Deep Brain Stimulation Insertion Research Articles

Microelectrode Recording During Deep Brain Stimulation Does Not Consistently Represent Lead Trajectory.

Long-term outcomes in deep brain stimulation (DBS) depend on accuracy of lead placement. Microelectrode recording (MER) is a long-used adjunct to leverage neurophysiological information to confirm satisfactory trajectory of implanted electrodes. The goal of this study was to evaluate the consistency in which electrodes are placed in sampled microelectrode trajectories. This is a retrospective study using intraoperative computed tomography to measure final electrode deviation from MER probe placement during the DBS insertion targeting subthalamic nucleus. Fifteen patients had 29 DBS leads placed using MER assistance. Radial distance between the probe and the lead were measured for each patient using intraoperative imaging. In addition, the preoperative target to final lead error was measured in 14 patients undergoing subthalamic nucleus implants without the use of MER and compared with the 15 patients in which MER was used as an adjunct. There was no significant difference in the mean radial target error (1.2 vs 1.0 mm, P = .156) when comparing the leads placed with or without MER assistance, respectively. The mean difference in final position of microelectrode compared with DBS lead was 0.9 ± 0.1 (range 0.4-2.0 mm). Of all MER-assisted electrodes placed, 44.8% (13) of electrode final positions radially deviated 1.0 mm or more from the MER probe. Electrode placement may deviate significantly from MER trajectories. Given the concern that physiological data may not be representative of the final electrode trajectory, surgeons should consider using intraoperative imaging or other adjunctive techniques during DBS to confirm accuracy and satisfactory trajectory of DBS leads.

Pericranial Flap Reconstruction in Pediatric Patients Undergoing Neuromodulatory Surgery: Impact on Wound Healing

Background: Pediatric patients with medically-intractable epilepsy may require modulation of seizure foci to reduce frequency and severity of seizures. These neuromodulatory procedures, which include responsive neurostimulator (RNS) and deep brain stimulator (DBS), involve the implantation of high-profile and long-term cranial hardware, placing patients at risk of wound healing complications, hardware exposure and infection. A multidisciplinary neurosurgical and plastic surgical approach utilizing pericranial flap coverage of hardware may decrease wound healing complications in these cases. This study compares the wound-healing outcomes in patients undergoing RNS/DBS insertion with and without pericranial flap coverage. Methods: A retrospective chart review was conducted of all patients who underwent RNS and DBS insertion with or without pericranial flap coverage at a level 1 pediatric medical center between 2014 and 2022. Wound healing outcomes at 60 days were evaluated. Data were compared using Fisher’s exact test. Results: Twenty-seven patients underwent 29 neuromodulatory epilepsy procedures (14 DBS, 15 RNS). Twenty of the procedures included a pericranial flap to cover hardware. Median length of stay was 2.0 days for both cohorts. Two subjects without pericranial flap reconstruction had a wound healing complication (22.2%), compared to none of the procedures that included a pericranial flap ( P = .09). Conclusion: In pediatric patients undergoing insertion of responsive neurostimulators and deep brain stimulators for medically-intractable epilepsy, a multidisciplinary neurosurgery and plastic surgery approach utilizing pericranial flap reconstruction may reduce the risk of postoperative wound complications.

Improved Side-Effect Stimulation Thresholds and Postoperative Transient Confusion With Asleep, Image-Guided Deep Brain Stimulation.

