Hardware-Related Complications of Deep Brain Stimulation: A Review of the Published Literature

Movement disorders and neuromodulation

Movement disorders are neurological conditions affecting speed, fluency, quality, and ease of movement. Deep brain stimulation (DBS) is used to treat advanced Parkinson's disease, essential tremor, and dystonia. Possible target sites for DBS include the ventral intermediate nucleus of the thalamus, the globus pallidus internus, and the subthalamic nucleus. High-frequency DBS leads to a kind of functional deafferentation of the stimulated structure and to the modulation of cortical activity. This has a profound effect on the efficiency of movement. Indications for the use of DBS include the need to improve function, reduce medication dependency, and avoid ablative neurosurgery. Appropriate patient selection is critical for success. The implantation technique is briefly described. Programming stimulation parameters are performed via telemetry. The adverse effects of DBS are discussed. The future should see the development of “closed-loop” systems. Its use has promoted interdisciplinary team work and provided an improved understanding of the complex neurocircuitry associated with these disorders. DBS is a highly effective, safe, and reversible surgical treatment for advanced Parkinson's disease, tremor, and dystonia. It is a useful therapeutic option in carefully selected patients that significantly improves motor symptoms, functional status, and quality of life.

Short circuit in deep brain stimulation

OBJECT

The authors undertook this study to investigate the incidence, cause, and clinical influence of short circuits in patients treated with deep brain stimulation (DBS).

METHODS

After the incidental identification of a short circuit during routine follow-up, the authors initiated a policy at their institution of routinely evaluating both therapeutic impedance and system impendence at every outpatient DBS follow-up visit, irrespective of the presence of symptoms suggesting possible system malfunction. This study represents a report of their findings after 1 year of this policy.

RESULTS

Implanted DBS leads exhibiting short circuits were identified in 7 patients (8.9% of the patients seen for outpatient follow-up examinations during the 12-month study period). The mean duration from DBS lead implantation to the discovery of the short circuit was 64.7 months. The symptoms revealing short circuits included the wearing off of therapeutic effect, apraxia of eyelid opening, or dysarthria in 6 patients with Parkinson disease (PD), and dystonia deterioration in 1 patient with generalized dystonia. All DBS leads with short circuits had been anchored to the cranium using titanium miniplates. Altering electrode settings resulted in clinical improvement in the 2 PD cases in which patients had specific symptoms of short circuits (2.5%) but not in the other 4 cases. The patient with dystonia underwent repositioning and replacement of a lead because the previous lead was located too anteriorly, but did not experience symptom improvement.

CONCLUSIONS

In contrast to the sudden loss of clinical efficacy of DBS caused by an open circuit, short circuits may arise due to a gradual decrease in impedance, causing the insidious development of neurological symptoms via limited or extended potential fields as well as shortened battery longevity. The incidence of short circuits in DBS may be higher than previously thought, especially in cases in which DBS leads are anchored with miniplates. The circuit impedance of DBS should be routinely checked, even after a long history of DBS therapy, especially in cases of miniplate anchoring.

Deep brain stimulation for the treatment of Parkinson's disease: efficacy and safety

Deep brain stimulation (DBS) surgery has become increasingly utilized in the treatment of advanced Parkinson's disease. Over the past decade, a number of studies have demonstrated that DBS is superior to best medical management in appropriately selected patients. The primary targets for DBS in Parkinson's disease include the subthalamic nucleus and the internal segment of the globus pallidus, both of which improve the cardinal motor features in Parkinson's disease. Recent randomized studies have revealed that both targets are similarly effective in treating the motor symptoms of Parkinson's disease, but emerging evidence suggests that the globus pallidus may be the preferred target in many patients, based on differences in nonmotor outcomes. Here, we review appropriate patient selection, and the efficacy and safety of DBS therapy in Parkinson's disease. Best outcomes are achieved if the problems of the individual patient are considered when evaluating surgical candidates and considering whether the subthalamic nucleus or the globus pallidus internus should be targeted.

Hardware complications in deep brain stimulation: electrode impedance and loss of clinical benefit

BACKGROUND

Deep brain stimulation (DBS) is an effective treatment in patients with movement disorders. Successful outcomes are correlated with patient selection, accurate placement of the electrodes in their surgical target and optimal programming of patients. The loss of clinical efficacy after successful treatment may be related to hardware complications.

OBJECTIVES

We studied the causes of loss of stimulation efficacy in patients with stable antiparkinsonian benefit after DBS.

