The abducens nerve: its topography and anatomical variations in intracranial course with clinical commentary

Background: The sixth cranial nerve (CN VI) — or the abducens nerve — in humans supplies only the lateral rectus muscle. Due to its topographic conditions, including angulations and fixation points along its course from the brainstem to the lateral rectus muscle, the CN VI is vulnerable to injury. Every case of CN VI palsy requires precise diagnostics, which is facilitated by an understanding of the anatomy. The present article’s aims include a detailed study of the intracranial course of the CN VI, determination of occurrence of its particular anatomical variations, as well as presentation of some essential anatomical conditions which may conduce to CN VI palsy. Special emphasis was put on the correlation between craniometric measurements and a particular variation of the CN VI, which complements the data that can be found in literature. Materials and methods: Twenty randomly selected specimens of cadaveric heads fixed in a 10% formalin solution were studied. The study used 40 specimens of the CN VI in order to examine its course variations within the section between the pontomedullary sulcus and the superior orbital fissure. Results: Detailed analysis of the CN VI topography and anatomy in its intracranial course revealed 3 anatomical variations of the nerve in the studied specimens. Variation I, found in 70% of cases, covers those cases in which the CN VI was found to be a single trunk. Those cases in which there was a branching of the CN VI exclusively inside the cavernous sinus were classified as variation II, occurring in 20% of cases. Cases of duplication of the CN VI were classified as variation III, found in 10% of the specimens. In 75% of cases of CN VI duplication one of the nerve trunks ran upwards from the petrosphenoidal ligament, outside Dorello’s canal. Conclusions: The CN VI throughout its intracranial course usually runs as a single trunk, however, common variations include also branching of the nerve in the cavernous sinus or duplication. Topographic relations of the CN VI with adjacent structures account for the risk of injuries which may be caused to the nerve as a result of a disease or surgical procedures.

Optical flow estimation preserving discontinuities : a survey

Motion estimation from image sequences is based on two assumptions : the brightness conservation assumption and the assumptio n of spatial, temporal or spatio-temporal continuity (i .e . smoothness constraint) of the apparent velocity field . The latter assumptio n holds locally, within the objects, but it results in blurring the boundaries between the projections, onto the image plane, of object s undergoing different motions . These boundaries are called motion discontinuities . The main subject of this paper is an overview of the existing techniques designed to estimate the apparent velocity fields while preserving the motion discontinuities . The firs t part deals with the methods based on an assumption which states that the motion discontinuities spatially coincide with imag e brightness boundaries . The second part reports the motion segmentation methods . The third part describes the methods whic h perform the motion field estimation while detecting the local discontinuities of the currently estimated field so as to avoid smoothin g in the areas likely to contain motion boundaries . These discontinuities are preserved by means of a line process, a robust estimato r or within an anisotropic diffusion scheme . The last part is devoted to the occlusions . The estimation errors in the occlusion area s are due to the violation of two basic assumptions : the continuity assumption and particularly the conservation assumption .L'estimation du mouvement à partir de séquences d'images bidimensionnelles s'appuie sur deux hypothèses de base : l'hypothèse de conservation de la luminance des objets au cours de leurs mouvements et l'hypothèse de continuité spatiale, temporelle ou spatio-temporelle, du champ de vitesses apparentes. Cette dernière hypothèse est valable localement, «à l'intérieur » des objets, mais elle provoque un lissage indésirable au voisinage des frontières entre les projections, dans le plan image, des objets animés de mouvements différents. Ces frontières sont appelées discontinuités de mouvement. Le sujet principal de cet article est la revue des techniques visant à estimer le champ de vitesses apparentes en évitant de lisser les discontinuités de mouvement. La première partie de l'article présente les méthodes s'appuyant sur l'hypothèse selon laquelle les discontinuités de mouvement coïncident spatialement avec certaines frontières photométriques. La deuxième partie rapporte les méthodes de segmentation du champ estimé courant en régions homogènes au sens du mouvement. La troisième partie s'intéresse aux méthodes qui réalisent simultanément l'estimation du champ de vitesses et la détection des ruptures locales de continuité de ce champ. Ceci permet d'inhiber localement le lissage, dans les zones susceptibles de contenir une discontinuité de mouvement. Cette inhibition peut être obtenue par introduction d'un « processus de ligne » binaire, grâce à l'utilisation d'un «estimateur robuste », ou dans un schéma de diffusion anisotrope. La dernière partie est consacrée à la gestion des occultations. Les estimations obtenues dans les zones d'occultation sont erronées à cause de la violation des deux hypothèses de base : conservation des propriétés photométriques et continuité

