A Practical Roadmap to Implementing Deep Learning Segmentation in the Clinical Neuroimaging Research Workflow.

Thanks to the proliferation of open-source tools, we are seeing an exponential growth of machine learning applications, and its integration has become more accessible, particularly for segmentation tools in neuroimaging. This article explores a generalised methodology that harnesses these tools and aims/enables to expedite and enhance the reproducibility of clinical research. Herein, critical re considerations include hardware, software, neural network training strategies and data labelling guidelines. More specifically, we advocate an iterative approach to model training and transfer learning, focusing on internal validation and outlier handling early in the labelling process and fine-tuning later on. The iterative refinement process allows experts to intervene and improve model reliability whilst cutting down on their time spent in manual work. A seamless integration of the final model's predictions into clinical research is proposed to ensure standardized and reproducible results. In short, this article provides a comprehensive framework for accelerating research using machine learning techniques for image segmentation.

Radiosurgical thalamotomy for essential tremor: state of the art, current challenges and future directions.

INTRODUCTION: Essential tremor (ET) is the most frequent movement disorder, affecting up to 5% of adults > 65 years old. In 30-50% of cases, optimal medical management provides insufficient tremor relief and surgical options are considered. Thalamotomy is a time-honored intervention, which can be performed using radiofrequency (RF), stereotactic radiosurgery (SRS), or magnetic resonance-guided focused ultrasounds (MRgFUS). While the latter has received considerable attention in the last decade, SRS has consistently been demonstrated as an effective and well-tolerated option. AREAS COVERED: This review discusses the evidence on SRS thalamotomy for ET. Modern workflows and emerging techniques are detailed. Current outcomes are analyzed, with a specific focus on tremor reduction, complications and radiological evolution of the lesions. Challenges for the field are highlighted. EXPERT OPINION: SRS thalamotomy improves tremor in > 80% patients. The efficacy appears comparable to other modalities, including DBS, RF and MRgFUS. Side effects result mostly from idiosyncratic hyper-responses to radiation, which occur in up to 10% of treatments, are usually self-resolving, and are symptomatic in < 4% of patients. Future research should focus on accumulating more data on bilateral treatments, collecting long-term outcomes, refining targeting, and improving lesion consistency.

Forelimb movements contribute to hindlimb cutaneous reflexes during locomotion in cats.

During quadrupedal locomotion, interactions between spinal and supraspinal circuits and somatosensory feedback coordinate forelimb and hindlimb movements. How this is achieved is not clear. To determine whether forelimb movements modulate hindlimb cutaneous reflexes involved in responding to an external perturbation, we stimulated the superficial peroneal nerve in six intact cats during quadrupedal locomotion and during hindlimb-only locomotion (with forelimbs standing on stationary platform) and in two cats with a low spinal transection (T12-T13) during hindlimb-only locomotion. We compared cutaneous reflexes evoked in six ipsilateral and four contralateral hindlimb muscles. Results showed similar occurrence and phase-dependent modulation of short-latency inhibitory and excitatory responses during quadrupedal and hindlimb-only locomotion in intact cats. However, the depth of modulation was reduced in the ipsilateral semitendinosus during hindlimb-only locomotion. Additionally, longer-latency responses occurred less frequently in extensor muscles bilaterally during hindlimb-only locomotion, whereas short-latency inhibitory and longer-latency excitatory responses occurred more frequently in the ipsilateral and contralateral sartorius anterior, respectively. After spinal transection, short-latency inhibitory and excitatory responses were similar to both intact conditions, whereas mid- or longer-latency excitatory responses were reduced or abolished. Our results in intact cats and the comparison with spinal-transected cats suggest that the absence of forelimb movements suppresses inputs from supraspinal structures and/or cervical cord that normally contribute to longer-latency reflex responses in hindlimb extensor muscles.NEW & NOTEWORTHY During quadrupedal locomotion, the coordination of forelimb and hindlimb movements involves central circuits and somatosensory feedback. To demonstrate how forelimb movement affects hindlimb cutaneous reflexes during locomotion, we stimulated the superficial peroneal nerve in intact cats during quadrupedal and hindlimb-only locomotion as well as in spinal-transected cats during hindlimb-only locomotion. We show that forelimb movement influences the modulation of hindlimb cutaneous reflexes, particularly the occurrence of long-latency reflex responses.

