Anterior Commissure-posterior Commissure Research Articles

Brain color-coded diffusion imaging: Utility of ACPC reorientation of gradients in healthy subjects and patients

Background and ObjectiveThe common structural interpretation of diffusion color-encoded (DCE) maps assumes that the brain is aligned with the gradients of the MRI machine. This is seldom achieved in the field, leading to incorrect red (R), green (G) and blue (B) DCE values for the expected orientation of fiber bundles. We studied the virtual reorientation of gradients according to the anterior commissure – posterior commissure (ACPC) system on the RGB derivatives. MethodsWe measured mean ± standard deviation of average, standard deviation, skewness and kurtosis of RGB derivatives, before (rO) and after (acpcO) gradient reorientation, in one healthy-subject group with head routinely positioned (HS-routine), and in two patient groups, one with essential tremor (ET-Opti), and one with Parkinson's disease (PD-Opti), with head position optimized according to ACPC before acquisition. We studied the pitch, roll and yaw angles of reorientation, and we compared rO and acpcO conditions, and groups (ad hoc statistics). ResultsPitch (maximum in the HS-routine group) was greater than roll and yaw. After reorientation of gradients, in the HS-routine group, DCE average increased, and Stddev, skewness and kurtosis decreased; R, G and B average increased, and R and B skewness and kurtosis decreased. By contrast, in the ET-Opti group and the PD-Opti group, R, G and B, average and Stddev increased, and skewness and kurtosis decreased. In both rO and acpcO conditions, in the ET-Opti and PD-Opti groups, average and standard deviation were higher, while skewness and kurtosis were lower. ConclusionsDCE map interpretability depends on brain orientation. Reorientation realigns gradients with the anatomic and physiologic position of the head and brain, as exemplified.

Tightened Sulci in the High Convexities as a Noteworthy Feature of Idiopathic Normal Pressure Hydrocephalus

The presence of tightened sulci in the high-convexities (THC) is a key morphological feature for the diagnosis of idiopathic normal pressure hydrocephalus (iNPH), but the exact localization of THC has yet to be defined. The purpose of this study was to define THC and compare its volume, percentage, and index between iNPH patients and healthy controls. According to the THC definition, the high-convexity part of the subarachnoid space was segmented and measured the volume and percentage from the 3D T1-weighted and T2-weighted magnetic resonance images in 43 patients with iNPH and 138 healthy controls. THC was defined as a decrease in the high-convexity part of the subarachnoid space located above the body of the lateral ventricles, with anterior end on the coronal plane perpendicular to the anterior commissure-posterior commissure (AC-PC) line passing through the front edge of the genu of corpus callosum, the posterior end in the bilateral posterior parts of the callosomarginal sulci, and the lateral end at 3cm from the midline on the coronal plane perpendicular to the AC-PC line passing through the midpoint between AC and PC. Compared to the volume and volume percentage, the high-convexity part of the subarachnoid space volume per ventricular volume ratio<0.6 was the most detectable index of THC on both 3D T1-weighted and T2-weighted magnetic resonance images. To improve the diagnostic accuracy of iNPH, the definition of THC was clarified, and high-convexity part of the subarachnoid space volume per ventricular volume ratio <0.6 proposed as the best index for THC detection in this study.

Improving tremor response to focused ultrasound thalamotomy.

