Ventral intermediate nucleus of the thalamus, dentatorubrothalamic tract, and caudal zona incerta: stimulation of which structure provides ongoing tremor control in patients with essential tremor?

OBJECTIVE: Essential tremor (ET) is the most common movement disorder. Deep brain stimulation (DBS) targeting the ventral intermediate nucleus (VIM) is known to improve symptoms in patients with medication-resistant ET. However, the clinical effectiveness of VIM-DBS may vary, and other targets have been proposed. The authors aimed to investigate whether the same anatomical structure is responsible for tremor control both immediately after VIM-DBS and at later follow-up evaluations. METHODS: Of 68 electrodes from 41 patients with ET, the authors mapped the distances of the active contact from the VIM, the dentatorubrothalamic tract (DRTT), and the caudal zona incerta (cZI) and compared them using Friedman's ANOVA and the Wilcoxon signed-rank follow-up test. The same distances were also compared between the initially planned target and the final implantation site after intraoperative macrostimulation. Finally, the comparison among the three structures was repeated for 16 electrodes whose active contact was changed after a mean 37.5 months follow-up to improve tremor control. RESULTS: After lead implantation, the VIM was statistically significantly closer to the active contact than both the DRTT (p = 0.008) and cZI (p < 0.001). This result did not change if the target was moved based on intraoperative macrostimulation. At the last follow-up, the active contact distance from the VIM was always significantly less than that of the cZI (p < 0.001), but the distance from the DRTT was reduced and even less than the distance from the VIM. CONCLUSIONS: In patients receiving VIM-DBS, the VIM itself is the structure driving the anti-tremor effect and remains more effective than the cZI, even years after implantation. Nevertheless, the role of the DRTT may become more important over time and may help sustain the clinical efficacy when the habituation from the VIM stimulation ensues.

Low-grade B-cell lymphoma of the central nervous system with plasmacytic differentiation and amyloid deposition.

A 65-year-old woman with a resolved history of epilepsy due to a motor vehicle accident and hippocampal sclerosis presented with recurrent de novo seizures. Brain imaging demonstrated enhancement in the left parieto-occipital lobe. At histopathological examination, the lesion displayed a diffuse lymphoid infiltrate comprised of small atypical lymphocytes, plasmacytoid lymphocytes, and scattered plasma cells with amyloid deposition. Pathology workup demonstrated a monotypic B-cell phenotype of the lymphoid infiltrate, expressing lambda light chain restriction and plasmacytic differentiation without MYD88 mutations. The patient had no systemic evidence of lymphoma, plasma cell dyscrasia, or amyloidosis. A diagnosis of low-grade B-cell lymphoma of the central nervous system with plasmacytic differentiation and amyloid deposition was made.

Deep Brain Stimulation of the Medial Forebrain Bundle for Treatment-Resistant Depression: A Systematic Review Focused on the Long-Term Antidepressive Effect.

OBJECTIVE: Major depression affects millions of people worldwide and has important social and economic consequences. Since up to 30% of patients do not respond to several lines of antidepressive drugs, deep brain stimulation (DBS) has been evaluated for the management of treatment-resistant depression (TRD). The superolateral branch of the medial forebrain bundle (slMFB) appears as a "hypothesis-driven target" because of its role in the reward-seeking system, which is dysfunctional in depression. Although initial results of slMFB-DBS from open-label studies were promising and characterized by a rapid clinical response, long-term outcomes of neurostimulation for TRD deserve particular attention. Therefore, we performed a systematic review focused on the long-term outcome of slMFB-DBS. MATERIALS AND METHODS: A literature search using Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria was conducted to identify all studies reporting changes in depression scores after one-year follow-up and beyond. Patient, disease, surgical, and outcome data were extracted for statistical analysis. The Montgomery-Åsberg Depression Rating Scale (ΔMADRS) was used as the clinical outcome, defined as percentage reduction from baseline to follow-up evaluation. Responders' and remitters' rates were also calculated. RESULTS: From 56 studies screened for review, six studies comprising 34 patients met the inclusion criteria and were analyzed. After one year of active stimulation, ΔMADRS was 60.7% ± 4%; responders' and remitters' rates were 83.8% and 61.5%, respectively. At the last follow-up, four to five years after the implantation, ΔMADRS reached 74.7% ± 4.6%. The most common side effects were stimulation related and reversible with parameter adjustments. CONCLUSIONS: slMFB-DBS appears to have a strong antidepressive effect that increases over the years. Nevertheless, to date, the overall number of patients receiving implantations is limited, and the slMFB-DBS surgical technique seems to have an important impact on the clinical outcome. Further multicentric studies in a larger population are needed to confirm slMFB-DBS clinical outcomes.