RESULTS

Seven out of 110 (6.3%) patients surgically treated with DBS showed a loss of clinical efficacy, and were included in the study. Five cases had subacute clinical worsening and two sudden deterioration. All of them had an impedance increment (>4000 Ω) with the active contacts. Further reprogramming was attempted in all the cases using the undamaged contacts. However, five patients had incomplete clinical control and were reoperated with an electrode replacement. X-rays provided information in all cases except one showing the disruption or rupture of electrode.

CONCLUSIONS

It is important to identify this hardware problem in view of the growing number of patients receiving this therapy. A protocol for patients with loss of stimulation efficacy and electrode impedance increment needs to be created in clinical visits in order to detect the failed stimulation mechanism.

[Stereotactic radiosurgery for movement disorders]

Nowadays, functional neurosurgery is an established treatment for movement disorders such as Parkinson's disease, essential tremor, and dystonia. The effectiveness and safety of neuromodulation procedures (deep brain stimulation) replaced in the last years ablative irreversible stereotactic lesions for movement disorders. Stereotactic radiosurgery with gamma knife is a non-invasive form of treatment for movement disorders. The main limitation of stereotactic radiosurgery is the impossibility of electrophysiological confirmation of the target structure. Nevertheless, patients with advanced age and significant medical conditions that preclude classic open stereotactic procedures or patients who must receive anticoagulation therapy may gain great functional benefit using gamma knife stereotactic radiosurgery.

DBS and electrical neuro-network modulation to treat neurological disorders

The use of neuromodulatory techniques in the treatment of neurological disorders is expanding and now includes devices targeting the motor cortex, basal ganglia, spinal cord, peripheral nervous system, and autonomic nervous system. In this chapter, we review and discuss the current and past literature as well as review indications for each of these devices in the ongoing management of many common neurological diseases including chronic pain, Parkinson's disease, tremor, dystonia, and epilepsy. We also discuss and update mechanisms of deep brain stimulation and electrical neuro-network modulation.

Electrode dysfunctions in patients with deep brain stimulation: a clinical retrospective study

BACKGROUND

Electrode fractures are known hardware problems in patients with deep brain stimulation (DBS) and require surgical revision. Short circuits, loose connections or disconnections of only single contacts of the common quadripolar stimulation electrodes are more subtle dysfunctions and can result in decreased efficacy of DBS. Measuring the impedances of electrodes helps detect such technical dysfunctions. This study evaluates the frequency and clinical implications of abnormal impedance measurements.

METHODS

We retrospectively analyzed findings of systematic impedance checks in 591 consecutive patients with DBS for various movement disorders treated in our DBS center between 2005 and 2010.

FINDINGS

A technical dysfunction was found in 36 out of 1,142 electrodes (3.2%). Short circuits (22 electrodes) were more frequent than disconnections of single contacts (8 electrodes) or loose contacts (6 electrodes). Moreover, after 109 replacements of impulse generators another 16 electrodes revealed technical dysfunctions, again with short circuits (9 electrodes) exceeding disconnections of single contacts (5 electrodes) and loose contacts (2 electrodes). Most of the short circuits occurred immediately after surgical interventions. In contrast, among dysfunctions occurring later during long-term DBS, disconnections and loose contacts prevailed. Surgical revision was performed in 4 of the overall 52 electrodes with dysfunctions, whereas in the other electrodes adjustment of stimulation parameters resulted in stable and satisfying symptom control.

CONCLUSIONS

Technical dysfunctions of stimulation electrodes or extension leads are rare but important sources of unsatisfying DBS efficacy. In the majority of cases DBS programming or reprogramming allows avoiding surgical revision.

DEEP BRAIN STIMULATION FOR THE TREATMENT OF EPILEPSY

During the last decade, deep brain stimulation (DBS) has been used to treat several neurologic disorders, including epilepsy. Promising results have been reported with stimulation in different brain regions. At present however, several issues remain unanswered. As an example, it is still unclear whether particular seizure types and syndromes should be treated with DBS in different targets or with different stimulation parameters. In addition, clinical, electrophysiological and anatomical features capable of predicting a good postoperative outcome are still unknown. We review the published literature on DBS, cortical and cerebellar stimulation for the treatment of epilepsy focusing predominantly on the rationale and clinical outcome in each target.

Role of Tc-Sulesomab Immunoscintigraphy in the Management of Infection following Deep Brain Stimulation Surgery

Infection constitutes a serious adverse event in patients submitted to deep brain stimulation, often leading to removal of the device. We set to evaluate the potential role of immunoscintigraphy with ^99mTc-labelled antigranulocyte antibody fragments (^99mTc-sulesomab) in the management of infection following DBS. ^99mTc-sulesomab immunoscintigraphy seems to correlate well with the presence and extent of infection, thus contributing to differentiate between patients who should remove the hardware entirely at presentation and those who could undergo a more conservative approach. Also, ^99mTc-sulesomab immunoscintigraphy has a role in determining the most appropriate timing for reimplantation. Finally, we propose an algorithm for the management of infection following DBS surgery, based on the results of the ^99mTc-sulesomab immunoscintigraphy.

