Aviva Abosch

An International Survey of Deep Brain Stimulation Procedural Steps

Background: Deep brain stimulation (DBS) surgery is standard of care for the treatment of certain movement disorders. Objective: We sought to characterize the spectrum of steps performed in DBS surgery, at centers around the world where this surgery is performed. Methods: We identified the main steps in DBS surgery workflow and grouped these 19 steps into 3 phases (preoperative, operative, and postoperative). A survey tool, informed by a pilot survey, was administered internationally by trained study personnel at high- and low-volume DBS centers. Procedural components, duration, and surgeon motivational factors were assessed. Cluster analysis was used to identify procedural and behavioral clusters. Results: One hundred eighty-five procedure workflow surveys (143 DBS centers) and 65 online surveys of surgeon motivational drivers were completed (45% response rate). Significant heterogeneity in technique, operative time, and surgeon motivational drivers was reported across centers. Conclusions: We provide a description of the procedural steps involved in DBS surgery and the duration of these steps, based on an international survey. These data will enable individual surgeons and centers to examine their own experience relative to colleagues at other centers and in other countries. Such information could also be useful in comparing efficiencies and identifying workflow obstacles between different hospital environments.

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

OBJECT 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. METHODS 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. RESULTS 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. CONCLUSIONS 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.

Biological basis for the surgical treatment of depression

An estimated 20% of patients with major depression are refractory to existing therapies. The purpose of this review is to provide a theoretical and neuroscientific framework in which to interpret new work in the field of surgical treatment for depression. This review focuses on existing clinical and imaging data, current disease models, and results of recent case reports and patient series that together may inform the construction of appropriate clinical trials for the surgical treatment of refractory depression.

Stereotactic neurosurgery for movement disorders.

Stereotactic neurosurgery for the treatment of movement disorders focuses primarily on the treatment of Parkinsons disease (PD), essential tremor (ET), and dystonia. The surgical targets in use are the subthalamic nucleus (STN) and the globus pallidus internus (GPi) for PD, GPi for dystonia, and ventralis intermedius (Vim) nucleus of the thalamus for ET. Following target selection, procedures include the generation of lesions or the placement of deep brain stimulating electrodes in the selected target. Additionally, transplantation has been used in the treatment of PD. The indications, outcomes, and risks of the various procedures are reviewed.

Attrition rates in neurosurgery residency: Analysis of 1361 consecutive residents matched from 1990 to 1999

OBJECT The objective of this study is to determine neurosurgery residency attrition rates by sex of matched applicant and by type and rank of medical school attended. METHODS The study follows a cohort of 1361 individuals who matched into a neurosurgery residency program through the SF Match Fellowship and Residency Matching Service from 1990 to 1999. The main outcome measure was achievement of board certification as documented in the American Board of Neurological Surgery Directory of Diplomats. A secondary outcome measure was documentation of practicing medicine as verified by the American Medical Association DoctorFinder and National Provider Identifier websites. Overall, 10.7% (n=146) of these individuals were women. Twenty percent (n=266) graduated from a top 10 medical school (24% of women [35/146] and 19% of men [232/1215], p=0.19). Forty-five percent (n=618) were graduates of a public medical school, 50% (n=680) of a private medical school, and 5% (n=63) of an international medical school. At the end of the study, 0.2% of subjects (n=3) were deceased and 0.3% (n=4) were lost to follow-up. RESULTS The total residency completion rate was 86.0% (n=1171) overall, with 76.0% (n=111/146) of women and 87.2% (n=1059/1215) of men completing residency. Board certification was obtained by 79.4% (n=1081) of all individuals matching into residency between 1990 and 1999. Overall, 63.0% (92/146) of women and 81.3% (989/1215) of men were board certified. Women were found to be significantly more at risk (p<0.005) of not completing residency or becoming board certified than men. Public medical school alumni had significantly higher board certification rates than private and international alumni (82.2% for public [508/618]; 77.1% for private [524/680]; 77.8% for international [49/63]; p<0.05). There was no significant difference in attrition for graduates of top 10-ranked institutions versus other institutions. There was no difference in number of years to achieve neurosurgical board certification for men versus women. CONCLUSIONS Overall, neurosurgery training attrition rates are low. Women have had greater attrition than men during and after neurosurgery residency training. International and private medical school alumni had higher attrition than public medical school alumni.

Prediction of STN-DBS Electrode Implantation Track in Parkinson's Disease by Using Local Field Potentials.

Optimal electrophysiological placement of the DBS electrode may lead to better long term clinical outcomes. Inter-subject anatomical variability and limitations in stereotaxic neuroimaging increase the complexity of physiological mapping performed in the operating room. Microelectrode single unit neuronal recording remains the most common intraoperative mapping technique, but requires significant expertise and is fraught by potential technical difficulties including robust measurement of the signal. In contrast, local field potentials (LFPs), owing to their oscillatory and robust nature and being more correlated with the disease symptoms, can overcome these technical issues. Therefore, we hypothesized that multiple spectral features extracted from microelectrode-recorded LFPs could be used to automate the identification of the optimal track and the STN localization. In this regard, we recorded LFPs from microelectrodes in three tracks from 22 patients during DBS electrode implantation surgery at different depths and aimed to predict the track selected by the neurosurgeon based on the interpretation of single unit recordings. A least mean square (LMS) algorithm was used to de-correlate LFPs in each track, in order to remove common activity between channels and increase their spatial specificity. Subband power in the beta band (11–32 Hz) and high frequency range (200–450 Hz) were extracted from the de-correlated LFP data and used as features. A linear discriminant analysis (LDA) method was applied both for the localization of the dorsal border of STN and the prediction of the optimal track. By fusing the information from these low and high frequency bands, the dorsal border of STN was localized with a root mean square (RMS) error of 1.22 mm. The prediction accuracy for the optimal track was 80%. Individual beta band (11–32 Hz) and the range of high frequency oscillations (200–450 Hz) provided prediction accuracies of 72 and 68% respectively. The best prediction result obtained with monopolar LFP data was 68%. These results establish the initial evidence that LFPs can be strategically fused with computational intelligence in the operating room for STN localization and the selection of the track for chronic DBS electrode implantation.

