Rotator cuff muscle fibrosis can be assessed using ultrashort echo time magnetization transfer MRI with fat suppression.

Muscle degeneration following rotator cuff tendon tearing is characterized by fatty infiltration and fibrosis. While tools exist for the characterization of fat, the ability to noninvasively assess muscle fibrosis is limited. The purpose of this study was to evaluate the capability of quantitative ultrashort echo time T1 (UTE-T1) and UTE magnetization transfer (UTE-MT) mapping with and without fat suppression (FS) for the differentiation of injured and control rotator cuff muscles and for the detection of fibrosis. A rat model of chronic massive rotator cuff tearing (n = 12) was used with tenotomy of the right supraspinatus and infraspinatus tendons and silicone implants to prevent healing. Imaging was performed on a 3-T scanner, and UTE-T1 mapping with and without FS and UTE-MT with and without FS for macromolecular fraction (MMF) mapping was performed. At 20 weeks postinjury, T1 and MMF were measured in the supraspinatus and infraspinatus muscles of the injured and contralateral, internal control sides. Histology was performed and connective tissue fraction (CTF) was measured, defined as the area of collagen-rich extracellular matrix divided by the total muscle area. Paired t-tests and correlation analyses were performed. Significant differences between injured and control sides were found for CTF in the supraspinatus (mean ± SD, 14.5% ± 3.9% vs. 11.3% ± 3.7%, p = 0.01) and infraspinatus (17.0% ± 5.4% vs. 12.5% ± 4.6%, p < 0.01) muscles, as well as for MMF using UTE-MT FS in the supraspinatus (9.7% ± 0.3% vs. 9.5% ± 0.2%, p = 0.04) and infraspinatus (10.9% ± 0.8% vs. 10.1% ± 0.5%, p < 0.01) muscles. No significant differences between sides were evident for T1 without or with FS or for MMF using UTE-MT. Only MMF using UTE-MT FS was significantly correlated with CTF for both supraspinatus (r = 0.46, p = 0.03) and infraspinatus (r = 0.51, p = 0.01) muscles. Fibrosis occurs in rotator cuff muscle degeneration, and the UTE-MT FS technique may be helpful to evaluate the fibrosis component, independent from the fatty infiltration process.

Quantitative evaluation of rat sciatic nerve degeneration using high-frequency ultrasound.

In this study, we evaluated the utility of using high-frequency ultrasound to non-invasively track the degenerative process in a rat model of peripheral nerve injury. Primary analyses explored spatial and temporal changes in quantitative backscatter coefficient (BSC) spectrum-based outcomes and B-mode textural outcomes, using gray level co-occurrence matrices (GLCMs), during the progressive transition from acute to chronic injury. As secondary analyses, correlations among GLCM and BSC spectrum-based parameters were evaluated, and immunohistochemistry were used to suggest a structural basis for ultrasound outcomes. Both mean BSC spectrum-based and mean GLCM-based measures exhibited significant spatial differences across presurgical and 1-month/2-month time points, distal stumps enclosed proximity to the injury site being particularly affected. The two sets of parameters sensitively detected peripheral nerve degeneration at 1-month and 2-month post-injury, with area under the receiver operating charactersitic curve > 0.8 for most parameters. The results also indicated that the many BSC spectrum-based and GLCM-based parameters significantly correlate with each other, and suggested a common structural basis for a diverse set of quantitative ultrasound parameters. The findings of this study suggest that BSC spectrum-based and GLCM-based analysis are promising non-invasive techniques for diagnosing peripheral nerve degeneration.

A guide to reducing adverse outcomes in rabbit models of sciatic nerve injury.

BACKGROUND: Peripheral nerve damage can have debilitating consequences. Rabbit sciatic nerve transection models allow the effective evaluation of surgical repair strategies for large nerve gaps. Despite advantages in size, ease of handling, and functional utility, rabbits can suffer from a number of side effects that affect animal welfare and the quality of scientific inquiry. Such side-effects, which include pressure ulcers and traumatic damage to the foot, are primarily a consequence of insensitivity of the distal hindlimb following sciatic nerve injury. In this study, we present a number of methodologies for identifying, treating, and preventing unintended adverse effects in rabbit sciatic nerve injury models. RESULTS: First, we categorize pressure ulcers according to their severity and describe the deployment of a padded bandaging technique to enable ulcer healing. We also introduce a proactive bandaging approach to reduce the likelihood of pressure ulcer formation. Second, we define phenotypes that distinguish between foot injuries resulting from self-mutilation (autotomy) from those caused by incidental traumatic injury secondary to sensori-motor damage. Finally, we detail an effective strategy to reduce the usage of Elizabethan collars; through a gradual weaning protocol, their usefulness in preventing autotomy is retained, while their propensity to impede rabbit grooming and cause abrasion-injury to the neck region is minimized. CONCLUSIONS: We suggest that application of these methods offer a practical and systematic approach to avoid adverse side effects associated with rabbit sciatic nerve damage, enabling improved animal welfare and scientific outcomes in a powerful nerve injury model.

