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Background: Tractography based on diffusion-weighted magnetic resonance imaging (DWI) models the structural connectivity of the human brain. Deep brain stimulation (DBS) targeting the subthalamic n...

The dentato-rubro-thalamic tract (DRTT) has been found to play a major role in the mechanisms of tremor alleviation by deep brain stimulation (DBS) in essential tremor (ET). Still, the influence of the two different parts of the DRTT, consisting of crossing and nondecussating fibers, is not yet clear with respect to tremor reduction. The aim of this study was to assess the influence of the crossing and the nondecussating part of the DRTT on tremor control in ET.We investigated 80 electrode contacts in ten patients with ET who received bilateral DBS of the Nucleus ventralis intermedius of the thalamus (VIM). Preoperatively and with patients under general anesthesia, 3T magnetic resonance imaging scans were performed, including Diffusion Tensor Imaging scans with 64 gradient directions. We calculated the course of the two parts of the DRTT based on a workflow for probabilistic fiber tracking including protocols for correction of susceptibility- and eddy current-induced distortions. Distances of electrode contacts were correlated with clinical data from neurologic single pole testing.Voltage- and current-steered systems were analyzed separately. Regarding postural tremor, effective contacts showed significantly lower distances to both parts of the DRTT (crossing p 0.001, nondecussating p 0.05) in voltage-steered systems. Regarding intentional tremor, significant results were only found for the crossing part (p 0.01). Regarding both tremor types, effective contacts were closer to the crossing part, unlike less effective contacts. Nonlinear regression analyses using a logistic model showed higher coefficients for the crossing part of the DRTT. Multivariate regression models including distances to both parts of the DRTT showed a significant influence of only the crossing part. Analysis of current-steered systems showed unstable data, probably because of the small number of analyzed patients.Our data suggest an involvement of both parts of the DRTT in tremor reduction, indicating mediation of DBS effects by both fiber bundles, although the crossing part showed stronger correlations with good clinical responses. Nevertheless, special attention should be paid to methodologic aspects when using probabilistic tractography for patient-specific targeting to avoid uncertain and inaccurate results.

Background: Sedatives and opioids used during deep brain stimulation (DBS) surgery interfere with optimal target localization and add to side effects and risks, and thus should be minimized. Objective: To retrospectively test the actual need for sedatives and opioids when cranial nerve blocks and specific therapeutic communication are applied. Methods: In a case series, 64 consecutive patients treated with a strong rapport, constant contact, non-verbal communication and hypnotic suggestions, such as dissociation to a “safe place,” reframing of disturbing noises and self-confirmation, were compared to 22 preceding patients under standard general anaesthesia or conscious sedation. Results: With introduction of the protocol the need for sedation dropped from 100% in the control group to 5%, and from a mean dose of 444 mg to 40 mg in 3 patients. Remifentanil originally used in 100% of the patients in an average dose of 813 µg was reduced in the study group to 104 µg in 31% of patients. There were no haemodynamic reactions indicative of stress during incision, trepanation, electrode insertion and closure. Conclusion: With adequate therapeutic communication, patients do not require sedation and no or only low-dose opioid treatment during DBS surgery, leaving patients fully awake and competent during surgery and testing.