Assessment of the effects of unilateral electrode dysfunction in patients with Parkinson disease undergoing bilateral subthalamic nucleus deep brain stimulation

BACKGROUND

Bilateral subthalamic nucleus deep brain stimulation (STN-DBS) is the gold standard surgical treatment for medically intractable Parkinson disease, and unilateral electrodes are reported to have beneficial effects. However, assessment of patients after electrode failure needs to be established.

OBJECTIVE

To assess the effects of the remaining unilateral electrode in Parkinson disease after bilateral STN-DBS.

METHODS

Between May 2000 and March 2009, 8 patients had unilateral STN-DBS after bilateral STN-DBS. We assessed clinical outcome by comparing the Unified Parkinson Disease Rating Scale (UPDRS) motor score, activities of daily living, levodopa-equivalent daily dosages, and quality of life according to the Short-Form 36 Health Survey between patients with unilateral and bilateral electrodes.

RESULTS

Although ipsilateral and axial UPDRS motor scores were compromised, UPDRS motor scores contralateral to the side of the implant remained unaltered after removal of 1 electrode. Although physical aspects of quality of life declined significantly with a unilateral electrode, pain and social functioning were not significantly affected. No significant changes in activities of daily living, Hoehn and Yahr stage, or levodopa-equivalent daily dosage were observed after removal of 1 electrode.

CONCLUSION

The UPDRS motor score with unilateral STN-DBS was compromised relative to bilateral STN-DBS for ipsilateral motor and axial symptoms. When 1 electrode is compromised, revision of that electrode will eventually be required, but not immediately in all patients. If a patient tolerates loss of 1 electrode according to motor score while maintaining activities of daily living and quality of life, it is possible to wait and observe the situation instead of immediately revising the electrode.

Deep brain stimulation hardware-related infections: a report of 12 cases and review of the literature

In this monocentric study, the median delay between deep brain stimulation implantation and infection was 28 days (range, 8-820). Infections limited to generator (n = 4) required partial hardware removal, whereas infections involving frontal or retroauricular sites (n = 7) required total removal. Surgical samples yielded Staphylococcus aureus (n = 6), Staphylococcus epidermidis (n = 2), Propionibacterium acnes, and Micrococcus species.

Severe agitation following deep brain stimulation for parkinsonism

The use of deep brain stimulation has become increasingly common for the treatment of movement disorders, including Parkinson disease. Although deep brain stimulation is generally very successful in alleviating the extrapyramidal symptoms of Parkinson disease, side effects can occur. This case report describes a patient presenting to the emergency department in a state of extreme aggression 3 days after a change in the parameters of his bilateral subthalamic nucleus stimulator. We review the complications of deep brain stimulation relevant to the emergency physician and provide some practical information on stimulator adjustment in an emergency.

Diagnosis and treatment of complications related to deep brain stimulation hardware

Deep brain stimulation is a therapeutic technique increasingly used in the treatment of a variety of neurological, psychiatric, and pain disorders. Although beneficial, it carries the immediate and long-term risks associated with implanted hardware in the brain parenchyma and subcutaneous tissue. The most common hardware complications include electrode migrations or misplacements, wire fractures, skin erosion, infections, and device malfunction. We systematically reviewed the literature on deep brain stimulation-related complications and propose a diagnostic and therapeutic algorithm. Our aim is to provide a guide for clinicians and medical staff involved in the treatment of patients with deep brain stimulation for rapid recognition and efficient management of these complications.

Twiddler's syndrome in a patient with a deep brain stimulation device for generalized dystonia

Deep brain stimulation (DBS) is the technique of neurostimulation of deep brain structures for the treatment of conditions such as essential tremor, dystonia, Parkinson's disease and chronic pain syndromes. The procedure uses implanted deep brain stimulation electrodes connected to extension leads and an implantable pulse generator (IPG). Hardware failure related to the DBS procedure is not infrequent, and includes electrode migration and disconnection. We describe a patient who received bilateral globus pallidus internus DBS for dystonia with initially good clinical response, but the device eventually failed. Radiographs showed multiple twisting of the extension leads with disconnection from the brain electrodes and a diagnosis of Twiddler's syndrome was made. Twiddler's syndrome was first described in patients with cardiac pacemakers. Patients with mental disability, elderly and obese patients are at increased risk. Twiddler's syndrome should be suspected whenever there is a failure of the DBS device to relieve symptoms previously responsive to stimulation. Surgical correction is usually required.