Characterization of Pediatric Infratentorial Arteriovenous Malformations: A Retrospective, Multicenter Cohort Study.

BACKGROUND AND OBJECTIVES: Infratentorial arteriovenous malformations (AVMs) harbor different characteristics compared with supratentorial AVMs. This study aims to explore the unique characteristics of pediatric infratentorial AVMs and their response to single session stereotactic radiosurgery (SRS). METHODS: The International Radiosurgery Research Foundation database of pediatric patients with AVM (age <18 years) who underwent SRS was retrospectively reviewed. Baseline demographics, AVM characteristics, outcomes, and complications post-SRS were compared between infratentorial and supratentorial pediatric AVMs. Unfavorable outcome was defined as the absence of AVM obliteration, post-SRS hemorrhage, or permanent radiation-induced changes at last follow-up. RESULTS: A total of 535 pediatric AVMs managed with SRS with a median follow-up of 67 months (IQR 29.0-130.6) were included, with 69 being infratentorial and 466 supratentorial. The infratentorial group had a higher proportion of deep location (58.4% vs 30.3%, P = <.001), deep venous drainage (79.8% vs 61.8%, P = .004), and prior embolization (26.1% vs 15.7%, P = .032). There was a higher proportion of hemorrhagic presentation in the infratentorial group (79.7% vs 71.3%, P = .146). There was no statistically significant difference in the odds of an unfavorable outcome (odds ratio [OR] = 1.36 [0.82-2.28]), AVM obliteration (OR = 0.85 [0.5-1.43]), post-SRS hemorrhage (OR = 0.83 [0.31-2.18]), or radiologic radiation-induced changes (OR = 1.08 [0.63-1.84]) between both cohorts. No statistically significant difference on the rates of outcomes of interest and complications were found in the adjusted model. CONCLUSION: Despite baseline differences between infratentorial and supratentorial pediatric AVMs, SRS outcomes, including AVM obliteration and post-SRS hemorrhage rates, were comparable amongst both groups. SRS appears to have a similar risk profile and therapeutic benefit to infratentorial pediatric AVMs as it does for those with a supratentorial location.

The relevance of biologically effective dose for pain relief and sensory dysfunction after Gamma Knife radiosurgery for trigeminal neuralgia: an 871-patient multicenter study.

OBJECTIVE: Recent studies have suggested that biologically effective dose (BED) is an important correlate of pain relief and sensory dysfunction after Gamma Knife radiosurgery (GKRS) for trigeminal neuralgia (TN). The goal of this study was to determine if BED is superior to prescription dose in predicting outcomes in TN patients undergoing GKRS as a first procedure. METHODS: This was a retrospective study of 871 patients with type 1 TN from 13 GKRS centers. Patient demographics, pain characteristics, treatment parameters, and outcomes were reviewed. BED was compared with prescription dose and other dosimetric factors for their predictive value. RESULTS: The median age of the patients was 68 years, and 60% were female. Nearly 70% of patients experienced pain in the V2 and/or V3 dermatomes, predominantly on the right side (60%). Most patients had modified BNI Pain Intensity Scale grade IV or V pain (89.2%) and were taking 1 or 2 pain medications (74.1%). The median prescription dose was 80 Gy (range 62.5-95 Gy). The proximal trigeminal nerve was targeted in 77.9% of cases, and the median follow-up was 21 months (range 6-156 months). Initial pain relief (modified BNI Pain Intensity Scale grades I-IIIa) was noted in 81.8% of evaluable patients at a median of 30 days. Of 709 patients who achieved initial pain relief, 42.3% experienced at least one pain recurrence after GKRS at a median of 44 months, with 49.0% of these patients undergoing a second procedure. New-onset facial numbness occurred in 25.3% of patients after a median of 8 months. Age ≥ 63 years was associated with a higher probability of both initial pain relief and maintaining pain relief. A distal target location was associated with a higher probability of initial and long-term pain relief, but also a higher incidence of sensory dysfunction. BED ≥ 2100 Gy2.47 was predictive of pain relief at 30 days and 1 year for the distal target, whereas physical dose ≥ 85 Gy was significant for the proximal target, but the restricted range of BED values in this subgroup could be a confounding factor. A maximum brainstem point dose ≥ 29.5 Gy was associated with a higher probability of bothersome facial numbness. CONCLUSIONS: BED and physical dose were both predictive of pain relief and could be used as treatment planning goals for distal and proximal targets, respectively, while considering maximum brainstem point dose < 29.5 Gy as a potential constraint for bothersome numbness.

