[Unicompartmental knee prosthesis]. / Prótesis unicompartimental de rodilla.

In a patient with severe unicompartmental knee osteoarthritis where conservative treatments have been exhausted, with painful symptoms located on the affected side and with a reducible axis, the unicompartmental knee prosthesis (UKP) is the first option for our work group. Within the study to confirm the diagnosis and plan the surgery, weight-bearing knee x-rays, Rosenberg x-rays, and teleradiographs of the lower extremities stand out. The objective of surgery is to replace the affected area, restoring the anatomy with an adequate balance of soft tissues. Regarding alignment, the challenge is not to overload the opposite side or that of the prosthesis. There are mobile and fixed plates and although the clinical and survival results are similar, in recent years with the incorporation of robotic surgery, the balance has tipped towards the use of fixed plates. The clinical and functional results are better and there are fewer complications than when total knee prostheses (TKP) are used in the same type of patients. The survival studied in registries is lower than for TKP, but when used in high-flow centers where the percentage of UKP is close to a third of the total with strict patient selection, the duration is as good as in PTR.

En un paciente con artrosis unicompartimental de rodilla grave, donde se agotaron los tratamientos conservadores que tiene clínica dolorosa localizada en el lado afectado y con alteración del eje reductible, la prótesis unicompartimenal de rodilla (PUR) es la primera opción para nuestro grupo de trabajo. Dentro del estudio para confirmar el diagnóstico y planificar la cirugía destacan las radiografías de rodillas con carga, radiografía de Rosenberg y telerradiografías de extremidades inferiores. El objetivo de la cirugía es reemplazar la zona afectada, restituyendo la anatomía con un adecuado balance de partes blandas. Respecto al alineamiento el desafío es no sobrecargar el lado contrario ni tampoco el de la prótesis. Existen de platillo móvil y fijo y aunque los resultados clínicos y de supervivencia son semejantes, en los últimos años con la incorporación de la cirugía robótica, la balanza se ha inclinado para el uso de los platillos fijos. En pacientes con artrosis unicompartimental los resultados clínicos y funcionales son mejores con PUR y tiene menos complicaciones que cuando se usan prótesis totales (PTR). La supervivencia estudiada en registros es menor que para PTR, pero cuando se usa en centros de alto flujo en que el porcentaje de PUR es cercano a un tercio del total con una estricta selección de pacientes, la duración es tan buena como en la PTR.

Prótesis unicompartimental de rodilla / Unicompartmental knee prosthesis

Resumen: En un paciente con artrosis unicompartimental de rodilla grave, donde se agotaron los tratamientos conservadores que tiene clínica dolorosa localizada en el lado afectado y con alteración del eje reductible, la prótesis unicompartimenal de rodilla (PUR) es la primera opción para nuestro grupo de trabajo. Dentro del estudio para confirmar el diagnóstico y planificar la cirugía destacan las radiografías de rodillas con carga, radiografía de Rosenberg y telerradiografías de extremidades inferiores. El objetivo de la cirugía es reemplazar la zona afectada, restituyendo la anatomía con un adecuado balance de partes blandas. Respecto al alineamiento el desafío es no sobrecargar el lado contrario ni tampoco el de la prótesis. Existen de platillo móvil y fijo y aunque los resultados clínicos y de supervivencia son semejantes, en los últimos años con la incorporación de la cirugía robótica, la balanza se ha inclinado para el uso de los platillos fijos. En pacientes con artrosis unicompartimental los resultados clínicos y funcionales son mejores con PUR y tiene menos complicaciones que cuando se usan prótesis totales (PTR). La supervivencia estudiada en registros es menor que para PTR, pero cuando se usa en centros de alto flujo en que el porcentaje de PUR es cercano a un tercio del total con una estricta selección de pacientes, la duración es tan buena como en la PTR.

