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The jugular tubercle is a rounded bony prominence that arises from the inferolateral margin of the clivus. In a previous publication, we described the surgical anatomy of the expanded endonasal approach to the jugular tubercle. To illustrate the translation of laboratory work to the operating room describing the anatomic and technical nuances of the endonasal approach to the jugular tubercle. We review the relevant surgical anatomy needed to perform an endonasal approach to the jugular tubercle, and we select 4 different lesions to illustrate the application of our laboratory findings. In the first case, exposure and partial drilling of the jugular tubercle was critical to gain an adequate corridor to the meningioma, particularly to its inferolateral margin. This allowed for early devascularization, safe extracapsular dissection, and preservation of surrounding neurovascular structures. In addition, the jugular tubercle was hyperostotic and its resection, along with generous dural removal, provided a grade I Simpson tumor resection. In the second (chondrosarcoma) and third (chordoma) cases, the jugular tubercle was infiltrated by tumor, and consequently its complete resection was essential to achieve total tumor removal. In the last case, an unusual adrenocorticotropic hormone-secreting adenoma recurrence at the jugular tubercle region, the technical modification of the transclival approach presented here was successfully applied to achieve complete resection and Cushing disease remission. The transjugular tubercle variant of the expanded endonasal transclival approach allows for direct access to ventrolateral lesions in the inferior clival/petroclival region with no cerebral or cerebellar retraction, or cranial nerve manipulation during the approach.

The endoscopic endonasal transclival approach is a valid alternative for treatment of lesions in the clivus. The major limitation of this approach is a significant lateral extension of the tumor. We aim to identify a safe corridor through the occipital condyle to provide more lateral exposure of the foramen magnum. Sixteen parameters were measured in 25 adult skulls to analyze the exact extension of a safe corridor through the condyle. Endonasal endoscopic anatomic dissections were carried out in nine colored latex-injected heads. Drilling at the lateral inferior clival area exposed two compartments divided by the hypoglossal canal: the jugular tubercle (superior) and the condylar (inferior). Completion of a unilateral ventromedial condyle resection opens a 3.5 mm (transverse length) * 10 mm (vertical length) lateral surgical corridor, facilitating direct access to the vertebral artery at its dural entry point into the posterior fossa. The supracondylar groove is a reliable landmark for locating the hypoglossal canal in relation to the condyle. The hypoglossal canal is used as the posterior limit of the condyle removal to preserve more than half of the condylar mass. The transjugular tubercle approach is accomplished by drilling above the hypoglossal canal, and increases the vertical length of the lateral surgical corridor by 8 mm, allowing for visualization of the distal cisternal segment of the lower cranial nerves. The transcondylar and transjugular tubercle \"far medial\" expansions of the endoscopic endonasal approach to the inferior third of the clivus provide a unique surgical corridor to the ventrolateral surface of the ponto- and cervicomedullary junctions.

Abstract BACKGROUND Understanding the course of the most medially located parasellar cranial nerve, the abducens, becomes critical when performing an expanded endonasal approach. OBJECTIVE We report an anatomoclinical study of the abducens nerve and describe relevant surgical nuances to avoid its injury. METHODS Ten anatomic specimens were dissected using endoscopes attached to an high-definition camera. A series of anatomic 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. The mean distance from the vertebrobasilar junction (VBJ) to the pontomedullary sulcus (PMS) was 4 mm; 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 upper limit of the lacerum segment of the internal carotid artery was at the same level of the dural entry point of the sixth cranial nerve posteriorly. The sellar floor at the sphenoid sinus marks the level of the gulfar segment in the craniocaudal axis. At the superior orbital fissure, the abducens nerve and V2 were at an average vertical distance of 11.5 mm. CONCLUSION Anatomic landmarks to localize the abducens nerve intraoperatively, such as the VBJ for the transclival approach, the lacerum segment of the carotid, and the sellar floor for the medial petrous apex approach, and V2 for Meckel's cave approach, are reliable and complementary to the use of intraoperative electrophysiological monitoring.

