970 resultados para peripheral nerve block
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<p>Many types of non-invasive brain stimulation alter corticospinal excitability (CSE). Paired associative stimulation (PAS) has attracted particular attention as its effects ostensibly adhere to Hebbian principles of neural plasticity. In prototypical form, a single electrical stimulus is directed to a peripheral nerve in close temporal contiguity with transcranial magnetic stimulation delivered to the contralateral primary motor cortex (M1). Repeated pairing of the two discrete stimulus events (i.e. association) over an extended period either increases or decreases the excitability of corticospinal projections from M1, contingent on the interstimulus interval. We studied a novel form of associative stimulation, consisting of brief trains of peripheral afferent stimulation paired with short bursts of high frequency (80 Hz) transcranial alternating current stimulation (tACS) over contralateral M1. Elevations in the excitability of corticospinal projections to the forearm were observed for a range of tACS frequency (80, 140 and 250 Hz), current (1, 2 and 3 mA) and duration (500 and 1000 ms) parameters. The effects were at least as reliable as those brought about by PAS or transcranial direct current stimulation. When paired with tACS, muscle tendon vibration also induced elevations of CSE. No such changes were brought about by the tACS or peripheral afferent stimulation alone. In demonstrating that associative effects are expressed when the timing of the peripheral and cortical events is not precisely circumscribed, these findings suggest that multiple cellular pathways may contribute to a long term potentiation-type response. Their relative contributions will differ depending on the nature of the induction protocol that is used.</p>
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<p>Paired Associative Stimulation (PAS) has come to prominence as a potential therapeutic intervention for the treatment of brain injury/disease, and as an experimental method with which to investigate Hebbian principles of neural plasticity in humans. Prototypically, a single electrical stimulus is directed to a peripheral nerve in advance of transcranial magnetic stimulation (TMS) delivered to the contralateral primary motor cortex (M1). Repeated pairing of the stimuli (i.e., association) over an extended period may increase or decrease the excitability of corticospinal projections from M1, in manner that depends on the interstimulus interval (ISI). It has been suggested that these effects represent a form of associative long-term potentiation (LTP) and depression (LTD) that bears resemblance to spike-timing dependent plasticity (STDP) as it has been elaborated in animal models. With a large body of empirical evidence having emerged since the cardinal features of PAS were first described, and in light of the variations from the original protocols that have been implemented, it is opportune to consider whether the phenomenology of PAS remains consistent with the characteristic features that were initially disclosed. This assessment necessarily has bearing upon interpretation of the effects of PAS in relation to the specific cellular pathways that are putatively engaged, including those that adhere to the rules of STDP. The balance of evidence suggests that the mechanisms that contribute to the LTP- and LTD-type responses to PAS differ depending on the precise nature of the induction protocol that is used. In addition to emphasizing the requirement for additional explanatory models, in the present analysis we highlight the key features of the PAS phenomenology that require interpretation.</p>
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<p>Malignant Triton tumor (MTT) is a malignant peripheral nerve sheath tumor showing rhabdomyoblastic differentiation. It is considered a high-grade neoplasm with poor outcome. This report describes an MTT appearing in the oral cavity. On histologic examination the encapsulated lesion was composed of interlacing fascicles of spindle cells and scattered, large, strap-like pleomorphic cells with abundant eosinophilic cytoplasm. No cross striations were seen. Examination of levels through the tissue showed a total of only 4 normal mitoses and no necrosis. Immunohistochemistry demonstrated diffuse S100 positivity in the spindle cells. The large pleomorphic cells were weakly positive for alpha-sarcomeric actin and myoglobin, although variably but strongly positive for desmin. Management involved a small en bloc resection of the maxilla. After 33 months there was no sign of recurrence or distant metastasis. It was concluded that low-grade variants of MTT occur that do not have an aggressive clinical course.</p>
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Tese de mestrado, Neurocincias, Faculdade de Medicina, Universidade de Lisboa, 2015
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The use, manipulation and application of electrical currents, as a controlled interference mechanism in the human body system, is currently a strong source of motivation to researchers in areas such as clinical, sports, neuroscience, amongst others. In electrical stimulation (ES), the current applied to tissue is traditionally controlled concerning stimulation amplitude, frequency and pulse-width. The main drawbacks of the transcutaneous ES are the rapid fatigue induction and the high discomfort induced by the non-selective activation of nervous fibers. There are, however, electrophysiological parameters whose response, like the response to different stimulation waveforms, polarity or a personalized charge control, is still unknown. The study of the following questions is of great importance: What is the physiological effect of the electric pulse parametrization concerning charge, waveform and polarity? Does the effect change with the clinical condition of the subjects? The parametrization influence on muscle recruitment can retard fatigue onset? Can parametrization enable fiber selectivity, optimizing the motor fibers recruitment rather than the nervous fibers, reducing contraction discomfort? Current hardware solutions lack flexibility at the level of stimulation control and physiological response assessment. To answer these questions, a miniaturized, portable and wireless controlled device with ES functions and full integration with a generic biosignals acquisition platform has been created. Hardware was also developed to provide complete freedom for controlling the applied current with respect to the waveform, polarity, frequency, amplitude, pulse-width and duration. The impact of the methodologies developed is successfully applied and evaluated in the contexts of fundamental electrophysiology, psycho-motor rehabilitation and neuromuscular disorders diagnosis. This PhD project was carried out in the Physics Department of Faculty of Sciences and Technology (FCT-UNL), in straight collaboration with PLUX - Wireless Biosignals S.A. company and co-funded by the Foundation for Science and Technology.