Deep Brain Stimulation of the Subgenual Cingulate Cortex for the Treatment of Chronic Low Back Pain.

OBJECTIVES: Despite converging basic scientific and clinical evidence of the link between chronic pain and depression, existing therapies do not often take advantage of this overlap. Here, we provide a critical review of the literature that highlights the intersection in brain networks between chronic low back pain (CLBP) and depression and discuss findings from previous deep brain stimulation (DBS) studies for pain. Based on a multidimensional model of pain processing and the connectivity of the subgenual cingulate cortex (SCC) with areas that are implicated in both CLBP and depression, we propose a novel approach to the treatment of CLBP using DBS of the SCC. MATERIALS AND METHODS: A narrative review with literature assessment. RESULTS: CLBP is associated with a shift away from somatosensory representation toward brain regions that mediate emotional processes. There is a high degree of overlap between these regions and those involved in depression, including the anterior cingulate cortex, medial prefrontal cortex, nucleus accumbens, and amygdala. Whereas target sites from previous DBS trials for pain were not anatomically positioned to engage these areas and their associated networks, the SCC is structurally connected to all of these regions as well as others involved in mediating sensory, cognitive, and affective processing in CLBP. CONCLUSIONS: CLBP and depression share a common underlying brain network interconnected by the SCC. Current data and novel technology provide an optimal opportunity to develop clinically effective trials of SCC DBS for CLBP.

Neurosurgery and neuromodulation for anorexia nervosa in the 21st century: a systematic review of treatment outcomes.

As current psychosocial and pharmacological interventions show limited efficacy in the treatment of anorexia nervosa (AN), interest in the potential value of neurosurgical intervention and neuromodulation in managing severe and enduring illness has grown. We conducted a systematic review of 20 trials of neurosurgical and neuromodulatory treatments for AN, including neurosurgical ablation, deep brain stimulation (DBS), repetitive transcranial magnetic stimulation (rTMS), and transcranial direct current stimulation (tDCS). Overall, there is evidence to support the role of stereotactic ablation and DBS in the treatment of AN. In contrast, results for rTMS and tDCS have been modest and generally more mixed. Neurosurgical treatment may offer important new avenues for the treatment of AN. Additional randomized clinical trials with comparable patient populations will be needed, in which change in affective, cognitive, and perceptual symptom phenomena, and interrogation of targeted circuits, pre- and post-intervention, are carefully documented.

Telemetric Intracranial Pressure Monitoring: A Systematic Review.