MRI-guided high-intensity focused ultrasound thalamotomy is an incisionless therapy for essential tremor. To reduce adverse effects, the field has migrated to treating at 2 mm above the anterior commissure-posterior commissure plane. We perform MRI-guided high-intensity focused ultrasound with an advanced imaging targeting technique, four-tract tractography. Four-tract tractography uses diffusion tensor imaging to identify the critical white matter targets for tremor control, the decussating and non-decussating dentatorubrothalamic tracts, while the corticospinal tract and medial lemniscus are identified to be avoided. In some patients, four-tract tractography identified a risk of damaging the medial lemniscus or corticospinal tract if treated at 2 mm superior to the anterior commissure-posterior commissure plane. In these patients, we chose to target 1.2-1.5 mm superior to the anterior commissure-posterior commissure plane. In these patients, post-operative imaging revealed that the focused ultrasound lesion extended into the posterior subthalamic area. This study sought to determine if patients with focused ultrasound lesions that extend into the posterior subthalamic area have a differnce in tremor improvement than those without. Twenty essential tremor patients underwent MRI-guided high-intensity focused ultrasound and were retrospectively classified into two groups. Group 1 included patients with an extension of the thalamic-focused ultrasound lesion into the posterior subthalamic area. Group 2 included patients without extension of the thalamic-focused ultrasound lesion into the posterior subthalamic area. For each patient, the percent change in postural tremor, kinetic tremor and Archimedes spiral scores were calculated between baseline and a 3-month follow-up. Two-tailed Wilcoxon rank-sum tests were used to compare the improvement in tremor scores, the total number of sonications, thermal dose to achieve initial tremor response, and skull density ratio between groups. Group 1 had significantly greater postural, kinetic, and Archimedes spiral score percent improvement than Group 2 (P values: 5.41 × 10-5, 4.87 × 10-4, and 5.41 × 10-5, respectively). Group 1 also required significantly fewer total sonications to control the tremor and a significantly lower thermal dose to achieve tremor response (P values: 6.60 × 10-4 and 1.08 × 10-5, respectively). No significant group differences in skull density ratio were observed (P = 1.0). We do not advocate directly targeting the posterior subthalamic area with MRI-guided high-intensity focused ultrasound because the shape of the focused ultrasound lesion can result in a high risk of adverse effects. However, when focused ultrasound lesions naturally extend from the thalamus into the posterior subthalamic area, they provide greater tremor control than those that only involve the thalamus.

Safety and precision of frontal trajectory of lateral habenula deep brain stimulation surgery in treatment-resistant depression.

The lateral habenula (LHb) is a promising deep brain stimulation (DBS) target for treatment-resistant depression (TRD). However, the optimal surgical trajectory and its safety of LHb DBS are lacking. We reported surgical trajectories for the LHb in six TRD patients treated with DBS at the General Hospital of the Chinese People's Liberation Army between April 2021 and May 2022. Pre-operative fusions of magnetic resonance imaging (MRI) and computed tomography (CT) were conducted to design the implantation trajectory of DBS electrodes. Fusions of MRI and CT were conducted to assess the safety or precision of LHb DBS surgery or implantable electrodes locations. Results showed that the optimal entry point was the posterior middle frontal gyrus. The target coordinates (electrode tips) were 3.25 ± 0.82 mm and 3.25 ± 0.82 mm laterally, 12.75 ± 0.42 mm and 13.00 ± 0.71 mm posterior to the midpoint of the anterior commissure-posterior commissure (AC-PC) line, and 1.83 ± 0.68 mm and 1.17 ± 0.75 mm inferior to the AC-PC line in the left and right LHb, respectively. The "Ring" angles (relative to the AC-PC level on the sagittal section plane) of the trajectories to the left and right LHb were 51.87° ± 6.67° and 52.00° ± 7.18°, respectively. The "Arc" angles (relative to the midline of the sagittal plane) were 33.82° ± 3.39° and 33.55° ± 3.72°, respectively. Moreover, there was small deviation of actual from planned target coordinates. No patient had surgery-, disease- or device-related adverse events during the perioperative period. Our results suggested that LHb-DBS surgery via frontal trajectory is safe, accurate, and feasible. This is an applicable work to report in detail the target coordinates and surgical path of human LHb-DBS. It has of great clinical reference value to treat more cases of LHb-DBS for TRD.

Direct targeting of the ventral intermediate nucleus of the thalamus in deep brain stimulation for essential tremor: a prospective study with comparison to a historical cohort.