Objective Subthalamic deep brain stimulation may alleviate bradykinesia in Parkinson patients. Research suggests that this stimulation effect may be mediated by brain networks like the corticocerebellar loop. This study investigated the connectivity between stimulation sites and cortical and subcortical structures to identify connections for effective stimulation. Methods We retrospectively investigated 21 patients with Parkinson disease with bilateral subthalamic deep brain stimulation. Stimulation effectiveness in reducing bradykinesia, tremor, and rigidity was evaluated for each electrode contact in brain hemispheres contralateral to the affected hemibody. Dysarthric side effects were also examined. Probabilistic tractography based on diffusion-weighted imaging was performed in individual patient-specific brains using electrode contacts as seeds. Connectivity profiles of contacts with effective and noneffective stimulation were compared. Results Connectivity profiles of effective and noneffective contacts differed. Moreover, the connectivity profile for bradykinesia differed from that for rigidity, tremor, or dysarthria. Regarding bradykinesia, effective contacts were significantly more often connected with the ipsilateral superior cerebellar peduncle and the ipsilateral dentate nucleus, which correspond to the ipsilateral portion of the cerebellothalamocortical pathway. Rigidity was mitigated by stimulation of ascending brainstem and intralaminar thalamic connections. Tremor alleviation was related to connections with the internal capsule (anterior limb) and the pallidum. Dysarthric side effects were associated with connections to the supplementary motor area and the decussating cerebellothalamocortical pathway. Interpretation Whereas bradykinesia seems to be mitigated by stimulation of the ascending, ipsilateral cerebellothalamocortical pathway, stimulation of the descending corticopontocerebellar pathway may be ineffective. Rigidity, tremor, and dysarthric side effects seem to be influenced by different neural networks. ANN NEUROL 2019;85:852-864.

Objective The aim of our study was to evaluate the influence of the stimulation site relative to the dentato-rubro-thalamic tract (DRTT) on the alleviation of tremor in deep brain stimulation. Methods Ten DRTTs in five patients were investigated using preoperative diffusion tensor imaging (DTI). Regions of interest for fiber tracking were located in the cerebellar dentate nucleus, the superior cerebellar peduncle and the contralateral red nucleus. The position and distance of all intraoperative stimulation sites to the DRTT were measured and correlated to the amount of tremor reduction. Results Nine of 10 DRTTs could be identified using DTI-based fiber tracking. Better tremor reduction was achieved in locations in or posterior and lateral to the DRTT than in medial and anterior positions (p = 0.001). Stimulation sites inferior to and in the DRTT achieved better results than locations superior to the DRTT (p < 0.05). The vicinity of the stimulation site to the DRTT did not correlate with tremor alleviation. Discussion In deep brain stimulation targeting for thalamic stimulation sites is limited to statistical, atlas-based coordinates. Diffusion tensor imaging and fiber tracking was used to visualize the dentato-rubro-thalamic tract as a potential, individualized target structure. However, we could not demonstrate that contacts closer to the DRTT provided better clinical effects than distant contacts, in any given direction. DTI sequences with a higher number of read-out directions, probabilistic fiber tracking and three Tesla MRI scanners may lead to different results in the depiction of the chosen fiber tract and may provide a better correlation with stimulation effects. Conclusions The results do not provide sufficient evidence to define the DRTT as a new DBS-target for tremor. Further investigations on different fiber tracts, DTI sequences, and fiber tracking algorithms are mandatory.

Deep brain stimulation (DBS) of the medial forebrain bundle (MFB) was reported to reduce symptoms in psychiatric disorders. The aim of our study was to find standardised parameters for diffusion tensor imaging (DTI) based fibre tracking to reliably visualise the MFB.Twenty-two cerebral hemispheres in 11 patients were investigated. Three different regions of interest (ROIs) were defined as seed regions for fibre tracking: the ipsilateral and contralateral superior cerebellar peduncle (SCP) and the nucleus raphe dorsalis (NRD). From each seed region the fibres were followed separately through the ventral tegmental area (VTA = second ROI) and their further courses and volumina were documented and compared. Minimal fibre length was set at 30 mm and the FA threshold at 0.12.The fibre tracts starting in seed regions in the ipsilateral SCP and the NRD follow a similar course along the lateral wall of the third ventricle (hypothalamus) and the anterior limb of the internal capsule (ALIC) to inferior fronto-medial brain areas. These fibres are in accordance with the course of the MFB as described in various anatomical atlases. Consistently, a branch leaves the main fibre tract laterally to take a course through the capsula externa to the temporo-parietal cortex. Fibre tracts starting from the contralateral SCP follow a more superior and lateral course, including the dentato-rubro-thalamic and the pyramidal tract.Deterministic fibre tracking with standardised ROIs provides constant and reproducible delineations of the medial forebrain bundle. Its visualisation might help to adjust targeting in DBS for psychiatric disorders.

