% CI: 50%-61.8%). Average reduction in dyskinesia following surgery was 69.1% (95% CI: 62.0%-76.2%). Average reduction in daily off periods was 68.2% (95% CI: 57.6%-78.9%). Average improvement in quality of life using PDQ-39 was 34.5% +/- 15.3%. Univariable regression showed improvements in UPDRS III scores were significantly greater in studies with higher baseline UPDRS III off scores, increasing disease duration prior to surgery, earlier year of publication, and higher baseline L-dopa responsiveness. Average baseline UPDRS III off scores were significantly lower (i.e., suggesting milder disease) in later than in earlier studies. In multivariable regression, L-dopa responsiveness, higher baseline motor scores, and disease duration were independent predictors of greater change in motor score. No evidence of publication bias in the available literature was found. The most common serious adverse event related to surgery was intracranial hemorrhage in 3.9% of patients. Psychiatric sequelae were common. Synthesis of the available literature indicates that STN DBS improves motor activity and activities of daily living in advanced PD. Differences between available studies likely reflect differences in patient populations and follow-up periods. These data provide an estimate of the magnitude of the treatment effects and emphasize the need for controlled and randomized studies.

Deep brain stimulation: Preoperative issues

Numerous factors need to be taken into account in deciding whether a patient with Parkinson's disease (PD) is a candidate for deep brain stimulation. Patient-related personal factors including age and the presence of other comorbid disorders need to be considered. Neuropsychological and neuropsychiatric concerns relate both to the presurgical status of the patient and to the potential for surgery to result in new problems postoperatively. A number of factors related to the underlying PD need to be considered, including the specific parkinsonian motor indications (e.g., tremor, bradykinesia, gait dysfunction), previous medical therapies, including benefit from current therapy and adverse effects, and past surgical treatments. Definable causes of Parkinsonism, particularly atypical Parkinsonisms, should be considered. Finally, methods of evaluating outcomes should be defined and formalized. This is a report from the Consensus on Deep Brain Stimulation for Parkinson's Disease, a project commissioned by the Congress of Neurological Surgeons and the Movement Disorder Society (MDS). The report has been endorsed by the Scientific Issues Committee of the MDS and the American Society of Stereotactic and Functional Neurosurgery. It outlines answers to a series of questions developed to address all aspects of deep brain stimulation preoperative decision-making.

Deep brain stimulation as a functional scalpel

Since 1995, at the Istituto Nazionale Neurologico "Carlo Besta" in Milan (INNCB,) 401 deep brain electrodes were implanted to treat several drug-resistant neurological syndromes (Fig. 1). More than 200 patients are still available for follow-up and therapeutical considerations. In this paper our experience is reviewed and pioneered fields are highlighted. The reported series of patients extends the use of deep brain stimulation beyond the field of Parkinson's disease to new fields such as cluster headache, disruptive behaviour, SUNCt, epilepsy and tardive dystonia. The low complication rate, the reversibility of the procedure and the available image guided surgery tools will further increase the therapeutic applications of DBS. New therapeutical applications are expected for this functional scalpel.

Deep brain stimulation: Postoperative issues

Numerous factors need to be taken into account when managing a patient with Parkinson's disease (PD) after deep brain stimulation (DBS). Questions such as when to begin programming, how to conduct a programming screen, how to assess the effects of programming, and how to titrate stimulation and medication for each of the targeted sites need to be addressed. Follow-up care should be determined, including patient adjustments of stimulation, timing of follow-up visits and telephone contact with the patient, and stimulation and medication conditions during the follow-up assessments. A management plan for problems that can arise after DBS such as weight gain, dyskinesia, axial symptoms, speech dysfunction, muscle contractions, paresthesia, eyelid, ocular and visual disturbances, and behavioral and cognitive problems should be developed. Long-term complications such as infection or erosion, loss of effect, intermittent stimulation, tolerance, and pain or discomfort can develop and need to be managed. Other factors that need consideration are social and job-related factors, development of dementia, general medical issues, and lifestyle changes. This report from the Consensus on Deep Brain Stimulation for Parkinson's Disease, a project commissioned by the Congress of Neurological Surgeons and the Movement Disorder Society, outlines answers to a series of questions developed to address all aspects of DBS postoperative management and decision-making with a systematic overview of the literature (until mid-2004) and by the expert opinion of the authors. The report has been endorsed by the Scientific Issues Committee of the Movement Disorder Society and the American Society of Stereotactic and Functional Neurosurgery.

Operative techniques and morbidity with subthalamic nucleus deep brain stimulation in 100 consecutive patients with advanced Parkinson's disease

OBJECTIVE

Subthalamic nucleus (STN) stimulation for patients with medically refractory Parkinson disease (PD) is expanding. Reported experience has provided some indication of techniques, efficacy, and morbidity, but few centres have reported more than 50 patients. To expand this knowledge, we reviewed our experience with a large series of consecutive patients.