Successful magnetic resonance-guided focused ultrasound treatment of tremor in patients with a skull density ratio of 0.4 or less.

OBJECTIVE: The use of magnetic resonance-guided focused ultrasound (MRgFUS) for the treatment of tremor-related disorders and other novel indications has been limited by guidelines advocating treatment of patients with a skull density ratio (SDR) above 0.45 ± 0.05 despite reports of successful outcomes in patients with a low SDR (LSDR). The authors' goal was to retrospectively analyze the sonication strategies, adverse effects, and clinical and imaging outcomes in patients with SDR ≤ 0.4 treated for tremor using MRgFUS. METHODS: Clinical outcomes and adverse effects were assessed at 3 and 12 months after MRgFUS. Outcomes and lesion location, volume, and shape characteristics (elongation and eccentricity) were compared between the SDR groups. RESULTS: A total of 102 consecutive patients were included in the analysis, of whom 39 had SDRs ≤ 0.4. No patient was excluded from treatment because of an LSDR, with the lowest being 0.22. Lesioning temperatures (> 52°C) and therapeutic ablations were achieved in all patients. There were no significant differences in clinical outcome, adverse effects, lesion location, and volume between the high SDR group and the LSDR group. SDR was significantly associated with total energy (rho = -0.459, p < 0.001), heating efficiency (rho = 0.605, p < 0.001), and peak temperature (rho = 0.222, p = 0.025). CONCLUSIONS: The authors' results show that treatment of tremor in patients with an LSDR using MRgFUS is technically possible, leading to a safe and lasting therapeutic effect. Limiting the number of sonications and adjusting the energy and duration to achieve the required temperature early during the treatment are suitable strategies in LSDR patients.

Neurotransmitter levels in the basal ganglia are associated with intracortical circuit activity of the primary motor cortex in healthy humans.

BACKGROUND: The basal ganglia are strongly connected to the primary motor cortex (M1) and play a crucial role in movement control. Interestingly, several disorders showing abnormal neurotransmitter levels in basal ganglia also present concomitant anomalies in intracortical function within M1. OBJECTIVE/HYPOTHESIS: The main aim of this study was to clarify the relationship between neurotransmitter content in the basal ganglia and intracortical function at M1 in healthy individuals. We hypothesized that neurotransmitter content of the basal ganglia would be significant predictors of M1 intracortical function. METHODS: We combined magnetic resonance spectroscopy (MRS) and transcranial magnetic stimulation (TMS) to test this hypothesis in 20 healthy adults. An extensive TMS battery probing common measures of intracortical, and corticospinal excitability was administered, and GABA and glutamate-glutamine levels were assessed from voxels placed over the basal ganglia and the occipital cortex (control region). RESULTS: Regression models using metabolite concentration as predictor and TMS metrics as outcome measures showed that glutamate level in the basal ganglia significantly predicted short interval intracortical inhibition (SICI) and intracortical facilitation (ICF), while GABA content did not. No model using metabolite measures from the occipital control voxel was significant. CONCLUSIONS: Taken together, these results converge with those obtained in clinical populations and suggest that intracortical circuits in human M1 are associated with the neurotransmitter content of connected but distal subcortical structures crucial for motor function.

Impact of Multiple Sclerosis Subtypes on Pain Management in Patients With Trigeminal Neuralgia After Stereotactic Radiosurgery: An International Multicenter Analysis.

