Left or right ear? A neuroimaging study using combined taVNS/fMRI to understand the interaction between ear stimulation target and lesion location in chronic stroke

BACKGROUND

Implanted vagus nerve stimulation (VNS) and transcutaneous auricular VNS (taVNS) have been primarily administered clinically to the unilateral-left vagus nerve. This left-only convention has proved clinically beneficial in brain disorders. However, in stroke survivors, the presence of a lesion in the brain may complicate VNS-mediated signaling, and it is important to understand the laterality effects of VNS in stroke survivors to optimize the intervention.

OBJECTIVE

To understand whether taVNS delivered to different ear targets relative to the lesion (ipsilesional vs contralesional vs bilateral vs sham) impacts blood oxygenation level dependent (BOLD) signal propagation in stroke survivors.

METHODS

We enrolled 20 adults with a prior history of stroke. Each participant underwent a single visit, during which taVNS was delivered concurrently during functional magnetic resonance imaging (fMRI) acquisition. Each participant received three discrete active stimulation conditions (ipsilesional, contralesional, bilateral) and one sham condition in a randomized order. Stimulation-related BOLD signal changes in the active conditions were compared to sham conditions to understand the interaction taVNS and laterality effects.

RESULTS

All active taVNS conditions deactivated the contralesional default mode network related regions compared to sham, however only ipsilesional taVNS enhanced the activations in the ipsilesional visuomotor and secondary visual cortex. Furthermore, we reveal an interaction in task activations between taVNS and cortical visuomotor areas, where ipsilesional taVNS significantly increased ipsilesional visuomotor activity and decreased contralesional visuomotor activity compared to sham.

CONCLUSION

Laterality of taVNS relative to the lesion is a critical factor in optimizing taVNS in a stroke population, with ipsilesional stimulation providing largest direct brain activation and should be explored further when designing taVNS studies in neurorehabilitation.

Transcranial Direct Current Stimulation for Chronic Stroke: Is Neuroimaging the Answer to the Next Leap Forward?

During rehabilitation, a large proportion of stroke patients either plateau or begin to lose motor skills. By priming the motor system, transcranial direct current stimulation (tDCS) is a promising clinical adjunct that could augment the gains acquired during therapy sessions. However, the extent to which patients show improvements following tDCS is highly variable. This variability may be due to heterogeneity in regions of cortical infarct, descending motor tract injury, and/or connectivity changes, all factors that require neuroimaging for precise quantification and that affect the actual amount and location of current delivery. If the relationship between these factors and tDCS efficacy were clarified, recovery from stroke using tDCS might be become more predictable. This review provides a comprehensive summary and timeline of the development of tDCS for stroke from the viewpoint of neuroimaging. Both animal and human studies that have explored detailed aspects of anatomy, connectivity, and brain activation dynamics relevant to tDCS are discussed. Selected computational works are also included to demonstrate how sophisticated strategies for reducing variable effects of tDCS, including electric field modeling, are moving the field ever closer towards the goal of personalizing tDCS for each individual. Finally, larger and more comprehensive randomized controlled trials involving tDCS for chronic stroke recovery are underway that likely will shed light on how specific tDCS parameters, such as dose, affect stroke outcomes. The success of these collective efforts will determine whether tDCS for chronic stroke gains regulatory approval and becomes clinical practice in the future.

Acetabular Wall Weakening in Total Hip Arthroplasty: A Pilot Study

Total hip arthroplasty is a widely performed operation allowing disabled patients to improve their quality of life to a degree greater than any other elective procedure. Planning for a THA requires adequate patient assessment and preoperative characterizations of acetabular bone loss via radiographs and specific classification schemes. Some surgeons may be inclined to ream at a larger diameter thinking it would lead to a more stable press-fit, but this could be detrimental to the acetabular wall, leading to intraoperative fracture. In the attempt to reduce the incidence of intraoperative fractures, the current study aims to identify how increased reaming diameter degrades and weakens the acetabular rim strength. We hypothesized that there is proportionality between the reaming diameter and the reduction in acetabular strength. To test this hypothesis, this study used bone surrogates, templated from CT scans, and reamed at different diameters. The obtained bone surrogate models were then tested using an Intron 8874 mechanical testing machine (Instron, Norwood, MA) equipped with a custom-made fixture. Analysis of variance (ANOVA) was used to identify differences among reamed diameters while linear regression was used to identify the relationship between reamed diameters and acetabular strength. We found a moderate correlation between increasing reaming diameter that induced thinning of the acetabular wall and radial load damage. For the simplified acetabular model used in this study, it supported our hypothesis and is a promising first attempt in providing quantitative data for acetabular weakening induced by reaming.