Asleep, image-guided deep brain stimulation (DBS) is a modern alternative to awake, microelectrode recording (MER) guidance. Studies demonstrate comparable efficacy and complications between techniques, although some report lower stimulation thresholds for side effects with image guidance. In addition, few studies directly compare the risk of postoperative transient confusion (pTC) across techniques. The purpose of this study was to compare clinical efficacy, stimulation thresholds for side effects, and rates of pTC with MER-guided DBS vs intraoperative 3D-fluoroscopy (i3D-F) guidance in Parkinson's disease and essential tremor. Consecutive patients from 2006 to 2021 were identified from the departmental database and grouped as having either MER-guided DBS or i3D-F-guided DBS insertion. Directional leads were used once commercially available. Changes in Unified Parkinson's Disease Rating Scale (UPDRS)-III scores, levodopa equivalent daily dose, Fahn-Tolosa-Marin scores, and stimulation thresholds were assessed, as were rates of complications including pTC. MER guidance was used to implant 487 electrodes (18 globus pallidus interna, GPi; 171 subthalamic nucleus; 76 ventrointermediate thalamus, VIM) in 265 patients. i3D-F guidance was used in 167 electrodes (19 GPi; 25 subthalamic nucleus; 41 VIM) in 85 patients. There were no significant differences in Unified Parkinson's Disease Rating III Scale, levodopa equivalent daily dose, or Fahn-Tolosa-Marin between groups. Stimulation thresholds for side effects were higher with i3D-F guidance in the subthalamic nucleus (MER, 2.80 mA ± 0.98; i3D-F, 3.46 mA ± 0.92; P = .002) and VIM (MER, 2.81 mA ± 1.00; i3D-F, 3.19 mA ± 1.03; P = .0018). Less pTC with i3D-F guidance (MER, 7.5%; i3D-F, 1.2%; P = .034) was also found. Although clinical efficacy between MER-guided and i3D-F-guided DBS was comparable, thresholds for stimulation side effects were higher with i3D-F guidance and the rate of pTC was lower. This suggests that image-guided DBS may affect long-term side effects and pose a decreased risk of pTC.

B - 32 Grief in Neuropsychological Assessment among Culturally Diverse Middle-Old Older Adults.

Bereavement, exacerbated by losses stemming from the COVID-19 pandemic, contributes to high rates of grief and associated mood disturbances among older adults, potentially impacting neurocognition. Middle-old cohorts (ages 75-84) are particularly vulnerable, due to elevated levels of baseline depression, complicated grief, and perceived lower quality of life. The contributory role of grief and culturally-relevant manifestations of bereavement should be carefully considered as potential confounds or performance contributors. Four cases seen for neuropsychological assessment in the Department of Neurological Surgery: A 75-year-old bilingual (Russian, English) patient with a meningioma who noticed cognitive changes following spouse's death from COVID-19; A 77-year-old monolingual (English) patient with Parkinson's disease undergoing a pre-surgical work-up prior to Deep Brain Stimulator insertion. Mood reportedly worsened sharply since spouse's recent death; An 81-year-old monolingual (Cantonese) patient undergoing a pre-surgical work-up prior to DBS insertion. Shared grieving the recent death of younger sibling from COVID-19; An 84-year-old, monolingual (English) patient who was evaluated due to longstanding cognitive challenges in the context of cerebrovascular disease (monitored by Neurological Surgery). Cognitive deficits reportedly precipitously worsened following spouse's death. While levels of neurocognitive and adaptive dysfunction varied, mood disturbance and affective distress likely reduced engagement in the testing process. Reluctance to disclose depressive and anxious symptomatology on questionnaires as a function of culture was noted. Thorough, culturally-sensitive, clinical interviewing and metrics are needed to elicit nuanced information. Grief and associated mood disturbances are to be prioritized and carefully considered in the evaluation and treatment plan with middle-old older adults.

Inhibitory concentration of propofol in combination with dexmedetomidine during microelectrode recording for deep brain stimulator insertion surgeries under general anesthesia.

Microelectrode recording (MER) for target refinement is widely used in deep brain stimulator insertion for Parkinson disease. Signals may be influenced by anesthetics when patients receive general anesthesia (GA). This study determined the inhibitory concentration (IC) of propofol on MER signals when it was coadministered with dexmedetomidine. Patients were anesthetized with dexmedetomidine (0.5 μg·kg loading, followed by infusion at 0.4 μg·kgh) and propofol through target-controlled infusion for GA with tracheal intubation. The surgeon conducted the online scoring of the background signals, spiking frequency, amplitude, and pattern of single-unit activities by using a 0-10 verbal numerical rating scale (NRS; 0, maximal suppression; 10, minimal suppression), and responses were grouped into suppression (NRS ≤ 6) and nonsuppression (NRS > 6). The median inhibitory concentration (IC50) of propofol (as target effect-site concentrations: Ceprop) was determined using modified Dixon's up-and-down method. Probit regression analysis was further used to obtain the dose-response relationship, and IC05 and IC95 were calculated. Twenty-three adult patients participated in this study. Under the concomitant infusion of dexmedetomidine, the predicted IC50 value (95% CI) of Ceprop for neuronal suppression during MER was 1.29 (1.24-1.34) μg·mL as calculated using modified Dixon's up-and-down method. Using probit analysis, the estimated IC05, IC50, and IC95 values (95% CIs) were 1.17 (0.87-1.23), 1.28 (1.21-1.34), and 1.40 (1.33-1.85) μg·mL, respectively. Our data provided reference values of propofol for dosage adjustment to avoid interference on MER under GA when anesthetics have to be continuously infused during recording.