Deep brain stimulation for Parkinson's disease has become an established treatment option in recent years. The method and its application in clinical practice has proved to be safe and effective. Nevertheless, procedure-related and hardware-related complications occur. We present a rare case of a patient with an allergic reaction to the impulse generator. The patient suffered from delayed wound-healing deficits with several wound revisions and generator repositionings. After diagnosis of an allergic reaction to components of the generator, a custom-made silicon-coated model was implanted. Hereafter, no wound healing-deficit occurred throughout long-term follow-up. Allergic reaction to hardware components may lead to wound-healing deficits. In such cases, custom-made silicon-coated models may be an effective treatment option.

Background Some patients under thalamic deep brain stimulation (DBS) for essential tremor (ET) experience habituation of tremor reduction. The nucleus ventralis intermedius (Vim) is the current main target side for ET in DBS. However, the dentatorubrothalamic tract (DRTT) is considered the relevant structure to stimulate. We investigated the distance between the active contact of the DBS electrode and the DRTT and compared this distance in patients with habituation of tremor reduction and good responders. Material and Methods In this retrospective study, we performed deterministic fiber tracking of the DRTT in 6 patients (12 hemispheres) with ET who underwent DBS in the Vim. We subsequently measured the distance between the active contact of the electrode and the ipsilateral DRTT in both hemispheres. The clinical tremor response of those 6 patients was analyzed accordingly. Results The distance between the active contact and the DRTT in patients with better and constant clinical tremor reduction was shorter (mean distance: 2.9 ± 2.2 mm standard deviation [SD]) than in patients who showed habituation of their response (mean distance: 6.1 ± 3.9 mm SD). After re-placement of a thalamic electrode inside the DRTT in one patient who experienced unsatisfying tremor reduction due to habituation of stimulation, the tremor alleviation was significant and persistent at a 13-month follow-up. Conclusion This retrospective analysis suggests that recurrence of ET tremor under chronic DBS might be associated with a larger distance between the DRTT and the active lead contact, in comparison with the smaller distances in patients with persistently good tremor control.

In glioma surgery, the extent of resection (EOR) is one important predictor of progression-free survival. In 2006, fluorescence-guided surgery using 5-aminolevulinic acid (5-ALA) was shown to improve the EOR in malignant gliomas. However, the use of 5-ALA is complex and causes certain side effects. Sodium fluorescein (FL) is a fluorescent dye that is used for angiography in ophthalmic surgery. FL accumulates in areas of the disturbed blood-brain barrier and can be visualized under a 560-nm wavelength fluorescent light source (YELLOW 560 nm, Carl Zeiss Meditec, Oberkochen, Germany). Here, we present the first experiences with low-dose FL and YELLOW 560 nm in 35 patients with malignant brain tumors. A total of 200 mg of FL (3–4 mg/kg bodyweight) was administered in 35 patients during craniotomy as an off-label use between May and August 2012. We retrospectively analyzed the histology, pre-treatment, clinical parameters pre- and postoperatively and occurrence of any adverse effects. The feasibility and efficacy (‘helpful,’ ‘not helpful’) of FL under YELLOW 560 nm (demarcation of the tumor margin) was assessed by the responsible neurosurgeon (n = 5) for each surgical procedure. Twenty-six patients had gliomas (1 WHO grade I, 3 WHO grade II, 5 WHO grade III, 17 WHO grade IV), 5 patients had cerebral metastases, 2 had non-malignant astrogliosis and 2 had post-radiation necrosis. The fluorescence signal was detected in all patients immediately after the FL administration. FL application was classified as ‘helpful’ in 28 patients, implying improved visualization of the tumor margins. The intensity of the fluorescence signal seemed to be correlated to the histology and was strongly dependent on the pre-treatment status. We did not record any allergic reactions or any other adverse effects. The use of FL for the resection of brain tumors is safe and feasible. Presumably, the visualization of the tumor margin depends on the histopathology and on the pre-treatment status. A randomized evaluation of FL under the YELLOW 560 nm filter is planned to prospectively analyze the extent of resection in patients with malignant brain tumors.