Abstract: In a patient with severe unicompartmental knee osteoarthritis where conservative treatments have been exhausted, with painful symptoms located on the affected side and with a reducible axis, the unicompartmental knee prosthesis (UKP) is the first option for our work group. Within the study to confirm the diagnosis and plan the surgery, weight-bearing knee x-rays, Rosenberg x-rays, and teleradiographs of the lower extremities stand out. The objective of surgery is to replace the affected area, restoring the anatomy with an adequate balance of soft tissues. Regarding alignment, the challenge is not to overload the opposite side or that of the prosthesis. There are mobile and fixed plates and although the clinical and survival results are similar, in recent years with the incorporation of robotic surgery, the balance has tipped towards the use of fixed plates. The clinical and functional results are better and there are fewer complications than when total knee prostheses (TKP) are used in the same type of patients. The survival studied in registries is lower than for TKP, but when used in high-flow centers where the percentage of UKP is close to a third of the total with strict patient selection, the duration is as good as in PTR.

Usefulness of Ultrasound in Assessing the Impact of Bariatric Surgery on Body Composition: a Pilot Study.

BACKGROUND: Bariatric surgery (BS) has a significant impact on body composition. The purpose of the study is to evaluate the usefulness of musculoskeletal ultrasound (MUS) to bioelectrical impedance (BIA) in the follow-up of patients undergoing BS in terms of body composition and quality of life (QoL). METHODS: This is a prospective pilot study including 32 subjects (75% female, mean age: 49.15 ± 1.9 years) who underwent BS. Fat mass (FM), lean mass (LM), and skeletal muscle index (SMI) were calculated by BIA. MUS measured subcutaneous fat (SF) and thigh muscle thickness (TMT) of the quadriceps. QoL was assessed by the Moorehead-Ardelt questionnaire. All these measurements were performed 1 month prior to BS and at 12-month follow-up. RESULTS: The mean BMI decreased by 6.63 ± 1.25 kg/m2 (p=0.001). We observed significant reductions in FM (p=0.001) and SF (p=0.007) and in LM (p=0.001) but not in SMI and TMT. We found a correlation between the FM and SF (pre-surgical, r=0.42, p=0.01; post-surgical, r=0.52, p=0.003) and between SMI and TMT (pre-surgical, r=0.35, p=0.04; post-surgical, r=0.38, p=0.03). QoL test showed significant improvement (p=0.001). In addition, a correlation between the QoL questionnaire and TMT post-surgery (r=0.91, p=0.019) was observed. However, we did not find any statistically significant correlation between QoL assessment and SMI or LM. CONCLUSIONS: Our results suggest that MUS can be complementary to BIA for the evaluation and the follow-up of body composition after BS. TMT of quadriceps can provide relevant information about regional sarcopenia and has a significant correlation with QoL.

GLUT2 expression by glial fibrillary acidic protein-positive tanycytes is required for promoting feeding-response to fasting.

Feeding behavior is a complex process that depends on the ability of the brain to integrate hormonal and nutritional signals, such as glucose. One glucosensing mechanism relies on the glucose transporter 2 (GLUT2) in the hypothalamus, especially in radial glia-like cells called tanycytes. Here, we analyzed whether a GLUT2-dependent glucosensing mechanism is required for the normal regulation of feeding behavior in GFAP-positive tanycytes. Genetic inactivation of Glut2 in GFAP-expressing tanycytes was performed using Cre/Lox technology. The efficiency of GFAP-tanycyte targeting was analyzed in the anteroposterior and dorsoventral axes by evaluating GFP fluorescence. Feeding behavior, hormonal levels, neuronal activity using c-Fos, and neuropeptide expression were also analyzed in the fasting-to-refeeding transition. In basal conditions, Glut2-inactivated mice had normal food intake and meal patterns. Implementation of a preceeding fasting period led to decreased total food intake and a delay in meal initiation during refeeding. Additionally, Glut2 inactivation increased the number of c-Fos-positive cells in the ventromedial nucleus in response to fasting and a deregulation of Pomc expression in the fasting-to-refeeding transition. Thus, a GLUT2-dependent glucose-sensing mechanism in GFAP-tanycytes is required to control food consumption and promote meal initiation after a fasting period.

[Effect of sports training in angular compartment of the lower limbs in children footballers aged 11 to 12 years old]. / Efecto de un entrenamiento deportivo en el compartimiento angular de la extremidad inferior en niños futbolistas de entre 11 y 12 años.

