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.

/pdf/the-challenge-of-mapping-the-human-connectome-based-on-xi6eaf30xo.pdf

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.

/pdf/the-neural-architecture-of-the-language-comprehension-jggc84bqof.pdf

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

/pdf/critical-care-management-of-patients-following-aneurysmal-pboo1fbve4.pdf

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

Contralateral Transmaxillary Corridor as an Extension to the Endoscopic Endonasal Approach to the Petrous Apex

Cranial base surgery is the surgical discipline that deals with disease processes that affect the skull base or related tissues. These include developmental, inflammatory, traumatic, vascular, and neoplastic problems. Over the last 30 years, there has been a radical transformation of cranial base surgery with parallel advances in diagnostic modalities, surgical technologies, and radiation therapy. Advances in surgery have been driven by new surgical technologies such as image-guided navigation, Hopkins rod-lens endoscopes, and reconstructive materials. Endoscopic techniques have been adopted by most surgical disciplines and now play a prominent role in the treatment of cranial base pathology.

Endoscopic Skull Base Surgery

Thank you for bringing this omission to our attention. The omission is understandable considering that the article by Rivera–Serrano et al1 was solely an online publication requiring journal subscription and was not available to us for review. A PubMed search for “inferior turbinate flap” does not list the publication presumably because it is described as a “posterior pedicle lateral nasal wall flap.” In our opinion, the inclusion of the septal mucosa as an extension of the inferior turbinate flap is a novel modification of the inferior turbinate flap that greatly enhances reconstructive options.2

/pdf/response-to-letter-to-the-editor-on-extended-inferior-fa9i8pgpvk.pdf

Response to Letter to the Editor on "Extended Inferior Turbinate Flap for Endoscopic Reconstruction of Skull Base Defects." J Neurol Surg B 2014;75(B4):225-230.

The prognosis for clival chordomas and chondrosarcomas is significantly improved following complete resection that achieves negative dural and bony margins. Endoscopic endonasal surgery (EES) provides direct access to many of these tumors and has quickly become a favored option for their surgical management. Chordomas are typically of midline origin and are almost always accessible by an endoscopic endonasal approach (EEA). This direct access avoids unnecessary neurovascular manipulation. EEA resection can be complemented by “open” approaches such as the far or extreme lateral approach for craniocervical junction chordomas and the anterior transpetrosal approach for clival chordomas. Chondrosarcomas generally originate from the petroclival synchondrosis and therefore are more likely to require treatment via a lateral approach or via EEA in combination with a lateral approach. Nevertheless, the majority of skull base chondrosarcomas can be accessed endonasally, minimizing morbidity. For both tumor types, significant experience and anatomic understanding is required to gain full access for maximal resection. Despite significant advances with vascularized flaps, reconstruction of dural defects with prevention of cerebrospinal fluid leak remains the primary source of complications. Team surgery, combining otolaryngology and neurosurgery, minimizes both the learning curve and reconstructive morbidity.

The Endoscopic Endonasal Approach to Chordomas and Chondrosarcomas

BACKGROUND: The vidian nerve is a landmark for safe identification of the petrous internal carotid artery during endonasal endoscopic approaches (EEAs) to the skull base. The surgical technique classically described involves sacrifice of the nerve. OBJECTIVE: To demonstrate the feasibility of vidian nerve transposition during EEA. METHODS: After exposure of the vidian canal aperture, the bone is removed along its inferior and medial aspect. Once the depth is understood, determining the position of the internal carotid artery, the bone superior to the vidian nerve is drilled. The vidian nerve can then be transposed from its canal and retracted superiorly, allowing the drill to come inferiorly and to remove the bone lateral to the nerve, finalizing freedom around the vidian nerve. RESULTS: Four patients underwent EEA with vidian transposition. Case illustration: a 20-year-old woman presented with partial numbness on the left side of the face and some tingling in the face, particularly inside her mouth. Magnetic resonance imaging scans demonstrated a Meckel cave tumor compatible with a left-side trigeminal schwannoma. EEA to the Meckel cave was performed and the vidian nerve was transposed. The tumor was totally resected and the vidian nerve preserved. The patient was discharged home in 2 days, stating improvement in facial sensation without new neurological deficits and denying dry eye. The patient was asymptomatic at the 9-month follow-up. None of the 4 patients who underwent this procedure complained of dry eye during the postoperative period. CONCLUSION: The vidian nerve transposition for EEAs to the skull base is an alternative technique that is feasible and conservative. It seems to be a good option that could prove beneficial to the quality of life of patients after surgery.

Juan C. Fernandez-Miranda

Papers

Contralateral Transmaxillary Corridor as an Extension to the Endoscopic Endonasal Approach to the Petrous Apex

Endoscopic Skull Base Surgery

Response to Letter to the Editor on "Extended Inferior Turbinate Flap for Endoscopic Reconstruction of Skull Base Defects." J Neurol Surg B 2014;75(B4):225-230.

The Endoscopic Endonasal Approach to Chordomas and Chondrosarcomas

Vidian Nerve Transposition for Endoscopic Endonasal Middle Fossa Approaches. Commentary