This study compared tractography approaches for identifying cerebellar-thalamic fiber bundles relevant to planning target sites for deep brain stimulation (DBS). In particular, probabilistic and deterministic tracking of the dentate-rubro-thalamic tract (DRTT) and differences between the spatial courses of the DRTT and the cerebello-thalamo-cortical (CTC) tract were compared. Six patients with movement disorders were examined by magnetic resonance imaging (MRI), including two sets of diffusion-weighted images (12 and 64 directions). Probabilistic and deterministic tractography was applied on each diffusion-weighted dataset to delineate the DRTT. Results were compared with regard to their sensitivity in revealing the DRTT and additional fiber tracts and processing time. Two sets of regions-of-interests (ROIs) guided deterministic tractography of the DRTT or the CTC, respectively. Tract distances to an atlas-based reference target were compared. Probabilistic fiber tracking with 64 orientations detected the DRTT in all twelve hemispheres. Deterministic tracking detected the DRTT in nine (12 directions) and in only two (64 directions) hemispheres. Probabilistic tracking was more sensitive in detecting additional fibers (e.g. ansa lenticularis and medial forebrain bundle) than deterministic tracking. Probabilistic tracking lasted substantially longer than deterministic. Deterministic tracking was more sensitive in detecting the CTC than the DRTT. CTC tracts were located adjacent but consistently more posterior to DRTT tracts. These results suggest that probabilistic tracking is more sensitive and robust in detecting the DRTT but harder to implement than deterministic approaches. Although sensitivity of deterministic tracking is higher for the CTC than the DRTT, targets for DBS based on these tracts likely differ.

The aim of our study was to evaluate discrepancies between the electrophysiologically and MRI-defined subthalamic nucleus (STN) in order to contribute to the ongoing debate of whether or not microelectrode recording (MER) provides additional information to image-guided targeting in deep brain stimulation.Forty-four STNs in 22 patients with Parkinson's disease were investigated. The three-dimensional MRI-defined STN was derived from segmentations of axial and coronal T2-weighted images. The electrophysiological STNs were generated from intraoperative MERs in 1,487 locations. The stereotactical coordinates of positive and negative STN recordings were re-imported to the planning software, where a three-dimensional reconstruction of the electrophysiological STN was performed and fused to the MRI data set. The estimated borders of the MRI- and MER-STN were compared. For statistical analysis Student's t, Mann-Whitney rank sum and Fisher's exact tests were used.MER-STN volumes, which were found outside the MRI-STN, ranged from 0 mm(3) to 87 mm(3) (mean: 45 mm(3)). A mean of 44% of the MER-STN volumes exceeded the MRI-STN (maximum: 85.1%; minimum: 15.1 %); 53.4% (n = 793) of the microelectrode recordings were concordant and 46.6% (n = 694) discordant with the MRI-defined anatomical STN. Regarding the dorsal borders, we found discrepancies between the MER- and MRI-STN of 0.27 mm (= mean; SD: 0.51 mm) on the first operated side and 1.51 mm (SD: 1.5 mm) on the second (p = 0.010, t-test).MER provides additional information to high-resolution anatomical MR images and may help to detect the amount and direction of brain shift.

