Multimodal MRI reveals brainstem connections that sustain wakefulness in human consciousness.

Consciousness is composed of arousal (i.e., wakefulness) and awareness. Substantial progress has been made in mapping the cortical networks that underlie awareness in the human brain, but knowledge about the subcortical networks that sustain arousal in humans is incomplete. Here, we aimed to map the connectivity of a proposed subcortical arousal network that sustains wakefulness in the human brain, analogous to the cortical default mode network (DMN) that has been shown to contribute to awareness. We integrated data from ex vivo diffusion magnetic resonance imaging (MRI) of three human brains, obtained at autopsy from neurologically normal individuals, with immunohistochemical staining of subcortical brain sections. We identified nodes of the proposed default ascending arousal network (dAAN) in the brainstem, hypothalamus, thalamus, and basal forebrain. Deterministic and probabilistic tractography analyses of the ex vivo diffusion MRI data revealed projection, association, and commissural pathways linking dAAN nodes with one another and with DMN nodes. Complementary analyses of in vivo 7-tesla resting-state functional MRI data from the Human Connectome Project identified the dopaminergic ventral tegmental area in the midbrain as a widely connected hub node at the nexus of the subcortical arousal and cortical awareness networks. Our network-based autopsy methods and connectivity data provide a putative neuroanatomic architecture for the integration of arousal and awareness in human consciousness.

Doing more with less: Realistic stereoscopic three-dimensional anatomical modeling from smartphone photogrammetry.

Traditional teaching methods struggle to convey three-dimensional concepts effectively. While 3D virtual models and virtual reality platforms offer a promising approach to teaching anatomy, their cost and specialized equipment pose limitations, especially in disadvantaged areas. A simpler alternative is to use virtual 3D models displayed on regular screens, but they lack immersion, realism, and stereoscopic vision. To address these challenges, we developed an affordable method utilizing smartphone-based 360° photogrammetry, virtual camera recording, and stereoscopic display (anaglyph or side-by-side technique). In this study, we assessed the feasibility of this method by subjecting it to various specimen types: osteological, soft organ, neuroanatomical, regional dissection, and a dedicated 3D-printed testing phantom. The results demonstrate that the 3D models obtained feature a complete mesh with a high level of detail and a realistic texture. Mesh and texture resolutions were estimated to be approximately 1 and 0.2 mm, respectively. Additionally, stereoscopic animations were both feasible and effective in enhancing depth perception. The simplicity and affordability of this method position it as a technique of choice for creating easily photorealistic anatomical models combined with stereoscopic depth visualization.

Direct Inside-Out Observation of Superficial White Matter Fasciculi in the Human Brain.

Background: Recent methodological advances in the study of the cerebral white matter have left short association fibers relatively underexplored due to their compact and juxtacortical nature, which represent significant challenges for both post-mortem post-cortex removal dissection and magnetic resonance-based diffusion imaging. Objective: To introduce a novel inside-out post-mortem fiber dissection technique to assess short association fiber anatomy. Methods: Six cerebral specimens were obtained from a body donation program and underwent fixation in formalin. Following two freezing and thawing cycles, a standardized protocol involving peeling fibers from deep structures towards the cortex was developed. Results: The inside-out technique effectively exposed the superficial white matter. The procedure revealed distinguishable intergyral fibers, demonstrating their dissectability and enabling the identification of their orientation. The assessment of layer thickness was possible through direct observation and ex vivo morphological magnetic resonance imaging. Conclusion: The inside-out fiber technique effectively demonstrates intergyral association fibers in the post-mortem human brain. It adds to the neuroscience armamentarium, overcoming methodological obstacles and offering an anatomical substrate essential for neural circuit modeling and the evaluation of neuroimaging congruence. Impact statement The inside-out fiber dissection technique enables a totally new perception of cerebral connectivity as the observer navigates inside the parenchyma and looks toward the cerebral surface with the subcortical white matter and the cortical mantle in place. This approach has proven very effective for exposing intergyral association fibers, which have shown to be much more distinguishable from an inner perspective. It gave rise to unprecedented images of the human superficial white matter and allowed, for the first time, direct observation of this vast mantle of fascicles on entire cerebral hemisphere aspects.

The legal and ethical framework governing body donation in Europe - 2nd update on current practice.