BACKGROUND AND OBJECTIVES: Trigeminal neuralgia affects approximately 2% of patients with multiple sclerosis (MS) and often shows higher rates of pain recurrence after treatment. Previous studies on the effectiveness of stereotactic radiosurgery (SRS) for trigeminal neuralgia did not consider the different MS subtypes, including remitting relapsing (RRMS), primary progressive (PPMS), and secondary progressive (SPMS). Our objective was to investigate how MS subtypes are related to pain control (PC) rates after SRS. METHODS: We conducted a retrospective multicenter analysis of prospectively collected databases. Pain status was assessed using the Barrow National Institute Pain Intensity Scales. Time to recurrence was estimated through the Kaplan-Meier method and compared groups using log-rank tests. Logistic regression was used to calculate the odds ratio (OR). RESULTS: Two hundred and fifty-eight patients, 135 (52.4%) RRMS, 30 (11.6%) PPMS, and 93 (36%) SPMS, were included from 14 institutions. In total, 84.6% of patients achieved initial pain relief, with a median time of 1 month; 78.7% had some degree of pain recurrence with a median time of 10.2 months for RRMS, 8 months for PPMS, 8.1 months for SPMS ( P = .424). Achieving Barrow National Institute-I after SRS was a predictor for longer periods without recurrence ( P = .028). Analyzing PC at the last available follow-up and comparing with RRMS, PPMS was less likely to have PC (OR = 0.389; 95% CI 0.153-0.986; P = .047) and SPMS was more likely (OR = 2.0; 95% CI 0.967-4.136; P = .062). A subgroup of 149 patients did not have other procedures apart from SRS. The median times to recurrence in this group were 11.1, 9.8, and 19.6 months for RRMS, PPMS, and SPMS, respectively (log-rank, P = .045). CONCLUSION: This study is the first to investigate the relationship between MS subtypes and PC after SRS, and our results provide preliminary evidence that subtypes may influence pain outcomes, with PPMS posing the greatest challenge to pain management.

Invasive Brain Computer Interface for Motor Restoration in Spinal Cord Injury: A Systematic Review.

STUDY DESIGN: Systematic review of the literature. OBJECTIVES: In recent years, brain-computer interface (BCI) has emerged as a potential treatment for patients with spinal cord injury (SCI). This is the first systematic review of the literature on invasive closed-loop BCI technologies for the treatment of SCI in humans. MATERIALS AND METHODS: A comprehensive search of PubMed MEDLINE, Web of Science, and Ovid EMBASE was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. RESULTS: Of 8316 articles collected, 19 studies met all the inclusion criteria. Data from 21 patients were extracted from these studies. All patients sustained a cervical SCI and were treated using either a BCI with intracortical microelectrode arrays (n = 18, 85.7%) or electrocorticography (n = 3, 14.3%). To decode these neural signals, machine learning and statistical models were used: support vector machine in eight patients (38.1%), linear estimator in seven patients (33.3%), Hidden Markov Model in three patients (14.3%), and other in three patients (14.3%). As the outputs, ten patients (47.6%) underwent noninvasive functional electrical stimulation (FES) with a cuff; one (4.8%) had an invasive FES with percutaneous stimulation, and ten (47.6%) used an external device (neuroprosthesis or virtual avatar). Motor function was restored in all patients for each assigned task. Clinical outcome measures were heterogeneous across all studies. CONCLUSIONS: Invasive techniques of BCI show promise for the treatment of SCI, but there is currently no technology that can restore complete functional autonomy in patients with SCI. The current techniques and outcomes of BCI vary greatly. Because invasive BCIs are still in the early stages of development, further clinical studies should be conducted to optimize the prognosis for patients with SCI.

Response Assessment in Brain Metastases Managed by Stereotactic Radiosurgery: A Reappraisal of the RANO-BM Criteria.

BACKGROUND: Brain metastases (BM) are increasingly being treated using stereotactic radiosurgery (SRS). Standardized response criteria are necessary to improve research and treatment protocols. This study's goal was to validate the RANO-BM criteria thresholds for tumor progression in a cohort of patients with brain metastases managed using SRS. METHODS: We performed a retrospective analysis of patients treated at least twice with SRS for brain metastases. Local progression, as defined by RANO-BM criteria, was compared to our multidisciplinary tumor board's treatment recommendation. A ROC curve was generated using varying diameter thresholds to assess the sensitivity and specificity of current RANO-BM criteria. RESULTS: 249 metastases in 67 patients were included in the analysis. RANO-BM criteria current progression thresholds yielded a sensitivity of 38%, a specificity of 95%, a positive predictive value of 71%, and a negative predictive value of 84% relative to our tumor board's treatment recommendation. Modified RANO-BM criteria using absolute diameter differences of 2.5 mm yielded a sensitivity of 83%, a specificity of 87%, a positive predictive value of 67% and a negative predictive value of 94%. CONCLUSIONS: Current RANO-BM criteria unreliably identifies clinically relevant tumor progression. The use of absolute diameter differences thresholds appears superior in our BM cohort.