Objective Dizziness, a common postoperative symptom in patients with vestibular schwannomas (VSs) has a negative effect on the course of recovery, particularly in patients with severe symptoms. Reports on incidence and possible risk factors contributing to these symptoms are inconsistent and sometimes even contradictory. In order to establish a profile of patients at risk of severe symptoms in the immediate postoperative phase we retrospectively analyzed data of patients with unilateral VSs focusing on the incidence of severe dizziness and nausea during the immediate postoperative period and up to 1 year after surgery. Methods In a retrospective study data of 104 consecutive patients with VSs were analyzed. All patients underwent microsurgical tumor resection via a lateral-suboccipital approach. Factors that were assumed to affect the development of severe dizziness, such as age, gender, tumor size, tumor side, and cranial nerve function, were analyzed by means of univariate and multivariate logistic regression analyses. A three step grading system was used to describe symptoms of patients included in this study: 0 = no symptoms of dizziness, 1 = slight dizziness including light-headedness or feeling of disequilibrium and 2 = severe dizziness with nausea including imbalance or insecurity when walking, requiring antiemetic treatment. Results Data of 92 patients, 41 men and 51 women, were available for analyses. Mean age of treated patients was 53 years (range 17–81). There was no predilection of side (52.2% right/47.8% left). Before surgery 39 patients (42.4%) were symptom free (grade 0), 13 patients (14.1%) had slight symptoms (grade 1) and 40 patients (43.5%) suffered from severe symptoms (grade 2). Immediately after surgery two patients (2.2%) where symptom free (grade 0), 19 patients (20.7%) had slight symptoms (grade 1) and 71 patients (77.2%) suffered from severe symptoms (grade 2). All patients with grade 2 symptoms required antiemetic treatment ranging between 1 and 10 days (mean 4 days). Logistic regression analyses showed young age, large tumor size (T3/T4), female gender, and severe preoperative symptoms to be main factors increasing the odds for patients to develop severe symptoms postoperatively. Conclusion Patients at risk to develop severe symptoms should receive antiemetic treatment even before surgery. If in doubt about the actual risk for a specific patient with a large tumor (T3 or T4) available data suggests that patients will benefit if antiemetic treatment is started early, even before surgery.

© 2015 AGA Institute. Irritable bowel syndrome (IBS) is a frequent gastrointestinal disorder that is difficult to treat. We describe findings from evaluation of a woman (55 years old) with obsessive compulsive disorder, which was treated with bilateral deep brain stimulation in the anterior limb of the internal capsule, and IBS. After the brain stimulation treatment she reported substantial relief of her IBS symptoms. This reduction depended on specific stimulation parameters, was reproducible over time, and was not directly associated with improvements in obsessive compulsive disorder symptoms. These observations indicate a specific effect of deep brain stimulation on IBS. This observation confirms involvement of specific brain structures in the pathophysiology of IBS and shows that symptoms can be reduced through modulation of neuronal activity in the central nervous system. Further studies of the effects of brain stimulation on IBS are required.

BACKGROUND Survival after first-line therapy is poor for patients with glioblastoma. The role of second-line treatment for recurrent disease is controversial. The authors studied the outcome in a subset of patients with glioblastoma who were selected for an aggressive reintervention strategy at the time of progression. Their objectives were to improve patients' overall survival with sustained quality of life and to make comparisons with overall survival in unselected patients. METHODS Overall, 168 patients were eligible for retrospective analysis. Ninety patients received specific therapy for disease recurrence (reintervention group) by specific criteria. RESULTS In the reintervention group, promising median overall survival (mOS) results after diagnosis (61.5 weeks) and progression (33 weeks) were obtained. The progression-free survival (PFS) rate at 12 months and the overall survival rate were superior in the reintervention group (71% at 12 months and 32% at 24 months) compared with the total cohort (45% and 20%, respectively) and the standard group (15% and 5%, respectively). A matched-pair analysis (n = 46 in each group), with an mOS period of 65.5 versus 28.5 weeks, confirmed these data. Quality of life was stable or slightly improved during reinterventions in a subset of patients treated within clinical studies. CONCLUSIONS The majority of patients in the current series were treated with a reintervention strategy, which had an impact on PFS and mOS. A second resection, focal radiotherapy (in selected cases), and additional chemotherapeutic regimens should be considered for patients with recurrent glioblastoma. Cancer 2003;98:2678–86. © 2003 American Cancer Society.

