Mechanisms of action of acute and subacute sphenopalatine ganglion stimulation for ischemic stroke

Promising Cerebral Blood Flow Enhancers in Acute Ischemic Stroke

Ischemic stroke presents a major global economic and public health burden. Although recent advances in available endovascular therapies show improved functional outcome, a good number of stroke patients are either ineligible or do not have access to these treatments. Also, robust collateral flow during acute ischemic stroke independently predicts the success of endovascular therapies and the outcome of stroke. Hence, adjunctive therapies for cerebral blood flow (CBF) enhancement are urgently needed. A very clear overview of the pial collaterals and the role of genetics are presented in this review. We review available evidence and advancement for potential therapies aimed at improving CBF during acute ischemic stroke. We identified heme-free soluble guanylate cyclase activators; Sanguinate, remote ischemic perconditioning; Fasudil, S1P agonists; and stimulation of the sphenopalatine ganglion as promising potential CBF-enhancing therapeutics requiring further investigation. Additionally, we outline and discuss the critical steps required to advance research strategies for clinically translatable CBF-enhancing agents in the context of acute ischemic stroke models.

Neuromodulation for Post-Stroke Motor Recovery: a Narrative Review of Invasive and Non‑Invasive Tools

PURPOSE OF REVIEW

Stroke remains a leading disabling condition, and many survivors have permanent disability despite acute stroke treatment and subsequent standard-of-care rehabilitation therapies. Adjunctive neuromodulation is an emerging frontier in the field of stroke recovery. In this narrative review, we aim to highlight and summarize various neuromodulation techniques currently being investigated to enhance recovery and reduce impairment in patients with stroke.

RECENT FINDINGS

For motor recovery, repetitive transcranial magnetic simulation (rTMS) and direct current stimulation (tDCS) have shown promising results in many smaller-scale trials. Still, their efficacy has yet to be proven in large-scale pivotal trials. A promising large-scale study investigating higher dose tDCS combined with constraint movement therapy to enhance motor recovery is currently underway. MRI-guided tDCS studies in subacute and chronic post-stroke aphasia showed promising benefits for picture-naming recovery. rTMS, particularly inhibitory stimulation over the contralesional homolog, could represent a pathway forward in post-stroke motor recovery in the setting of a well-designed and adequately powered clinical trial. Recently evidenced-based guideline actually supported Level A (definite efficacy) for the use of low-frequency rTMS of the primary motor cortex for hand motor recovery in the post-acute stage of stroke based on the meta-analysis result. Adjunctive vagal nerve stimulation has recently received FDA approval to enhance upper limb motor recovery in chronic ischemic stroke with moderate impairment, and progress has been made to implement it in real-world practice. Despite a few small and large-scale studies in epidural stimulation (EDS), further research on the utilization of EDS in post-stroke recovery is needed. Deep brain stimulation or stent-based neuromodulation has yet to be further tested regarding safety and efficacy. Adjunctive neuromodulation to rehabilitation therapy is a promising avenue for promoting post-stroke recovery and decreasing the overall burden of disability. The pipeline for neuromodulation technology remains strong as they span from the preclinical stage to the post-market stage. We are optimistic to see that more neuromodulation tools will be available to stroke survivors in the not-to-distant future.

The Effect of Epipharyngeal Abrasive Therapy (EAT) on the Baroreceptor Reflex (BR)