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RESUMO: Na clnica, a recuperao funcional que se segue a uma leso nervosa raramente atingida na sua totalidade. A reinervao, quer motora, quer sensitiva, ocorre geralmente com maior ou menor deficit. Interessa, ento, identificar os factores que podem interferir na regenerao nervosa. O neurnio a unidade anatmica fundamental do sistema nervoso perifrico e muito vulnervel isquemia pela grande distncia que existe entre o corpo neuronal e a extenso do axnio, que pode ser de apenas alguns milmetros ou at atingir um metro. , por isso, fundamental o estudo da vascularizao do nervo perifrico e da sua influncia na regenerao nervosa. O resultado deste estudo pode levar ao desenvolvimento de tcnicas cirrgicas que criem as condies que garantam, por sua vez, a revascularizao precoce do nervo perifrico em caso de leso, ou mesmo em caso de doenas, nas quais a vascularizao do nervo est alterada como, por exemplo, na neuropatia diabtica. O estudo da vascularizao do nervo perifrico realizou-se atravs da investigao da vascularizao do nervo mediano do cadver humano, pela investigao da vascularizao do nervo isquitico do rato Wistar e do Plexo Braquial (PB) do mesmo. A vascularizao do PB do rato no muito diferente daquela que reportada na espcie humana, existindo uma homologia entre o rato e o Homem no que diz respeito morfologia e vascularizao do PB. Atravs da comparao angiomorfolgica entre o nervo isquitico do rato e o nervo mediano humano, concluu-se que a microvascularizao do nervo isquitico do rato e do mediano humano so muito semelhantes, o que suporta a utilizao do rato como modelo experimental de leses do nervo mediano humano. Para a avaliao da influncia da vascularizao na regenerao nervosa foi feita a anlise da eficcia de enxerto de tubo de membrana amnitica humana imunologicamente inerte, de enxerto de veia jugular externa autloga e de auto-enxerto de nervo, na reparao de um defeito de 10 milmetros no nervo isquitico do rato, na presena de um fornecimento vascular axial, comparando-se com os mesmos procedimentos em estudos realizados anteriormente, sem suprimento vascular. Os ratos foram avaliados funcionalmente atravs do estudo das pegadas, da electroneurografia e da fora de flexo ao nvel do tornozelo, e estruturalmente, atravs das avaliaes histolgicas e morfomtricas, da taxa de recuperao do peso dos msculos gastrocnmio e solhear e da marcao axonal retrgrada com True Blue s 4, 8 e 12 semanas. Os nervos reconstrudos apresentaram uma arquitectura normal, incluindo a arquitectura vascular. A membrana amnitica foi bem tolerada, persistindo imunologicamente em torno do nervo at 12. semana. Concluiu-se tambm que, na presena de um suprimento vascular axial local, a membrana amnitica humana e as veias autlogas so, pelo menos, to eficazes como os auto-enxertos nervosos na reconstruo de defeitos nervosos de 10 milmetros.--------------------------------------ABSTRACT: At the clinic, the functional recovery that follows a nerve lesion is rarely achieved in full. The neuron is very vulnerable to ischemia thats why it is essential to study the vascularization of the peripheral nerve and its influence on the nerves regeneration. The outcome of this study may lead to the development of surgical techniques that create the conditions which are necessary to ensure an early revascularization in case of a peripheral nerve injury. This study investigated the vascularization of the median nerve of the human cadaver and the vascularization of the sciatic nerve of the Wistar rat and his Brachial Plexus (BP) through animal experimentation. The mouse's BP vascularization is not so different from the one that is reported in the human species. An angiomorphological comparison between the mouse sciatic nerve and the human median nerve concluded that the microvascularizations are very similar, which supports the use of the mouse as an experimental model for the study of median nerves lesions. To evaluate the influence of vascularization in the nerves regeneration, it was made an assessment of the effectiveness of the human amniotic immuno-inert membrane grafts, of the autologous external jugular vein grafts and of the nerve auto-graft in the repair of a defect of 10 mm on the sciatic nerve of the rat, in the presence of an axial vascular supply, comparing these with the same procedures that were adopted in the previous studies, without vascular supply. The rats were functionally assessed and structurally evaluated (through histological and morphometric evaluations) at the 4.th, 8.th and 12.th weeks. The nerves reconstructed presented a normal architecture, including vascular architecture. The amniotic membrane was well-tolerated immunologically, persisting around the nerve until the 12.th week. As a result, it was also concluded that in the presence of a local axial vascular supply, the human amniotic membrane and the autologous veins are, at least, as effective as the nerve auto-grafts in the reconstruction of the nerves defects of 10 mm.