Abstract 1: Vagus Nerve Stimulation Paired With Rehabilitation For Upper Limb Motor Function After Ischaemic Stroke: Sub-group Analysis Of The Randomised, Blinded, Pivotal, Vns-Rehab Device Trial

Background: Vagus Nerve Stimulation (VNS) paired with rehabilitation improved upper extremity impairment and function in a recent pivotal, randomised, blinded, sham-controlled trial. Here we report post-hoc sub-group analyses from the VNS Rehab trial. We aimed to determine whether treatment effects were consistent across subgroups.

Methods: VNS Rehab included 108 participants with moderate to severe arm /hand weakness, at least nine months after ischaemic stroke. They were randomised to receive rehabilitation paired with active VNS or rehabilitation paired with sham stimulation (Control). The primary outcome was the change in iFugl-Meyer Assessment Upper Extremity (FMA-UE) score on the first day after completion of in-clinic therapy. The trial was registered on ClinicalTrials.gov (NCT03131960). We explored the effect of VNS treatment by sex (n=70 males; n=38 females), age (≤ 65 or >65 years)), time from stroke (median time, 2 years) and baseline FMA-UE score (<=33 severe, >33 moderate). We assessed whether there was any interaction with treatment. No hypotheses were specified prior to this analysis and no formal adjustment was made for multiplicity.

Findings: On the first day after completion of in-clinic therapy, the mean (±SD) FMA-UE score increased by 5.0 points (SD 4.4) in the VNS group and by 2.4 points (SD 3.8) in the Control group (p=0.001, between group difference 2.6, 95% CI 1.03 to 4.2). The between group difference was similar across all subgroups (figure). No significant treatment interactions were observed with baseline characteristics.

Interpretation: Participants with moderate to severe arm and hand impairment after ischaemic stroke showed clinically meaningful improvements in motor impairment and function with rehabilitation paired with VNS compared to rehabilitation with sham VNS. The response appeared similar across pre-defined subgroups of interest.

Hypermobile Ehlers-Danlos syndromes: Complex phenotypes, challenging diagnoses, and poorly understood causes

The Ehlers-Danlos syndromes (EDS) are a group of heritable, connective tissue disorders characterized by joint hypermobility, skin hyperextensibility, and tissue fragility. There is phenotypic and genetic variation among the 13 subtypes. The initial genetic findings on EDS were related to alterations in fibrillar collagen, but the elucidation of the molecular basis of many of the subtypes revealed several genes not involved in collagen biosynthesis or structure. However, the genetic basis of the hypermobile type of EDS (hEDS) is still unknown. hEDS is the most common type of EDS and involves generalized joint hypermobility, musculoskeletal manifestations, and mild skin involvement along with the presence of several comorbid conditions. Variability in the spectrum and severity of symptoms and progression of patient phenotype likely depend on age, gender, lifestyle, and expression domains of the EDS genes during development and postnatal life. In this review, we summarize the current molecular, genetic, epidemiologic, and pathogenetic findings related to EDS with a focus on the hypermobile type.

Abstract TMP48: Subcortical Volumes Associated With Post-Stroke Motor Performance Vary Across Impairment Severity, Time Since Stroke, and Lesion Laterality: an ENIGMA Stroke Recovery Analysis

Associations between subcortical gray matter volume and motor performance post-stroke are unclear, partly because many stroke MRI studies are underpowered. Potential influences of the severity of motor impairment, lesion laterality, and time since stroke on these associations is also unknown.