Airway Management With a Stereotactic Headframe In Situ-A Mannequin Study.

Stereotactic headframe-based imaging is often needed for target localization during surgery for insertion of deep brain stimulators. A major concern during this surgery is the need for emergency airway management while an awake or sedated patient is in the stereotactic headframe. The aim of our study was to determine the ease of emergency airway management with a stereotactic headframe in situ. We conducted an observational study using a mannequin. A Leksell stereotactic headframe was placed on a mannequin in the operating room and the frame was fixed to the operating room table. Anesthesia personnel were asked to insert a #4 laryngeal mask and then to intubate the mannequin, using both direct (DL) and video laryngoscopy (VL). In addition, participants were asked to perform the same airway techniques in the mannequin without the headframe. Data were analyzed for time taken for airway management using different devices with and without the headframe. In addition, we compared the time taken to secure the airway between different participant groups. Thirty anesthesia personnel (7 residents, 12 fellows, and 11 consultants) participated in the study. With the headframe in situ, 97% of participants were able to insert a laryngeal mask on their first attempt; 93% and 97% of participants were able to intubate the mannequin using DL and VL respectively on their first attempt. Without the stereotactic headframe, all participants were able to insert the laryngeal mask and intubate on the first attempt. The average time taken to insert a laryngeal mask and intubate the mannequin using DL and VL with the headframe in situ was 39.3, 58.6, and 54.8 seconds, respectively. Our study showed that both laryngeal mask insertion and tracheal intubation can be performed with a stereotactic headframe in situ. A laryngeal mask is the quickest airway device to insert and can be inserted while the mannequin is in the standard surgical position. Further study is needed to validate the results in patients.

PRO: General Anesthesia for Deep Brain Stimulator Insertion in Patients With Parkinson Disease.

PRO: General Anesthesia for Deep Brain Stimulator Insertion in Patients With Parkinson Disease.

CON: Deep Brain Stimulator Insertion for Functional Neurosurgery Under General Anesthesia.

CON: Deep Brain Stimulator Insertion for Functional Neurosurgery Under General Anesthesia.

The Effect of General Anesthesia on the Microelectrode Recordings From Pallidal Neurons in Patients With Dystonia.

The most common anesthetic technique for patients undergoing insertion of deep brain stimulators (DBS) is local anesthesia with or without conscious sedation as this facilitates intraoperative microelectrode recordings (MERs) for target localization. However, general anesthesia (GA) may be needed in some of the patients especially those with dystonia. The purpose of our study was to determine the effects of GA on MERs from pallidal neurons in patients with dystonia undergoing DBS implantation surgery. After IRB approval, we retrospectively reviewed the medical records of all patients who had insertion of DBS from January 2009 to December 2013. Data collected and analyzed included demographics, indications for DBS, targets of insertion, MER, and anesthetic management. From the records we identified patients with dystonia who received GA for DBS insertion. We then compared the MER data under GA with the data from patients who had surgery under local anesthesia only during the same time period. Because of the small sample size, the effects of various anesthetic regiments on MER and localization of target nuclei were compared qualitatively. Of the 435 patients who underwent DBS insertion during the study period, 20 (4.3%) patients had GA for the procedure. Dystonia was the most common indication for GA (16/20 patients, 80%). Good-quality MER data obtained from 10 patients with dystonia under GA was compared with 8 patients who had no sedation for the procedure. Administration of GA made target localization difficult due to suppression of both spontaneous and evoked neuronal discharges from internal globus pallidus. Although not studied systematically, propofol (>100 mcg/kg/min) seemed to suppress pallidal discharges more than GA with a lower dose of propofol (<75 mcg/kg/min), remifentanil, and 0.2% to 0.4% end-tidal sevoflurane or desflurane. Our retrospective review suggests that there was a difference in spontaneous and evoked neuronal discharges with MER performed under GA compared with no sedation. MER recordings during GA appeared most robust during a combination of anesthetics including low-dose propofol infusion, remifentanil, and a low concentration of either sevoflurane or desflurane. Our findings can inform a power analysis to determine the sample size that would be required to prospectively test the hypothesis that there is a difference in spontaneous and evoked neuronal discharges with MER performed under GA compared with no sedation.