Introduction Epipharyngeal Abrasive Therapy (EAT) has been used as a treatment for chronic epipharyngitis, and although autonomic nerve stimulation has been pointed out as one of the mechanisms by which EAT produces therapeutic effects, there have been few reports examining this mechanism of action. This study investigated the effects of repeated EAT on autonomic nervous system activity in chronic epipharyngitis patients over time, using heart rate variability analysis. In addition, we conducted a loading test using the active standing test (AS test) to examine the effects of EAT on the baroreceptor reflex (BR). Subjects and methods A retrospective study was conducted on 39 patients who visited our clinic between July 2017 and November 2019 and underwent autonomic function tests with a diagnosis of chronic nasopharyngeal inflammation. The subjects were divided into two groups: the improvement group and the invariant group for comparison. Electrocardiographic recordings and blood pressure measurements were made under the stress of the AS test. Heart rate, high-frequency (HF) component, low-frequency (LF) component, and Coefficient of Variation on R-R interval were evaluated as indices of autonomic function. Component coefficient of variance high frequency was used as an index of parasympathetic function. ccvLF/ccvHF ratio was calculated by dividing the component coefficient of variance low frequency by ccvHF. The AS test was conducted in phase 1 in the initial resting sitting position, in phase 2 in the standing position, in phase 3 in the standing and holding the standing position, and in phase 4 in the seated and holding the sitting position. Systolic blood pressure, mean arterial pressure, and diastolic blood pressure were obtained in each phase. A paired t-test was used to compare the improved and invariant groups before and after treatment. The post-treatment comparison between the improved group and the invariant group was performed by unpaired t-test. Variation of the evaluation index over time was evaluated by repeated measures ANOVA. Multiple comparisons were corrected by the Bonferroni method. Results The EAT showed that parasympathetic activity was significantly suppressed in the improvement group, while the AS test showed significant fluctuations over time for the improvement and invariant groups. The interaction between the time course and the two factors in the improvement and invariant groups was not statistically evident. Although no significant difference was found, the improvement group showed a tendency to suppress parasympathetic activity and a tendency to stimulate sympathetic activity compared to the invariant group. Blood pressure in the improvement group showed a tendency to decrease. Conclusions EAT was found to suppress parasympathetic activity over time, and the AS test did not reveal an interaction effect of EAT on BR. However, there was a trend toward suppression of parasympathetic activity and stimulation of sympathetic activity in the improved group compared to the invariant group. Blood pressure in the improved group tended to decrease. It is possible that EAT may have a positive effect on autonomic neuropathy symptoms such as orthostatic dysregulation (OD), postural orthostatic tachycardia syndrome (POTS), etc. by stimulating the BRs. It is thought that the autonomic nervous system stimulating action and the immune system stimulating action act synergistically to express the therapeutic effect of EAT.

Therapeutic Induction of Collateral Flow

Therapeutic induction of collateral flow as a means to salvage tissue and improve outcome from acute ischemic stroke is a promising approach in the era in which endovascular therapy is no longer time-dependent but collateral-dependent. The importance of collateral flow enhancement as a therapeutic for acute ischemic stroke extends beyond those patients with large amounts of salvageable tissue. It also has the potential to extend the time window for reperfusion therapies in patients who are ineligible for endovascular thrombectomy. In addition, collateral enhancement may be an important adjuvant to neuroprotective agents by providing a more robust vascular route for which treatments can gain access to at risk tissue. However, our understanding of collateral hemodynamics, including under comorbid conditions that are highly prevalent in the stroke population, has hindered the efficacy of collateral flow augmentation for improving stroke outcome in the clinical setting. This review will discuss our current understanding of pial collateral function and hemodynamics, including vasoactivity that is critical for enhancing penumbral perfusion. In addition, mechanisms by which collateral flow can be increased during acute ischemic stroke to limit ischemic injury, that may be different depending on the state of the brain and vasculature prior to stroke, will also be reviewed.

Zebrafish: A Model Deciphering the Impact of Flavonoids on Neurodegenerative Disorders

Over the past century, advances in biotechnology, biochemistry, and pharmacognosy have spotlighted flavonoids, polyphenolic secondary metabolites that have the ability to modulate many pathways involved in various biological mechanisms, including those involved in neuronal plasticity, learning, and memory. Moreover, flavonoids are known to impact the biological processes involved in developing neurodegenerative diseases, namely oxidative stress, neuroinflammation, and mitochondrial dysfunction. Thus, several flavonoids could be used as adjuvants to prevent and counteract neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Zebrafish is an interesting model organism that can offer new opportunities to study the beneficial effects of flavonoids on neurodegenerative diseases. Indeed, the high genome homology of 70% to humans, the brain organization largely similar to the human brain as well as the similar neuroanatomical and neurochemical processes, and the high neurogenic activity maintained in the adult brain makes zebrafish a valuable model for the study of human neurodegenerative diseases and deciphering the impact of flavonoids on those disorders.

