eMedicine创建于1996年，由近万名临床医师作为作者或编辑参与此临床医学知识库的建设，其中编辑均是来自美国哈佛、耶鲁、斯坦福、芝加哥、德克萨斯、加州大学等各分校医学院的教授或副教授。

eMedicine

Pathological perturbations of the brain are rarely confined to a single locus; instead, they often spread via axonal pathways to influence other regions. Patterns of such disease propagation are constrained by the extraordinarily complex, yet highly organized, topology of the underlying neural architecture; the so-called connectome. Thus, network organization fundamentally influences brain disease, and a connectomic approach grounded in network science is integral to understanding neuropathology. Here, we consider how brain-network topology shapes neural responses to damage, highlighting key maladaptive processes (such as diaschisis, transneuronal degeneration and dedifferentiation), and the resources (including degeneracy and reserve) and processes (such as compensation) that enable adaptation. We then show how knowledge of network topology allows us not only to describe pathological processes but also to generate predictive models of the spread and functional consequences of brain disease.

The connectomics of brain disorders

Tractography based on non-invasive diffusion imaging is central to the study of human brain connectivity. To date, the approach has not been systematically validated in ground truth studies. Based on a simulated human brain data set with ground truth tracts, we organized an open international tractography challenge, which resulted in 96 distinct submissions from 20 research groups. Here, we report the encouraging finding that most state-of-the-art algorithms produce tractograms containing 90% of the ground truth bundles (to at least some extent). However, the same tractograms contain many more invalid than valid bundles, and half of these invalid bundles occur systematically across research groups. Taken together, our results demonstrate and confirm fundamental ambiguities inherent in tract reconstruction based on orientation information alone, which need to be considered when interpreting tractography and connectivity results. Our approach provides a novel framework for estimating reliability of tractography and encourages innovation to address its current limitations.

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The challenge of mapping the human connectome based on diffusion tractography

While traditional models of language comprehension have focused on the left posterior temporal cortex as the neurological basis for language comprehension, lesion and functional imaging studies indicate the involvement of an extensive network of cortical regions. However, the full extent of this network and the white matter pathways that contribute to it remain to be characterized. In an earlier voxel-based lesion-symptom mapping analysis of data from aphasic patients (Dronkers et al., 2004), several brain regions in the left hemisphere were found to be critical for language comprehension: the left posterior middle temporal gyrus (MTG), the anterior part of Brodmann’s area 22 in the superior temporal gyrus (anterior STG/BA22), the posterior superior temporal sulcus (STS) extending into Brodmann’s area 39 (STS/BA39), the orbital part of the inferior frontal gyrus (BA47) and the middle frontal gyrus (BA46). Here, we investigated the white matter pathways associated with these regions using diffusion tensor imaging from healthy subjects. We also used resting-state functional magnetic resonance imaging data to assess the functional connectivity profiles of these regions. Fiber tractography and functional connectivity analyses indicated that the left MTG, anterior STG/BA22, STS/BA39 and BA47 are part of a richly interconnected network that extends to additional frontal, parietal and temporal regions in the two hemispheres. The inferior occipito-frontal fasciculus, the arcuate fasciculus and the middle and inferior longitudinal fasciculi, as well as transcallosal projections via the tapetum were found to be the most prominent white matter pathways bridging the regions important for language comprehension. The left posterior MTG showed a particularly extensive structural and functional connectivity pattern which is consistent with the severity of the impairments associated with MTG lesions and which suggests a central role for this region in language comprehension.

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The Neural Architecture of the Language Comprehension Network: Converging Evidence from Lesion and Connectivity Analyses

Subarachnoid hemorrhage (SAH) is an acute cerebrovascular event which can have devastating effects on the central nervous system as well as a profound impact on several other organs SAH patients are routinely admitted to an intensive care unit and are cared for by a multidisciplinary team A lack of high quality data has led to numerous approaches to management and limited guidance on choosing among them Existing guidelines emphasize risk factors, prevention, natural history, and prevention of rebleeding, but provide limited discussion of the complex critical care issues involved in the care of SAH patients The Neurocritical Care Society organized an international, multidisciplinary consensus conference on the critical care management of SAH to address this need Experts from neurocritical care, neurosurgery, neurology, interventional neuroradiology, and neuroanesthesiology from Europe and North America were recruited based on their publications and expertise A jury of four experienced neurointensivists was selected for their experience in clinical investigations and development of practice guidelines Recommendations were developed based on literature review using the GRADE system, discussion integrating the literature with the collective experience of the participants and critical review by an impartial jury Recommendations were developed using the GRADE system Emphasis was placed on the principle that recommendations should be based not only on the quality of the data but also tradeoffs and translation into practice Strong consideration was given to providing guidance and recommendations for all issues faced in the daily management of SAH patients, even in the absence of high quality data