Telemetric intracranial pressure (ICP) monitoring is a new method of measuring ICP which eliminates some of the shortcomings of previous methods. However, there are limited data on specific characteristics, including the advantages and disadvantages of this method. The main aim of this study was to demonstrate the indications, benefits, and complications of telemetric ICP monitoring. PubMed, MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials were searched for relevant studies without language or date restriction in May 2019. Human studies in which telemetric ICP monitoring was the main subject of the study were included. Our initial search resulted in 1650 articles from which 50 studies were included. There were no randomized controlled trials. The majority of the studies were case reports or case series (68%). The most common aim of studies was testing of the device (52%), and monitoring the disease progression or recovery (46%). The most common indications for telemetric ICP monitoring in these studies were testing cerebrospinal fluid shunt function (46%), ICP control after the procedure (36%), and diagnosing intracranial hypertension (22%) and hydrocephalus (12%). In total, 1423 brain disease patients had been monitored in studies. The possibility of long-term ICP monitoring as the main benefit was reported in 38 (76%) studies. The associated complication rate was 7.1%. Despite the increasing application of telemetric monitoring devices, studies to evaluate specific characteristics of this method have been infrequent and inadequate. Future research using a higher level of scientific methods is needed to evaluate advantage and disadvantages.

Biofluid Biomarkers in Traumatic Brain Injury: A Systematic Scoping Review.

Emerging evidence suggests that biofluid-based biomarkers have diagnostic and prognostic potential in traumatic brain injuries (TBI). However, owing to the lack of a conceptual framework or comprehensive review, it is difficult to visualize the breadth of materials that might be available. We conducted a systematic scoping review to map and categorize the evidence regarding biofluid-based biochemical markers of TBI. A comprehensive search was undertaken in January 2019. Of 25,354 records identified through the literature search, 1036 original human studies were included. Five hundred forty biofluid biomarkers were extracted from included studies and classified into 19 distinct categories. Three categories of biomarkers including cytokines, coagulation tests, and nerve tissue proteins were investigated more than others and assessed in almost half of the studies (560, 515, and 502 from 1036 studies, respectively). S100 beta as the most common biomarker for TBI was tested in 21.2% of studies (220 articles). Cortisol was the only biomarker measured in blood, cerebrospinal fluid, urine, and saliva. The most common sampling time was at admission and within 24 h of injury. The included studies focused mainly on biomarkers from blood and central nervous system sources, the adult population, and severe and blunt injuries. The most common outcome measures used in studies were changes in biomarker concentration level, Glasgow coma scale, Glasgow outcome scale, brain computed tomography scan, and mortality rate. Biofluid biomarkers could be clinically helpful in the diagnosis and prognosis of TBI. However, there was no single definitive biomarker with accurate characteristics. The present categorization would be a road map to investigate the biomarkers of the brain injury cascade separately and detect the most representative biomarker of each category. Also, this comprehensive categorization could provide a guiding framework to design combined panels of multiple biomarkers.

Symptomatic Pneumocephalus after Deep Brain Stimulation Surgery: Report of 2 Cases.

BACKGROUND: Symptomatic pneumocephalus is an uncommon complication of cranial surgery. Reports of symptomatic pneumocephalus in deep brain stimulation (DBS) surgery are lacking, due to the rarity of this condition. The -authors describe 2 patients who experienced clinically significant intraparenchymal pneumocephalus as a consequence of DBS surgery and report their clinical presentations, treatments, and outcomes. Cases Descriptions: The first patient was a 69-year-old woman with Parkinson disease and the second was a 73-year-old woman with medically refractory essential tremor. Both patients underwent DBS implantation and developed focal neurological deficits in the days after surgery. In each case, immediate postoperative head computed tomography scans showed extra-axial pneumocephalus which redistributed on subsequent imaging along the dorsal length of the lead. For each patient, a second surgery was carried out to evacuate the pneumocephalus without lead removal. Clinical symptoms and radiological signs of intracranial air were resolved on the last follow-up. CONCLUSION: Symptomatic intraparenchymal pneumocephalus is a rare complication of DBS surgery which can be treated with surgical evacuation.

Charting the road forward in psychiatric neurosurgery: proceedings of the 2016 American Society for Stereotactic and Functional Neurosurgery workshop on neuromodulation for psychiatric disorders.