The Potential Role of Neuromodulation in Subarachnoid Hemorrhage

OBJECTIVES

Aneurysmal subarachnoid hemorrhage (SAH) continues to be a difficult cerebrovascular disease with limited pharmacologic treatment options. Cerebral vasospasm (CV) and delayed cerebral ischemia (DCI) are leading causes of morbidity and mortality after SAH. Despite the advances in the understanding of its pathophysiology and tremendous efforts to date, nimodipine is currently the sole Food and Drug Administration-approved treatment for patients with SAH, with benefits that are marginal at best. The neuromodulation therapies are promising, especially those that target CV and DCI to improve functional outcomes. The aim of this review is therefore to summarize the available evidence for each type of neuromodulation for CV and DCI, with a special focus on its pathophysiological mechanisms, in addition to their clinical utility and drawbacks, which we hope will lead to future translational therapy options after SAH.

MATERIALS AND METHODS

We conducted a comprehensive review of preclinical and clinical studies demonstrating the use of neuromodulation for SAH. The literature search was performed using PubMed, Embase, and ClinicalTrials.gov. A total of 21 articles published from 1992 to 2021 and eight clinical trials were chosen.

RESULTS

The studies reviewed provide a compelling demonstration that neuromodulation is a potentially useful strategy to target multiple mechanisms of DCI and thus to potentially improve functional outcomes from SAH. There are several types of neuromodulation that have been tested to treat CV and DCI, including the trigeminal/vagus/facial nerve stimulation, sphenopalatine ganglion and spinal cord stimulation, transcranial direct electrical stimulation, transcutaneous electrical neurostimulation, and electroacupuncture. Most of them are in the preclinical or early phases of clinical application; however, they show promising results.

CONCLUSIONS

DCI has a complex pathogenesis, making the unique anatomical distribution and pleiotropic capabilities of various types of neuromodulation a promising field of study. We may be at the cusp of a breakthrough in the use of these techniques for the treatment of this stubbornly difficult disease.

Osteopathic Manipulation of the Sphenopalatine Ganglia Versus Sham Manipulation, in Obstructive Sleep Apnoea Syndrom: A Randomised Controlled Trial

(1) Background: osteopathic manipulation of the sphenopalatine ganglia (SPG) blocks the action of postganglionic sensory fibres. This neuromodulation can reduce nasal obstruction and enhance upper airway stability. We investigated the manipulation of the SPG in 31 patients with obstructive sleep apnoea syndrome (OSAS); (2) Methods: Randomised, controlled, double-blind, crossover study. Participants received active (AM), then sham manipulation (SM), or vice versa. The primary endpoint was apnoea-hypopnoea index (AHI). Secondary endpoints were variation of nasal obstruction evaluated by peak nasal inspiratory flow (PNIF) and upper airways stability evaluated by awake critical closing pressure [awake Pcrit]), at 30 min and 24 h. Schirmer’s test and pain were assessed immediately post-manipulation. Tactile/gustatory/olfactory/auditory/nociceptive/visual sensations were recorded. Adverse events were collected throughout. (3) Results: SPG manipulation did not reduce AHI (p = 0.670). PNIF increased post-AM but not post-SM at 30 min (AM-SM: 18 [10; 38] L/min, p = 0.0001) and 24 h (23 [10; 30] L/min, p = 0.001). There was no significant difference on awake Pcrit (AM-SM) at 30 min or 24 h). Sensations were more commonly reported post-AM (100% of patients) than post-SM (37%). Few adverse events and no serious adverse events were reported. (4) Conclusions: SPG manipulation is not supported as a treatment for OSAS but reduced nasal obstruction. This effect remains to be confirmed in a larger sample before using this approach to reduce nasal congestion in CPAP-treated patients or in mild OSAS.