The ventral intermediate nucleus of the thalamus (VIM) is an effective target for deep brain stimulation (DBS) to control symptoms related to essential tremor. The VIM is typically targeted using indirect methods, although studies have reported visualization of the VIM on proton density-weighted MRI. This study compares the outcomes between patients who underwent VIM DBS with direct and indirect targeting. Between August 2013 and December 2019, 230 patients underwent VIM DBS at the senior author's institution. Of these patients, 92 had direct targeting (direct visualization on proton density 3-T MRI). The remaining 138 patients had indirect targeting (relative to the third ventricle and anterior commissure-posterior commissure line). Coordinates of electrodes placed with direct targeting were significantly more lateral (p < 0.001) and anterior (p < 0.001) than those placed with indirect targeting. The optimal stimulation amplitude for devices measured in voltage was lower for those who underwent direct targeting than for those who underwent indirect targeting (p < 0.001). Patients undergoing direct targeting had a greater improvement only in their Quality of Life in Essential Tremor Questionnaire hobby score versus those undergoing indirect targeting (p = 0.04). The direct targeting group had substantially more symptomatic hemorrhages than the indirect targeting group (p = 0.04). All patients who experienced a postoperative hemorrhage after DBS recovered without intervention. Patients who underwent direct VIM targeting for DBS treatment of essential tremor had similar clinical outcomes to those who underwent indirect targeting. Direct VIM targeting is safe and effective.

Long-Term Results of Deep Brain Stimulation for Treatment-Resistant Depression: Outcome Analysis and Correlation With Lead Position and Electrical Parameters.

Long-term efficacy and mechanisms of action of deep brain stimulation (DBS) for treatment-resistant depression (TRD) are under investigation. To compare long-term outcomes with active electrode's coordinates and its electrical parameters in patients with TRD treated with DBS in the subgenual cingulate gyrus (SCG-DBS). Seventeen patients with TRD underwent SCG-DBS. Demographic and baseline characteristics were recorded. The 17-item Hamilton Depression Rating Scale was used to measure the response to the therapy. The anterior commissure-posterior commissure coordinates of the active contacts and the total electrical energy delivered were calculated and correlated with clinical outcomes. Patient-specific tractographic analysis was performed to identify the modulated pathways in responders. Twelve women (70.6%) and 5 men (29.4%) with a median age of 48 yr (34-70 years) were included. Along the 5-year follow-up, 3 main clinical trajectories were observed according to symptom's improvement: great responders (≥80%), medium responders (≥50%-79%), and poor responders (<50%). Active contacts' coordinates and total electrical energy delivered showed no correlation with clinical outcomes. Brodmann area 10 medial was the most frequently stimulated area and the forceps minor, the most frequently modulated tract. SCG-DBS for TRD is clearly effective in some patients. Active contacts' coordinates were highly variable within the region and, like electrical parameters, did not seem to correlate with clinical outcomes. In the current series, Brodmann area 10 medial and the forceps minor were the most frequently targeted area and modulated pathway, respectively.

Study of Anterior Commissure-Posterior Commissure Distance among Nepalese Cohort.

Introduction:The main aim of this study is to determine the anterior commissure-posterior commissure (AC-PC) distance in Nepalese cohort and has comparison of intercommissural distance of Nepalese cohort with some other races.Materials and Methods:The 47 patients, with mean age of 50 years, included in the study had undergone DBS or lesioning (Pallidotomy). Data were collected through the magnetic resonance imaging under DBS protocol and the manipulation, marking of AC and PC was done in Inomed Planning Software (IPS).Results:The data revealed average AC-PC distance of Nepalese cohort to be 24.86 ± 2.08 mm, ranging from 16 mm to 30 mm. The study among 29 males and 18 females illustrated male to have longer AC-PC as compared to female (25.38 mm male and 24.02 mm female). The results also confirmed age related changes in AC-PC distance which was linearly increasing with the age.Conclusion:Comparison of data from other studies revealed Nepalese cohort to have almost similar AC-PC distance with Asian population, while that was longer in Caucasian and shorter in Hispanic Population.