Here, we addressed these questions using a large dataset (n=629) from the ENIGMA Stroke Recovery working group (http://enigma.usc.edu). Regression analyses examined brain volumes as predictors of motor scores. ENIGMA FreeSurfer protocols extracted volumes from 16 subcortical regions on T1-weighted MRIs; segmentations were manually quality controlled. Motor scores were calculated as a percentage of the maximum possible score (100% = no impairment). Covariates (e.g., age, sex, intracranial volume) were modeled. Statistical significance was assessed nonparametrically by permutation. Separate analyses were performed, stratifying by motor severity and time since stroke. Each analysis was also subdivided by lesioned hemisphere.

The motor severity analysis (Table 1A) used subgroups of mild (66.7-99.9%), moderate (33.3-66.6%), and severe (0-33.2%). Significant associations were found for mild and moderate, but not severe, stroke; only the left hemisphere stroke group showed further significant results.

The time since stroke analysis (Table 1B) used subgroups of acute (<1 month), subacute (1-6 months), and chronic (>6 months). Significant associations were found in chronic stroke, but not acute, subacute. Left versus right hemisphere lesions generated different results in chronic stroke.

Overall, these results show that the most significant associations between subcortical volumes and motor outcomes are in chronic mild-to-moderate stroke. Stroke subgroups may recover via disparate mechanisms; establishing biomarkers of impairment and disability across stroke subgroups may be useful for clinical trials.

Transcranial Direct Current Stimulation Post-Stroke Upper Extremity Motor Recovery Studies Exhibit a Dose-Response Relationship

BACKGROUND AND PURPOSE

Transcranial direct current stimulation (tDCS) has shown mixed results in post-stroke motor recovery, possibly because of tDCS dose differences. The purpose of this meta-analysis was to explore whether the outcome has a dose-response relationship with various dose-related parameters.

METHODS

The literature was searched for double-blind, randomized, sham-controlled clinical trials investigating the role of tDCS (≥5 sessions) in post-stroke motor recovery as measured by the Fugl-Meyer Upper Extremity (FM-UE) scale. Improvements in FM-UE scores were compared between active and sham groups by calculating standardized mean differences (Hedge's g) to derive a summary effect size. Inverse-variance-weighted linear meta-regression across individual studies was performed between various tDCS parameters and Hedge's g to test for dose-response relationships.

RESULTS

Eight studies with total of 213 stroke subjects were included. Summary Hedge's g was statistically significant in favor of the active group (Hedge's g = 0.61, p = 0.02) suggesting moderate effect. Specifically, studies that used bihemispheric tDCS montage (Hedge's g = 1.30, p = 0.08) or that recruited chronic stroke patients (Hedge's g = 1.23, p = 0.02) showed large improvements in the active group. A positive dose-response relationship was found with current density (p = 0.017) and charge density (p = 0.004), but not with current amplitude. Moreover, a negative dose-response relationship was found with electrode size (p < 0.001, smaller electrodes were more effective).

CONCLUSIONS

Our meta-analysis and meta-regression results suggest superior motor recovery in the active group when compared to the sham group and dose-response relationships relating to electrode size, charge density and current density. These results need to be confirmed in future dedicated studies.

Review of transcranial direct current stimulation in poststroke recovery

Motor impairment, dysphagia, aphasia, and visual impairment are common disabling residual deficits experienced by stroke survivors. Recently, many novel rehabilitative modalities have been investigated for their potential to ameliorate such deficits and to improve functional outcomes. Noninvasive brain stimulation techniques, such as transcranial direct current stimulation (tDCS), have emerged as a promising tool to facilitate stroke recovery. tDCS can alter cortical excitability to induce brain plasticity by modulating the lesioned, contralesional, or bilateral hemispheres with various stimulation modalities. Along with peripheral therapies, tDCS can lead to subsequent sustained behavioral and clinical gains in patients with stroke. In this review, we summarize characteristics of tDCS (method of stimulation, safety profile, and mechanism) and its application in the treatment of various stroke-related deficits, and we highlight future directions for tDCS in this capacity.