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Soft tissue sarcomas (STS) with complex genomic profiles (50% of all STS) are predominantly composed of spindle cell/pleomorphic sarcomas, including leiomyosarcoma, myxofibrosarcoma, pleomorphic liposarcoma, pleomorphic rhabdomyosarcoma, malignant peripheral nerve sheath tumor, angiosarcoma, extraskeletal osteosarcoma, and spindle cell/pleomorphic unclassified sarcoma (previously called spindle cell/pleomorphic malignant fibrous histiocytoma). These neoplasms show, characteristically, gains and losses of numerous chromosomes or chromosome regions, as well as amplifications. Many of them share recurrent aberrations (e.g., gain of 5p13-p15) that seem to play a significant role in tumor progression and/or metastatic dissemination. In this paper, we review the cytogenetic, molecular genetic, and clinicopathologic characteristics of the most common STS displaying complex genomic profiles. Features of diagnostic or prognostic relevance will be discussed when needed.
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La stimulation lectrique directe (SED), pour une heure, amliore la rgnration de nerfs priphriques chez le rat aprs la rparation. Cliniquement, ceci augmenterait le temps opratoire, rehaussant les risques de complications priopratoires. Objectif: Cette tude examine si la stimulation lectrique transcutane (SETC) est aussi efficace amliorer la rgnration de nerfs priphriques que la stimulation lectrique directe. Mthode: Le nerf sciatique droit de 28 souris a t axotomis. Une rparation par microsuture est effectue. Quatre groupes sont tudis : (1) sham; (2) suture seulement; (3) suture et SED; (4) suture et SETC. La stimulation est applique pour 1 heure 20 Hz. Les souris sont tudies pour un total de 12 semaines. La rcupration sciatique est value aux semaines 0, 1, 2 et aux 2 semaines par la suite par analyse de dmarche sur la poutre. Rsultats: La cinmatique post-rcupration dmontre un index fonctionnel sciatique et angle de dcollement significativement amliors pour les groupes SED et SETC aux semaines 8, 10 et 12. Conclusions: 12 semaines aprs laxotomie du nerf sciatique, la rcupration fonctionnelle est significativement amliore avec la SED et la SETC. Donc, la SETC est aussi bnfique pour la promotion de la rgnration nerveuse et rinnervation musculaire fonctionnelle que la SED.
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El dolor oncolgico representa una de las principales causas de dolor crnico, siendo los opioides la primera lnea de manejo, sin embargo 10% de los pacientes requieren estrategias analgsicas multimodales. La eficacia analgsica de la clonidina como coadyuvante ha sido demostrada para diversos modelos de dolor. Sin embargo no hay revisiones sistemticas que validen su eficacia y seguridad en dolor crnico oncolgico. Se realiz una revisin sistemtica de la literatura a noviembre 26 de 2012, encontrando 15 trabajos (12 reportes de caso y tres ensayos clnicos controlados), n=138 pacientes. La intervencin tuvo una eficacia entre 44,7 y 100%, mostrando mayor beneficio en pacientes con componente de dolor neuroptico. La adicin de clonidina fue bien tolerada, siendo la sedacin y la disminucin en tensin arterial y frecuencia cardiaca los efectos secundarios ms frecuentes, con relacin dosis dependiente, de resolucin espontnea y en ninguno de los casos se document lesin secundaria en los pacientes. La va de administracin ms frecuente fue neuroaxial (intratecal y peridural). La revisin sistemtica no fue susceptible de metaanlisis por la heterogeneidad clnica de los estudios. Los resultados obtenidos sugieren que la adicin de clonidina puede ser una opcin terapetica eficaz y segura en los pacientes con dolor crnico oncolgico severo refractario a opioides a altas dosis asociado o no a infusin neuroaxial de anestsico local, en especial en presencia de componente neuroptico. Sin embargo se identific la necesidad de un mayor nmero de ensayos clnicos controlados aleatorios que permitan establecer conclusiones definitivas.