Predictive Value of Temporal Muscle Thickness Measurements on Cranial Magnetic Resonance Images in the Prognosis of Patients With Primary Glioblastoma.

Objective: To investigate the predictive value of prognosis of primary GBM patients using TMT on three-dimensional (3D) MR images of the brain.Methods: Data of 130 patients with primary GBM from the TCGA-GBM database were analyzed retrospectively. TMT was measured on the axial plane by multi-planar reformation (MPR) of T1WI MR images perpendicular to the long axis of the temporal muscle at the level of the orbital roof. The axial MR plane was oriented parallel to the anterior commissure-posterior commissure line. Student's t-test or Mann–Whitney U-test was utilized to determine whether there were significant differences in the TMT and OS between male and female patients. The Pearson correlation analysis was adopted to evaluate the correlation between the age at GBM diagnosis and TMT. All patients were divided into two groups based on their median TMT, and the Kaplan–Meier curve was used to calculate the OS curve. The association between TMT and OS of GBM patients, as well as the multivariate analysis of TMT and other clinical factors affecting the survival time, was evaluated with Cox regression model.Results: TMT was a risk factor for the prognosis of GBM with its hazard ratio (HR) of 0.802 (95% CI 0.698–0.922; P = 0.002; Cox regression model). Grouped by median TMT, the group with above-median TMT demonstrated a significant increase in survival time (15.6 months) compared with the one with below-median TMT (11.2 months) (P < 0.001; log-rank test). In the multivariate survival analysis using a Cox regression model, TMT (HR 0.863; 95% CI 0.748–0.996; P = 0.044), age at the diagnosis of GBM (HR 1.042; 95% CI 1.024–1.060; P < 0.001), and concurrent chemoradiotherapy (HR 0.510; 95% CI 0.336–0.775; P = 0.002) were significantly associated with survival time.Conclusion: TMT as an independent predictor is sensitive to the survival prognosis of primary GBM patients, which has potential to predict the survival time.

Automatic Alignment of Cranial CT Examinations to the Anterior Commissure/Posterior Commissure (ACPC) Reference Plane forReliable Interpretation and Quality Assurance.

Alignment of cranial CT scans (cCTs) to a common reference plane simplifies anatomical-landmark-based orientation and eases follow-up assessment of intracranial findings. We developed and open sourced a fully automated system, which aligns cCTs to the Anterior Commissure/Posterior Commissure (ACPC) line and exports the results to the PACS. FMRIB's Linear Image Registration Tool (FLIRT) with an ACPC-aligned atlas is used in the alignment step. Five mm mean slabs are generated with the top non-air slice as the starting point. For evaluation, 301 trauma cCTs from the CQ500 dataset were processed. In visual comparison with the respective ACPC-aligned atlas, all were successfully aligned. Image quality (IQ) and ease of identification of the central sulcus (CS) were rated on a Likert scale (5 = excellent IQ/immediate CS identification). The median IQ was 4 (range: 2-4) in the original series and 5 (range: 4-5) in the ACPC-aligned series (p < 0.0001). The CS was more easily identified after fatbACPC (original scans: 4 (range: 2-5); ACPC-aligned: 5 (range: 4-5); p < 0.0001). The mean rotation to achieve alignment was|X| = 6.4 ± 5.2° ([-X,+X] = -26.8°-24.2°), |Y| = 2.1 ± 1.7°([-Y,+Y] = -8.7°-9.8°), and |Z| = 3.1 ± 2.4° ([-Z,+Z] = -14.3°-12.5°). The developed system can robustly and automatically align cCTs to the ACPC line. Degrees of deviation from the ideal alignment could be used for quality assurance. KEY POINTS:: · fatbACPC automatically aligns cranial CT scans to the Anterior Commissure/Posterior Commissure plane.. · ACPC-aligned images simplify anatomical-landmark-based orientation.. · fatbACPC does not impact image quality.. · fatbACPC is robust, fully PACS-integrated, and Open Source: https://github.com/BrainImAccs. CITATION FORMAT: · Rubbert C, Turowski B, Caspers J. Automatic Alignment ofCranial CT Examinations to the Anterior Commissure/Posterior Commissure (ACPC) Reference Plane for Reliable Interpretation and Quality Assurance. Fortschr Röntgenstr 2021; 193: 61 - 67.