Background During awake craniotomies, patients may either be awake for the entire duration of the surgical intervention (awake-awake-awake craniotomy, AAA) or initially sedated (asleep-awake-asleep craniotomy, SAS). Objective To examine whether prior sedation in SAS may restrict brain mapping, we conducted neuropsychological tests in patients by means of a standardized anesthetic regimen comparable to an SAS. Methods We prospectively examined patients undergoing surgery either under total intravenous anesthesia (TIVA) or under regional anesthesia with slight sedation (RAS). The tests included the DO40 picture-naming test, the digit span, the Regensburg Word Fluency Test, and the finger-tapping test. Each test was conducted 3 times for every patient in the TIVA and RAS groups, once before surgery and twice within about 35 minutes after the end of sedation. Patients undergoing AAA were examined preoperatively and intraoperatively. Results In the AAA group, no significant difference was found between preoperative and intraoperative test results. In the TIVA and RAS groups, postoperative tests showed worse results than preoperative tests. In most tests, patients improved from the first to the second postoperative test. Conclusion Cognitive and motor performance were significantly influenced by prior sedation in the TIVA and RAS groups, but not in the AAA group. Therefore, prior sedation may be assumed to cause a change in the baselines, which may compromise brain mapping and thus endanger a patient's neurological outcome in the case of an SAS.

Dear Editor, We would like to thank Josue M. Avecillas-Chasin for his appreciation of our study BThe variability of atlas-based targets in relation to surrounding major fibre tracts in thalamic deep brain stimulation^ [1] and for his valuable comments on the study. We fully agree with the concerns regarding the limitations of tractography, as already discussed in our article [1] and earlier reports by our group [2, 6, 10]. His own work constitutes a further valuable contribution to the topic [3]. Several studies in the past have used diffusion tensor imaging (DTI) and tractography to visualise fibre tracts in the region of the ventro-lateral thalamus [5, 7, 8, 11]. However the reliability of the depicted connections is yet unclear. First approaches to comparing diffusion tensor imaging-based fibre tracts with clinical effects have been made [3–5, 10] and have shown promising results. But, as demanded by Avecillas-Chasin, the method needs to be optimised and standardised. Optimal parameters for data acquisition (number of read-out directions, field strengths of MR scanner or voxel size) have to be generated, as well as optimal algorithms such as a mixture of tensors, Q-ball imaging, diffusion spectrum imaging and others [10]. As also mentioned by Avecillas-Chasin, it will be necessary in the future to compare deterministic algorithms with the probabilistic method, especially in tracts such as the dentate-rubro-thalamic tract (DRTT) that intersect regions with multiple fibre orientations. Furthermore, different software packages lead to different results in the depiction of chosen fibre tracts [6]. We are aware that the used method of DTI with deterministic tractography has its limitations and is not yet elaborate and reliable enough for implementation in routine clinical use as a standard tool. Therefore, today we still depend on neurophysiological and clinical information for targeting by means of micro-electrode recording (MER) and clinical testing in the setting of awake-surgeries [9].