OBJECTIVE: Refractory psychiatric disease is a major cause of morbidity and mortality worldwide, and there is a great need for new treatments. In the last decade, investigators piloted novel deep brain stimulation (DBS)-based therapies for depression and obsessive-compulsive disorder (OCD). Results from recent pivotal trials of these therapies, however, did not demonstrate the degree of efficacy expected from previous smaller trials. To discuss next steps, neurosurgeons, neurologists, psychiatrists and representatives from industry convened a workshop sponsored by the American Society for Stereotactic and Functional Neurosurgery in Chicago, Illinois, in June of 2016. DESIGN: Here we summarise the proceedings of the workshop. Participants discussed a number of issues of importance to the community. First, we discussed how to interpret results from the recent pivotal trials of DBS for OCD and depression. We then reviewed what can be learnt from lesions and closed-loop neurostimulation. Subsequently, representatives from the National Institutes of Health, the Food and Drug Administration and industry discussed their views on neuromodulation for psychiatric disorders. In particular, these third parties discussed their criteria for moving forward with new trials. Finally, we discussed the best way of confirming safety and efficacy of these therapies, including registries and clinical trial design. We close by discussing next steps in the journey to new neuromodulatory therapies for these devastating illnesses. CONCLUSION: Interest and motivation remain strong for deep brain stimulation for psychiatric disease. Progress will require coordinated efforts by all stakeholders.

Speech and language adverse effects after thalamotomy and deep brain stimulation in patients with movement disorders: A meta-analysis.

BACKGROUND: The thalamus has been a surgical target for the treatment of various movement disorders. Commonly used therapeutic modalities include ablative and nonablative procedures. A major clinical side effect of thalamic surgery is the appearance of speech problems. OBJECTIVE: This review summarizes the data on the development of speech problems after thalamic surgery. METHODS: A systematic review and meta-analysis was performed using nine databases, including Medline, Web of Science, and Cochrane Library. We also checked for articles by searching citing and cited articles. We retrieved studies between 1960 and September 2014. RESULTS: Of a total of 2,320 patients, 19.8% (confidence interval: 14.8-25.9) had speech difficulty after thalamotomy. Speech difficulty occurred in 15% (confidence interval: 9.8-22.2) of those treated with a unilaterally and 40.6% (confidence interval: 29.5-52.8) of those treated bilaterally. Speech impairment was noticed 2- to 3-fold more commonly after left-sided procedures (40.7% vs. 15.2%). Of the 572 patients that underwent DBS, 19.4% (confidence interval: 13.1-27.8) experienced speech difficulty. Subgroup analysis revealed that this complication occurs in 10.2% (confidence interval: 7.4-13.9) of patients treated unilaterally and 34.6% (confidence interval: 21.6-50.4) treated bilaterally. After thalamotomy, the risk was higher in Parkinson's patients compared to patients with essential tremor: 19.8% versus 4.5% in the unilateral group and 42.5% versus 13.9% in the bilateral group. After DBS, this rate was higher in essential tremor patients. CONCLUSION: Both lesioning and stimulation thalamic surgery produce adverse effects on speech. Left-sided and bilateral procedures are approximately 3-fold more likely to cause speech difficulty. This effect was higher after thalamotomy compared to DBS. In the thalamotomy group, the risk was higher in Parkinson's patients, whereas in the DBS group it was higher in patients with essential tremor. Understanding the pathophysiology of speech disturbance after thalamic procedures is a priority. © 2017 International Parkinson and Movement Disorder Society.

The rationale for deep brain stimulation in Alzheimer's disease.