Usefulness of the frontal lobe bottom and cerebellum tuber vermis line as an alternative clue to set the axial angle parallel to the AC-PC line in I-123 IMP SPECT imaging: a retrospective study.

We aimed to investigate whether the frontal lobe bottom and cerebellum tuber vermis (FLB-CTV) line on brain perfusion scintigraphy, using iodine-123 isopropyl iodoamphetamine single photon emission computed tomography (I-123 IMP SPECT) images, is useful to determine an axial angle parallel to the anterior commissure-posterior commissure (AC-PC) line. We measured the angular differences between the AC-PC line and the FLB-CTV line on midsagittal brain magnetic resonance imaging (MRI) scans of 100 patients. We also evaluated the angular differences of the FLB-CTV line between the IMP SPECT images and the computed tomography for attenuation correction (CTAC) images in the same 100 patients, using a reference line on the CTAC images. Furthermore, the inter-reader reproducibility of the FLB-CTV line measurements on IMP SPECT images of 50 patients between two readers was evaluated using the intra-class correlation coefficient (ICC) and 95% confidence interval (CI). The mean and standard deviation of the angular differences between the AC-PC and FLB-CTV lines on midsagittal brain MRI scans were - 1.24° and 1.14°, respectively. The mean and the standard deviation of the angular differences of the FLB-CTV line in the IMP SPECT and CTAC images were 0.87° and 0.48°, respectively. The ICC of the FLB-CTV line measurements on IMP SPECT images was 0.99 (95% CI 0.98-0.99). We demonstrated that the FLB-CTV line was almost parallel to the AC-PC line and could be reconstructed using IMP SPECT images. The FLB-CTV line can be used as additional evidence to set the axial angle parallel to the AC-PC line.

Invisible cortex sign: A highly accurate feature to localize the inferolateral central sulcus.

The central sulcus is a key landmark on MRI of the brain, but its inferolateral portion is difficult to identify if unable to trace the sulcus superoinferiorly. The authors observed that the cortex abutting the central sulcus appears isointense to the adjacent white matter on DWI, we named this the 'invisible cortex sign' and our study evaluates whether it could be used to identify the inferolateral central sulcus. Observational study of 108 consecutive 'normal' MRI studies performed from May 2016 to January 2017. A single axial DWI image - obtained in the anterior commissure-posterior commissure plane - was selected from each scan just above the subcentral gyrus such that it included the most inferolateral portion of the central sulcus. These single images were given to 10 readers (neuroradiologists, a neuroradiology fellow and radiology trainees) who marked the central sulcus based on the presence of the 'invisible cortex sign'. Their accuracy in identifying the central sulcus was compared with that of the principal investigators, who used tri-planar T1 volumetric MRI sequences. One hundred and eight consecutive patients (55 female, 53 male) were selected, ranging from 18 to 81years old (mean=40.5, σ=18.2). The central sulcus was correctly identified in 95.5% of cases (σ=3.7%; range 89.4-99.1%). The 'invisible cortex sign' is a highly accurate method of identifying the inferolateral central sulcus on a single axial DWI slice without relying on the more superior aspects of the sulcus.