Anterior Cruciate Ligament (ACL) injury is an important cause of days lost in athletes. Most ACL injuries are non-contact and are associated with biomechanical risk factors that increase tension in the ACL: increased knee valgus (KV) and hip flexion (HF) and decreased flexion of knee (KF). Muscle around the knee contributes to knee stability, so fatigue produced by exercise could alter knee balance, increasing LCA tension. The aim of the study is to determine the angular behavior before and after a physical load for CF, RR and RV in children born in 2002-2003. A non-randomized clinical trial was conducted. The sample consisted of 50 students from soccer schools born between 2002 and 2003. The angular behavior of CF, RR and VR was compared, before and after performing standardized training. The angular behavior was measured by performing the DJ test with data obtained by inertial sensors. After exercise, the 3 variables increased, but only HF reached significant difference. Other important finding was the difference found in KV between the dominant leg and the support limb, at both times: rest and post exercise. It was concluded that the angular behavior of CF increases significantly in both limbs post-exercise and that preventive measures should be applied for the management of valgus in the supporting limb.

La lesión del ligamento cruzado anterior (LCA) constituye una causa importante de reposo en deportistas. En su mayoría, las lesiones del LCA no requieren contacto externo y se asocian con factores de riesgo biomecánicos que aumentan la tensión en el LCA: el aumento del ángulo de valgo de rodilla (VR), flexión de cadera (FC) y una menor flexión de rodilla (FR). El LCA requiere cooperación de los grupos musculares perirrodilla, por lo que la fatiga producida por el ejercicio alteraría el balance y pondría en riesgo a este ligamento. El objetivo del estudio es determinar el comportamiento angular antes y después de una carga física para FC, FR y VR en niños nacidos en los años 2002-2003. Se realizó un estudio clínico no aleatorizado. La muestra consistió en 50 alumnos de escuelas de fútbol nacidos en los años 2002 y 2003. Se comparó el comportamiento angular de FC, FR y VR antes y después de realizar un entrenamiento estandarizado. El comportamiento angular fue medido a través de la realización de la prueba DJ, con datos obtenidos por sensores inerciales. Posterior al ejercicio, aumentaron las tres variables; sólo fue significativo el incremento en la flexión de cadera. Por otra parte, destaca la diferencia encontrada tanto en reposo como postejercicios entre la extremidad de apoyo y la hábil en el peak de valgo angular. Se concluyó que el comportamiento angular de FC aumenta significativamente en ambas extremidades postentrenamiento y que se deben aplicar medidas preventivas para el manejo del valgo en la extremidad de apoyo.

Efecto de un entrenamiento deportivo en el compartimiento angular de la extremidad inferior en niños futbolistas de entre 11 y 12 años / Effect of sports training in angular compartment of the lower limbs in children footballers aged 11 to 12 years old

Resumen: La lesión del ligamento cruzado anterior (LCA) constituye una causa importante de reposo en deportistas. En su mayoría, las lesiones del LCA no requieren contacto externo y se asocian con factores de riesgo biomecánicos que aumentan la tensión en el LCA: el aumento del ángulo de valgo de rodilla (VR), flexión de cadera (FC) y una menor flexión de rodilla (FR). El LCA requiere cooperación de los grupos musculares perirrodilla, por lo que la fatiga producida por el ejercicio alteraría el balance y pondría en riesgo a este ligamento. El objetivo del estudio es determinar el comportamiento angular antes y después de una carga física para FC, FR y VR en niños nacidos en los años 2002-2003. Se realizó un estudio clínico no aleatorizado. La muestra consistió en 50 alumnos de escuelas de fútbol nacidos en los años 2002 y 2003. Se comparó el comportamiento angular de FC, FR y VR antes y después de realizar un entrenamiento estandarizado. El comportamiento angular fue medido a través de la realización de la prueba DJ, con datos obtenidos por sensores inerciales. Posterior al ejercicio, aumentaron las tres variables; sólo fue significativo el incremento en la flexión de cadera. Por otra parte, destaca la diferencia encontrada tanto en reposo como postejercicios entre la extremidad de apoyo y la hábil en el peak de valgo angular. Se concluyó que el comportamiento angular de FC aumenta significativamente en ambas extremidades postentrenamiento y que se deben aplicar medidas preventivas para el manejo del valgo en la extremidad de apoyo.