Morphology and a proposed model of innervation of the human deltoid muscle: a pilot study

Background: The deltoid muscle (DM) plays an essential role in retaining the stability and correct function of the upper limb. The aims of the study were to perform a detailed morphological analysis of the DM including its innervation, structure, attachments and relationship with adjacent structures.Materials and methods: The study was carried out on 17 formalin-fixed cadavericupper limbs. After dissection of the shoulders, the DM was visualised and analysed.The following measurements of the muscle were performed for all cases: width of attachments (acromial, clavicular, spinal), entire width of origin, length of the component parts (acromial, clavicular, and spinal) and length of the arm.Results: In all specimens, a characteristic ‘segmented’ innervation scheme of the DM was observed. The axillary nerve (AN) was always divided into an anterior branch (abAN) and a posterior branch (pbAN). Two variations of the DM innervation were distinguished: variation I, where the clavicular and the acromial parts were innervated by the abAN, while the spinal part was supplied both by abAN (anterior fibres) and by pbAN (posterior fibres), and variation II, in which the spinal part did not have double innervation — the abAN innervation area covered only the acromial and clavicular parts, and the entire spinal part was supplied by pbAN. Both variations had a segmented arrangement of sub-branches reaching individual parts of the DM, which was particularly distinct in the clavicular and acromial parts. Correlations were found between the entire width of the DM originand the length of the arm (p = 0.001), between the length of the acromial part of the DM and the length of the arm (p = 0.003), between the width of the spinal attachment and the length of the spinal part (p = 0.002), and between the width of the spinal attachment and the length of the arm (p = 0.0008).Conclusions: The study confirmed the existence of a characteristic segmented innervation scheme of the DM which corresponds with the segmented morphology of its individual parts. An analysis of the internal structure of the muscle specific architectonics based on the tendon system was also presented

GAUSSPY+: A fully automated Gaussian decomposition package for emission line spectra

Our understanding of the dynamics of the interstellar medium is informed by the study of the detailed velocity structure of emission line observations. One approach to study the velocity structure is to decompose the spectra into individual velocity components; this leads to a description of the data set that is significantly reduced in complexity. However, this decomposition requires full automation lest it become prohibitive for large data sets, such as Galactic plane surveys. We developed GAUSSPY+, a fully automated Gaussian decomposition package that can be applied to emission line data sets, especially large surveys of HI and isotopologues of CO. We built our package upon the existing GAUSSPY algorithm and significantly improved its performance for noisy data. New functionalities of GAUSSPY+ include: (i) automated preparatory steps, such as an accurate noise estimation, which can also be used as stand-alone applications; (ii) an improved fitting routine; (iii) an automated spatial refitting routine that can add spatial coherence to the decomposition results by refitting spectra based on neighbouring fit solutions. We thoroughly tested the performance of GAUSSPY+ on synthetic spectra and a test field from the Galactic Ring Survey. We found that GAUSSPY+ can deal with cases of complex emission and even low to moderate signal-to-noise values

Vessel Segmentation on Computed Tomography Angiography

International audienceThis short paper describes our contribution in the research aimed at model based vessel segmentation on CTA. Although each partner was involved in a main subject among what follows, the contribution is a joint effort of all the partners, as a result of regular visits in France and Israel, as well as between partners in each country. The French Hospital Partner in Lyon provided a large set of CTA studies, including sets with two studies performed on each patient and about 20 studies suitable for work on other aspects of cardiac vessel segmentation

MicroRNA profile changes in human immunodeficiency virus type 1 (HIV-1) seropositive individuals

MicroRNAs (miRNAs) play diverse roles in regulating cellular and developmental functions. We have profiled the miRNA expression in peripheral blood mononuclear cells from 36 HIV-1 seropositive individuals and 12 normal controls. The HIV-1-positive individuals were categorized operationally into four classes based on their CD4+ T-cell counts and their viral loads. We report that specific miRNA signatures can be observed for each of the four classes