Abstract WP44: Acute Damage to Corticospinal Tract Detected by Diffusional Kurtosis Correlates with Motor Outcome at 3 Months After Stroke - A Preliminary Report

Background: Diffusional kurtosis imaging (DKI) is a recently developed diffusion MRI method that yields, in addition to conventional diffusion information, the diffusional kurtosis (K) and white-matter-specific metrics (WMM) that may better characterize tissue microstructure after stroke. This study aims to quantitatively test the hypothesis that motor impairment 3 months post- stroke is correlated with the acute damage to the corticospinal tract (CST) measured by kurtosis metrics.

Methods: DKI was acquired from 15 first-time acute ischemic stroke patients in the acute phase (within 48 hours) with various degrees of motor deficit. Patients were assessed at baseline (between 2 to 5 days from onset of symptom) and at 90 days (+/- 14 days) after stroke using the Fugl-Meyer Motor Scale (FMMS). Kurtosis metrics, including WMM (intra-axonal diffusivity (D a ), extra-axonal axial (D e,// ) and radial (D e,// ) diffusivity ) as well as fractional anisotropy (FA), mean diffusivity (MD), mean Kurtosis (MK) were measured in the lesional CST. Correlation analyses were applied among these metrics and FMMS at 90 days.

Results: Corticospinal tract intra-axonal environment was altered by acute ischemia. D a ( r = 0.75, p = 0.001) and D e,// ( r = 0.52, p=0.048) measured in the acute phase correlated with motor outcome at 3 months. FA, MD, MK and D e,// showed no significant correlations.

Conclusions: The preliminary data supports acute damage to CST detected by WMM with DKI correlated with motor outcome at 3 months. The WMM has potential to be an early imaging biomarker for motor outcome prediction.

Early insulin therapy prevents beta cell loss in a mouse model for permanent neonatal diabetes (Munich Ins2(C95S))

AIMS

Heterozygous male Munich Ins2(C95S) mutant mice, a model for permanent neonatal diabetes mellitus, demonstrate a progressive diabetic phenotype with severe loss of functional beta cell mass. The aim of this study was to investigate the influence of early insulin treatment on glucose homeostasis and beta cell destruction in male Munich Ins2(C95S) mutants.

METHODS

One group of male Ins2(C95S) mutants was treated with subcutaneous insulin pellets, as soon as blood glucose levels began to rise; placebo-treated mutants and wild-type mice served as controls. An additional group of mutant mice received a sodium-dependent glucose transporter 2 (SGLT2) inhibitor (AVE2268) via rodent chow.

RESULTS

Insulin treatment normalised blood glucose concentrations, improved oral glucose tolerance, preserved insulin sensitivity and inhibited oxidative stress of Munich Ins2(C95S) mutant mice. Pancreatic C-peptide content, as well as total beta cell and isolated beta cell volumes, of insulin-treated mutant mice were higher than those of placebo-treated mutants. In addition, alpha cell dysfunction and hyperplasia of non-beta cells were completely normalised in insulin-treated mutant mice. Treatment with the SGLT2 inhibitor lowered blood glucose, improved glucose tolerance and normalised insulin sensitivity as well as oxidative stress of Ins2(C95S) mutants. The abundance of the endoplasmic reticulum (ER) stress markers binding Ig protein (BiP) and phosphorylated eukaryotic translation initiation factor 2 alpha (P-eIF2α) was significantly increased in the islets of mutants, before onset of hyperglycaemia, vs wild-type mice.

CONCLUSIONS

We conclude that early insulin treatment protects Munich Ins2(C95S) mutant mice from insulin resistance, alpha cell hyperfunction, beta cell loss and hyperplasia of non-beta cells, some well-known features of human diabetes mellitus. Therefore, insulin treatment may be considered early for human patients harbouring INS mutations.