Biomarkers of Angiogenesis and Neuroplasticity as Promising Clinical Tools for Stroke Recovery Evaluation

Several key issues impact the clinical practice of stroke rehabilitation including a patient’s medical history, stroke experience, the potential for recovery, and the selection of the most effective type of therapy. Until clinicians have answers to these concerns, the treatment and rehabilitation are rather intuitive, with standard procedures carried out based on subjective estimations using clinical scales. Therefore, there is a need to find biomarkers that could predict brain recovery potential in stroke patients. This review aims to present the current state-of-the-art stroke recovery biomarkers that could be used in clinical practice. The revision of biochemical biomarkers has been developed based on stroke recovery processes: angiogenesis and neuroplasticity. This paper provides an overview of the biomarkers that are considered to be ready-to-use in clinical practice and others, considered as future tools. Furthermore, this review shows the utility of biomarkers in the development of the concept of personalized medicine. Enhancing brain neuroplasticity and rehabilitation facilitation are crucial concerns not only after stroke, but in all central nervous system diseases.

Flavonoids as a Natural Enhancer of Neuroplasticity-An Overview of the Mechanism of Neurorestorative Action

Neuroplasticity is a complex physiological process occurring in the brain for its entire life. However, it is of particular importance in the case of central nervous system (CNS) disorders. Neurological recovery largely depends on the ability to reestablish the structural and functional organization of neurovascular networks, which must be pharmacologically supported. For this reason, new forms of therapy are constantly being sought. Including adjuvant therapies in standard treatment may support the enhancement of repair processes and restore impaired brain functions. The common hallmark of nerve tissue damage is increased by oxidative stress and inflammation. Thus, the studies on flavonoids with strong antioxidant and anti-inflammatory properties as a potential application in neuro intervention have been carried out for a long time. However, recent results have revealed another important property of these compounds in CNS therapy. Flavonoids possess neuroprotective activity, and promote synaptogenesis and neurogenesis, by, among other means, inhibiting oxidative stress and neuroinflammation. This paper presents an overview of the latest knowledge on the impact of flavonoids on the plasticity processes of the brain, taking into account the molecular basis of their activity.

Role of Non-Perfusion Factors in Mildly Symptomatic Large Vessel Occlusion Stroke

INTRODUCTION

Uncertainty regarding reperfusion of mildly-symptomatic (minor) large vessel occlusion (LVO)-strokes exists. Recently, benefits from reperfusion were suggested. However, there is still no strong data to support this. Furthermore, a proportion of those patients don't improve even after non-hemorrhagic reperfusion. Our study evaluated whether or not non-perfusion factors account for such persistent deconditioning.

METHODS

Patients with identified minor LVO-strokes (NIHSS ≤ 8) from our stroke alert registry between January-2016 and May-2018 were included. Variables/ predictors of outcome were tested using univariate/multivariate logistic and linear regression analyses. Three month-modified ranking scale (mRS) was used to differentiate between favorable (mRS = 0-2) and unfavorable outcomes (mRS = 3-6).

RESULTS

Eighty-one patients were included. Significant differences between the two outcome groups regarding admission-NIHSS and discharge-NIHSS existed (OR = 0.47, 0.49 / p = 0.0005, <0.0001 respectively).The two groups had matching perfusion measures. In the poor outcome group, discharge-NIHSS was unchanged from the admission-NIHSS while in the good outcome group, discharge-NIHSS significantly improved.

CONCLUSION

Admission and discharge NIHSS are independent predictors of outcome in patients with minor-LVO strokes. Unchanged discharge-NIHSS predicts worse outcomes while improved discharge-NIHSS predicts good outcomes. Unchanged NIHSS in the poor outcome group was independent of the perfusion parameters. In literature, complement activation and pro-inflammatory responses to ischemia might account for the progression of stroke symptoms in major-strokes. Our study concludes similar phenomena might be present in minor-strokes. Therefore, discharge-NIHSS may be useful as a clinical marker for future therapies.