Deep Brain Stimulator insertion: What should we know as anaesthetists?

Correction: On 17th February 2016 the spelling of the second author's name was changed FROM Wasim Ali TO Wisam Ali. Abstract: Deep brain stimulation is the surgical treatment modality of choice for otherwise treatment resistant and affective disorders such as dystonia, tremor and Parkinson’s disease. Furthermore, DBS is now being used or investigated in the management of other conditions such as chronic pain, depression, obsessive compulsive disorder, Tourette syndrome, obesity, epilepsy and Alzheimer disease. The exact mechanism of action of DBS is not completely understood. The primary target sites vary according to patient’s symptoms. The various target sites are subthalamic nucleus, globus pallidus, pars internal and ventralis intermedius nucleus of thalamus. The surgical procedure involves insertion of electrodes into the target area of the brain through a burr hole. This is achieved through a combination of anatomical/imaging techniques (MRI and CT) and neurophysiological verification such as macro stimulation or micro-electrode recording. Once confirmed the electrode is connected via the cable to the pulse generator. The anaesthetic management describes the common and special consideration for awake DBS insertion and insertion under general anaesthesia and postoperative management of these patients. In our institute DBS has been practiced for well over a decade, allowing our multi-disciplinary team to build a large experience spanning both the main and experimental indications and across both the paediatric and adult age groups. The scope of this article is to understand the surgical steps and describe the practical aspect of conducting anaesthesia for patients undergoing

Anterior Nucleus Deep Brain Stimulation for Refractory Epilepsy

Anterior nucleus (AN) deep brain stimulation (DBS) is a palliative treatment for medically refractory epilepsy. The long-term efficacy and the optimal target localization for AN DBS are not well understood. To analyze the long-term efficacy of AN DBS and its predictors. We performed a retrospective review of 16 patients who underwent AN DBS. We selected only patients with reliable seizure frequency data and at least a 1-year follow-up. We studied the duration of the seizure reduction after DBS insertion and before stimulation (the insertional effect) and its association with long-term outcome. We modeled the volume of activation using the active contacts, stimulation parameters, and postoperative imaging. The overlap of this volume was plotted in Montreal Neurological Institute 152 space in 7 patients with significant clinical efficacy. Nine patients reported a decrease in seizure frequency immediately after electrode insertion (insertional or microthalamotomy effect). The duration of insertional effect varied from 2 to 4 months. However, 1 patient had a long-term insertional effect of 36 months. Altogether, 11 patients reported >50% decrease in seizure frequency with long-term stimulation. The most common pattern of seizure control was immediate and sustained stimulation benefit (n = 8). In patients with long-term stimulation benefit, the efficacious target was localized in the anteroventral AN in close proximity to the mammillothalamic tract. AN DBS is efficacious in the control of seizure frequency in selected patients. An insertional effect is commonly observed (56%). The most efficacious site of stimulation appears to be the anteroventral AN. AN, anterior nucleusDBS, deep brain stimulationMNI, Montreal Neurological InstituteMRE, medical refractory epilepsyMT, mammillothalamic tractSANTE, Stimulation of the Anterior Nucleus of the Thalamus for EpilepsyVNS, vagal nerve stimulation.

The effect of dopaminergic therapy on intraoperative microelectrode recordings for subthalamic deep brain stimulation under GA: can we operate on patients ‘on medications’?