Abstract: Anterior Cruciate Ligament (ACL) injury is an important cause of days lost in athletes. Most ACL injuries are non-contact and are associated with biomechanical risk factors that increase tension in the ACL: increased knee valgus (KV) and hip flexion (HF) and decreased flexion of knee (KF). Muscle around the knee contributes to knee stability, so fatigue produced by exercise could alter knee balance, increasing LCA tension. The aim of the study is to determine the angular behavior before and after a physical load for CF, RR and RV in children born in 2002-2003. A non-randomized clinical trial was conducted. The sample consisted of 50 students from soccer schools born between 2002 and 2003. The angular behavior of CF, RR and VR was compared, before and after performing standardized training. The angular behavior was measured by performing the DJ test with data obtained by inertial sensors. After exercise, the 3 variables increased, but only HF reached significant difference. Other important finding was the difference found in KV between the dominant leg and the support limb, at both times: rest and post exercise. It was concluded that the angular behavior of CF increases significantly in both limbs post-exercise and that preventive measures should be applied for the management of valgus in the supporting limb.

Prediction of allosteric sites and mediating interactions through bond-to-bond propensities.

Allostery is a fundamental mechanism of biological regulation, in which binding of a molecule at a distant location affects the active site of a protein. Allosteric sites provide targets to fine-tune protein activity, yet we lack computational methodologies to predict them. Here we present an efficient graph-theoretical framework to reveal allosteric interactions (atoms and communication pathways strongly coupled to the active site) without a priori information of their location. Using an atomistic graph with energy-weighted covalent and weak bonds, we define a bond-to-bond propensity quantifying the non-local effect of instantaneous bond fluctuations propagating through the protein. Significant interactions are then identified using quantile regression. We exemplify our method with three biologically important proteins: caspase-1, CheY, and h-Ras, correctly predicting key allosteric interactions, whose significance is additionally confirmed against a reference set of 100 proteins. The almost-linear scaling of our method renders it suitable for high-throughput searches for candidate allosteric sites.

Effects of whole linseed and rumen-protected conjugated linoleic acid enriched diets on beef quality.

Instrumental assessments and sensory tests were performed to evaluate the effects of diet and postmortem ageing time (1, 7 and 21 days) on beef quality. A total of 48 Friesian calves were randomly allocated to four dietary treatments: control, whole linseed (10% linseed), conjugated linoleic acid (CLA) (2% protected CLA), and whole linseed+CLA (10% linseed and 2% protected CLA). Animals were slaughtered at 458±16.6 kg live weight and 11 months of age. Ageing was more significant than diet on most instrumental parameters. Meat from linseed enriched diets had greater drip loss (P⩽0.001) and intramuscular fat (P⩽0.01) than meat from animals fed CLA. Beef aged for 7 and 21 days had lower cooking losses (P⩽0.01) and shear force (P⩽0.001) than beef aged for 1 day. Lightness was affected only by display time. The addition of CLA in the diet increased hue and yellowness, whereas the inclusion of linseed decreased these values, as well as increased redness. Linseed in the diet decreased fat odour (P⩽0.05), but increased beef (P⩽0.01) and liver (P⩽0.05) flavours. Meat aged for 21 days was significantly more rancid (P⩽0.001), even under vacuum storage. Several organoleptic properties were improved with the inclusion of linseed in the diet, whereas they remained unaffected by the inclusion of CLA.

Association between functional candidate genes and organoleptic meat traits in intensively-fed beef.

The aim of this study was to assess the associations between the single nucleotide polymorphisms in CAPN1, CAST, DGAT1, FABP4, LEP, RORC and SCD1 genes and the sensory meat quality in an intensively fed commercial population (Charolais, Limousin and Retinta breed). This work carried out analyses on a common Spanish population and evaluated the association between the markers and sensory traits. A total of 161 bulls were allocated to two different feedlots with two different finishing diets. Steaks aged for 7 and 21 days were assessed by both untrained and trained sensory panels. A significant association and allelic substitution effect were observed for markers UoG-CAST, LEP: g.73C>T and SCD1: g.878T>C on different descriptors evaluated by a consumer panel (tenderness and overall acceptability). There are no precedents of these kinds of association studies in a Spanish commercial population. The study suggested that CAST, LEP and SCD1 genes have a potential effect on the different measurements of sensory meat quality.