This study aims to evaluate the improvements of cardinal motor symptoms depending on the stimulation site relative to a standardized, reconstructed three-dimensional MRI-defined subthalamic nucleus (STN.) This retrospective, clinical study includes 22 patients with idiopathic Parkinson’s disease, who consecutively underwent bilateral subthalamic nucleus stimulation. Intraoperative microelectrode recording and clinical testing were performed. The location of the best stimulation site, found intraoperatively, and the positions of the active electrode contacts 12 months after the operation were correlated to a standardized, reconstructed three-dimensional MRI-defined STN. Further, the impact of the stimulation site on rigidity, tremor and akinesia was analysed. Significant improvement of the contralateral akinesia was observed if the intraoperative stimulation site was located more lateral and superior in the MRI-STN. Furthermore, active electrode contacts located superior to or in the superior part of the MRI-STN had a significantly better effect on the tremor of the contralateral hand than in other locations inside the STN. For rigidity and akinesia, these correlations were statistically not significant. Although we found significantly better results for tremor suppression in superior and lateral aspects of the STN, for overall clinical improvement, several patients fared better with randomly distributed stimulation sites in medial, posterior or inferior parts of the MRI-defined STN. Locations of stimulation sites with the best improvements of motor symptoms were distributed randomly throughout the whole MRI-defined STN, indicating that MRI-based targeting alone is not sufficient, but intraoperative clinical testing is necessary to determine the optimal stimulation site for each individual patient.

Objective: The generally used asleep-awake-asleep protocol makes reliable intra-operative testing difficult as patients are frequently disoriented when woken-up from sedation. Furthermore, this protocol carries potential risks for the patient, the most common among them being respiratory complications. In an effort to eliminate potential risks for the patient during awake craniotomies, and in order to improve reliability of intra-operative test results, we implemented a new protocol for awake craniotomies, the continuous awake craniotomy protocol, where the patient is not sedated during the entire procedure. We present first results of this new protocol. Methods: In a prospective study we analyzed awake craniotomies that were performed between September 2006 and June 2008. Data included OR-records, anesthesiological protocols, patient charts, and neuropsychological records. Results: Data of 12 consecutive primary brain tumor patients (six men/six women) with a mean age of 46 years who underwent 13 awake craniotomies were analyzed. A gross total resection was achieved in ten patients (83.3%), of which one patient (8.3%) suffered from a new neurological deficit postoperatively. One patient suffered a generalized seizure and one a focal seizure triggered by direct cortical stimulation. There were no anesthesiological or surgical complications in this study. Conclusion: This study shows that the continuous awake craniotomy protocol is safe, was tolerated well by all patients, and created a very controllable situation during all surgeries. Applying this method, sedation related complications, such as respiratory complications and hemodynamic dysregulation, can be avoided, as are potential risks during an intra-operative wake-up phase. Furthermore, intra-operative neuropsychological test results become more reliable.

The goal of our study was to investigate the influence of intraoperative microelectrode recordings and clinical testing on the location of the final stimulation site in deep brain stimulation in Parkinson's disease.In 22 patients with Parkinson's disease we compared magnetic resonance imaging (MRI)-based and atlas-based targets with the adjusted stimulation sites after intraoperative, multitrack microelectrode recording (MER) and intraoperative and postoperative clinical testing. The investigation included 176 target/stimulation sites in 44 subthalamic nuclei (STNs), which were related to a standardised three-dimensional, MRI-defined STN.Atlas-based targets were positioned more superior and more medial than the MRI-based targets, which were located in the centre of the MRI-STN. The optimal stimulation sites, found intraoperatively after MER and clinical testing, were located more lateral and slightly more superior than both planned targets. In the majority of the cases the location of the active contact was the most superior and most lateral of all target sites. The differences in the distributions of those four targets reached statistical significance. However, final active contacts were distributed throughout the MRI-defined STN and its immediate surroundings.The adoption of microelectrode recordings and extensive clinical testing allows the adjustment of anatomical targeting even to unexpected stimulation sites in and around the MRI-defined STN.