Phenotypic and pathomorphological characteristics of a novel mutant mouse model for maturity-onset diabetes of the young type 2 (MODY 2)

Several mutant mouse models for human diseases such as diabetes mellitus have been generated in the large-scale Munich ENU (N-ethyl-N-nitrosourea) mouse mutagenesis project. The aim of this study was to identify the causal mutation of one of these strains and to characterize the resulting diabetic phenotype. Mutants exhibit a T to G transversion mutation at nt 629 in the glucokinase (Gck) gene, leading to an amino acid exchange from methionine to arginine at position 210. Adult Munich Gck(M210R) mutant mice demonstrated a significant reduction of hepatic glucokinase enzyme activity but equal glucokinase mRNA and protein abundances. While homozygous mutant mice exhibited growth retardation and died soon after birth in consequence of severe hyperglycemia, heterozygous mutant mice displayed only slightly elevated blood glucose levels, present from birth, with development of disturbed glucose tolerance and glucose-induced insulin secretion. Additionally, insulin sensitivity and fasting serum insulin levels were slightly reduced in male mutant mice from an age of 90 days onward. While beta-cell mass was unaltered in neonate heterozygous and homozygous mutant mice, the total islet and beta-cell volumes and the total volume of isolated beta-cells were significantly decreased in 210-day-old male, but not female heterozygous mutant mice despite undetectable apoptosis. These findings indicate that reduced total islet and beta-cell volumes of male mutants might emerge from disturbed postnatal islet neogenesis. Considering the lack of knowledge about the pathomorphology of maturity-onset diabetes of the young type 2 (MODY 2), this glucokinase mutant model of reduced total islet and total beta-cell volume provides the opportunity to elucidate the impact of a defective glucokinase on development and maintenance of beta-cell mass and its relevance in MODY 2 patients.

Rare or remarkable microfungi from Oaxaca (south Mexico)--Part II

Microfungi were collected in southern Mexico in the vicinity of Puerto Escondido, Oaxaca in 2007. In 2006, samples were gathered from Acacia myrmecophytes [(Remarkable microfungi from Oaxaca of Acacia species) Part I]. In the present investigation [Part II], we collected microfungi from different parts of a variety of wild and cultivated higher plants belonging to the families Anacardiaceae, Caricaceae, Fabaceae, Moraceae, and Nyctaginacae. The microfungi found here live as parasites or saprophytes. Interestingly, the species Colletotrichum lindemuthianum (Sacc. and Magn.) Briosi and Cavara has repeatedly been used to cause fungal infections of Phaseolus lunatus leaves in laboratory experiments. We could now find the same fungus as parasite on the same host plants under field conditions showing that results obtained in the laboratory are also relevant in nature. Most of the fungal species collected belong to the classes Ascomycotina, Basidiomycotina and Deuteromycotina. Until now, some of the microfungi identified in this study have been rarely observed before or have been reported for the first time in Mexico, for example: Pestalotia acaciae Thüm. on Acacia collinsii Safford; Corynespora cassiicola (Berk. and M.A. Curtis) C.T. Wei on Carica papaya L.; Botryosphaeria ribis Grossenb. and Duggar and Cercosporella leucaenae (Raghu Ram and Mallaiah) U. Braun (new for Mexico) and Camptomeris leucaenae (F. Stevens and Dalbey) Syd. (new for Mexico) on Leucaena leucocephala (Lam.) de Wit.; Oidium clitoriae Narayanas. and K. Ramakr. and Phakopsora cf. pachyrhizi Sydow and Sydow (new for Mexico) on Clitoria ternatea L.; Botryosphaeria obtusa (Schw.) Shoemaker on Prosopis juliflora (Sw.) DC.; Cylindrocladium scoparium Morg. on Ficus benjamina L.; Acremonium sp. on Bougainvillea sp. All specimens are located in the herbarium ESS. Mycotheca Parva collection G.B. Feige and N. Ale-Agha.