Placenta percreta con invasión vesical: una causa infrecuente de hematuria en la embarazada / Placenta percreta with bladder invasion: an uncommon cause of hematuria during pregnancy

La placenta percreta con invasión de la vejiga es una entidad muy infrecuente que puede producir complicaciones muy graves para la embarazada. Aunque a menudo se diagnostica en el momento del parto, las técnicas de imagen son muy útiles para diagnosticarla precozmente, lo que resulta fundamental para la planificación quirúrgica y evitar complicaciones potencialmente mortales. Presentamos un caso de esta entidad, y realizamos un breve repaso bibliográfico, con énfasis en el papel de las técnicas de imagen. Se trata de una gestante con antecedente de cesárea previa, hematuria y dolor lumbar. Tras realizar una ecografía y una resonancia magnética, se sugirió el diagnóstico de placenta percreta con invasión vesical, que se confirmó quirúrgicamente (AU)

Placenta percreta with bladder invasion is a very uncommon condition that can lead to very severe complications in pregnant women. Although it is often diagnosed during delivery, imaging techniques are very useful for early diagnosis, which is fundamental for planning surgery and avoiding potentially lethal complications. We present the case of a woman with a history of cesarean section who presented with hematuria and low back pain. The diagnosis of placenta percreta with bladder invasion was suggested after ultrasonography and magnetic resonance imaging and was confirmed at surgery. We provide a brief review of the literature, emphasizing the role of imaging techniques (AU)

Efficacy and feasibility of basal-bolus insulin regimens and a discharge-strategy in hospitalised patients with type 2 diabetes--the HOSMIDIA study.

AIMS: Guidelines recommend use of basal-bolus insulin in hospitalised patients with hyperglycaemia, but information about implementation and medication reconciliation at discharge is scarce. The HOSMIDIA study evaluated a management program involving basal-bolus insulin and an algorithm for medication reconciliation at discharge in non-critically ill hospitalised patients with type 2 diabetes in clinical practice. METHODS: HOSMIDIA was a prospective, observational study performed during routine clinical practice at 15 Spanish hospitals during hospitalisation, with follow-up 3 months postdischarge. Study patients (n = 134) received a basal-bolus regimen with insulin glargine during hospitalisation and treatment at discharge was adjusted according to a simple algorithm. The control group (n = 62) included patients with similar characteristics hospitalised during the month before study initiation and had no follow-up after discharge. RESULTS: Compared with control subjects, patients in the prospective study achieved lower mean total (167.7 ± 41.1 vs. 190.5 ± 53.3 mg/dl) preprandial (164.2 ± 42.4 vs. 189.6 ± 52.6 mg/dl; p < 0.001) and fasting (137.0 ± 42.2 vs. 165.8 ± 56.5 mg/dl) blood glucose levels while hospitalised, without increased hypoglycaemic episodes (17.7% vs. 19.3% patients). In the prospective study, glycaemic control improved from admission to discharge, with control maintained 3 months after discharge. The main treatment modification at discharge compared with admission was addition of basal insulin, and treatment at discharge was maintained at 3 months in 89% of patients. CONCLUSION: The HOSMIDIA study confirmed that management of hyperglycaemia with basal-bolus insulin is feasible and effective in routine clinical practice, and that a simple strategy facilitating the reconciliation of medication on discharge can improve glycaemic control postdischarge.

Uncovering allosteric pathways in caspase-1 using Markov transient analysis and multiscale community detection.

Allosteric regulation at distant sites is central to many cellular processes. In particular, allosteric sites in proteins are major targets to increase the range and selectivity of new drugs, and there is a need for methods capable of identifying intra-molecular signalling pathways leading to allosteric effects. Here, we use an atomistic graph-theoretical approach that exploits Markov transients to extract such pathways and exemplify our results in an important allosteric protein, caspase-1. Firstly, we use Markov stability community detection to perform a multiscale analysis of the structure of caspase-1 which reveals that the active conformation has a weaker, less compartmentalised large-scale structure compared to the inactive conformation, resulting in greater intra-protein coherence and signal propagation. We also carry out a full computational point mutagenesis and identify that only a few residues are critical to such structural coherence. Secondly, we characterise explicitly the transients of random walks originating at the active site and predict the location of a known allosteric site in this protein quantifying the contribution of individual bonds to the communication pathway between the active and allosteric sites. Several of the bonds we identify have been shown experimentally to be functionally critical, but we also predict a number of as yet unidentified bonds which may contribute to the pathway. Our approach offers a computationally inexpensive method for the identification of allosteric sites and communication pathways in proteins using a fully atomistic description.