Microelectrode recording (MER) plays an important role in target refinement in deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson's disease (PD). Traditionally, patients were operated on in the 'off-medication' state to allow intraoperative assessment of the patient response to direct STN stimulation. The development of intraoperative microelectrode recording (MER) has facilitated the introduction of general anaesthesia (GA). However, the routine withdrawal of dopaminergic medications has remained as standard practice. This retrospective review examines the effect of continuing these medications on intraoperative MER for subthalamic DBS insertion under GA and discusses the clinical implication of this approach. Retrospective review of PD patients who had bilateral STN DBS insertion was conducted. A cohort of seven patients (14 STN microelectrodes) between 2012 and 2013, who inadvertently underwent the procedure while 'on medication', was identified. This 'on-medication' group was compared to all other patients who underwent the same procedure between 2012 and 2013 and had their medications withdrawn preoperatively, the 'off-medication' group, n = 26 (52 STN DBS). The primary endpoint was defined as the number of microelectrode tracks required to obtain adequate STN recordings. A second endpoint was the length of MERs that was finally used to guide the DBS lead insertion. The Reduction of the levo-dopa equivalent daily dose (LEDD) was also examined as a surrogate marker for clinical outcome 12 months postoperatively for both groups. For the on-medication group further analysis of the clinical outcome was done relying on the change in the motor examination at 12 months following STN DBS using the following parameters (Hoehn and Yahr scale, the number of waking hours spent in the OFF state as well as the duration of dyskinesia during the ON periods). The on-medication group was statistically comparable in all baseline characteristics to the off-medication group, including age at operation 57 ± 9.9 years vs. 61.5 ± 9.2 years, p = 0.34 (mean ± SD); duration of disease (11.6 ± 5 years vs. 11.3 ± 4 years, p = 0.68); gender F:M ratio (1:6 vs. 9:17, p = 0.40). Both groups had similar PD medication regimes preoperatively expressed as levodopa equivalent daily dose (LEDD) 916 mg (558-1850) vs. 744 mg (525-3591), respectively, p = 0.77. In the on-medication group, all seven patients (14 STN electrodes) had satisfactory STN recording from a single brain track versus 15 out of 26 patients (57.7 %) in the off-medication group, p = 0.06. The length of MER was 4.5 mm (3.0-5.5) in the on-medication group compared to 3.5 mm (3.0-4.5) in the off-medication group, p = 0.16. The percentage of reduction in LEDD postoperatively for the on-medication group was comparable to that in the off-medication group, 62 % versus 58 %, respectively, p > 0.05. All patients in the on-medication group had clinically significant improvement in their PD motor symptoms as assessed by the Hoehn and Yahr scale; the number of hours (of the waking day) spent in the OFF state dropped from 6.9 (±2.3) h to 0.9 (±1.6) h; the duration of dyskinesia during the ON state dropped from 64 % (±13 %) of the ON period to only 7 % (±12 %) at 12 months following STN DBS insertion. STN DBS insertion under GA can be performed without the need to withdraw dompaminergic treatment preoperatively. In this review the inadvertent continuation of medications did not affect the physiological localisation of the STN or the clinical effectiveness of the procedure. The continuation of dopamine therapy is likely to improve the perioperative experience for PD patients, avoid dopamine-withdrawal complications and improve recovery. A prospective study is needed to verify the results of this review.

Profound hypertension with dexmedetomidine during insertion of deep brain stimulator

AbstractDexmedetomidine is now frequently used in the anaesthetic management of patients undergoing deep brain stimulator insertion for movement disorders. We present two patients with Parkinson’s disease and dystonia who developed marked increase in blood pressure and level of sedation during the infusion of a loading dose of dexmedetomidine (1 mcg/kg over 10 min). Both patients required treatment of their blood pressure. The first patient also had a computed tomography of the brain to rule out an intracranial event. The patients recovered from these untoward events in approximately 30 min. The possible explanations for both the hypertension and oversedation were underestimation of the severity of the patients’ underlying disease process and a relative overdose of the loading dose of dexmedetomidine.

Acute complications of movement disorders surgery: Effects of age and comorbidities