Alzheimer's disease is a major worldwide health problem with no effective therapy. Deep brain stimulation (DBS) has emerged as a useful therapy for certain movement disorders and is increasingly being investigated for treatment of other neural circuit disorders. Here we review the rationale for investigating DBS as a therapy for Alzheimer's disease. Phase I clinical trials of DBS targeting memory circuits in Alzheimer's disease patients have shown promising results in clinical assessments of cognitive function, neurophysiological tests of cortical glucose metabolism, and neuroanatomical volumetric measurements showing reduced rates of atrophy. These findings have been supported by animal studies, where electrical stimulation of multiple nodes within the memory circuit have shown neuroplasticity through stimulation-enhanced hippocampal neurogenesis and improved performance in memory tasks. The precise mechanisms by which DBS may enhance memory and cognitive functions in Alzheimer's disease patients and the degree of its clinical efficacy continue to be examined in ongoing clinical trials.

Common cerebral networks associated with distinct deep brain stimulation targets for cluster headache.

BACKGROUND: Several centers have reported efficacious cluster headache suppression with deep brain stimulation (DBS) of the hypothalamic region using a variety of targets. While the connectivity of some of these targets has individually been studied, commonalities across these targets, especially with respect to network-level connectivity, have not previously been explored. METHODS: We examined the anatomic connectivity of the four distinct DBS targets reported in the literature using probabilistic diffusion tensor tractography in normal subjects. RESULTS: Despite being described as hypothalamic, the DBS targets localized in the midbrain tegmentum posterior to the hypothalamus. Common tracts across DBS targets and subjects included projections to the ipsilateral hypothalamus, reticular formation, and cerebellum. DISCUSSION: Although DBS target coordinates are not located within the hypothalamus, a strong connection between DBS targets and the hypothalamus likely exists. Moreover, a common projection to the medial ipsilateral cerebellum was identified. Understanding the common connectivity of DBS-targeted regions may elucidate anatomic pathways that are involved in modulating cluster headache attacks and facilitate more precise patient-specific targeting of DBS.

Assessing the cost of contemporary pituitary care.

OBJECT: Knowledge of the costs incurred through the delivery of neurosurgical care has been lagging, making it challenging to design impactful cost-containment initiatives. In this report, the authors describe a detailed cost analysis for pituitary surgery episodes of care and demonstrate the importance of such analyses in helping to identify high-impact cost activities and drive value-based care. METHODS: This was a retrospective study of consecutively treated patients undergoing an endoscopic endonasal procedure for the resection of a pituitary adenoma after implementation and maturation of quality-improvement initiatives and the implementation of cost-containment initiatives. RESULTS: The cost data pertaining to 27 patients were reviewed. The 2 most expensive cost activities during the index hospitalization were the total operating room (OR) and total bed-assignment costs. Together, these activities represented more than 60% of the cost of hospitalization. Although value-improvement initiatives contributed to the reduction of variation in the total cost of hospitalization, specific cost activities remained relatively variable, namely the following: 1) OR charged supplies, 2) postoperative imaging, and 3) use of intraoperative neuromonitoring. These activities, however, each contributed to less than 10% of the cost of hospitalization. Bed assignment was the fourth most variable cost activity. Cost related to readmission/reoperation represented less than 5% of the total cost of the surgical episode of care. CONCLUSIONS: After completing a detailed assessment of costs incurred throughout the management of patients undergoing pituitary surgery, high-yield opportunities for cost containment should be identified among the most expensive activities and/or those with the highest variation. Strategies for safely reducing the use of the targeted resources, and related costs incurred, should be developed by the multidisciplinary team providing care for this patient population.

Functional Stimulation and Imaging to Predict Neuromodulation of Chronic Low Back Pain.

Back pain is one of the most common aversive sensations in human experience. Pain is not limited to the sensory transduction of tissue damage; rather, it encompasses a range of nervous system activities including lateral modulation, long-distance transmission, encoding, and decoding. Although spine surgery may address peripheral pain generators directly, aberrant signals along canonical aversive pathways and maladaptive influence of affective and cognitive states can result in persistent subjective pain refractory to classical surgical intervention. The clinical identification of who will benefit from surgery-and who will not-is increasingly grounded in neurophysiology.

Connectivity-based segmentation of the thalamic motor region for deep brain stimulation in essential tremor: A comparison of deterministic and probabilistic tractography.