[Placenta percreta with bladder invasion: an uncommon cause of hematuria during pregnancy]. / Placenta percreta con invasión vesical: una causa infrecuente de hematuria en la embarazada.

Placenta percreta with bladder invasion is a very uncommon condition that can lead to very severe complications in pregnant women. Although it is often diagnosed during delivery, imaging techniques are very useful for early diagnosis, which is fundamental for planning surgery and avoiding potentially lethal complications. We present the case of a woman with a history of cesarean section who presented with hematuria and low back pain. The diagnosis of placenta percreta with bladder invasion was suggested after ultrasonography and magnetic resonance imaging and was confirmed at surgery. We provide a brief review of the literature, emphasizing the role of imaging techniques.

Effect of whole linseed and rumen-protected conjugated linoleic acid enriched diets on feedlot performance, carcass characteristics, and adipose tissue development in young Holstein bulls.

Forty-eight young Holstein bulls (slaughtered at 458.6±9.79 kg body weight) were used to evaluate the effect of whole linseed and conjugated linoleic acid (CLA) supplementation on animal performance, adipose tissue development, and carcass characteristics. The animals were fed with one of four isoenergetic and isoproteic diets: control (0% linseed, 0% CLA), linseed (10% linseed, 0% CLA), CLA (0% linseed, 2% CLA), and linseed plus CLA (10% linseed, 2% CLA). Animal performance and carcass characteristics were unaffected by diet composition. Adding linseed or CLA to the concentrate diet did not result in significant differences in adipocyte size and number or lipogenic enzyme activity. However, while the frequency distribution of subcutaneous adipocyte diameters followed a normal distribution, the frequency distribution of intramuscular adipocyte diameters was not normal in any dietary group (skewness coefficients: 0.8, 1.2, 0.9, 0.8 for control, linseed, CLA, and linseed plus CLA, respectively; P<0.05), indicative of adipocyte proliferation in the intramuscular adipose tissue.

Case report. Primary mucosa-associated lymphoid tissue lymphoma as a pleural mass.

Primary pleural lymphoma is a rare entity that has been described in association with human immunodeficiency virus (HIV) infection or pyothorax. It occurs in only 7% of primary lymphoma cases. We report the case of a 52-year-old male with no history of HIV infection or pyothorax who was diagnosed of obstructive sleep apnoea syndrome (OSAS) and underwent a routine chest X-ray to screen for any organic cause of the symptoms. The radiograph revealed two voluminous masses with extraparenchymatous features but without pleural effusion. A contrast-enhanced CT was performed and confirmed the existence of the pleural masses that showed homogeneous attenuation. Neither mediastinal lymphadenopathy nor pleural effusion were present. A percutaneous CT-guided fine needle aspiration cytology (FNAC) with a 25-G needle was performed (two samples were obtained) and the first diagnosis was of non-Hodgkin's lymphoma. The final diagnosis of primary pleural mucosa-associated lymphoid tissue (MALT) lymphoma was confirmed by a CT-guided core biopsy with a 20-G needle. To the best of our knowledge, no cases of MALT lymphoma presenting as pleural masses without pleural effusion have been reported in immunocompetent patients. In this report, we describe the case of a patient with a primary pleural MALT lymphoma and include a short review of the literature.

Protein multi-scale organization through graph partitioning and robustness analysis: application to the myosin-myosin light chain interaction.

Despite the recognized importance of the multi-scale spatio-temporal organization of proteins, most computational tools can only access a limited spectrum of time and spatial scales, thereby ignoring the effects on protein behavior of the intricate coupling between the different scales. Starting from a physico-chemical atomistic network of interactions that encodes the structure of the protein, we introduce a methodology based on multi-scale graph partitioning that can uncover partitions and levels of organization of proteins that span the whole range of scales, revealing biological features occurring at different levels of organization and tracking their effect across scales. Additionally, we introduce a measure of robustness to quantify the relevance of the partitions through the generation of biochemically-motivated surrogate random graph models. We apply the method to four distinct conformations of myosin tail interacting protein, a protein from the molecular motor of the malaria parasite, and study properties that have been experimentally addressed such as the closing mechanism, the presence of conserved clusters, and the identification through computational mutational analysis of key residues for binding.