The most common indication for movement disorder surgery is Parkinson's disease (PD), and the incidence of PD increases with age. The analysis reported here was undertaken with the primary goal of examining whether there is a relationship between peri-operative complications and age. The Nationwide Inpatient Sample (Agency for Healthcare Research and Quality, Rockville, MD, USA) was queried for 10 years beginning in 1999 for patients undergoing deep brain stimulator insertion, pallidotomy, and thalamotomy for treatment of PD, essential tremor, and dystonia. Inpatient complications, including death, stroke (both ischemic and hemorrhagic), and other overall complications were examined. The relative risks associated with advanced age; primary diagnosis; treatment modality; the diagnoses of hypertension, diabetes, and nicotinism; and the cumulative number of comorbidities were examined. There were 5464 patients who met inclusion criteria, including 4145 patients treated for PD and 4961 patients treated with deep brain stimulation (DBS). Overall in-hospital mortality was 0.26%, with 0.15% related to surgical factors. There was a correlation between in-hospital mortality, increasing age, and number of medical comorbidities. After multivariate regression no factor remained predictive of mortality. Having more than 1 medical comorbidity or PD increased the risk of in-hospital complications. Patients with PD were more likely to suffer hemorrhage or stroke. Hypertension, diabetes, nicotinism, and modality of treatment were not associated with increased mortality, hemorrhage or stroke risk, or in-hospital mortality in univariate or multivariate analysis. Both age and medical comorbidity are correlated with in-hospital complications, but age appears to serve as a surrogate for comorbidity. Surgery for PD appears to carry an increased risk of hemorrhage or stroke and in-hospital complications.

An S-shaped incision for the insertion of deep brain stimulators

The S-shaped incision is a novel technique we have developed to minimise wound complications for the insertion of bilateral deep brain stimulators. An S-shaped incision incorporating both burrholes allows better exposure compared to the traditional bilateral incisions. The burrholes are drilled under each limb of the S and the incision does not run across them, decreasing the risk of infection. The electrodes are subsequently tunneled down the right side and connected to the battery. The use of the S-shaped incision results in less wound and electrode complications compared to the traditional bilateral linear incisions in our experience.

Rechargeable vs. Nonrechargeable Internal Pulse Generators in the Management of Dystonia

To test if deep brain stimulation (DBS) treatment of dystonia was similar in patients before and after implantation of rechargeable internal pulse generators (IPGs). The Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) severity and disability scores were compared in patients before DBS insertion, 24 months after DBS insertion with a nonrechargeable IPG, and after implantation of a rechargeable IPG. No significant differences were observed between dystonia control in patients before and after implantation of a rechargeable IPG. Rechargeable IPGs should be the IPGs of choice for dystonic patients receiving DBS as IPGs offer similar treatment efficacy to nonrechargeable IPGs with advantages in terms of costs and reductions in reimplantation frequency.

General anaesthesia for deep brain stimulator electrode insertion in Parkinson’s disease

This paper compares the use of general and local anaesthetic in patients having deep brain stimulator (DBS) surgery. It is a retrospective case note study of 46 patients treated consecutively with subthalamic nucleus stimulation for Parkinson's disease as practise changed in a Neurosurgical unit. The first 20 patients (LA group) had permanent electrodes placed under local anaesthesia. The remaining 26 patients (GA group) had the entire procedure under general anaesthesia. The groups were similar for age, sex, duration of Parkinson's disease and preoperative levodopa requirement. The clinical results were similar in that within each group, the reduction in levodopa was not only clinically but also statistically significant (p < 0.001 for both, paired t test): for the LA group, the 6-month requirement was 39.4% (29.5-52.6%) of the preoperative requirement and for the GA group, the 6-month requirement was 32.3% (25.2-41.5%) of the preoperative requirement. The reduction in levodopa was maintained at 1year. Of note, duration of surgery and length of stay were reduced. The mean duration of surgery was 8.2h (7.8-8.6) for the LA group and 7.5h (7.2-7.8) for the GA group (p = 0.003). The geometric mean of length of hospital stay was 5.4days(4.6-6.3) for the LA group and 3.8days (3.4-4.4) for the GA group (p = 0.001) There was no difference in electrophysiological recording. This study describes benefits in the GA group for the entire procedure of STN DBS. In these samples, there was no difference in the adverse effects seen in patients undergoing deep brain stimulator insertion with general anaesthetic compared with local anaesthetic. The use of general anaesthetic did not detract from the known benefits of surgery.