BACKGROUND: In 2008, members of the TEPARG provided first insights into the legal and ethical framework governing body donation in Europe. In 2012, a first update followed. This paper is now the second update on this topic and tries to extend the available information to many more European countries. METHODS: For this second update, we have asked authors from all European countries to contribute their national perspectives. By this enquiry, we got many contributions compiled in this paper. When we did not get a personal contribution, one of us (EB) searched the internet for relevant information. RESULTS: Perspectives on the legal and ethical framework governing body donation in Europe. CONCLUSIONS: We still see that a clear and rigorous legal framework is still unavailable in several countries. We found national regulations in 18 out of 39 countries; two others have at least federal laws. Several countries accept not only donated bodies but also utilise unclaimed bodies. These findings can guide policymakers in reviewing and updating existing laws and regulations related to body donation and anatomical studies.

ProbaStem, a pipeline towards the first high-resolution probabilistic atlas of the whole human brainstem.

The brainstem plays an essential role in many vital functions, such as autonomic control, consciousness and sleep, motricity, somatic afferent function, and cognition. Its involvement in several neurological diseases and the definition of brainstem targets for deep brain stimulation (DBS) explain the need for brainstem atlases describing its structural organization and connectivity from several modalities, from histology to ultrahigh field ex vivo MRI. Nonetheless, these atlases are often limited to a subpart of the brainstem or only include a single subject, the brainstem variability being considered low. This paper proposes a pipeline to create a high-resolution multisubject probabilistic atlas of the whole human brainstem based on four ultrahigh field ex vivo MRI datasets. The variability of the brainstem structures appears higher than usually considered, both for the volume and position of the central gray matter structures of the brainstem. This justifies the creation of atlases that capture the anatomical variability across subjects. The one we present here only included four specimens, but can easily be incremented due to its highly flexible design.

Anatomical characterisation of three different psychosurgical targets in the subthalamic area: from the basal ganglia to the limbic system.

Effective neural stimulation for the treatment of severe psychiatric disorders needs accurate characterisation of surgical targets. This is especially true for the medial subthalamic region (MSR) which contains three targets: the anteromedial STN for obsessive compulsive disorder (OCD), the medial forebrain bundle (MFB) for depression and OCD, and the "Sano triangle" for pathological aggressiveness. Blocks containing the subthalamic area were obtained from two human brains. After obtaining 11.7-Tesla MRI, blocks were cut in regular sections for immunohistochemistry. Fluorescent in situ hybridisation was performed on the macaque MSR. Electron microscopic observation for synaptic specialisation was performed on human and macaque subthalamic fresh samples. Images of human brain sections were reconstructed in a cryoblock which was registered on the MRI and histological slices were then registered. The STN contains glutamatergic and fewer GABAergic neurons and has no strict boundary with the adjacent MSR. The anteromedial STN has abundant dopaminergic and serotoninergic innervation with very sparse dopaminergic neurons. The MFB is composed of dense anterior dopaminergic and posterior serotoninergic fibres, and fewer cholinergic and glutamatergic fibres. Medially, the Sano triangle presumably contains orexinergic terminals from the hypothalamus, and neurons with strong nuclear oestrogen receptor-alpha staining with a decreased anteroposterior and mediolateral gradient of staining. These findings provide new insight regarding MSR cells and their fibre specialisation, forming a transition zone between the basal ganglia and the limbic systems. Our 3D reconstruction enabled us to visualize the main histological features of the three targets which should enable better targeting and understanding of neuromodulatory stimulation results in severe psychiatric conditions.

Sustaining wakefulness: Brainstem connectivity in human consciousness.