OBJECTIVE: Deep brain stimulation (DBS) studies have shown that stimulation of the motor segment of the thalamus based on probabilistic tractography is predictive of improvement in essential tremor (ET). However, probabilistic methods are computationally demanding, requiring the need for alternative tractography methods for use in the clinical setting. The purpose of this study was to compare probabilistic vs deterministic tractography methods for connectivity-based targeting in patients with ET. METHODS: Probabilistic and deterministic tractography methods were retrospectively applied to diffusion-weighted data sets in 36 patients with refractory ET. The thalamus and precentral gyrus were selected as regions of interest and fiber tracking was performed between these regions to produce connectivity-based thalamic segmentations, per prior methods. The resultant deterministic target maps were compared with those of thresholded probabilistic maps. The center of gravity (CG) of each connectivity map was determined and the differences in spatial distribution between the tractography methods were characterized. Furthermore, the intersection between the connectivity maps and CGs with the therapeutic volume of tissue activated (VTA) was calculated. A mixed linear model was then used to assess clinical improvement in tremor with volume of overlap. RESULTS: Both tractography methods delineated the region of the thalamus with connectivity to the precentral gyrus to be within the posterolateral aspect of the thalamus. The average CG of deterministic maps was more medial-posterior in both the left (3.7 ± 1.3 mm3) and the right (3.5 ± 2.2 mm3) hemispheres when compared to 30 %-thresholded probabilistic maps. Mixed linear model showed that the volume of overlap between CGs of deterministic and probabilistic targeting maps and therapeutic VTAs were significant predictors of clinical improvement. CONCLUSIONS: Deterministic tractography can reconstruct DBS thalamic target maps in approximately 5 min comparable to those produced by probabilistic methods that require > 12 h to generate. Despite differences in CG between the methods, both deterministic-based and probabilistic targeting were predictive of clinical improvement in ET.

Somatotopic organization of the ventral nuclear group of the dorsal thalamus: deep brain stimulation for neuropathic pain reveals new insights into the facial homunculus.

Deep Brain Stimulation (DBS) is an experimental treatment for medication-refractory neuropathic pain. The ventral posteromedial (VPM) and ventral posterolateral (VPL) nuclei of the thalamus are popular targets for the treatment of facial and limb pain, respectively. While intraoperative testing is used to adjust targeting of patient-specific pain locations, a better understanding of thalamic somatotopy may improve targeting of specific body regions including the individual trigeminal territories, face, arm, and leg. To elucidate the somatotopic organization of the ventral nuclear group of the dorsal thalamus using in vivo macrostimulation data from patients undergoing DBS for refractory neuropathic pain. In vivo macrostimulation data was retrospectively collected for 14 patients who underwent DBS implantation for neuropathic pain syndromes at our institution. 56 contacts from 14 electrodes reconstructed with LeadDBS were assigned to macrostimulation-related body regions: tongue, face, arm, or leg. 33 contacts from 9 electrodes were similarly assigned to one of three trigeminal territories: V1, V2, or V3. MNI coordinates in the x, y, and z axes were compared by using MANOVA. Across the horizontal plane of the ventral nuclear group of the dorsal thalamus, the tongue was represented significantly medially, followed by the face, arm, and leg most laterally (p < 0.001). The trigeminal territories displayed significant mediolateral distribution, proceeding from V1 and V2 most medial to V3 most lateral (p < 0.001). Along the y-axis, V2 was also significantly anterior to V3 (p = 0.014). While our results showed that the ventral nuclear group of the dorsal thalamus displayed mediolateral somatotopy of the tongue, face, arm, and leg mirroring the cortical homunculus, the mediolateral distribution of trigeminal territories did not mirror the established cortical homunculus. This finding suggests that the facial homunculus may be inverted in the ventral nuclear group of the dorsal thalamus.