Dravet syndrome and deep brain stimulation: Seizure control after 10 years of treatment

Dravet syndrome is a genetically determined severe epilepsy associated with cognitive decline and ataxia. The many types of seizures seen in these patients are typically pharmacoresistant. Here we describe two adults with Dravet syndrome who were treated with thalamic deep brain stimulation (DBS) and followed for 10 years. One patient with partial onset seizures received DBS at age 19 and showed a marked improvement in seizure control after DBS insertion and stimulation. The other patient with generalized onset seizures received DBS at age 34 and did not show any immediate benefit. No side effects or changes in cognition were observed in either of the patients. This is the first report of (short- and) long-term results in Dravet patients treated with thalamic DBS. We speculate that the results of DBS for epilepsy in patients with Dravet syndrome may be related to age at initiation of DBS treatment and seizure type.

Brain penetration effects of microelectrodes and deep brain stimulation leads in ventral intermediate nucleus stimulation for essential tremor

Microelectrode recording (MER) and macrostimulation (test stimulation) are used to refine the optimal deep brain stimulation (DBS) lead placement within the operative setting. It is well known that there can be a microlesion effect with microelectrode trajectories and DBS insertion. The aim of this study was to determine the impact of intraoperative MER and lead placement on tremor severity in a cohort of patients with essential tremor. Consecutive patients with essential tremor undergoing unilateral DBS (ventral intermediate nucleus stimulation) for medication-refractory tremor were evaluated. Tremor severity was measured at 5 time points utilizing a modified Tremor Rating Scale: 1) immediately before MER; 2) immediately after MER; 3) immediately after lead implantation; 4) 6 months after DBS implantation in the off-DBS condition; and 5) 6 months after implantation in the on-DBS condition. To investigate the impact of the MER and DBS lead placement, Wilcoxon signed-rank tests were applied to test changes in tremor severity scores over the surgical course. In addition, a generalized linear mixed model including factors that potentially influenced the impact of the microlesion was also used for analysis. Nineteen patients were evaluated. Improvement was noted in the total modified Tremor Rating Scale, postural, and action tremor scores (p < 0.05) as a result of MER and DBS lead placement. The improvements observed following lead placement were similar in magnitude to what was observed in the chronically programmed clinic setting parameters at 6 months after lead implantation. Improvement in tremor severity was maintained over time even in the off-DBS condition at 6 months, which was supportive of a prolonged microlesion effect. The number of macrostimulation passes, the number of MER passes, and disease duration were not related to the change in tremor severity score over time. Immediate improvement in postural and intention tremors may result from MER and DBS lead placement in patients undergoing DBS for essential tremor. This improvement could be a predictor of successful DBS lead placement at 6 months. Clinicians rating patients in the operating room should be aware of these effects and should consider using rating scales before and after lead placement to take these effects into account when evaluating outcome in and out of the operating room.

Safety of magnetic resonance imaging of deep brain stimulator systems: a serial imaging and clinical retrospective study

With the expanding indications and increasing number of patients undergoing deep brain stimulation (DBS), postoperative MR imaging is becoming even more important in guiding clinical care and practice-based learning; important safety concerns have recently emerged, however. Although phantom model studies have driven conservative recommendations regarding imaging parameters, highlighted by 2 recent reports describing adverse neurological events associated with MR imaging in patients with implanted DBS systems, the risks of MR imaging in such patients in clinical practice has not been well addressed. In this study, the authors capitalized on their large experience with serial MR imaging (3 times per patient) to use MR imaging itself and clinical outcomes to examine the safety of MR imaging in patients who underwent staged implantation of DBS electrodes for Parkinson disease, tremor, and dystonia. Sixty-four patients underwent staged bilateral lead implantations between 1997 and 2006, and each patient underwent 3 separate MR imaging sessions subsequent to DBS placement. The first of these was performed after the first DBS placement, the second occurred prior to the second DBS placement, and third was after the second DBS placement. Follow-up was conducted to examine adverse events related either to MR imaging or to DBS-induced injury. One hundred and ninety-two MR images were obtained, and the mean follow-up time was 3.67 years. The average time between the first and second, and second and third MR imaging sessions was 19.4 months and 14.7 hours, respectively. Twenty-two MR imaging-detected new findings of hemorrhage were documented. However, all new findings were related to acute DBS insertion, whereas there were no new findings after imaging of the chronically implanted electrode. Although potential risks of MR imaging in patients undergoing DBS may be linked to excessive heating, induced electrical currents, disruption of the normal operation of the device, and/or magnetic field interactions, MR imaging can be performed safely in these patients and provides useful information on DBS lead location to inform patient-specific programming and practice-based learning.