Consciousness is comprised of arousal (i.e., wakefulness) and awareness. Substantial progress has been made in mapping the cortical networks that modulate awareness in the human brain, but knowledge about the subcortical networks that sustain arousal is lacking. We integrated data from ex vivo diffusion MRI, immunohistochemistry, and in vivo 7 Tesla functional MRI to map the connectivity of a subcortical arousal network that we postulate sustains wakefulness in the resting, conscious human brain, analogous to the cortical default mode network (DMN) that is believed to sustain self-awareness. We identified nodes of the proposed default ascending arousal network (dAAN) in the brainstem, hypothalamus, thalamus, and basal forebrain by correlating ex vivo diffusion MRI with immunohistochemistry in three human brain specimens from neurologically normal individuals scanned at 600-750 µm resolution. We performed deterministic and probabilistic tractography analyses of the diffusion MRI data to map dAAN intra-network connections and dAAN-DMN internetwork connections. Using a newly developed network-based autopsy of the human brain that integrates ex vivo MRI and histopathology, we identified projection, association, and commissural pathways linking dAAN nodes with one another and with cortical DMN nodes, providing a structural architecture for the integration of arousal and awareness in human consciousness. We release the ex vivo diffusion MRI data, corresponding immunohistochemistry data, network-based autopsy methods, and a new brainstem dAAN atlas to support efforts to map the connectivity of human consciousness.

Spinal lesions in multiple myeloma: Primary bone tumors with distinct prognostic factors.

PURPOSE: Although prognostic factors of spinal multiple myeloma (MM) seem to differ from those of other spine metastases (SpM), the data in the literature remains scarce. METHODS: A prospective population of 361 patients treated for spine MM lesions between January 2014 and 2017. RESULTS: OS for our series was 59.6 months (SD 6.0 months; CI 95%: 47.7-71.3). Cox multivariate proportional-hazards analysis showed that bone marrow transplant [HR: 0.390, 95% CI 0.264-0.577; p < 0.0001] and light-chain isotype [HR: 0.748, 95% CI 0.318-1.759; p = 0.005] were independent predictors of longer survival. In contrast, age >80 years [HR: 2.7, 95% CI 1.6-4.3; p < 0.0001], ISS III [HR: 2.510, 95% CI 2.01-3.124; p = 0.001], IgA isotype [HR: 1.475, 95% CI 1.031-2.11; p = 0.034] and IgD/M isotype [HR: 2.753, 95% CI 1.230-6.130; p = 0.013] were independent poor prognostic factors. However, ECOG (p = 0.486), spine surgery (p = 0.391), spine radiotherapy (p = 0.260), epidural involvement (p = 0.259), the number of vertebra lesions (p = 0.222), and synchronous/metachronous timeline (p = 0.412) were not significantly associated with improved OS. CONCLUSIONS: Spinal involvement in the context of MM does not influence OS. The main prognostic factors to consider before spinal surgery are the characteristics of the primary MM disease (ISS score, IgG isotype and systemic treatment).

[Donation of the body to science: A new regulatory framework that answers some questions but raises many others!] / Don du corps à la science - Un nouveau cadre de régulation qui répond à certaines questions mais en soulève bien d'autres !

In France, between 2,500 and 3,000 people donate their bodies to science each year after their death; they contribute therefore to the teaching of anatomy, to research and to the learning and improvement of surgical practices. The decision to donate must be made during the donor's lifetime and consent must be expressed in writing to one of the 27 donation centers throughout the country. Following the scandal of the Parisian center of the Saints Pères, which revealed a lack of respect for bodies and fundamental ethical principles, the decree of April 27, 2022 concerning the donation of bodies for teaching and research purposes, which is part of the new bioethic laws, was eagerly awaited to clarify certain practices. However, this decree raises new questions because many of the rules it proposes do not appear to be relevant to the values of donation and the functioning of donation centers. The new modes of regulation proposed by the decree generate questions among donors and professionals in the field with a risk of poor regulation, detrimental to all with regard to major ethical issues. If the public authorities do not commit themselves to a regulation that is better adapted to the field, if the ethical stakes are not better clarified and if the universities do not have the means to implement these new organizations, the perpetuation of body donation and of donation centers could become challenging.