Deep brain stimulation in clinical trials and animal models of depression

Deep brain stimulation (DBS) is currently being investigated as a therapy for the treatment of depression. Despite promising results of recent clinical trials, neural and chemical mechanisms responsible for the effects of stimulation are still unclear. In this article, we review clinical and laboratory findings on DBS for depression. Particular emphasis will be given to aspects involved in the translation of data from animal models to humans and in our findings on the potential substrates involved in the antidepressant effects of DBS in rats.

The pedunculopontine nucleus as a target for deep brain stimulation

The pedunculopontine nucleus (PPN) is a brain stem locomotive center that is also involved in the processing of sensory and behavioral information. The PPN has been recently proposed as a potential target for the treatment of axial symptoms in Parkinson's disease (PD). To date, results of the first series of PD patients treated with PPN deep brain stimulation (DBS) have shown promising results. In this article, we review some of the basic aspects of the PPN as a target and the outcome of the recently published clinical trials.

Deep brain stimulation for Parkinson disease: an expert consensus and review of key issues

OBJECTIVE

To provide recommendations to patients, physicians, and other health care providers on several issues involving deep brain stimulation (DBS) for Parkinson disease (PD).

DATA SOURCES AND STUDY SELECTION

An international consortium of experts organized, reviewed the literature, and attended the workshop. Topics were introduced at the workshop, followed by group discussion.

DATA EXTRACTION AND SYNTHESIS

A draft of a consensus statement was presented and further edited after plenary debate. The final statements were agreed on by all members.

CONCLUSIONS

(1) Patients with PD without significant active cognitive or psychiatric problems who have medically intractable motor fluctuations, intractable tremor, or intolerance of medication adverse effects are good candidates for DBS. (2) Deep brain stimulation surgery is best performed by an experienced neurosurgeon with expertise in stereotactic neurosurgery who is working as part of a interprofessional team. (3) Surgical complication rates are extremely variable, with infection being the most commonly reported complication of DBS. (4) Deep brain stimulation programming is best accomplished by a highly trained clinician and can take 3 to 6 months to obtain optimal results. (5) Deep brain stimulation improves levodopa-responsive symptoms, dyskinesia, and tremor; benefits seem to be long-lasting in many motor domains. (6) Subthalamic nuclei DBS may be complicated by increased depression, apathy, impulsivity, worsened verbal fluency, and executive dysfunction in a subset of patients. (7) Both globus pallidus pars interna and subthalamic nuclei DBS have been shown to be effective in addressing the motor symptoms of PD. (8) Ablative therapy is still an effective alternative and should be considered in a select group of appropriate patients.

Gamma Knife thalamotomy for treatment of essential tremor: long-term results

Object

The goal of this report was to describe the safety and effectiveness of nucleus ventralis intermedius (VIM) thalamotomy performed with the Leksell Gamma Knife (GK) for the treatment of essential tremor (ET).

Methods

One hundred seventy-two patients underwent a total of 214 VIM thalamotomy procedures with the Leksell GK between February 1994 and March 2007 for treatment of disabling ET. Eleven patients were lost to follow-up less than 1 year after the procedures, so that in this report the authors describe the results in 161 patients who underwent a total of 203 thalamotomies (119 unilateral and 42 bilateral).

Results

There were statistically significant decreases (p < 0.0001) in tremor scores for both writing and drawing. The mean postoperative follow-up duration for all patients was 44 ± 33 months. Fifty-four patients have been followed for more than 60 months posttreatment. There were 14 patients who suffered neurological side effects that were temporary (6) or permanent (8), which accounted for 6.9% of the 203 treatments. All complications were related to lesions that grew larger than expected.

Conclusions

A VIM thalamotomy with the Leksell GK offers a safe and effective alternative for surgical treatment of ET. It is particularly applicable to patients who are not ideal candidates for deep brain stimulation but can be offered to all patients who are considering surgical intervention for ET.

"Twiddler syndrome" in two patients with deep brain stimulation

Twiddler syndrome occurs when a patient intentionally or unintentionally manipulates an implantable generator (usually a pacemaker) and dislodges the pacing leads, causing malfunction of the device. Though the syndrome has been described in patients with pacemakers, to our knowledge only one spontaneous case has been described in patients undergoing deep brain stimulation for movement disorders. We report the clinical cases of two patients with Parkinson's disease who had subthalamic bilateral electrodes implanted and presented the twiddler syndrome 2 and 3 years after surgery. We analysed the possible mechanisms of this syndrome and note that twiddler syndrome should be suspected in patients undergoing deep brain stimulation and showing hardware dysfunction.