METHODS

From March 1999 to September 2003, 191 subthalamic stimulator devices (19 unilateral) were implanted in 100 patients with PD at New York Presbyterian Hospital/Columbia University Medical Center. Sixteen patients had undergone a prior surgery for PD (pallidotomy, thalamotomy, or fetal transplant). Microelectrode guided implantations were performed using techniques similar to those described previously. Electrode implantation occurred 1-2 weeks before outpatient pulse generator implantation.

RESULTS

Reductions of dyskinesias and off severity/duration were similar to prior published reports. Morbidity included: 7 device infections (3.7%), 1 cerebral infarct, 1 intracerebral haematoma, 1 subdural haematoma, 1 air embolism, 2 wound haematomas requiring drainage (1.0%), 2 skin erosions over implanted hardware (1.0%), 3 periprocedural seizures (1.6%), 6 brain electrode revisions (3.1%), postoperative confusion in 13 patients (6.8%), and 16 battery failures (8.4%). Of the 100 patients, there were no surgical deaths or permanent new neurological deficits. The average hospital stay for all 100 patients was 3.1 days.

CONCLUSION

Subthalamic stimulator implantation in a large consecutive series of patients with PD produced significant clinical improvement without mortality or major neurological morbidity. Morbidity primarily involved device infections and hardware/wound revisions.

Deep brain stimulation in Parkinson disease: a metaanalysis of patient outcomes

Object. Deep brain stimulation (DBS) to treat advanced Parkinson disease (PD) has been focused on one of two anatomical targets: the subthalamic nucleus (STN) and the globus pallidus internus (GPI). Authors of more than 65 articles have reported on bilateral DBS outcomes. With one exception, these studies involved pre- and postintervention comparisons of a single target. Despite the paucity of data directly comparing STN and GPI DBS, many clinicians already consider the STN to be the preferred target site. In this study the authors conducted a metaanalysis of the existing literature on patient outcomes following DBS of the STN and the GPI.

Methods. This metaanalysis includes 31 STN and 14 GPI studies. Motor function improved significantly following stimulation (54% in patients whose STN was targeted and 40% in those whose GPI was stimulated), with effect sizes (ESs) of 2.59 and 2.04, respectively. After controlling for participant and study characteristics, patients who had undergone either STN or GPI DBS experienced comparable improved motor function following surgery (p = 0.094). The performance of activities of daily living improved significantly in patients with either target (40%). Medication requirements were significantly reduced following stimulation of the STN (ES = 1.51) but did not change when the GPI was stimulated (ES = −0.02).

Conclusions. In this analysis the authors highlight the need for uniform, detailed reporting of comprehensive motor and nonmotor DBS outcomes at multiple time points and for a randomized trial of bilateral STN and GPI DBS.

Stimulation of the subthalamic nucleus in Parkinson's disease: a 5 year follow up

BACKGROUND

The short term benefits of bilateral stimulation of the subthalamic nucleus (STN) in patients with advanced levodopa responsive Parkinson's disease (PD) are well documented, but long term benefits are still uncertain.

OBJECTIVES

This study provides a 5 year follow up of PD patients treated with stimulation of the STN.

METHODS

Thirty seven consecutive patients with PD treated with bilateral STN stimulation were assessed prospectively 6, 24, and 60 months after neurosurgery. Parkinsonian motor disability was evaluated with and without levodopa treatment, with and without bilateral STN stimulation. Neuropsychological and mood assessments included the Mattis Dementia Rating Scale, the frontal score, and the Montgomery-Asberg Depression Rating Scale (MADRS).

RESULTS

No severe peri- or immediate postoperative side effects were observed. Six patients died and one was lost to follow up. Five years after neurosurgery: (i) activity of daily living (Unified Parkinson Disease Rating Scale (UPDRS) II) was improved by stimulation of the STN by 40% ("off" drug) and 60% ("on" drug); (ii) parkinsonian motor disability (UPDRS III) was improved by 54% ("off" drug) and 73% ("on" drug); (iii) the severity of levodopa related motor complications was decreased by 67% and the levodopa daily doses were reduced by 58%. The MADRS was unchanged, but cognitive performance declined significantly. Persisting adverse effects included eyelid opening apraxia, weight gain, addiction to levodopa treatment, hypomania and disinhibition, depression, dysarthria, dyskinesias, and apathy.

CONCLUSIONS

Despite moderate motor and cognitive decline, probably due to disease progression, the marked improvement in motor function observed postoperatively was sustained 5 years after neurosurgery.

Bilateral Subthalamic Nucleus Stimulation for Parkinson's Disease: A Systematic Review of the Clinical Literature

OBJECTIVE:

To evaluate the benefits and adverse effects of bilateral subthalamic nucleus stimulation in the treatment of Parkinson's disease (PD) by systematically reviewing the published literature.

METHODS:

A search of the PubMed database using the key words subthalamic, nucleus, and stimulation yielded 624 articles published between 1966 and December 2003. Only articles that included original, nonduplicated descriptions of patients with PD treated with bilateral subthalamic nucleus stimulation were selected for further analysis.