Trends and disparities in deep brain stimulation utilization in the United States: a Nationwide Inpatient Sample analysis from 1993 to 2017.

Background: Deep brain stimulation (DBS) is an approved treatment option for Parkinson's Disease (PD), essential tremor (ET), dystonia, obsessive-compulsive disorder and epilepsy in the United States. There are disparities in access to DBS, and clear understanding of the contextual factors driving them is important. Previous studies aimed at understanding these factors have been limited by single indications or small cohort sizes. The aim of this study is to provide an updated and comprehensive analysis of DBS utilization for multiple indications to better understand the factors driving disparities in access. Methods: The United States based National Inpatient Sample (NIS) database was utilized to analyze the surgical volume and trends of procedures based on indication, using relevant ICD codes. Predictors of DBS use were analyzed using a logistic regression model. DBS-implanted patients in each indication were compared based on the patient-, hospital-, and outcome-related variables. Findings: Our analysis of 104,356 DBS discharges from 1993 to 2017 revealed that the most frequent indications for DBS were PD (67%), ET (24%), and dystonia (4%). Although the number of DBS procedures has consistently increased over the years, radiofrequency ablation utilization has significantly decreased to only a few patients per year since 2003. Negative predictors for DBS utilization in PD and ET cohorts included age increase and female sex, while African American status was a negative predictor across all cohorts. Significant differences in patient-, hospital-, and outcome-related variables between DBS indications were also determined. Interpretation: Demographic and socioeconomic-based disparities in DBS use are evident. Although racial disparities are present across all indications, other disparities such as age, sex, wealth, and insurance status are only relevant in certain indications. Funding: This work was supported by Alan & Susan Hudson Cornerstone Chair in Neurosurgery at University Health Network.

Classification of subdural hematomas: proposal for a new system improving the ICD Coding Tools.

Background: The International Statistical Classification of Diseases (ICD) classifies subdural hematoma (SDH) as traumatic or non-traumatic. In clinical settings, however, SDH is typically described as either acute or chronic. Objective: The goal of this study was to assess how the ICD Coding Tools captures the clinical terminology and propose an improved classification that would increase the system's usefulness in administrative, statistical and research applications. Methods: We performed a retrospective analysis of patients who presented to our center with an ICD diagnostic code for either traumatic or non-traumatic SDH. A qualitative analysis of patients' charts was performed to identify elements relevant to management and prognosis, following which a meeting between expert investigators was held to elaborate a new classification of SDH. Imaging from all patients was then reviewed and cases were reclassified according to our proposed system. Results: A total of 277 SDH cases were included. Themes documented in the charts included chronicity, etiology, side, and symptoms. We created a new classification which distinguishes acute SDH (aSDH) from membrane-associated SDH (mSDH). aSDH were further divided into traumatic aSDH (taSDH) and non-traumatic aSDH (ntaSDH), while mSDH were divided into acute on chronic (a/cSDH), subacute (sSDH) and chronic (cSDH) categories. Conclusion: The ICD coding system correctly identifies taSDH and ntaSDH. However, it remains non-specific for mSDH. We propose this new SDH classification system to better capture chronicity and etiology - factors felt to impact management and prognosis.

Use of Invasive Brain-Computer Interfaces in Pediatric Neurosurgery: Technical and Ethical Considerations.

Invasive brain-computer interfaces hold promise to alleviate disabilities in individuals with neurologic injury, with fully implantable brain-computer interface systems expected to reach the clinic in the upcoming decade. Children with severe neurologic disabilities, like quadriplegic cerebral palsy or cervical spine trauma, could benefit from this technology. However, they have been excluded from clinical trials of intracortical brain-computer interface to date. In this manuscript, we discuss the ethical considerations related to the use of invasive brain-computer interface in children with severe neurologic disabilities. We first review the technical hardware and software considerations for the application of intracortical brain-computer interface in children. We then discuss ethical issues related to motor brain-computer interface use in pediatric neurosurgery. Finally, based on the input of a multidisciplinary panel of experts in fields related to brain-computer interface (functional and restorative neurosurgery, pediatric neurosurgery, mathematics and artificial intelligence research, neuroengineering, pediatric ethics, and pragmatic ethics), we then formulate initial recommendations regarding the clinical use of invasive brain-computer interfaces in children.