Corrigendum: A structural connectivity atlas of limbic brainstem nuclei.

[This corrects the article DOI: 10.3389/fnimg.2022.1009399.].

Deep brain stimulation of thalamic nuclei for the treatment of drug-resistant epilepsy: Are we confident with the precise surgical target?

Deep brain stimulation (DBS) of the thalamic nuclei for the treatment of drug-resistant epilepsy (DRE) has been investigated for decades. In recent years, DBS targeting the anterior nucleus of the thalamus (ANT) was approved by CE and FDA for the treatment of focal-onset DRE in light of the results from the multicentric randomized controlled SANTE trial. However, stereotactic targeting of thalamic nuclei is not straightforward because of the low contrast definition among thalamic nuclei on the current MRI sequences. When the FGATIR sequence is added to the preoperative MRI protocol, the mammillothalamic tract can be identified and used as a visible landmark to directly target ANT. According to the current evidence, the trans-ventricular trajectory allows the placement of stimulating contact into the nucleus more frequently than the trans-cortical trajectory. Another thalamic nucleus whose stimulation for the treatment of generalized DRE is receiving increasing attention is the centromedian nucleus (CM). CM-DBS seems to be particularly efficacious in patients suffering from Lennox-Gastault syndrome (LGS) and the recent monocentric randomized controlled ESTEL trial also described a beneficial "sweet-spot". However, CM targeting is still based on indirect stereotactic coordinates, since acquisition times and post-processing techniques of the actual MRI sequences are not applicable in clinical practice. Moreover, the results of the ESTEL trial await confirmation from similar studies accounting for epileptic syndromes other than LGS. Therefore, novel neuroimaging approaches are advisable to improve the surgical targeting of CM and potentially tailor the stimulation based on the patient's specific epileptic phenotype.

Metastatic secondary gliosarcoma: patient series.

BACKGROUND: Gliosarcoma is a rare and highly malignant cancer of the central nervous system with the ability to metastasize. Secondary gliosarcoma, or the evolution of a spindle cell-predominant tumor after the diagnosis of a World Health Organization grade IV glioblastoma, has also been shown to metastasize. There is little information on metastatic secondary gliosarcoma. OBSERVATIONS: The authors present a series of 7 patients with previously diagnosed glioblastoma presenting with recurrent tumor and associated metastases with repeat tissue diagnosis consistent with gliosarcoma. The authors describe the clinical, imaging, and pathological characteristics in addition to carrying out a systematic review on metastases in secondary gliosarcoma. LESSONS: The present institutional series and the systematic review of the literature show that metastatic secondary gliosarcoma is a highly aggressive disease with a poor prognosis.

Connectivity-based parcellation of the amygdala and identification of its main white matter connections.

The amygdala plays a role in emotion, learning, and memory and has been implicated in behavioral disorders. Better understanding of the amygdala circuitry is crucial to develop new therapies for these disorders. We used data from 200 healthy-subjects from the human connectome project. Using probabilistic tractography, we created population statistical maps of amygdala connectivity to brain regions involved in limbic, associative, memory, and reward circuits. Based on the amygdala connectivity with these regions, we applied k-means clustering to parcellate the amygdala into three clusters. The resultant clusters were averaged across all subjects and the main white-matter pathways of the amygdala from each averaged cluster were generated. Amygdala parcellation into three clusters showed a medial-to-lateral pattern. The medial cluster corresponded with the centromedial and cortical nuclei, the basal cluster with the basal nuclei and the lateral cluster with the lateral nuclei. The connectivity analysis revealed different white-matter pathways consistent with the anatomy of the amygdala circuit. This in vivo connectivity-based parcellation of the amygdala delineates three clusters of the amygdala in a mediolateral pattern based on its connectivity with brain areas involved in cognition, memory, emotion, and reward. The human amygdala circuit presented in this work provides the first step for personalized amygdala circuit mapping for patients with behavioral disorders.