Diffusion tensor imaging (DTI)-based tractography has become an integral part of preoperative diagnostic imaging in many neurosurgical centers, and other nonsurgical specialties depend increasingly on DTI tractography as a diagnostic tool. The aim of this study was to analyze the anatomic accuracy of visualized white matter fiber pathways using different, readily available DTI tractography software programs.Magnetic resonance imaging scans of the head of 20 healthy volunteers were acquired using a Siemens Symphony TIM 1.5T scanner and a 12-channel head array coil. The standard settings of the scans in this study were 12 diffusion directions and 5-mm slices. The fornices were chosen as an anatomic structure for the comparative fiber tracking. Identical data sets were loaded into nine different fiber tracking packages that used different algorithms. The nine software packages and algorithms used were NeuroQLab (modified tensor deflection [TEND] algorithm), Sörensen DTI task card (modified streamline tracking technique algorithm), Siemens DTI module (modified fourth-order Runge-Kutta algorithm), six different software packages from Trackvis (interpolated streamline algorithm, modified FACT algorithm, second-order Runge-Kutta algorithm, Q-ball [FACT algorithm], tensorline algorithm, Q-ball [second-order Runge-Kutta algorithm]), DTI Query (modified streamline tracking technique algorithm), Medinria (modified TEND algorithm), Brainvoyager (modified TEND algorithm), DTI Studio modified FACT algorithm, and the BrainLab DTI module based on the modified Runge-Kutta algorithm. Three examiners (a neuroradiologist, a magnetic resonance imaging physicist, and a neurosurgeon) served as examiners. They were double-blinded with respect to the test subject and the fiber tracking software used in the presented images. Each examiner evaluated 301 images. The examiners were instructed to evaluate screenshots from the different programs based on two main criteria: (i) anatomic accuracy of the course of the displayed fibers and (ii) number of fibers displayed outside the anatomic boundaries.The mean overall grade for anatomic accuracy was 2.2 (range, 1.1-3.6) with a standard deviation (SD) of 0.9. The mean overall grade for incorrectly displayed fibers was 2.5 (range, 1.6-3.5) with a SD of 0.6. The mean grade of the overall program ranking was 2.3 with a SD of 0.6. The overall mean grade of the program ranked number one (NeuroQLab) was 1.7 (range, 1.5-2.8). The mean overall grade of the program ranked last (BrainLab iPlan Cranial 2.6 DTI Module) was 3.3 (range, 1.7-4). The difference between the mean grades of these two programs was statistically highly significant (P0.0001). There was no statistically significant difference between the programs ranked 1-3: NeuroQLab, Sörensen DTI Task Card, and Siemens DTI module.The results of this study show that there is a statistically significant difference in the anatomic accuracy of the tested DTI fiber tracking programs. Although incorrectly displayed fibers could lead to wrong conclusions in the neurosciences field, which relies heavily on this noninvasive imaging technique, incorrectly displayed fibers in neurosurgery could lead to surgical decisions potentially harmful for the patient if used without intraoperative cortical stimulation. DTI fiber tracking presents a valuable noninvasive preoperative imaging tool, which requires further validation after important standardization of the acquisition and processing techniques currently available.

A prospective study is presented on the amount of targeting error that is due to rotational deviations between the atlas and the stereotactic coordinate system.We investigated 14 volunteers with a stereotactic frame fixed to their heads by tight adhesive bands. Sagittal, coronal and axial T2-weighted MRI scans, as well as MPRage sequences, were performed. The anterior and posterior commissures and one additional point on the midline (the septum pellucidum) were determined on the axial T2-weighted images. Bilateral atlas coordinates for the subthalamic nucleus (STN), globus pallidus pars interna (GPi) and nucleus ventralis intermedius (Vim) were transformed to stereotactic frame coordinates, either without correction or by 2-point or 3-point correction. A total of 896 coordinates (x, y, z for the STN, GPi and Vim in both hemispheres) were calculated.Although the mean differences between the two algorithms (0.24 +/- standard deviation of 0.33 mm) were within the range of system-immanent inaccuracies in MRI-guided stereotaxy, deviations of up to 2.8 mm occurred. No significant correlation was found regarding the amount of rotational angle and the differences in x-, y-, or z-coordinates when 2-point and 3-point transformations were compared.The reliability of meticulous trajectory planning might be compromised significantly by using only 2-point-based correction or no calculations at all.