Physiological response to cycling with both circular and noncircular chainrings

The purpose of this study was to compare physiological variables of endurance-trained cyclists riding with four different chainring designs: round, Shimano Biopace, and two engineered ellipse designs. The ellipse designated Eng10 had the crank arm oriented 10 degrees forward of the major (i.e. longer) axis. Eighty degrees further forward, along the minor axis, was the crank arm orientation for the second ellipse, Eng90. With the major to minor axis ratio of 22.9 cm/16.8 cm (1.36), both ellipses imposed a crank angular velocity variation of 27% relative to the highest velocity assuming constant chain velocity. Best described as a skewed ellipse (i.e., major and minor axes not perpendicular), the Biopace had a major to minor axis ratio of 1.09 thus giving a crank angular velocity variation of 8%. Eleven male cyclists rode at a high (80% of maximum VO2) and a low (60% of maximum VO2) workrate using each chainring. The study was conducted over four consecutive days with the presentation order of the chainrings randomized. Open circuit spirometry was used to collect continuous respiratory data. Heart rate, blood lactate, and cadence values also were measured. None of the physiological variables including rates of oxygen consumption showed significant differences among the chainrings. Thus, the gross efficiency of cycling was not improved by any of the noncircular chainrings. For cycling events where efficiency is a determinant of performance, the noncircular chainrings do not offer any advantage over round chainrings.

Characterization of pGA1, a new plasmid from Corynebacterium glutamicum LP-6

A new plasmid, pGA1, has been isolated from Corynebacterium glutamicum LP-6, and its detailed restriction map has been prepared. The 4.9-kb plasmid has a G + C content of 57%. It replicates in C. glutamicum ATCC13032 and is compatible with the three other plasmids, pCC1, pBL1 and pHM1519, commonly used for vector construction for amino acid-producing corynebacteria. Fusions of pGA1 with different Escherichia coli replicons (transferred from E. coli to Corynebacterium via transformation of spheroplasts or by filter mating experiments with intact cells) are shown to be suitable as shuttle plasmids; some of them are highly stable in C. glutamicum, even when propagated without any selection pressure.

An angular velocity profile in cycling derived from mechanical energy analysis

The contributions of this article are twofold. One is procedure for determining the angular velocity profile in seated cycling that maintains the total mechanical energy of both legs constant. A five-bar linkage model (thigh, shank, foot, crank and frame) of seated (fixed hip) cycling served for the derivation of the equations to compute potential and kinetic energies of the leg segments over a complete crank cycle. With experimentally collected pedal angle data as input, these equations were used to compute the total combined mechanical energy (sum of potential and kinetic energies of the segments of both legs) for constant angular velocity pedalling at 90 rpm. Total energy varied indicating the presence of internal work. Motivated by a desire to test the hypothesis that reducing internal work in cycling will reduce energy expenditure, a procedure was developed for determining the angular velocity profile that eliminated any change in total energy. Using data recorded from five subjects, this procedure was used to determine a reference profile for an average equivalent cadence of 90 rpm. The phase of this profile is such that highest and lowest angular velocities occur when the cranks are near vertical and horizontal respectively. The second contribution is the testing of the hypothesis that the reference angular velocity profile serves to effectively reduce internal work for the subjects whose data were used to develop this profile over the range of pedalling rates (80-100 rpm) naturally preferred. In this range, the internal work was decreased a minimum of 48% relative to the internal work associated with constant angular velocity pedalling. The acceptance of this hypothesis has relevance to the protocol for future experiments which explore the effect of reduced internal work on energy expenditure in cycling.

Heterogenic mRNAs with an identical protein-coding region of the human embryonic myosin alkali light chain in skeletal muscle cells

The formation of human myotubes in culture is accompanied by the induction of developmentally regulated, muscle-specific genes. We have studied the expression of human myosin light chain proteins and mRNAs during myogenesis in culture, in particular the skeletal embryonic myosin light chain 1 (MC1emb), which is indistinguishable from MLC1 of adult atrial cardiac muscle (MLC1A) as has been shown for rodent and bovine MLC1emb. We have identified distinct MLC1emb/MLC1A mRNAs in cultured human skeletal muscle cells that differ in their 5' and 3' untranslated regions but contain identical protein-coding regions. The alternative 3' untranslated region is detectable also in RNA of human atria. The different MLC1emb RNAs are likely to be encoded by one gene. It appears that the two MLC1emb 5' untranslated regions of the human gene are specific for man. In the mouse, only one 5' untranslated region of the MLC1emb gene has been detected.