Gamma Knife Stereotactic Radiosurgery for Trigeminal Neuralgia Secondary to Multiple Sclerosis: A Case-Control Study.

BACKGROUND: The efficacy of stereotactic radiosurgery (SRS) for the relief of trigeminal neuralgia (TN) is well established. Much less is known, however, about the benefit of SRS for multiple sclerosis (MS)-related TN (MS-TN). OBJECTIVE: To compare outcomes in patients who underwent SRS for MS-TN vs classical/idiopathic TN and identify relative risk factors for failure. METHODS: We conducted a retrospective, case-control study of patients who underwent Gamma Knife radiosurgery at our center for MS-TN between October 2004 and November 2017. Cases were matched 1:1 to controls using a propensity score predicting MS probability using pretreatment variables. The final cohort consisted of 154 patients (77 cases and 77 controls). Baseline demographics, pain characteristics, and MRI features were collected before treatment. Pain evolution and complications were obtained at follow-up. Outcomes were analyzed using the Kaplan-Meir estimator and Cox regressions. RESULTS: There was no statistically significant difference between both groups with regards to initial pain relief (modified Barrow National Institute IIIa or less), which was achieved in 77% of patients with MS and 69% of controls. In responders, 78% of patients with MS and 52% of controls eventually had recurrence. Pain recurred earlier in patients with MS (29 months) than in controls (75 months). Complications were similarly distributed in each group and consisted, in the MS group, of 3% of new bothersome facial hypoesthesia and 1% of new dysesthesia. CONCLUSION: SRS is a safe and effective modality to achieve pain freedom in MS-TN. However, pain relief is significantly less durable than in matched controls without MS.

Subarachnoid Hemorrhage, Delayed Cerebral Ischemia, and Milrinone Use in Canada.

INTRODUCTION: Delayed cerebral ischemia (DCI) is a complication of aneurysmal subarachnoid hemorrhage (aSAH) and is associated with significant morbidity and mortality. There is little high-quality evidence available to guide the management of DCI. The Canadian Neurosurgery Research Collaborative (CNRC) is comprised of resident physicians who are positioned to capture national, multi-site data. The objective of this study was to evaluate practice patterns of Canadian physicians regarding the management of aSAH and DCI. METHODS: We performed a cross-sectional survey of Canadian neurosurgeons, intensivists, and neurologists who manage aSAH. A 19-question electronic survey (Survey Monkey) was developed and validated by the CNRC following a DCI-related literature review (PubMed, Embase). The survey was distributed to members of the Canadian Neurosurgical Society and to Canadian members of the Neurocritical Care Society. Responses were analyzed using quantitative and qualitative methods. RESULTS: The response rate was 129/340 (38%). Agreement among respondents was limited to the need for intensive care unit admission, use of clinical and radiographic monitoring, and prophylaxis for the prevention of DCI. Several inconsistencies were identified. Indications for starting hyperdynamic therapy varied. There was discrepancy in the proportion of patients who felt to require IV milrinone, IA vasodilators, or physical angioplasty for treatment of DCI. Most respondents reported their facility does not utilize a standardized definition for DCI. CONCLUSION: DCI is an important clinical entity for which no homogeneity and standardization exists in management among Canadian practitioners. The CNRC calls for the development of national standards in the definition, identification, and treatment of DCI.

Side bending radiographs and lowest instrumented vertebra in adolescent idiopathic scoliosis: A French quality-of-care study.