Title: Don du corps à la science - Un nouveau cadre de régulation qui répond à certaines questions mais en soulève bien d'autres ! Abstract: En France, entre 2 500 et 3 000 personnes donnent leur corps à la science chaque année après leur mort ; elles contribuent ainsi à l'enseignement de l'anatomie, à la recherche et à l'apprentissage et l'amélioration des pratiques chirurgicales. La décision doit être prise de son vivant et le consentement exprimé par écrit auprès d'un des vingt-sept centres de don du corps répartis sur le territoire national. Suite au scandale du centre parisien des Saints-Pères, le décret du 27 avril 2022 relatif au don de corps à des fins d'enseignement et de recherche, qui s'inscrit dans le cadre des nouvelles lois de bioéthique, était très attendu pour clarifier certaines pratiques. Mais ce décret soulève de nouvelles questions car nombreuses sont les règles qu'il propose qui ne nous apparaissent pas pertinentes au regard des valeurs du don et du fonctionnement des centres de don. Les nouveaux modes de régulation proposés génèrent des questions chez les donneurs et les professionnels de terrain avec un risque de mauvaise régulation. Nous pensons que si la puissance publique ne s'engage pas dans une régulation plus adaptée au terrain, si les enjeux éthiques ne sont pas mieux clarifiés et si les universités n'ont pas les moyens pour mettre en œuvre ces nouvelles organisations, la pérennisation du don du corps et des centres de don pourrait devenir difficile.

Using ex vivo arterial injection and dissection to assess white matter vascularization.

Advances in the techniques for assessing human cerebral white matter have recently contributed to greater attention to structural connectivity. Yet, little is known about the vascularization of most white matter fasciculi and the fascicular composition of the vascular territories. This paper presents an original method to label the arterial supply of macroscopic white matter fasciculi based on a standardized protocol for post-mortem injection of colored material into main cerebral arteries combined with a novel fiber dissection technique. Twelve whole human cerebral hemispheres obtained post-mortem were included. A detailed description of every step, from obtaining the specimen to image acquisition of its dissection, is provided. Injection and dissection were reproducible and manageable without any sophisticated equipment. They successfully showed the arterial supply of the dissected fasciculi. In addition, we discuss the challenges we faced and overcame during the development of the presented method, highlight its originality. Henceforth, this innovative method serves as a tool to provide a precise anatomical description of the vascularization of the main white matter tracts.

Anatomical study of the carotid-trigeminal interface: The missing link in the trigeminovascular system?

The trigeminal system is considered a prominent actor in brain nociceptive innervation. The trigeminovascular system is mainly composed of pseudounipolar neurons located within the trigeminal ganglion, whose dendrites originate in cerebral blood vessels. Anatomical studies demonstrating anatomical continuity between perivascular fibers and the trigeminal system are lacking. This issue is addressed in this study. Eleven cadaveric heads obtained from a body donation program were fixed in formalin. We performed a microanatomical study of the cavernous carotid-trigeminal interface and a histological examination of the tissue bridges crossing the virtual space between the medial aspect of the trigeminal ganglion and ophthalmic nerve and the lateral aspect of the cavernous segment of the internal carotid artery. Very strong adhesion was observed between the horizontal segment of the artery and the ophthalmic nerve in all specimens. The virtual space in this interface was crossed by a web of delicate filaments. Histological examination demonstrated the presence of nerve fibers in all samples. In this study, the carotid-trigeminal interface has been described in greater detail than ever before and could provide insight into disorders related to the trigeminovascular system. As the present results do not allow the exact nature of the axons to be affirmed, further investigation is necessary.

3D molecular phenotyping of cleared human brain tissues with light-sheet fluorescence microscopy.

The combination of optical tissue transparency with immunofluorescence allows the molecular characterization of biological tissues in 3D. However, adult human organs are particularly challenging to become transparent because of the autofluorescence contributions of aged tissues. To meet this challenge, we optimized SHORT (SWITCH-H2O2-antigen Retrieval-TDE), a procedure based on standard histological treatments in combination with a refined clearing procedure to clear and label portions of the human brain. 3D histological characterization with multiple molecules is performed on cleared samples with a combination of multi-colors and multi-rounds labeling. By performing fast 3D imaging of the samples with a custom-made inverted light-sheet fluorescence microscope (LSFM), we reveal fine details of intact human brain slabs at subcellular resolution. Overall, we proposed a scalable and versatile technology that in combination with LSFM allows mapping the cellular and molecular architecture of the human brain, paving the way to reconstruct the entire organ.

The trigeminal pathways.