HCN emission from translucent gas and UV-illuminated cloud edges revealed by wide-field IRAM 30m maps of Orion B GMC: Revisiting its role as tracer of the dense gas reservoir for star formation

We present 5 deg^2 (~250 pc^2) HCN, HNC, HCO+, and CO J=1-0 maps of the Orion B GMC, complemented with existing wide-field [CI] 492 GHz maps, as well as new pointed observations of rotationally excited HCN, HNC, H13CN, and HN13C lines. We detect anomalous HCN J=1-0 hyperfine structure line emission almost everywhere in the cloud. About 70% of the total HCN J=1-0 luminosity arises from gas at A_V < 8 mag. The HCN/CO J=1-0 line intensity ratio shows a bimodal behavior with an inflection point at A_V < 3 mag typical of translucent gas and UV-illuminated cloud edges. We find that most of the HCN J=1-0 emission arises from extended gas with n(H2) < 10^4 cm^-3, even lower density gas if the ionization fraction is > 10^-5 and electron excitation dominates. This result explains the low-A_V branch of the HCN/CO J=1-0 intensity ratio distribution. Indeed, the highest HCN/CO ratios (~0.1) at A_V < 3 mag correspond to regions of high [CI] 492 GHz/CO J=1-0 intensity ratios (>1) characteristic of low-density PDRs. Enhanced FUV radiation favors the formation and excitation of HCN on large scales, not only in dense star-forming clumps. The low surface brightness HCN and HCO+ J=1-0 emission scale with I_FIR (a proxy of the stellar FUV radiation field) in a similar way. Together with CO J=1-0, these lines respond to increasing I_FIR up to G0~20. On the other hand, the bright HCN J=1-0 emission from dense gas in star-forming clumps weakly responds to I_FIR once the FUV radiation field becomes too intense (G0>1500). The different power law scalings (produced by different chemistries, densities, and line excitation regimes) in a single but spatially resolved GMC resemble the variety of Kennicutt-Schmidt law indexes found in galaxy averages. As a corollary for extragalactic studies, we conclude that high HCN/CO J=1-0 line intensity ratios do not always imply the presence of dense gas.Comment: accepted for publication in A&A. 24 pages, 18 figures, plus Appendix. Abridged Abstract. English language not edite

Bias versus variance when fitting multi-species molecular lines with a non-LTE radiative transfer model

Robust radiative transfer techniques are requisite for efficiently extracting the physical and chemical information from molecular rotational lines.We study several hypotheses that enable robust estimations of the column densities and physical conditions when fitting one or two transitions per molecular species. We study the extent to which simplifying assumptions aimed at reducing the complexity of the problem introduce estimation biases and how to detect them.We focus on the CO and HCO+ isotopologues and analyze maps of a 50 square arcminutes field. We used the RADEX escape probability model to solve the statistical equilibrium equations and compute the emerging line profiles, assuming that all species coexist. Depending on the considered set of species, we also fixed the abundance ratio between some species and explored different values. We proposed a maximum likelihood estimator to infer the physical conditions and considered the effect of both the thermal noise and calibration uncertainty. We analyzed any potential biases induced by model misspecifications by comparing the results on the actual data for several sets of species and confirmed with Monte Carlo simulations. The variance of the estimations and the efficiency of the estimator were studied based on the Cram{\'e}r-Rao lower bound.Column densities can be estimated with 30% accuracy, while the best estimations of the volume density are found to be within a factor of two. Under the chosen model framework, the peak 12CO(1--0) is useful for constraining the kinetic temperature. The thermal pressure is better and more robustly estimated than the volume density and kinetic temperature separately. Analyzing CO and HCO+ isotopologues and fitting the full line profile are recommended practices with respect to detecting possible biases.Combining a non-local thermodynamic equilibrium model with a rigorous analysis of the accuracy allows us to obtain an efficient estimator and identify where the model is misspecified. We note that other combinations of molecular lines could be studied in the future.Comment: Astronomy and Astrophysics - A\&A, In pres