A comparative assessment of lengthening followed by end-to-end repair and isograft repair of chronically injured peripheral nerves.

In order to repair chronic nerve injuries (injuries repaired after a long delay), the damaged nerve segments are resected and stumps are bridged by grafts. Autografts remain the gold-standard, but outcomes are typically poor, even after long periods of recovery. In a recent study, we described the use of a nerve lengthening device to gradually elongate the proximal stump of a transected nerve towards the distal stump, enabling a tension-free end-to-end repair. This approach showed significantly improved outcomes in comparison to autografts in repairing acutely injured nerves. In this study, we compared the use of nerve lengthening/end-to-end repair (LETER) to isograft repair of chronically transected nerves in a rat model. Structural and functional regenerative outcomes following LETER were comparable to isograft-based repair, with no significant differences found in outcomes involving functional recovery or axon growth. These data demonstrate the feasibility of nerve lengthening as a viable graft-free strategy for repairing chronically injured nerves. Not unexpectedly, outcomes for chronic nerve injuries were less favorable in both groups compared to repair of acutely injured nerves. Nonetheless, the findings provide insight into barriers to restoring function after chronic nerve injury through novel comprehensive characterization of a diverse set of neuromuscular outcomes. This analysis revealed key parameters predicting functional recovery.

Does cryoneurolysis result in persistent motor deficits? A controlled study using a rat peroneal nerve injury model.

BACKGROUND: Cryoneurolysis of peripheral nerves uses localised intense cold to induce a prolonged block over multiple weeks that has the promise of providing potent analgesia outlasting the duration of postoperative pain following surgery, as well as treat other acute and chronic pain states. However, it remains unclear whether persistent functional motor deficits remain following cryoneurolysis of mixed sensorimotor peripheral nerves, greatly limiting clinical application of this modality. To help inform future research, we used a rat peroneal nerve injury model to evaluate if cryoneurolysis results in persistent deficits in motor function. METHODS: Male Lewis rats (n=30) had their common peroneal nerves exposed bilaterally at the proximal lateral margin of the knee and subsequently underwent cryoneurolysis on one limb and sham treatment on the contralateral limb. Outcomes were evaluated on days 3, 14, 30, 90 and 180. The primary end point was motor function, based on ankle dorsiflexion torque. In addition, sensory function was tested based on von Frey's filament sensitivity to the peroneal sensory distribution. A subset of animals was sacrificed following functional testing at each time point, and general tissue morphology, connective tissue deposition, and axon counts were evaluated. RESULTS: Motor deficits in treated limbs were observed at 3 and 14 days but had resolved at time points beyond 1 month. Bilateral sensory deficits were also observed at 3 and 14 days, and also resolved within 1 month. Consistent with motor functional deficits, axon counts trended lower in treated nerves compared with contralateral controls at 3 days; however, axon counts were not significantly different at later time points. CONCLUSIONS: When applied to a mixed sensorimotor nerve, cryoneurolysis did not result in persistent motor deficits.

Decoupled epineurial and axonal deformation in mouse median and ulnar nerves.

INTRODUCTION: Peripheral nerves accommodate mechanical loads during joint movement. Hypothesized protective features include increased nerve compliance near joints and axonal undulation. How axons perceive nerve deformation is poorly understood. We tested whether nerves increase local axonal undulation in regions of high epineurial strain to protect nerve fibers from strain-induced damage. METHODS: Regional epineurial strain was measured near the elbow in median and ulnar nerves of mice expressing axonal fluorescence before and after decompression. Regional axonal tortuosity was quantified under confocal microscopy. RESULTS: Nerves showed higher epineurial strain just distal to the medial epicondyle; these differences were eliminated after decompression. Axonal tortuosity also varied regionally; however, unlike in the epineurium, it was greater in proximal regions. DISCUSSION: In this study we have proposed a neuromechanical model whereby axons can unravel along their entire length due to looser mechanical coupling to the peri/epineurium. Our findings have major implications for understanding nerve biomechanics and dysfunction. Muscle Nerve 59:619-619, 2019.