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Introduccin: La herniorrafia inguinal se asocia hasta en un 50% de los casos con dolor crnico posoperatorio (DCP), y en algunos puede ser incapacitante. En este estudio se evaluaron los factores asociados al DCP en pacientes llevados a herniorrafia inguinal. Mtodologa: Se realiz un estudio de cohorte multicntrico. Se obtuvo informacin sociodemogrfica y de antecedentes personales. Se determin la presencia e intensidad de dolor agudo posoperatorio (DAP) y se evaluaron los factores asociados al DCP con seguimiento a los dos meses del posoperatorio. Se establecieron asociaciones con la prueba chi cuadrado. Mediante una regresin lineal se evalu el papel de los factores de confusin. Resultados: Se analizaron 108 pacientes. 54.7% presentaron DCP. La edad menor de 40 aos, el DAP no controlado, el DAP severo, y el dolor no controlado entre la primera y tercera semanas del POP se relacionaron con mayor riesgo de DCP. La edad mayor a 65, el uso de opioides intratecales, la visualizacin y preservacin de los nervios durante la ciruga, y el uso de tres o ms analgsicos intravenosos con bloqueo ilioinguinal/iliohipogstrico fueron factores protectores. Discusin: El DCP es frecuente en nuestro medio. La prevencin y manejo eficientes del DAP utilizando analgesia multimodal, el uso de opioide intratecal, y la identificacin y preservacin de los nervios en el rea quirrgica ayudan a prevenir el desarrollo de DCP. Estudios de este tipo realizados a una escala ms grande, permitirn identificar otros factores relacionados con esta patologa. Palabras clave: Dolor crnico postoperatorio, herniorrafia inguinal, inguinodina, factores asociados.
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INTRODUCCIN. El ultrasonido es fundamental en la medicina de emergencias, no se conoce cual debera ser la curva de aprendizaje para obtener las competencias tcnicas y operativas; ACEP recomienda por cada ventana ecogrfica realizar 25 repeticiones. No existe una curva de aprendizaje para ventana de VCI en la poblacin de residentes colombianos. OBJETIVO: Determinar la curva de aprendizaje necesaria para obtener una proporcin mayor al 80% de xitos en la toma de la ventana ecogrfica de la VCI, usando la escala de calificacin para el aseguramiento de la calidad sugerida por ACEP, en residentes de I a III ao de medicina de emergencias. METODOLOGA: Estudio experimental no comparativo, que evalu la proporcin de xito en funcin del las tomas repetidas de la VCI por ultrasonido, mediciones que se tomaron luego de participar en una capacitacin terica y demostrativa de la tcnica propuesta; se calificaron los videos segn la escala publicada por ACEP. El anlisis estadstico se realiz con un modelo logstico multinivel para la proporcin del xito, agrupado por repeticin y agrupado por sujeto. RESULTADOS: Se obtuvo informacin de 8 residentes, cada uno realizo 25 repeticiones a 3 modelos sanos con asignacin aleatoria. Se realiz la curva de aprendizaje obteniendo en 11 repeticiones una proporcin de 0.80 (rango 0.54 a 0.92) y en 21 repeticiones una proporcin de 0.9 (rango 0.75 a 0.96), datos ajustados por numero de repeticin y residente. CONCLUSIN: La curva de aprendizaje para la ventana ecogrfica de la VCI es de 11 y 21 repeticiones para obtener el 80% y 90% de xito en residentes de medicina de emergencias de I a III ao de la universidad del rosario.