Skin complications in deep brain stimulation for Parkinson's disease: frequency, time course, and risk factors

PURPOSE

Deep brain stimulation (DBS) has been recognized as an efficacious treatment for movement disorders. Its beneficial effects however may be lost due to skin complications such as erosions or infections over the implanted foreign material. We sought to document skin complications in the entire Parkinson's disease patient population who received a DBS system at the Marburg/Kassel implantation centre since the start of our DBS program in January 2002 to analyze frequency, time course, and possible risk factors.

METHODS

We investigated 85 consecutive patients with Parkinson's disease (PD) from a single center/single surgeon DBS series for the occurrence of skin complications and analyzed localization, time course, and possible risk factors. Mean follow-up was 3 years (range 1-7 years).

RESULTS

In total, 21/85 patients (24.7%) suffered a total of 30 single skin complications. Sixty percent of all incidents occurred within the first post-operative year. Forty percent of all incidents occurred later than the first year following primary implantation. Complications involved the burr hole cap in 37%, the course of the cables in 33%, and the impulse generator (IPG) site in 30%. Six of 21 patients suffered recurring skin complications. Eight patients permanently lost their DBS system. Factor analysis for age, gender, disease duration, disease severity, the incidence of hypertension or diabetes as well as a 2-day period with externalized electrodes for continuous test stimulation did not have any statistically significant impact on skin complications.

CONCLUSIONS

We conclude that (1) PD patients have a risk for skin complications after DBS as long as the system remains in situ and (2) there are at present no identifiable risk factors for skin complications after DBS, other than PD itself.

Lead Fractures in Deep Brain Stimulation during Long-Term Follow-Up

The purpose was to determine the incidence of lead fracture in patients with DBS over a long period of time. We present a retrospective study of 208 patients who received 387 DBS electrodes. Fourteen patients had sixteen lead fractures (4% of the implanted leads) and two patients suffered from 2 lead fractures. Of all lead fractures, five patients had the connection between the leads and the extension cables located in mastoids region, ten in cervical area and one in thoracic region. The mean distance from the connection between the electrode and the extension cable and the lead fracture was 10.7 mm. The lead fracture is a common, although long-term complication in DBS surgery. In our experience, the most common site of electrode cable breakage is approximately between 9 and 13 mm from the junction between the lead and the extension cable. The most important cause of lead fracture is the rotational movement of the lead-extension cable system. If we suspect lead fracture, we must check the impedance of the electrode and to evaluate the side effects of voltage. Finally, we must conduct a radiological screening.

Deep brain stimulation in Parkinson's disease

During the last 15 years deep brain stimulation (DBS) has been established as a highly-effective therapy for advanced Parkinson's disease (PD). Patient selection, stereotactic implantation, postoperative stimulator programming and patient care requires a multi-disciplinary team including movement disorders specialists in neurology and functional neurosurgery. To treat medically refractory levodopa-induced motor complications or resistant tremor the preferred target for high-frequency DBS is the subthalamic nucleus (STN). STN-DBS results in significant reduction of dyskinesias and dopaminergic medication, improvement of all cardinal motor symptoms with sustained long-term benefits, and significant improvement of quality of life when compared with best medical treatment. These benefits have to be weighed against potential surgery-related adverse events, device-related complications, and stimulus-induced side effects. The mean disease duration before initiating DBS in PD is currently about 13 years. It is presently investigated whether the optimal timing for implantation may be at an earlier disease-stage to prevent psychosocial decline and to maintain quality of life for a longer period of time.

Occipital nerve stimulator lead pathway length changes with volunteer movement: an in vitro study

BACKGROUND

Occipital nerve stimulation is a modality reserved for refractory headache disorders. Leads (wires) are inserted subcutaneously in the occipital region to stimulate the distal C1-3 nerves; lead migration may result from repeated mechanical forces on the lead associated with patient movement. The primary aim of this study was to determine implantation pathways associated with the least pathway length change secondary to body movement in an in vitro model of an occipital stimulator system.

METHODS

After institutional review board approval, 10 volunteers were recruited. The expected pathway of an occipital stimulator system was identified and measured externally, and then changes in pathway length were measured during various volunteer movements, including neck and low back flexion, extension, rotation, and lateral flexion. The pathways studied included those that connect internal pulse generators in the gluteal, low abdominal, and infraclavicular regions to occipital leads inserted via a cervical or retromastoid approach.

RESULTS

The flexion/extension pathway length changes associated with midline occipital and retromastoid sites to the infraclavicular site were significantly less than those pathways to the periscapular site. Also, the abdominal site was associated with less pathway length change during flexion/extension than the gluteal site.