Exploring the time-frequency content of high frequency oscillations for automated identification of seizure onset zone in epilepsy

OBJECTIVE High frequency oscillations (HFOs) in intracranial electroencephalography (iEEG) recordings are considered as promising clinical biomarkers of epileptogenic regions in the brain. The aim of this study is to improve and automatize the detection of HFOs by exploring the time-frequency content of iEEG and to investigate the seizure onset zone (SOZ) detection accuracy during the sleep, awake and pre-ictal states in patients with epilepsy, for the purpose of assisting the localization of SOZ in clinical practice. APPROACH Ten-minute iEEG segments were defined during different states in eight patients with refractory epilepsy. A three-stage algorithm was implemented to detect HFOs in these segments. First, an amplitude based initial detection threshold was used to generate a large pool of HFO candidates. Then distinguishing features were extracted from the time and time-frequency domain of the raw iEEG and used with a Gaussian mixture model clustering to isolate HFO events from other activities. The spatial distribution of HFO clusters was correlated with the seizure onset channels identified by neurologists in seven patient with good surgical outcome. MAIN RESULTS The overlapping rates of localized channels and seizure onset locations were high in all states. The best result was obtained using the iEEG data during sleep, achieving a sensitivity of 81%, and a specificity of 96%. The channels with maximum number of HFOs identified epileptogenic areas where the seizures occurred more frequently. SIGNIFICANCE The current study was conducted using iEEG data collected in realistic clinical conditions without channel pre-exclusion. HFOs were investigated with novel features extracted from the entire frequency band, and were correlated with SOZ in different states. The results indicate that automatic HFO detection with unsupervised clustering methods exploring the time-frequency content of raw iEEG can be efficiently used to identify the epileptogenic zone with an accurate and efficient manner.

THALAMIC DEEP BRAIN STIMULATION FOR ESSENTIAL TREMOR

OBJECTIVE Thalamic deep brain stimulation (DBS) is commonly used to treat essential tremor, but the optimal lead location within the thalamus has not been systematically evaluated. We examined the relation of lead location to clinical outcome in a series of essential tremor patients treated by thalamic DBS. METHODS Fifty-seven leads in 37 patients were studied. Lead locations were measured by postoperative magnetic resonance imaging. Contralateral arm tremor was assessed in the DBS-on and DBS-off states using the Fahn-Tolosa-Marin tremor rating scale, with a mean follow-up of 26 months. Lead locations were statistically correlated, using analysis of variance, with percent improvement in tremor resulting from DBS activation. RESULTS Improvement in tremor score was significantly correlated with lead location in both the anteroposterior and lateral dimensions. In the plane of the commissures, the optimal electrode location was determined statistically to be 6.3 mm anterior to the posterior commissure and 12.3 mm lateral to the midline, or 10.0 mm lateral to the third ventricle. CONCLUSION Optimal electrode location for thalamic DBS in essential tremor corresponds to the anterior margin of the ventralis intermedius nucleus. Leads located greater than 2 mm (in the plane of the commissures) from the optimal coordinates are more likely to be associated with poor tremor control than leads within 2 mm of the optimal location. The incidence of true physiological tolerance to the antitremor effect of thalamic DBS (defined as poor tremor control in spite of lead location within 2 mm of the optimal site) was found to be 9%.

Subthalamic Deep Brain Stimulation for Parkinson’s Disease

An appreciation of the important modulatory role played by the subthalamic nucleus (STN) in regulating basal ganglia projections to the motor thalamus and brainstem, has led to interest in the STN as a target for the treatment of Parkinson’s disease (PD). In 1990, DeLong and colleagues first demonstrated the reversal of motor symptoms by lesioning the STN in monkeys with MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-induced parkinsonism (1). Concern about the possibility of irreversible side effects from the generation of bilateral STN lesions, and experience with the safety (2) but limited efficacy of thalamic stimulation, prompted Benabid and colleagues to attempt STN deep brain stimulation (DBS) (3). Recent reports from several centers demonstrating the safety and efficacy of chronic high-frequency STN DBS have generated interest in the STN as a target of choice in the surgical treatment of PD.

Localization of subthalamic nucleus borders using macroelectrode local field potential recordings.

Deep brain stimulation of the subthalamic nucleus (STN) is a highly effective treatment for motor symptoms of Parkinsons disease. However, precise intraoperative localization of STN remains a procedural challenge. In the present study, local field potentials (LFPs) were recorded from DBS macroelectrodes during trajectory to STN, in six patients. The frequency-vs-depth map of LFP activity was extracted and further analyzed within different sub-bands, to investigate whether LFP activity can be used for STN border identification. STN borders identified by LFPs were compared to border predictions by the neurosurgeon, based on microelectrode-derived, single-unit recordings (MER-SUA). The results demonstrate difference between MER-SUA and macroelectrode LFP recording with respect to the dorsal STN border of -1.00 ±0.84 mm and -0.42 ±1.07 mm in the beta and gamma frequency bands, respectively. For these sub-bands, RMS of these distances was found to be 1.26 mm and 1.06 mm, respectively. Analysis of other sub-bands did not allow for distinguishing the caudal border of STN. In conclusion, macroelectrode-derived LFP recordings may provide an alternative approach to MER-SUA, for localizing the target STN borders during DBS surgery.