The role of the trigeminal system in facial and dural sensitivity has been recognized for a long time. More recently, the trigeminal system has also been considered a prominent actor in brain nociceptive innervation. It is the anatomical substrate of several frequent conditions, such as primary or secondary headaches, trigeminal neuralgia, and other orofacial pains. Appreciation of the delicate anatomical arrangement of the trigeminal pathway is one of the keys to understanding these conditions' pathophysiology and to proposing innovative treatments. This review provides a structured presentation of existing knowledge about the trigeminal system, from classical anatomical data to the most recent literature. First, we present the organization of the trigeminal pathway from the trigeminal divisions, nerve, and nuclei to the thalamus and somatosensory cortex. We describe the neurons and fibers' repartition at each level, depending on the location (somatotopic organization) and the type of receptors (modal organization). Such a dual somatotopic-modal arrangement of the trigeminal fibers is especially clear for the juxtapontine segment of the trigeminal nerve and the trigeminal nuclei of the brainstem. It has significant clinical consequences both for diagnosis and treatment. Second, we explore how the trigeminal system is modulated and involved in reflexes, for instance the trigemino-cardiac and the trigemino-autonomic reflexes, which could play an essential role in the autonomic symptoms observed in cluster headache. Finally, we present how to interact with this complex system to relieve pain mediated by the trigeminal system. This section covers both neuromodulatory and lesional approaches.

Chronic low back pain during COVID-19 lockdown: is there a paradox effect?

PURPOSE: The coronavirus 2019 (COVID-19) pandemic led to a compulsory lockdown of 3 months with strict restrictions. The impact of the COVID-19 pandemic has shown broad repercussions on patients with chronic pain; especially for conditions that present a significant emotional participation such as chronic low back pain (cLBP). METHODS: We performed a prospective study on 50 patients. Pre- and 1-month post-lockdown questionnaires such as: the Impact of Event Scale (IES), the Oswestry Disability Index (ODI), the Roland-Morris questionnaire (RMQ) and the visual analogue scale (VAS) for back and leg pain intensity were collected. RESULTS: The mean time of the evolution of cLBP was 33.04 months (range 5-120 months). Eighteen (36%) patients improved their cLBP (i-cLBP), whereas for 14 (28%) it was worse (w-cLBP). Cox multivariate proportional hazard model identified that MODIC 1 disc disease [OR 19.93, IC95% (2.81-102.13), p = 0.015] and at-home workouts [OR 18.854, IC95% (1.151-204.9), p = 0.040] were good prognosis factors of the improvement of cLBP while subclinical/mild Covid-19 anxiety (IES score < 26) was a poor prognosis factor in improving cLBP [OR 0.21, IC95% (0.001-0.384), p = 0.009]. Furthermore, pre-lockdown benzodiazepine medication [OR 2.554, IC95% (1.20-9.9), p = 0.002] was a prognosis factor of worse cLBP. In contrast, patients with severe Covid-19 anxiety (IES score > 26) significantly improved their cLBP [OR 0.58, IC95% (0.025-0.834), p = 0.01]. CONCLUSION: Lockdown affected the somatic component of cLBP by decreasing activities and physical measures, whereas the SARS-CoV-2 pandemic spectrum paradoxically improved the psychic and emotional component of cLBP.

Exploring the human cerebral cortex using confocal microscopy.

Cover-all mapping of the distribution of neurons in the human brain would have a significant impact on the deep understanding of brain function. Therefore, complete knowledge of the structural organization of different human brain regions at the cellular level would allow understanding their role in the functions of specific neural networks. Recent advances in tissue clearing techniques have allowed important advances towards this goal. These methods use specific chemicals capable of dissolving lipids, making the tissue completely transparent by homogenizing the refractive index. However, labeling and clearing human brain samples is still challenging. Here, we present an approach to perform the cellular mapping of the human cerebral cortex coupling immunostaining with SWITCH/TDE clearing and confocal microscopy. A specific evaluation of the contributions of the autofluorescence signals generated from the tissue fixation is provided as well as an assessment of lipofuscin pigments interference. Our evaluation demonstrates the possibility of obtaining an efficient clearing and labeling process of parts of adult human brain slices, making it an excellent method for morphological classification and antibody validation of neuronal and non-neuronal markers.

Cauda Equina Syndrome: Poor Recovery Prognosis Despite Early Treatment.