7.0T ultrahigh-field MRI directly visualized the pedunculopontine nucleus in Parkinson's disease patients

OBJECTIVES:The pedunculopontine nucleus (PPN) is considered a promising new target for neurostimulation in Parkinson's disease (PD) patients with postural instability and gait disturbance that is refractory to other treatment modalities. However, the PPN is typically difficult to visualize with magnetic resonance imaging (MRI) at clinical field strengths, which greatly limits the PPN as a viable surgical target for deep brain stimulation (DBS). Thus, the aim of this study is to directly visualize the PPN based on 7.0T ultrahigh-field MRI.METHODS:Five PD patients were enrolled and scanned using the MP2RAGE sequence on a 7.0T ultrahigh-field MRI scanner. Then, the MP2RAGE sequences were imported into a commercially available navigation system. The coordinates of the directly localized PPN poles were recorded in the navigation system relative to the anterior commissure-posterior commissure plane.RESULTS:Our results indicated that the PPN presented intermediate signal intensity in the 7.0T ultrahigh-field MR images in comparison with the surrounding structure, such as the hypo-intensity of the periaqueductal gray and the hyperintensity of the neighboring white matter tracts, in PD patients. The mean coordinates for the rostral and caudal poles of PPN were 6.50 mm and 7.20 mm lateral, 1.58 mm and 2.21 mm posterior, and 8.89 mm and 13.83 mm relative to the posterior commissure.CONCLUSION:Our findings provide, for the first time, direct visualization of the PPN using the MP2RAGE sequence on a 7.0T ultrahigh-field MRI, which may improve the accuracy of stereotactic targeting of the PPN and improve the outcomes in patients undergoing DBS.

A novel mesial temporal stereotactic coordinate system.

OBJECTIVE Stereotactic laser ablation and neurostimulator placement represent an evolution in staged surgical intervention for epilepsy. As this practice evolves, optimal targeting will require standardized outcome measures that compare electrode lead or laser source with postprocedural changes in seizure frequency. The authors propose and present a novel stereotactic coordinate system based on mesial temporal anatomical landmarks to facilitate the planning and delineation of outcomes based on extent of ablation or region of stimulation within mesial temporal structures. METHODS The body of the hippocampus contains a natural axis, approximated by the interface of cornu ammonis area 4 and the dentate gyrus. The uncal recess of the lateral ventricle acts as a landmark to characterize the anterior-posterior extent of this axis. Several volumetric rotations are quantified for alignment with the mesial temporal coordinate system. First, the brain volume is rotated to align with standard anterior commissure-posterior commissure (AC-PC) space. Then, it is rotated through the axial and sagittal angles that the hippocampal axis makes with the AC-PC line. RESULTS Using this coordinate system, customized MATLAB software was developed to allow for intuitive standardization of targeting and interpretation. The angle between the AC-PC line and the hippocampal axis was found to be approximately 20°-30° when viewed sagittally and approximately 5°-10° when viewed axially. Implanted electrodes can then be identified from CT in this space, and laser tip position and burn geometry can be calculated based on the intraoperative and postoperative MRI. CONCLUSIONS With the advent of stereotactic surgery for mesial temporal targets, a mesial temporal stereotactic system is introduced that may facilitate operative planning, improve surgical outcomes, and standardize outcome assessment.

Flat Posterior Cranial Fossa Affects Outcomes of Microvascular Decompression for Trigeminal Neuralgia.

To investigate the prognostic factors for microvascular decompression (MVD) in patients with primary trigeminal neuralgia (TN), with a particular focus on the morphology of the posterior cranial fossa (PCF). The present study investigated 126 surgically treated patients with primary TN with more than 1-year follow-up who underwent high-resolution magnetic resonance imaging between April 2003 and September 2015. We retrospectively reviewed clinical information and operative findings. Outcomes of MVD were also evaluated and patients were classified into "success" and "failure" groups. Furthermore, length, width, and height of the PCF were measured by approximation to an ellipsoid with reference to the anterior commissure-posterior commissure line. These values were compared between groups. Atypical type 2 TN (P < 0.001) and weak neurovascular compression (P < 0.001) correlated significantly with poor outcomes of MVD for primary TN. In terms of PCF morphology, the failure group showed a flatter PCF than the success group, whereas sex, age, affected side, topography of facial pain, interval between onset and surgery, responsible vessel, location of compression along the nerve, and site of compression around the circumference of the nerve root did not significantly affect outcomes of MVD for primary TN. The present study identified type 2 TN, weak neurovascular compression, and flatness of the PCF as predictors of poor prognosis after MVD for primary TN.