RESULTS:

A total of 38 studies from 34 neurosurgical centers in 13 countries were identified for critical review. The outcomes for 471 patients with PD treated with bilateral subthalamic nucleus stimulation were assessed according to the Unified Parkinson's Disease Rating Scale in both on-medication and off-medication conditions. With stimulation, Unified Parkinson's Disease Rating Scale motor scores in the off-medication condition improved by 50% after 6 months, 56% after 12 months, 51% after 2 years, and 49% after 5 years compared with preoperative off-medication scores. At 12 months of subthalamic nucleus stimulation, the mean improvement in tremor was 81%, in rigidity was 63%, in bradykinesia was 52%, in gait was 64%, and in postural instability was 69% when compared with preoperative off-medication subscores. On-medication dyskinesias were reduced by 94%, as assessed 12 months after stimulation using the Unified Parkinson's Disease Rating Scale IV complications of therapy score. There was an overall 52% reduction in the l-dopa-equivalent dose intake after 12 months of stimulation. Most adverse effects were mild to moderate. There was a 1 to 2% incidence of severe adverse effects (death or permanent neurological deficits related to intracerebral hemorrhages). Nineteen percent of the patients had adverse effects related to stimulation that could be reversed by changing stimulation parameters. There was a 9% incidence of adverse effects related to the hardware (infections, lead and pulse generator problems).

CONCLUSION:

Bilateral subthalamic nucleus stimulation is effective in the treatment of PD. Further refinements in patient selection and surgical technique may lessen the incidence of complications associated with this procedure.

Location of the active contact within the subthalamic nucleus (STN) in the treatment of idiopathic Parkinson's disease

BACKGROUND

Chronic electrical stimulation of the subthalamic nucleus (STN) has been shown to be safe and effective in the treatment of medically refractory idiopathic Parkinson's disease. The clinically most relevant location of stimulation within the physiologically defined STN has not been confirmed. We reviewed the locations of active electrical contacts in 33 patients who underwent simultaneous bilateral STN deep brain stimulator (DBS) implantation.

METHODS

The location of the microelectrode-defined dorsal STN border was compared to the location of the center of the active contact(s) employed in achieving optimal clinical results 6 to 18 months postoperatively. Furthermore, the location of this optimal contact was determined with respect to each individual patient's midcommissural point. Bilateral monopolar stimulation was employed in 30 patients using quadripolar DBS electrodes.

RESULTS

After a minimum follow-up period of 6 months, the motor subscores (UPDRS Part III) in the postoperative on-stimulation/off-medication state were 64 +/- 18% (mean +/- SD) improved as compared to the preoperative off-medication state (p < 0.01). Additionally, an improvement of 53 +/- 38% was noted when comparing the postoperative on-stimulation/on-medication state to the preoperative on-medication state (p < 0.01). On average, the center of the optimal contact was 13.3 mm lateral, 0.5 mm posterior, 0.1 mm inferior to the mid-commissural point and was 0.1 +/- 2.1 mm dorsal to the physiologically defined dorsal STN border.

CONCLUSIONS

While the achieved clinical results are comparable to those published in the literature, it appears that monopolar electrical stimulation at the anterior dorsolateral border of the STN yields optimal clinical results. Further studies are crucial in determining the precise mechanism of various modes of DBS in an effort to maximize clinical outcome.

A Simple Method to Assess Accuracy of Deep Brain Stimulation Electrode Placement: Pre-Operative Stereotactic CT + Postoperative MR Image Fusion

OBJECTIVE

To describe a method for the measurement of the accuracy of deep brain stimulation (DBS) electrode placement with the use of image fusion technologies.

PATIENTS AND METHODS

Ten consecutive patients suffering from movement disorders underwent DBS electrode placement. Postoperative MR images were fused with the pre-operative stereotactic CT. The placement error in the anteroposterior, lateral and vertical planes was calculated.

RESULTS

The anteroposterior mean error +/- SD was 0.61 +/- 0.22 mm (range 0.2-0.9 mm). The lateral mean error +/- SD was 0.65 +/- 0.27 mm (range 0.2-2.2 mm). The vertical mean error +/- SD was 0.82 +/- 0.31 mm (range 0.3-1.6 mm).

CONCLUSIONS

This technique provides a simple and precise method for the evaluation of the accuracy of DBS electrode placement.

Transient dystonia following magnetic resonance imaging in a patient with deep brain stimulation electrodes for the treatment of Parkinson disease. Case report

Data from previous studies have shown that magnetic resonance (MR) imaging of the head can be performed safely in patients with deep brain stimulators. The authors report on a 73-year-old patient with bilaterally implanted deep brain electrodes for the treatment of Parkinson disease, who exhibited dystonic and partially ballistic movements of the left leg immediately after an MR imaging session. Such dystonic or ballistic movements had not been previously observed in this patient. In the following months, this focal movement disorder resolved completely. This case demonstrates the possible risks of MR imaging in patients with deep brain stimulators.

Softly spoken strokes: two patients with marked hypophonia as a feature of strokes involving the anterior thalamus

Two patients with strokes involving thalamic structures are described. Both displayed marked hypophonia as part of their clinical syndromes. This speech disorder and its possible localizing value are discussed.