CONCLUSIONS

Internal pulse generators in sites other than the buttock, including infraclavicular or low abdomen, may be associated with lower lead migration risk. There are many considerations when selecting insertion sites and lead pathways for occipital nerve stimulation. Implanters and patients may consider these results when contemplating surgical approaches to this challenging form of peripheral nerve stimulation.

Unilateral pedunculopontine stimulation improves falls in Parkinson's disease

Postural instability and falls are a major source of disability in patients with advanced Parkinson's disease. These problems are currently not well addressed by either pharmacotherapy nor by subthalamic nucleus deep-brain stimulation surgery. The neuroanatomical substrates of posture and gait are poorly understood but a number of important observations suggest a major role for the pedunculopontine nucleus and adjacent areas in the brainstem. We conducted a double-blinded evaluation of unilateral pedunculopontine nucleus deep-brain stimulation in a pilot study in six advanced Parkinson's disease patients with significant gait and postural abnormalities. There was no significant difference in the double-blinded on versus off stimulation Unified Parkinson's Disease Rating Scale motor scores after 3 or 12 months of continuous stimulation and no improvements in the Unified Parkinson's Disease Rating Scale part III scores compared to baseline. In contrast, patients reported a significant reduction in falls in the on and off medication states both at 3 and 12 months after pedunculopontine nucleus deep-brain stimulation as captured in the Unified Parkinson's Disease Rating Scale part II scores. Our results suggest that pedunculopontine nucleus deep-brain stimulation may be effective in preventing falls in patients with advanced Parkinson's disease but that further evaluation of this procedure is required.

Human cortical prostheses: lost in translation?

Direct brain control of a prosthetic system is the subject of much popular and scientific news. Neural technology and science have advanced to the point that proof-of-concept systems exist for cortically-controlled prostheses in rats, monkeys, and even humans. However, realizing the dream of making such technology available to everyone is still far off. Fortunately today there is great public and scientific interest in making this happen, but it will only occur when the functional benefits of such systems outweigh the risks. In this article, the authors briefly summarize the state of the art and then highlight many issues that will directly limit clinical translation, including system durability, system performance, and patient risk. Despite the challenges, scientists and clinicians are in the desirable position of having both public and fiscal support to begin addressing these issues directly. The ultimate challenge now is to determine definitively whether these prosthetic systems will become clinical reality or forever unrealized.

Deep brain stimulation of the subthalamic nucleus for the treatment of Parkinson's disease

High-frequency deep brain stimulation (DBS) of the subthalamic nucleus (STN-HFS) is the preferred surgical treatment for advanced Parkinson's disease. In the 15 years since its introduction into clinical practice, many studies have reported on its benefits, drawbacks, and insufficiencies. Despite limited evidence-based data, STN-HFS has been shown to be surgically safe, and improvements in dopaminergic drug-sensitive symptoms and reductions in subsequent drug dose and dyskinesias are well documented. However, the procedure is associated with adverse effects, mainly neurocognitive, and with side-effects created by spread of stimulation to surrounding structures, depending on the precise location of electrodes. Quality of life improves substantially, inducing sudden global changes in patients' lives, often requiring societal readaptation. STN-HFS is a powerful method that is currently unchallenged in the management of Parkinson's disease, but its long-term effects must be thoroughly assessed. Further improvements, through basic research and methodological innovations, should make it applicable to earlier stages of the disease and increase its availability to patients in developing countries.

Infection following deep brain stimulator implantation performed in the conventional versus magnetic resonance imaging–equipped operating room

Object

Risk factors for deep brain stimulator (DBS) infection are poorly defined. Because DBS implants are not frequently performed in the MR imaging–equipped operating room (OR), no specific data about infection of DBS implants performed in the MR imaging environment are available in the literature. In this study the authors focus on the incidence of infection in patients undergoing surgery in the conventional versus MR imaging–equipped OR.

Methods

To identify cases of DBS-associated infection, the authors performed a retrospective cohort study with nested case-control analysis of all patients undergoing DBS implantation at the University of California Los Angeles Medical Center. Cases of DBS infection were identified using standardized clinical and microbiological criteria.