BACKGROUND: Determining which spinal levels to instrument during surgical treatment of Lenke Type 1 adolescent idiopathic scoliosis (AIS) depends on the reducibility of the primary and secondary curve patterns. This reducibility can be evaluated in several ways, with the most popular being radiographs in bending for moderate thoracic and lumbar curvatures. Hypothesis Side-bending radiographs will alter the choice of the lowest instrumented vertebra (LIV) for the surgical treatment of AIS. METHODS: Thirteen experienced French spine surgeons were invited to perform surgical planning on 23 patients based on stereoradiographs with and without (standing) side-bending views. The surgical planning was repeated a second time to assess the intra- and inter-rater reliability. Variations in the choice of LIV were analyzed for each evaluation. RESULTS: The intra-rater reliability was moderate to substantial. The inter-rater reliability was low to moderate. The study compared 879 surgical plans. Selective fusion was chosen in 0.3% of the plans. The median LIV was L2. The availability of side bending views changed the plan in 39% of cases. However, 36% of the plans were changed in the control (test-retest) condition. No significant difference was found between the variations with side-bending radiographs and "control" variations (p>0.05). CONCLUSION: The use of radiographs in bending has no significant effect on the LIV choice in this study. This result is derived from statistically robust analysis made possible by one of the largest datasets available on this topic. Large inter-rater variability was observed and will be explored further in a future study. LEVEL OF EVIDENCE: II; non-randomized controlled comparative study.

Superior Longitudinal Fasciculus: A Review of the Anatomical Descriptions With Functional Correlates.

The superior longitudinal fasciculus (SLF) is part of the longitudinal association fiber system, which lays connections between the frontal lobe and other areas of the ipsilateral hemisphere. As a dominant association fiber bundle, it should correspond to a well-defined structure with a clear anatomical definition. However, this is not the case, and a lot of confusion and overlap surrounds this entity. In this review/opinion study, we survey relevant current literature on the topic and try to clarify the definition of SLF in each hemisphere. After a comparison of postmortem dissections and data obtained from diffusion MRI studies, we discuss the specifics of this bundle regarding its anatomical landmarks, differences in lateralization, as well as individual variability. We also discuss the confusion regarding the arcuate fasciculus in relation to the SLF. Finally, we recommend a nomenclature based on the findings exposed in this review and finalize with a discussion on relevant functional correlates of the structure.

Neuroimaging of psychiatric disorders.

Psychiatry remains the only medical specialty where diagnoses are still based on clinical syndromes rather than measurable biological abnormalities. As imaging technology and analytical methods evolve, it is becoming clear that subtle but measurable radiological characteristics exist and can be used to experimentally classify psychiatric disorders, predict response to treatment and, hopefully, develop new, more effective therapies. This review highlights advances in neuroimaging modalities that are now allowing assessment of brain structure, connectivity and neural network function, describes technical aspects of the most promising methods, and summarizes observations made in some frequent psychiatric disorders.

Comparison of four correction techniques for posterior spinal fusion in adolescent idiopathic scoliosis.

INTRODUCTION: When performing posterior spinal fusion for adolescent idiopathic scoliosis (AIS), it is of major importance to address both coronal and sagittal deformities. Although several techniques have been described, few data exist comparing them. Our objective was to compare four techniques (in situ bending (ISB), rod derotation (RD), cantilever (C) and posteromedial translation (PMT)) for the correction of spinal deformity in AIS including thoracic deformity. MATERIAL AND METHODS: We conducted a multicenter retrospective study including 562 AIS patients with thoracic deformity with at least 24-month follow-up. Radiographic analysis was performed preoperatively, postoperatively and at last follow-up. The main outcomes were main curve correction and thoracic kyphosis restoration (TK). RESULTS: Coronal correction rate was significantly different among the four treatment groups (ISB 64% vs C 57% vs RD 55% vs PMT 67%, p < 0.001). Multivariate regression revealed that correction technique did not influence correction rate, whereas implant density, convex side compression and use of derotation connectors did. TK increase was significantly higher in the PMT group (average + 13°) than in DR (+ 3°), while ISB (-3°) and cantilever (-13°) resulted in TK decrease (p < 0.001). Multivariate analysis revealed that TK increase was only influenced by the reduction technique (p < 0.001) and preoperative TK (p < 0.001). DISCUSSION: The four techniques had the same ability to correct spinal deformity in the coronal plane. Three factors were identified to improve correction rate: implant density, convex compression and use of derotation connectors. On the other hand, PMT was more effective in restoring TK, particularly in hypokyphotic patients.