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Neuropathic pain may arise following peripheral nerve injury though the molecular mechanisms associated with this are unclear. We used proteomic profiling to examine changes in protein expression associated with the formation of hyper-excitable neuromas derived from rodent saphenous nerves. A two-dimensional difference gel electrophoresis ( 2D-DIGE) profiling strategy was employed to examine protein expression changes between developing neuromas and normal nerves in whole tissue lysates. We found around 200 proteins which displayed a > 1.75-fold change in expression between neuroma and normal nerve and identified 55 of these proteins using mass spectrometry. We also used immunoblotting to examine the expression of low-abundance ion channels Nav1.3, Nav1.8 and calcium channel alpha 2 delta-1 subunit in this model, since they have previously been implicated in neuronal hyperexcitability associated with neuropathic pain. Finally, S(35)methionine in vitro labelling of neuroma and control samples was used to demonstrate local protein synthesis of neuron-specific genes. A number of cytoskeletal proteins, enzymes and proteins associated with oxidative stress were up-regulated in neuromas, whilst overall levels of voltage-gated ion channel proteins were unaffected. We conclude that altered mRNA levels reported in the somata of damaged DRG neurons do not necessarily reflect levels of altered proteins in hyper-excitable damaged nerve endings. An altered repertoire of protein expression, local protein synthesis and topological re-arrangements of ion channels may all play important roles in neuroma hyper-excitability.
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Many human behaviours and pathologies have been attributed to the putative mirror neuron system, a neural system that is active during both the observation and execution of actions. While there are now a very large number of papers on the mirror neuron system, variations in the methods and analyses employed by researchers mean that the basic characteristics of the mirror response are not clear. This review focuses on three important aspects of the mirror response, as measured by modulations in corticospinal excitability: (1)muscle specificity, (2)direction, and (3)timing of modulation. We focus mainly on electromyographic (EMG) data gathered following single-pulse transcranial magnetic stimulation (TMS), because this method provides precise information regarding these three aspects of the response. Data from paired-pulse TMS paradigms and peripheral nerve stimulation (PNS) are also considered when we discuss the possible mechanisms underlying the mirror response. In this systematic review of the literature, we examine the findings of 85 TMS and PNS studies of the human mirror response, and consider the limitations and advantages of the different methodological approaches these have adopted in relation to discrepancies between their findings. We conclude by proposing a testable model of how action observation modulates corticospinal excitability in humans. Specifically, we propose that action observation elicits an early, non-specific facilitation of corticospinal excitability (at around 90ms from action onset), followed by a later modulation of activity specific to the muscles involved in the observed action (from around 200ms). Testing this model will greatly advance our understanding of the mirror mechanism and provide a more stable grounding on which to base inferences about its role in human behaviour.
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The secreted metalloprotease ADAMTS5 is implicated in destruction of the cartilage proteoglycan aggrecan in arthritis, but its physiological functions are unknown. Its expression profile during embryogenesis and in adult tissues is therefore of considerable interest. β-Galactosidase (β-gal) histochemistry, enabled by a LacZ cassette inserted in the Adamts5 locus, and validated by in situ hybridization with an Adamts5 cRNA probe and ADAMTS5 immunohistochemistry, was used to profile Adamts5 expression during mouse embryogenesis and in adult mouse tissues. Embryonic expression was scarce prior to 11.5 days of gestation (E11.5) and noted only in the floor plate of the developing brain at E9.5. After E11.5 there was continued expression in brain, especially in the choroid plexus, peripheral nerves, dorsal root ganglia, cranial nerve ganglia, spinal and cranial nerves, and neural plexuses of the gut. In addition to nerves, developing limbs have Adamts5 expression in skeletal muscle (from E13.5), tendons (from E16.5), and inter-digital mesenchyme of the developing autopod (E13.5–15.5). In adult tissues, there is constitutive Adamts5 expression in arterial smooth muscle cells, mesothelium lining the peritoneal, pericardial and pleural cavities, smooth muscle cells in bronchi and pancreatic ducts, glomerular mesangial cells in the kidney, dorsal root ganglia, and in Schwann cells of the peripheral and autonomic nervous system. Expression of Adamts5 during neuromuscular development and in smooth muscle cells coincides with the broadly distributed proteoglycan versican, an ADAMTS5 substrate. These observations suggest the major contexts in which developmental and physiological roles could be sought for this protease.<br />
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Neurological complications of systemic cancer—those arising outside the nervous system—can be distressing, disabling, and sometimes fatal. Diagnosis is often difficult because different neurological disorders may present with similar signs and symptoms. Furthermore, comorbid neurological illnesses, common in elderly patients with cancer, can complicate diagnosis. Early diagnosis and aggressive treatment can improve neurological symptoms and can substantially enhance a patient's quality of life. We approach the problem of neurological complications of systemic cancer as would a neurologist: first by identifying the anatomical area or areas that are affected (ie, brain, spinal cord, peripheral nerve), then by evaluating the diagnostic approach, considering the symptoms and signs and including appropriate laboratory tests, and finally, by recommending treatment. We focus on disorders that are difficult to diagnose, need neurological consultation, and for which effective treatments exist.