Results

Between January 1998 and September 2003, 228 DBSs were implanted. Forty-seven operations (20.6%) were performed in the conventional OR and 181 (79.4%) in the MR imaging–equipped OR. There was definite infection in 13 cases (5.7%) and possible infection in 7 cases (3%), for an overall infection rate of 8.7% (20 of 228 cases). There was no significant difference in infection rates in the conventional (7 [14.89%] of 47) versus MR imaging–equipped OR (13 [7.18%] of 181) (p = 0.7). Staphylococcus aureus was isolated in 62% of cases. Twelve of 13 confirmed cases underwent complete hardware removal. On case-control analysis, younger age (≤ 58.5 years) was a significant predictor of DBS infection (odds ratio 3.4, p = 0.027)

Conclusions

Infection is a serious complication of DBS implantation and commonly requires device removal for cure. The authors found that DBS implantation can be safely performed in MR imaging–equipped suites, possibly allowing improved lead placement. Young age was associated with an increased risk of DBS infection.

Cumulative and after-effects of short and weak coordinated reset stimulation: a modeling study

We show that the dynamical multistability of a network of bursting subthalamic neurons, caused by synaptic plasticity has a strong impact on the stimulus-response properties when exposed to weak and short desynchronizing stimuli. Intriguingly, such stimuli can reliably shift the network from a stable state with pathological synchrony and connectivity to a stable desynchronized state with down-regulated connectivity. However, unlike in the case of stronger coordinated reset stimulation, after termination of weaker stimulation the network may undergo a transient rebound of synchrony. When the coordinated reset stimulation is even weaker and/or shorter, so that a single stimulation epoch is not effective, the network dynamics and connectivity can still be reshaped in a cumulative manner by repetitive stimulation delivery.

Reoperation for suboptimal outcomes after deep brain stimulation surgery

OBJECTIVE

To examine a case series of reoperations for deep brain stimulation (DBS) leads in which clinical scenarios revealed suboptimal outcome from a previous operation. Suboptimally placed DBS leads are one potential reason for unsatisfactory results after surgery for Parkinson's disease (PD), essential tremor (ET), or dystonia. In a previous study of patients who experienced suboptimal results, 19 of 41 patients had misplaced leads. Similarly, another report commented that lead placement beyond a 2- to 3-mm window resulted in inadequate clinical benefit, and, in 1 patient, revision improved outcome. The goal of the current study was to perform an unblinded retrospective chart review of DBS patients with unsatisfactory outcomes who presented for reoperation.

METHODS

Patients who had DBS lead replacements after reoperation were assessed with the use of a retrospective review of an institutional review board-approved movement disorders database. Cases of reoperation for suboptimal clinical benefit were included, and cases of replacement of DBS leads caused by infection or hardware malfunction were excluded. Data points studied included age, disease duration, diagnosis, motor outcomes (the Unified Parkinson Disease Rating Scale III in PD, the Tremor Rating Scale in ET, and the Unified Dystonia Rating Scale in dystonia), quality of life (Parkinson's Disease Questionnaire-39 in PD), and the Clinician Global Impression scale. The data from before and after reoperation were examined to determine the estimated impact of repeat surgery.

RESULTS

There were 11 patients with PD, 7 with ET, and 4 with dystonia. The average age of the PD group was 52 years, the disease duration was 10 years, and the average vector distance of the location of the active DBS contact was adjusted 5.5 mm. Six patients (54%) with PD had preoperative off medication on DBS Unified Parkinson Disease Rating Scale scores that could be compared with postoperative off medication on DBS scores. The average improvement across this group of patients was 24.4%. The Parkinson's Disease Questionnaire-39 improved in the areas of mobility (28.18), activities of daily living (14.77), emotion (14.72), stigma (17.61), and discomfort (17.42). The average age of the ET group was 66 years, the disease duration was 29 years, and the average adjusted distance was 6.1 mm. Five ET patients (83.3%) in the cohort had a prereplacement on DBS Tremor Rating Scale and a postreplacement on DBS Tremor Rating Scale with the average improvement of 60.4%. The average age of the dystonia group was 39 years, the average disease duration was 7 years, and the average adjusted lead distance was 6.7 mm. Three patients (75%) with dystonia had prereplacement on DBS Unified Dystonia Rating Scale and postreplacement on DBS Unified Dystonia Rating Scale scores. Across these 3 dystonia patients, the improvement was 12.8%. Clinician Global Impression scale scores (1, very much improved; 2, much improved; 3, minimally improved; 4, no change; 5, minimally worse; 6, much worse; 7, very much worse) after replacement revealed the following results in patients with PD: 1, 7 patients; 2, 3 patients; 3, 1 patient); with ET (1, 4 patients; 2, 3 patients); and with dystonia (1, 1 patient; 2, 2 patients; 3, 1 patient). The latency from original lead placement to reoperation (repositioning/revision) overall was 28.9 months (range, 2-104 mo); however, in leads referred from outside institutions (n = 11 patients), this latency was 48 months (range, 12-104 mo) compared with leads implanted by surgeons from the University of Florida (n = 11 patients), which was 9.7 months (range, 2-19 mo). The most common clinical history was failure to achieve a perceived outcome; however, history of an asymmetric benefit was present in 4 (18.2%) of 22 patients, and lead migration was present in 3 (13.6%) of 22 patients.

