Tractography-based automated identification of the retinogeniculate visual pathway with novel microstructure-informed supervised contrastive learning.

The retinogeniculate visual pathway (RGVP) is responsible for carrying visual information from the retina to the lateral geniculate nucleus. Identification and visualization of the RGVP are important in studying the anatomy of the visual system and can inform the treatment of related brain diseases. Diffusion MRI (dMRI) tractography is an advanced imaging method that uniquely enables in vivo mapping of the 3D trajectory of the RGVP. Currently, identification of the RGVP from tractography data relies on expert (manual) selection of tractography streamlines, which is time-consuming, has high clinical and expert labor costs, and is affected by inter-observer variability. In this paper, we present a novel deep learning framework, DeepRGVP , to enable fast and accurate identification of the RGVP from dMRI tractography data. We design a novel microstructure-informed supervised contrastive learning method that leverages both streamline label and tissue microstructure information to determine positive and negative pairs. We propose a simple and successful streamline-level data augmentation method to address highly imbalanced training data, where the number of RGVP streamlines is much lower than that of non-RGVP streamlines. We perform comparisons with several state-of-the-art deep learning methods that were designed for tractography parcellation, and we show superior RGVP identification results using DeepRGVP. In addition, we demonstrate a good generalizability of DeepRGVP to dMRI tractography data from neurosurgical patients with pituitary tumors and we show DeepRGVP can successfully identify RGVPs despite the effect of lesions affecting the RGVPs. Overall, our study shows the high potential of using deep learning to automatically identify the RGVP.

Brain AVM surgery without endovascular embolization in a low to middle income country.

We treated a 20-year-old woman in Paraguay with a ruptured intraventricular Spetzler-Martin Grade 3 AVM, and illustrate microsurgical resection without embolization in this video.

Directionally encoded color track density imaging in brain tumor patients: A potential application to neuro-oncology surgical planning.

BACKGROUND: Diffusion magnetic resonance imaging white matter tractography, an increasingly popular preoperative planning modality used for pre-surgical planning in brain tumor patients, is employed with the goal of maximizing tumor resection while sparing postoperative neurological function. Clinical translation of white matter tractography has been limited by several shortcomings of standard diffusion tensor imaging (DTI), including poor modeling of fibers crossing through regions of peritumoral edema and low spatial resolution for typical clinical diffusion MRI (dMRI) sequences. Track density imaging (TDI) is a post-tractography technique that uses the number of tractography streamlines and their long-range continuity to map the white matter connections of the brain with enhanced image resolution relative to the acquired dMRI data, potentially offering improved white matter visualization in patients with brain tumors. The aim of this study was to assess the utility of TDI-based white matter maps in a neurosurgical planning context compared to the current clinical standard of DTI-based white matter maps. METHODS: Fourteen consecutive brain tumor patients from a single institution were retrospectively selected for the study. Each patient underwent 3-Tesla dMRI scanning with 30 gradient directions and a b-value of 1000 s/mm2. For each patient, two directionally encoded color (DEC) maps were produced as follows. DTI-based DEC-fractional anisotropy maps (DEC-FA) were generated on the scanner, while DEC-track density images (DEC-TDI) were generated using constrained spherical deconvolution based tractography. The potential clinical utility of each map was assessed by five practicing neurosurgeons, who rated the maps according to four clinical utility statements regarding different clinical aspects of pre-surgical planning. The neurosurgeons rated each map according to their agreement with four clinical utility statements regarding if the map 1 identified clinically relevant tracts, (2) helped establish a goal resection margin, (3) influenced a planned surgical route, and (4) was useful overall. Cumulative link mixed effect modeling and analysis of variance were performed to test the primary effect of map type (DEC-TDI vs. DEC-FA) on rater score. Pairwise comparisons using estimated marginal means were then calculated to determine the magnitude and directionality of differences in rater scores by map type. RESULTS: A majority of rater responses agreed with the four clinical utility statements, indicating that neurosurgeons found both DEC maps to be useful. Across all four investigated clinical utility statements, the DEC map type significantly influenced rater score. Rater scores were significantly higher for DEC-TDI maps compared to DEC-FA maps. The largest effect size in rater scores in favor of DEC-TDI maps was observed for clinical utility statement 2, which assessed establishing a goal resection margin. CONCLUSION: We observed a significant neurosurgeon preference for DEC-TDI maps, indicating their potential utility for neurosurgical planning.

Global cancer surgery in low-resource settings: A strengths, weaknesses, opportunities, and threats analysis.