STUDY DESIGN: A prospective patient's database operated on a cauda equina syndrome (CES). OBJECTIVE: The aim of our study was to identify prognosis factors for favorable functional recovery after CES. SUMMARY OF BACKGROUND DATA: CES is a neurologic impairment of variable symptoms associating urinary, bowel, and sexual dysfunctions with or without motor or sensitive deficits caused by nerve root compression of the cauda equina. The definition of CES remains debated, as well as the prognosis factors for favorable functional recovery and the benefit of early surgery. METHODS: One hundred forty patients were included between January 2010 and 2019. Univariate and multivariate cox proportional hazard regression models were conducted. RESULTS: The patients were young with a median age of 46.8 years (range 18-86 yrs). At presentation, 60% were affected by a motor deficit, 42.8% a sensitive deficit, 70% urinary dysfunctions, and 44% bowel dysfunctions. The mean follow-up was 15.5 months. Bilateral motor deficit (P = 0.017) and an initial deficit severity of 0 to 2 (P = 0.001) represented prognosis factors of poor motor recovery. Initial anal incontinence (P = 0.007) was associated with poor bowel recovery. Only 32.8% of the patients went back to work. Initial motor deficit (P = 0.015), motor sequelae (P = 0.001), sphincter dysfunctions sequelae (P = 0.02), and long LOS (P = 0.02) were poor return-to-work prognosis factors. Time to surgery within an early timing < 24 or 48 hours or later did not represent a prognosis factor of recovery in CES. Incomplete versus complete CES did not show better recovery. CONCLUSION: CES remains a profound disabling syndrome with poor functional prognosis: in the long run, few patients go back to work. The main prognosis factors established in our series regarded the initial severity of deficits whether motor or sphincteral. Early or later surgical cauda equina decompression did not show to represent a prognosis factor for functional recovery.Level of Evidence: 4.

Comparison of Different Tissue Clearing Methods for Three-Dimensional Reconstruction of Human Brain Cellular Anatomy Using Advanced Imaging Techniques.

The combination of tissue clearing techniques with advanced optical microscopy facilitates the achievement of three-dimensional (3D) reconstruction of macroscopic specimens at high resolution. Whole mouse organs or even bodies have been analyzed, while the reconstruction of the human nervous system remains a challenge. Although several tissue protocols have been proposed, the high autofluorescence and variable post-mortem conditions of human specimens negatively affect the quality of the images in terms of achievable transparency and staining contrast. Moreover, homogeneous staining of high-density epitopes, such as neuronal nuclear antigen (NeuN), creates an additional challenge. Here, we evaluated different tissue transformation approaches to find the best solution to uniformly clear and label all neurons in the human cerebral cortex using anti-NeuN antibodies in combination with confocal and light-sheet fluorescence microscopy (LSFM). Finally, we performed mesoscopic high-resolution 3D reconstruction of the successfully clarified and stained samples with LSFM.

Cerebral white matter vasculature: still uncharted?

White matter vasculature plays a major role in the pathophysiology of permanent neurological deficits following a stroke or progressive cognitive alteration related to small vessel disease. Thus, knowledge of the complex vascularization and functional aspects of the deep white matter territories is paramount to comprehend clinical manifestations of brain ischaemia. This review provides a structured presentation of the existing knowledge of the vascularization of the human cerebral white matter from seminal historical studies to the current literature. First, we revisit the highlights of prenatal development of the endoparenchymal telencephalic vascular system that are crucial for the understanding of vessel organization in the adult. Second, we reveal the tangled history of debates on the existence, clinical significance and physiological role of leptomeningeal anastomoses. Then, we present how conceptions on white matter vascularization transitioned from the mixed ventriculopetal/ventriculofugal theory, in which a low-flow area was interposed in between concurrent arterial flows, to the purely ventriculopetal theory. The latter model explains variable white matter sensitivity to ischaemia by various organizations of ventriculopetal vessel terminals having different origin/length properties and interconnection patterns. Next, arteries supplying primarily the white matter are described according to their length and overall structure. Furthermore, the known distribution territories, to date, are studied in relation to primary anatomical structures of the human cerebral white matter, emphasizing the sparsity of the 'ground truth' data available in the literature. Finally, the implications for both large vessel occlusion and chronic small vessel disease are discussed, as well as the insights from neuroimaging. All things considered, we identify the need for further research on deep white matter vascularization, especially regarding the arterial supply of white matter fibre tracts.