CONCLUSION

There are many potential causes of suboptimal benefit after DBS. Timely identification of suboptimal lead placements followed by reoperation and repositioning/replacement in a subset of patients may improve outcomes.

Neurosurgical strategies for Gilles de la Tourette's syndrome

Tourette's syndrome (TS) is a neurological disorder characterized by motor and vocal tics that typically begin in childhood and often are accompanied by psychiatric comorbidities. Symptoms of TS may be socially disabling and cause secondary medical complications. Pharmacological therapies remain the mainstay of symptom management. For the subset of patients in whom TS symptoms are medically recalcitrant and do not dissipate by adulthood, neurosurgery may offer an alternative treatment strategy. Greater understanding of the neuroanatomic and pathophysiologic basis of TS has facilitated the development of surgical procedures that aim to ameliorate TS symptoms by lesions or deep brain stimulation of cerebral structures. Herein, the rationale for the surgical management of TS is discussed and neurosurgical experiences since the 1960s are reviewed. The necessity for neurosurgical strategies to be performed with appropriate ethical considerations is highlighted.

Surgery for movement disorders

Movement disorders, such as Parkinson's disease, tremor, and dystonia, are among the most common neurological conditions and affect millions of patients. Although medications are the mainstay of therapy for movement disorders, neurosurgery has played an important role in their management for the past 50 years. Surgery is now a viable and safe option for patients with medically intractable Parkinson's disease, essential tremor, and dystonia. In this article, we provide a review of the history, neurocircuitry, indication, technical aspects, outcomes, complications, and emerging neurosurgical approaches for the treatment of movement disorders.

Methods of scalp revision for deep brain stimulator hardware: case report

OBJECTIVE

The use of deep brain stimulation (DBS) to treat a variety of disorders has expanded and will result in an increasingly larger number of patients and implanted electrodes. Hardware failure can result from malfunction, lead migration, fracture, and infection. Scalp erosion with exposure of underlying hardware can lead to potential infectious complications and is, in itself, a strong indication for explantation of the neurostimulation system. The patient's relief of symptoms after DBS will be limited by hardware-related complications and thus, strategies to revise scalp overlying hardware are important in the widespread application of DBS.

CLINICAL PRESENTATION

We describe strategies to address complications related to implanted DBS neurostimulator hardware specifically designed to address breach of the integrity of the scalp over the burr hole site. The aim of these approaches is to treat scalp erosion to allow for the reimplantation of previously explanted, infected hardware, or to treat thinned scalp with threatened erosion and prevent the need to remove exposed hardware that is otherwise functioning.

INTERVENTION

Two different approaches are presented: 1) a temporoparieto-occipital flap based on the superficial temporal artery with or without scalp expansion, and 2) a scalp fasciocutaneous flap with or without cranioplasty.

CONCLUSION

Stimulation of various deep brain targets helps patients with a wide range of diseases. In the future, with continued refinement, hardware complications can be minimized. Until then, novel approaches need to be developed to save DBS systems and provide symptomatic relief to patients.

Deep brain stimulator hardware-related infections: incidence and management in a large series

OBJECTIVE

Device-related infection is a common complication of deep brain stimulator (DBS) implantation. We reviewed the incidence and management of early hardware-related infections in a large series.

METHODS

All patients undergoing DBS implantation surgery between 1998 and 2006 at a single institution were entered into a prospectively designed database. After database verification by cross-referencing manufacturer implantation records, a query was performed to include all new Medtronic (Minneapolis, MN) implantations performed with standard operating room technique. Hardware-related infections requiring further surgery were identified, and charts were reviewed to assess the success of lead-sparing partial hardware removal in this group.

RESULTS

Four hundred twenty patients received 759 new DBS electrodes and 615 new internal pulse generators for the treatment of movement disorders or pain. Nineteen patients (4.5%) had an early (<6 mo) hardware-related infection requiring further surgery. There were no intracranial infections. Four patients presented with extensive cellulitis or wound dehiscence and were treated with total hardware removal. Fourteen patients presented with more localized infections and were treated by removal of the involved components only, followed by intravenously administered antibiotics. In nine of these patients, partial hardware removal successfully resolved the infection without requiring removal of the DBS electrodes. Wound washout alone was attempted in one patient and failed.

CONCLUSION

In a large series of new DBS hardware implantations, the incidence of postoperative hardware-related infection requiring further surgery was 4.5%. When only one device component was involved, partial hardware removal was often successful.