Síndrome de rumiación: dificultades diagnósticas y terapéuticas de un proceso no tan infrecuente / Rumination syndrome: Diagnostic and therapeutic difficulties of a not so uncommon disorder

Introducción: El Síndrome de rumiación es un trastorno gastrointestinal funcional poco común. De diagnóstico difícil, por el desconocimiento del mismo dentro del colectivo médico, acaba conllevando la realización de múltiples pruebas complementarias, la aplicación de diferentes tratamientos, y diagnósticos tardíos o erróneos, en la mayoría de los casos. Su tratamiento es difícil y complejo dada su naturaleza multifactorial. El objetivo de este estudio es presentar nuestra casuística analizando sus datos clínicos, diagnósticos y terapéuticos. Pacientes y método: Estudio descriptivo y retrospectivo de todos los casos diagnosticados entre enero del 2010 y mayo del 2016, controlados en las unidades de Gastroenterología Pediátrica del Consorci Sanitari de Terrassa y del Hospital Materno-Infantil Vall d'Hebron. Resultados: Se analizó a un total de 12 pacientes. Una media de edad al inicio de los síntomas de 9 anos y un mes, con un tiempo medio de evolución antes de llegar al diagnóstico de 2 años y 3 meses, y una media de pruebas complementarias realizadas hasta del diagnóstico de 8,1. En 10 de los 12 pacientes se había probado, antes del diagnóstico de rumiación, algún tipo de tratamiento que resultó ineficaz en todos los casos. Como novedad terapéutica, 10 de nuestros casos se sometieron a un tratamiento experimental de biofeedback. Conclusiones: Debido al conocimiento limitado de esta entidad, entre nuestros profesionales, en cuanto a su presentación clínica, diagnóstico y tratamiento, estos pacientes son frecuentemente mal diagnosticados y, a menudo, se ven sometidos a pruebas complementarias y tratamientos evitables, invasivos y costosos (AU)

Introduction: Rumination syndrome is an uncommon gastrointestinal functional disorder that may be difficult to diagnose, as not many physicians are aware of this condition. In many cases, patients undergo numerous tests and are prescribed several treatments based on erroneous diagnoses. When the correct diagnosis is eventually made, therapy for the syndrome can be difficult and complex because of its multifactorial nature. The aim of this study was to present our experience with this condition, by presenting an analysis of the clinical, diagnostic, and therapeutic data of our patients. Patients and method: A prospective and retrospective study was conducted on all cases of rumination syndrome diagnosed between January 2010 and May 2016 in patients attending the Paediatric Gastroenterology Departments of two hospitals: Consorci Sanitari de Terrassa and Hospital Materno-Infantil Vall d’Hebron (Barcelona, Spain). Results: The analysis included 12 patients, with a mean age at the onset of symptoms of 9 years and 1 month, and the mean time period to make the diagnosis was 2 years and 3 months. A mean of 8.1 complementary tests were carried out before establishing the diagnosis. In 10 of the 12 patients, some type of treatment had been given before the diagnosis of rumination syndrome, but was unsuccessful in all cases. Ten of our patients underwent the novel, experimental biofeedback therapy. Conclusions: Due to the limited knowledge of this condition among attending professionals in terms of the clinical presentation, diagnosis, and treatment, patients with rumination syndrome are often misdiagnosed and undergo numerous avoidable complementary tests, and invasive, costly treatments (AU)

[Rumination syndrome: Diagnostic and therapeutic difficulties of a not so uncommon disorder]. / Síndrome de rumiación: dificultades diagnósticas y terapéuticas de un proceso no tan infrecuente.

INTRODUCTION: Rumination syndrome is an uncommon gastrointestinal functional disorder that may be difficult to diagnose, as not many physicians are aware of this condition. In many cases, patients undergo numerous tests and are prescribed several treatments based on erroneous diagnoses. When the correct diagnosis is eventually made, therapy for the syndrome can be difficult and complex because of its multifactorial nature. The aim of this study was to present our experience with this condition, by presenting an analysis of the clinical, diagnostic, and therapeutic data of our patients. PATIENTS AND METHOD: A prospective and retrospective study was conducted on all cases of rumination syndrome diagnosed between January 2010 and May 2016 in patients attending the Paediatric Gastroenterology Departments of two hospitals: Consorci Sanitari de Terrassa and Hospital Materno-Infantil Vall d'Hebron (Barcelona, Spain). RESULTS: The analysis included 12 patients, with a mean age at the onset of symptoms of 9 years and 1 month, and the mean time period to make the diagnosis was 2 years and 3 months. A mean of 8.1 complementary tests were carried out before establishing the diagnosis. In 10 of the 12 patients, some type of treatment had been given before the diagnosis of rumination syndrome, but was unsuccessful in all cases. Ten of our patients underwent the novel, experimental biofeedback therapy. CONCLUSIONS: Due to the limited knowledge of this condition among attending professionals in terms of the clinical presentation, diagnosis, and treatment, patients with rumination syndrome are often misdiagnosed and undergo numerous avoidable complementary tests, and invasive, costly treatments.

mTOR regulates peripheral nerve response to tensile strain.