The medial opticocarotid recess (MOCR) has become an important landmark for endoscopic approaches to the cranial base. To examine the anatomy of the MOCR and outline its role as a \"key landmark\" for approaches to the sellar and suprasellar regions. Ten silicone-injected cadaveric specimens and 96 dry crania were examined. Dissections were done endoscopically and microscopically. The lateral tubercular recess is an osseous depression located at the lateral edge of the tuberculum when viewed from the sphenoid sinus. Intracranially, it corresponds to the lateral tubercular crest (LTC), a ridge situated at the superomedial aspect of the carotid sulcus. The MOCR is a teardrop-shaped osseous indentation formed at the medial junction of the paraclinoid carotid canal and the optic canal. Dorsally, it is represented by a teardrop-shaped area with vertices at the inferior aspect of the LTC, the medial aspect of the junction of the superior and posterior surfaces of the optic strut, and the superolateral aspect of the tuberculum. The middle clinoid process is situated inferior to the LTC. The distal osseous arch of the carotid sulcus connects the lateral opticocarotid recess to the lateral tubercular recess and is a landmark for the paraclinoid internal carotid artery. Only 44% of the specimens had middle clinoid processes. The MOCR and middle clinoid process are distinct structures. Because of its location at the confluence of the optic canal, the carotid canal, the sella, and the anterior cranial base, the MOCR is a key landmark for endoscopic approaches.

Understanding the course of the most medially located parasellar cranial nerve, the abducens, becomes critical when performing an expanded endonasal approach. We report an anatomoclinical study of the abducens nerve and describe relevant surgical nuances to avoid its injury. Ten anatomic specimens were dissected using endoscopes attached to an high-definition camera. A series of anatomic measurements and relationships of the abducens nerve were noted. Illustrative clinical cases are described to translate those findings into practice. Cisternal, interdural, gulfar, and cavernous segments of the abducens were identified intracranially. The mean distance from the vertebrobasilar junction (VBJ) to the pontomedullary sulcus (PMS) was 4 mm; 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 upper limit of the lacerum segment of the internal carotid artery was at the same level of the dural entry point of the sixth cranial nerve posteriorly. The sellar floor at the sphenoid sinus marks the level of the gulfar segment in the craniocaudal axis. At the superior orbital fissure, the abducens nerve and V2 were at an average vertical distance of 11.5 mm. Anatomic landmarks to localize the abducens nerve intraoperatively, such as the VBJ for the transclival approach, the lacerum segment of the carotid, and the sellar floor for the medial petrous apex approach, and V2 for Meckel's cave approach, are reliable and complementary to the use of intraoperative electrophysiological monitoring.

In this work, we propose and analyze a new concept of gamma ray imaging that corresponds to a gamma camera with a mobile collimator, which can be used in vivo, during surgical interventions for oncological patients for localizing regions of interest such as tumors or ganglia. The benefits are a much higher sensitivity, better image quality and, consequently, a dose reduction for the patient and medical staff. This novel approach is a practical solution to the overlapping problem which is inherent to multi-pinhole gamma camera imaging and single photon emission computed tomography and which translates into artifacts and/or image truncation in the final reconstructed image. The key concept consists in introducing a relative motion between the collimator and the detector. Moreover, this design could also be incorporated into most commercially available gamma camera devices, without any excessive additional requirements. We use Monte Carlo simulations to assess the feasibility of such a device, analyze three possible designs and compare their sensitivity, resolution and uniformity. We propose a final design of a gamma camera with a high sensitivity ranging from 0.001 to 0.006 cps/Bq, and a high resolution of 0.5–1.0 cm (FWHM), for source-to-detector distances of 4–10 cm. Additionally, this planar gamma camera provides information about the depth of source (with approximate resolution of 1.5 cm) and excellent image uniformity.

One of the most fundamental questions in ecology is how many species inhabit the Earth. However, due to massive logistical and financial challenges and taxonomic difficulties connected to the species concept definition, the global numbers of species, including those of important and well-studied life forms such as trees, still remain largely unknown. Here, based on global ground-sourced data, we estimate the total tree species richness at global, continental, and biome levels. Our results indicate that there are ∼73,000 tree species globally, among which ∼9,000 tree species are yet to be discovered. Roughly 40% of undiscovered tree species are in South America. Moreover, almost one-third of all tree species to be discovered may be rare, with very low populations and limited spatial distribution (likely in remote tropical lowlands and mountains). These findings highlight the vulnerability of global forest biodiversity to anthropogenic changes in land use and climate, which disproportionately threaten rare species and thus, global tree richness.

The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers. Examining drivers of the latitudinal biodiversity gradient in a global database of local tree species richness, the authors show that co-limitation by multiple environmental and anthropogenic factors causes steeper increases in richness with latitude in tropical versus temperate and boreal zones.