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Critical Care Management of Patients Following Aneurysmal Subarachnoid Hemorrhage: Recommendations from the Neurocritical Care Society’s Multidisciplinary Consensus Conference

BACKGROUND Regenerated oxidized cellulose (ROC) sheets have gained popularity as an adjunct to a vascularized nasoseptal flap for closure of dural defects after endoscopic endonasal skull-base approaches (EESBS). However, evidence supporting its impact on the healing process is uncertain. This study was performed to evaluate the impact of ROC on the nasal mucosa and assess its effects on tissue pH, structure, and cell viability. METHODS In 5 patients, a 1-cm2 piece of ROC gauze was placed on the surface of the middle turbinate before it was resected as part of a standard EESBS. Mucosa treated with ROC was separated from untreated mucosa and a histologic examination of structural changes in the respiratory epithelium was performed. To assess the effect of ROC on pH, increasing amounts of ROC were added to culture medium. Nasal fibroblasts viability was assessed in the presence of ROC before and after the pH was neutralized. RESULTS Compared with unexposed controls, treated mucosa exhibited a higher incidence of cell necrosis and epithelial cell detachment. When added to Dulbecco's modified Eagle medium, ROC caused a dose-dependent decrease in pH of the medium. Only 1 ± 0.8% of cultured fibroblasts exposed to the ROC-induced acidic medium were alive, whereas 98.25 ± 0.5% of the cells were viable when the pH was neutralized (p < 0.001). CONCLUSION ROC applied in vivo to nasal mucosa induced epithelial necrosis likely by diminishing the medium pH, because pH neutralization prevents its effect. The ultimate effect of this material on the healing process is yet to be determined.

Effect of oxidized cellulose on human respiratory mucosa and submucosa and its implications for endoscopic skull-base approaches.

Endonasal Suturing of Nasoseptal Flap to the Nasopharyngeal Fascia Using the V-Loc Wound Closing Device

Risk Factors Associated with Postoperative CSF Leak

Endoscopic Endonasal Approach to the Optic Canal: Anatomical Considerations and Surgical Relevance

Introduction: Understanding the course of the most medially located parasellar cranial nerve, the abducens, becomes critical when performing an expanded endonasal approach (EEA). We report an anatomoclinical study of the abducens nerve and describe relevant surgical nuances to avoid its injury acquired during 1300 + EEAs. Material and Methods: Ten anatomical specimens were dissected using endoscopes attached to an HD camera. A series of anatomical measurements and relationships of the abducens nerve were noted. Illustrative clinical cases are described to translate those findings into practice. Results: Cisternal, interdural, gulfar, and cavernous segments of the abducens were identified intracranially. Traditional anatomical concepts such as Dorello's canal and Gruber's ligament were challenged. The mean distance from the vertebrobasilar junction (VBJ) to the pontomedullary sulcus (PMS) was 4 mm; the horizontal distance between both abducens nerves at the PMS was 10 mm, and between both abducens at the interdural segment was 18.5 mm. The vertical distance from the lacerum segment of ICA to the abducens nerve was 13 mm. At the superior orbital fissure, the abducens nerve and V2 were at an average vertical distance of 11.5 mm. The upper limit of the lacerum segment of the ICA was noted to be at the same level of the interdural portion of the VI nerve posteriorly. Conclusions: Anatomical landmarks to localize the abducens nerve intraoperatively, such as the VBJ for the transclival approach, the lacerum segment of the carotid for the medial petrous apex approach, and V2 for Meckel's cave approach, are reliable and complementary to the use of intraoperative electrophysiological monitoring.

Juan C. Fernandez-Miranda

Papers

Effect of oxidized cellulose on human respiratory mucosa and submucosa and its implications for endoscopic skull-base approaches.

Endonasal Suturing of Nasoseptal Flap to the Nasopharyngeal Fascia Using the V-Loc Wound Closing Device

Risk Factors Associated with Postoperative CSF Leak

Endoscopic Endonasal Approach to the Optic Canal: Anatomical Considerations and Surgical Relevance

Avoiding Injury to the Abducens Nerve in Expanded Endonasal Endoscopic Surgery: Anatomical and Clinical Case Studies.