Global cancer surgery is an essential and complex component of oncologic care. This study aims to describe global cancer surgery literature since the 2015 Lancet Commission on Global Surgery and Cancer Surgery and perform a strengths, weaknesses, opportunities, and threats (SWOT) analysis. A systematic search was performed in PubMed of global cancer surgery articles. Themes were extracted from the included studies based on the following criteria: (1) performed in low- or low-middle-income countries, (2) published during or after 2015, (3) published in peer-reviewed journals, (4) written in the English language, and (5) accessible to the authors. Themes were further grouped into strengths, weaknesses, opportunities, and threats (SWOT analysis). The search strategy identified 154 articles published from 1992 to 2022. Forty-six articles were included in the qualitative synthesis and SWOT analysis. Recurring themes included local epidemiologic studies, local innovations and feasibility studies, prioritizing quality of life outcomes, multidisciplinary team approaches, limited resources, health system gaps, lack of economic analyses, diverse cancer management strategies and priorities, inter-setting collaboration, research expansion, the coronavirus disease 2019 pandemic, and unchecked technological advancements. These strengths, weaknesses, opportunities, and threats were described and related to the themes of research, surgical systems strengthening, economics and financing, and political framing of the 2015 Lancet Commission on Global Cancer Surgery. SWOT analyses of global cancer surgery may be helpful in suggesting future strategies for this expanding field. PLAIN LANGUAGE SUMMARY: Cancer surgery is a resource-intensive yet essential component of cancer care. In the face of projected growth of cancer burden, the present gap in cancer surgery care in low-resource settings with stressed health care and surgical infrastructure risks further exacerbation. We present a strengths, weaknesses, opportunities, and threats analysis of recent global cancer surgery literature pertaining to low-resource settings.

Surgical Management in Herpes Simplex Encephalitis: Illustrative Case Report and Systematic Review of the Literature.

BACKGROUND: Herpes simplex virus (HSV) is a common cause of viral encephalitis and can result in refractory seizures. Although HSV encephalitis (HSVE) is treated primarily with acyclovir, surgery can play a role in medically intractable cases. OBJECTIVE: To systematically review cases describing surgery for the treatment of severe HSVE. We also present an illustrative case of anterior temporal lobectomy (ATL) for refractory status epilepticus in a patient with unilateral HSVE. This case demonstrates one clinical context in which surgery can be a useful adjunct. METHODS: We performed a systematic review using PubMed and Google Scholar, including case reports and series describing surgical interventions for HSVE. Clinical data were extracted from 54 publications that incorporated 67 patient cases. RESULTS: Surgical decompression occurred at a wide range of times after the onset of illness, although most patients were operated on 4 or more days after HSVE symptoms began. Numerous reports indicated that decompressive craniectomy, temporal lobectomy, and hematoma removal could treat intractably elevated intracranial pressure because of HSVE with favorable long-term outcomes. We describe an additional case in which a 52-year-old woman with HSVE developed refractory right temporal lobe seizures. After ATL, the seizures resolved with significant clinical improvement. CONCLUSION: Surgical treatment can be a useful adjunct for treatment of HSVE. There is substantial variability in the timing of surgical decompression in patients with HSVE, which can be necessary up to approximately 3 weeks after illness onset. ATL should be considered for refractory status epilepticus in HSVE with a unilateral seizure focus.

Stereotactic radiosurgery and stereotactic fractionated radiotherapy for metastatic tumors of the spine.

OBJECTIVES: The objectives of this paper are to describe pain control, neurologic improvement, local tumor control, progression-free survival, and overall survival of spine SRS/SFRT patients, and to compare our outcomes with other studies on spine stereotactic radiotherapy for metastatic tumors. METHODS: A chart review of patients who underwent spine SRS/SFRT was done. Information was collected on patient age, sex, histology, site treated, pain relief, local control, neurologic function, prescription dose, and complications. Descriptive statistics, median local control rates, progression-free survival, and overall survival were calculated. RESULTS: Twenty eight SRS and 3 SFRT target volumes in 21 patients were studied. Eighteen underwent SRS and 3 underwent SFRT for metastasis from August 2012 to February 2016. Follow-up ranged from 4 to 41 months. Average dose was 16.6 ± 3.9 Gy. Spine SRS mean target volume was 31.1 cc (95% CI, 21.7-40.6 cc). Median overall survival after treatment was 16 months (95% CI, 9.7-22.3 months) and median progression-free survival was 13 months (95% CI, 8.4-17.6 months). Local control was 46%, 30%, and 15% at 6, 8, and 10 months, respectively. Average onset of pain relief is 4.9 days (95% CI, 0.8-8.9 days). One patient (5%) developed post SRS vertebral compression fracture. CONCLUSION: SRS/SFRT is a safe and effective alternative to EBRT for the treatment of spine metastasis. Improvement in pain control and motor strength and incidence of adverse events are comparable with other studies. Local tumor control was lower in our series due to a lower mean prescribed dose.