While excessive tensile strain can be detrimental to nerve function, strain can be a positive regulator of neuronal outgrowth. We used an in vivo rat model of sciatic nerve strain to investigate signaling mechanisms underlying peripheral nerve response to deformation. Nerves were deformed by 11% and did not demonstrate deficits in compound action potential latency or amplitude during or after 6 h of strain. As revealed by Western blotting, application of strain resulted in significant upregulation of mammalian target of rapamycin (mTOR) and S6 signaling in nerves, increased myelin basic protein (MBP) and ß-actin levels, and increased phosphorylation of neurofilament subunit H (NF-H) compared with unstrained (sham) contralateral nerves (P < 0.05 for all comparisons, paired two-tailed t-test). Strain did not alter neuron-specific ß3-tubulin or overall nerve tubulin levels compared with unstrained controls. Systemic rapamycin treatment, thought to selectively target mTOR complex 1 (mTORC1), suppressed mTOR/S6 signaling, reduced levels of MBP and overall tubulin, and decreased NF-H phosphorylation in nerves strained for 6 h, revealing a role for mTOR in increasing MBP expression and NF-H phosphorylation, and maintaining tubulin levels. Consistent with stretch-induced increases in MBP, immunolabeling revealed increased S6 signaling in Schwann cells of stretched nerves compared with unstretched nerves. In addition, application of strain to cultured adult dorsal root ganglion neurons showed an increase in axonal protein synthesis based on a puromycin incorporation assay, suggesting that neuronal translational pathways also respond to strain. This work has important implications for understanding mechanisms underlying nerve response to strain during development and regeneration.NEW & NOTEWORTHY Peripheral nerves experience tensile strain (stretch) during development and movement. Excessive strain impairs neuronal function, but moderate strains are accommodated by nerves and can promote neuronal growth; mechanisms underlying these phenomena are not well understood. We demonstrated that levels of several structural proteins increase following physiological levels of nerve strain and that expression of a subset of these proteins is regulated by mTOR. Our work has important implications for understanding nerve development and strain-based regenerative strategies.

Aspectos prácticos para la manometría esofágica de alta resolución / Practical aspects of high resolution esophageal manometry

La manometría esofágica de alta resolución (MAR) está en fase de desarrollo, como se evidencia por las diferentes clasificaciones de Chicago. Con el fin de unificar criterios en algunos aspectos prácticos con limitada evidencia científica se llevó a cabo la Primera Reunión Nacional de Consenso en Manometría de Alta Resolución del Grupo Español de Motilidad Digestiva, en la que participaron un amplio grupo de expertos. Las propuestas se basaron en una encuesta previa con 47 preguntas, la exhaustiva revisión de la bibliografía disponible y la experiencia de los participantes. Se plantearon aspectos metodológicos sobre criterios de análisis poco definidos de algunos nuevos parámetros de alta resolución y otros aspectos no considerados, como la actividad espontánea o las ondas secundarias, elaborándose conclusiones finales con utilidad práctica (AU)

High resolution esophageal manometry (HRM) is currently under development as can be seen in the various Chicago classifications. In order to standardize criteria in certain practical aspects with limited scientific evidence, the First National Meeting for Consensus in High Resolution Manometry of the Spanish Digestive Motility Group took place, bringing together a wide group of experts. The proposals were based on a prior survey composed of 47 questions, an exhaustive review of the available literature and the experience of the participants. Methodological aspects relating to the poorly defined analysis criteria of certain new high resolution parameters were discussed, as well as other issues previously overlooked such as spontaneous activity or secondary waves. Final conclusions were drawn with practical application (AU)

Practical aspects of high resolution esophageal manometry.

High resolution esophageal manometry (HRM) is currently under development as can be seen in the various Chicago classifications. In order to standardize criteria in certain practical aspects with limited scientific evidence, the First National Meeting for Consensus in High Resolution Manometry of the Spanish Digestive Motility Group took place, bringing together a wide group of experts. The proposals were based on a prior survey composed of 47 questions, an exhaustive review of the available literature and the experience of the participants. Methodological aspects relating to the poorly defined analysis criteria of certain new high resolution parameters were discussed, as well as other issues previously overlooked such as spontaneous activity or secondary waves. Final conclusions were drawn with practical applications.