Optimization of Reformatting Angle Using Orbitomeatal Base Line in Dopamine Transporter Scintigraphy.

Recently, dopamine transporter (DaT) scintigraphy, which contributes to the early diagnosis of Parkinson's disease and Lewy body dementia, has been widely spread. It has been revealed that analytical results can be affected by the image-reformatting angle, and a horizontal section is recommended for the anterior commissure-posterior commissure (AC-PC) line according to the clinical guidelines for ioflupane. However, it is difficult to identify AC-PC line visually, as there is no remarkable accumulation in the cerebral parenchyma in DaT scintigraphy with poor contrast resolution. The objective of this study was to establish and optimize an adjustment method for the image-reformatting angle by using orbitomeatal base line (OM line). Evaluations were made on items such as comparison of image reformatting angles by an analyst, comparison of measurement angles of OM line, the angle formed by the intersection of OM line and AC-PC line, and the change in specific biding ratio (SBR) according to the difference in the image-reformatting angle. Consequently, the difference in analytical results among technicians became smaller, and consistent results were obtained by adjusting the image-reformatting angle.

The role of diffusion tensor imaging tractography for Gamma Knife thalamotomy planning.

OBJECTIVE The role of tractography in Gamma Knife thalamotomy (GK-T) planning is still unclear. Pyramidal tractography might reduce the risk of radiation injury to the pyramidal tract and reduce motor complications. METHODS In this study, the ventralis intermedius nucleus (VIM) targets of 20 patients were bilaterally defined using Iplannet Stereotaxy Software, according to the anterior commissure-posterior commissure (AC-PC) line and considering the localization of the pyramidal tract. The 40 targets and tractography were transferred as objects to the GammaPlan Treatment Planning System (GP-TPS). New targets were defined, according to the AC-PC line in the functional targets section of the GP-TPS. The target offsets required to maintain the internal capsule (IC) constraint of < 15 Gy were evaluated. In addition, the strategies available in GP-TPS to maintain the minimum conventional VIM target dose at > 100 Gy were determined. RESULTS A difference was observed between the positions of both targets and the doses to the IC. The lateral (x) and the vertical (z) coordinates were adjusted 1.9 mm medially and 1.3 mm cranially, respectively. The targets defined considering the position of the pyramidal tract were more medial and superior, based on the constraint of 15 Gy touching the object representing the IC in the GP-TPS. The best strategy to meet the set constraints was 90° Gamma angle (GA) with automatic shaping of dose distribution; this was followed by 110° GA. The worst GA was 70°. Treatment time was substantially increased by the shaping strategy, approximately doubling delivery time. CONCLUSIONS Routine use of DTI pyramidal tractography might be important to fine-tune GK-T planning. DTI tractography, as well as anisotropy showing the VIM, promises to improve Gamma Knife functional procedures. They allow for a more objective definition of dose constraints to the IC and targeting. DTI pyramidal tractography introduced into the treatment planning may reduce the incidence of motor complications and improve efficacy. This needs to be validated in a large clinical series.

EP 24. Contralateral smiles induced by deep brain stimulation of the nucleus accumbens region in a patient with major depressive disorder