Flow graphs: interweaving dynamics and structure.

The behavior of complex systems is determined not only by the topological organization of their interconnections but also by the dynamical processes taking place among their constituents. A faithful modeling of the dynamics is essential because different dynamical processes may be affected very differently by network topology. A full characterization of such systems thus requires a formalization that encompasses both aspects simultaneously, rather than relying only on the topological adjacency matrix. To achieve this, we introduce the concept of flow graphs, namely weighted networks where dynamical flows are embedded into the link weights. Flow graphs provide an integrated representation of the structure and dynamics of the system, which can then be analyzed with standard tools from network theory. Conversely, a structural network feature of our choice can also be used as the basis for the construction of a flow graph that will then encompass a dynamics biased by such a feature. We illustrate the ideas by focusing on the mathematical properties of generic linear processes on complex networks that can be represented as biased random walks and their dual consensus dynamics, and show how our framework improves our understanding of these processes.

Síndrome de hipotensión intracraneal: revisión de hallazgos en resonancia magnética / Intracranial hypotension syndrome: a review of the magnetic resonance findings

Introducción. El síndrome de hipotensión intracraneal (SHI) es un síndrome de etiología y presentación clínica variable, causada, en la mayoría de casos, por fuga de líquido cefalorraquídeo a través del saco tecal. La cefalea ortostática asociada a los hallazgos típicos en resonancia magnética (RM), secundarios a la depleción del líquido cefalorraquídeo, constituye a clave para el diagnóstico. Objetivo. Mostrar los hallazgos radiológicos que en un contexto clínico adecuado permiten identificar y diagnosticar esta entidad. Desarrollo. La disminución del volumen del líquido cefalorraquídeo desempeña un papel importante en el SHI, que lleva a un aumento del volumen de sangre compensatorio, fundamentalmente dependiente del sistema venoso. La RM es una técnica sensible en el diagnóstico del SHI. No obstante, los hallazgos por separado son inespecíficos. Entre los hallazgos en RM se encuentran el realce dural difuso y homogéneo, la presencia de pequeñas colecciones subdurales bilaterales, desplazamiento caudal de las estructuras encefálicas (pseudo-Chiari), dilatación de venas corticales y medulares, y el reciente signo de la distensión venosa. Este último signo constituye un hallazgo altamente sensible de SHI, que tiende adesaparecer tras la mejoría clínica del paciente incluso antes de la desaparición del realce paquimeníngeo, y que podría utilizarse como marcador de respuesta al tratamiento. Conclusión. El SHI es una entidad de difícil diagnóstico clínico en la que se han descrito hallazgos típicos en la RM con los que el neurólogo y el radiólogo deben estar familiarizados (AU)

Introduction. Intracranial hypotension syndrome (IHS) is a syndrome with a variable aetiology and clinical presentation that is, in most cases, caused by leakage of cerebrospinal fluid (CSF) through the thecal sac. Orthostatic headache associated to the typical magnetic resonance imaging (MRI) findings, secondary to depletion of CSF, is the key to a correct diagnosis. Aims. To show the imaging findings that, within a suitable clinical context, allow this condition to be identified and diagnosed. Development. Decreased CSF volume plays an important role in IHS, which leads to an increase in the compensatory volume of blood, essentially dependent on the venous system. MRI is a sensitive technique in the diagnosis of IHS. Yet, separate findings are unspecific. The MRI findings include diffuse and homogeneous dural enhancement, the presence of small bilateral subdural collections, caudal displacement of the encephalic structures (pseudo-Chiari), dilatation of thecortical and medullar veins, and the recent sign of venous distension. This last sign is a highly sensitive finding of IHS, which tends to disappear following the patient’s clinical improvement even before the disappearance of the pachymeningeal enhancement, and could be used as a marker for response to treatment. Conclusions. IHS is a condition that is difficult to diagnose clinically for which several typical MRI findings have been reported; both neurologists and radiologists must be familiar with these findings (AU)