Introduction Deep brain stimulation (DBS) is a well-established procedure for the treatment of therapy-refractory movement disorders. Limited evidence suggests that DBS of the nucleus accumbens region (NACC) may be effective for the treatment of psychiatric disorders, such as obsessive compulsive disorder and major depressive disorder (MDD). Hitherto, little is known concerning behavioural responses upon acute high-frequency stimulation of the NACC region in patients suffering from MDD. Objective To further characterize behavioural responses and clinical effects elicited upon acute unilateral DBS of the NACC area. Intra- and postoperative observations (including video-sequences) as well as a two-month outcome are presented. Material and Methods We performed bilateral NACC-DBS in a female patient (age: 47) with MDD refractory to psycho-, pharmaco- and electroconvulsive (>50 sessions) therapy on a compassionate-use basis. The stereotactic procedure was performed under local anaesthesia. The NACC was targeted (x) 7 mm lateral to the midline, (y) 3 mm anterior to the anterior commissure, (z) 4 mm below the anterior commissure-posterior commissure plane. A commercially available DBS lead with 4 contacts (model 3391, Medtronic Co., MN, USA; contact length: 3 mm; interelectrode distance: 4 mm) was inserted bilaterally for permanent stimulation. Results Upon test-stimulation in the operating room, acute unilateral NACC-DBS on both hemispheres stereotypically induced a visible facial reaction with a contralateral smile (bipolar stimulation of the ventralmost contacts (0− cathodal vs. 1+ anodal); pulse width: 90 μs; frequency: 130 Hz). This smile could repeatedly be elicited either when stimulation amplitude was slowly ramped up to 7 mA, or abruptly switched on to 4–5 mA. The smile was invariably associated with a significantly improved mood (as assessed by an analog scale). This effect was documented by different examiners and clearly reproducible in the subsequent clinical course. A dramatic improvement of the depression scores, patient’s mood and social behaviour was documented at a first follow-up (6 weeks postoperatively). Conclusion Albeit preliminary, the patient’s beneficial response tentatively suggests that NACC-DBS may be a viable option for selected patients with MDD. In line with previous reports on stimulation-induced smile responses in patients with obsessive compulsive disorder, our intraoperative observations support and expand the notion of the NACC area constituting or containing an important interface between limbic and motor networks, respectively, that may be involved in the pathophysiology of MDD. It is suggested that the results of long-term NACC-DBS in patients with MDD should be evaluated by larger patient samples and randomized, controlled trials.

Optic radiation injury in a patient with intraventricular hemorrhage: a diffusion tensor tractography study.

Optic radiation injury in a patient with intraventricular hemorrhage: a diffusion tensor tractography study.

Traumatic axonal injury of the medial lemniscus pathway in a patient with traumatic brain injury: validation by diffusion tensor tractography.

Traumatic axonal injury of the medial lemniscus pathway in a patient with traumatic brain injury: validation by diffusion tensor tractography.

What You See Is What You Get: Lead Location Within Deep Brain Structures Is Accurately Depicted by Stereotactic Magnetic Resonance Imaging.

Magnetic resonance imaging (MRI)-verified deep brain stimulation relies on the correct interpretation of stereotactic imaging documenting lead location in relation to visible anatomic target. However, it has been suggested that local signal distortion from the lead itself renders its depiction on MRI unreliable. To compare lead location on stereotactic MRI with subsequent location of its brain track after removal. Patients underwent deep brain stimulation with the use of MRI-guided and MRI-verified Leksell frame approach. Infection or suboptimal efficacy required lead removal and subsequent reimplantation by using the same technique. Postimplantation stereotactic MR images were analyzed. Lateral (x) and anteroposterior (y) distances from midcommissural point to center of the lead hypointensity were recorded at the anterior commissure-posterior commissure plane (pallidal electrode) or z = -4 (subthalamic electrode). Stereotactic MRI before the second procedure, x and y distances from the center of the visible lead track hypointensity to midcommissural point were independently recorded. Vectorial distance from center of the lead hypointensity to the center of its track was calculated. Sixteen electrode tracks were studied in 10 patients. Mean differences between lead artifact location and lead track location were: x coordinate 0.4 mm ± 0.2; y coordinate 0.6 mm ± 0.3. Mean vectorial distance was 0.7 mm ± 0.2. Stereotactic distance between lead location and subsequent brain track location on MRI was small. The mean discrepancy was approximately half the deep brain stimulation lead width. This suggests that lead hypointensity seen on postimplantation MRI is indeed an accurate representation of its real location within deep brain structures.