Vagus nerve stimulation inhibits cortical spreading depression

Vagus Nerve Stimulation Paired with Tones for the Treatment of Tinnitus: A Prospective Randomized Double-blind Controlled Pilot Study in Humans

The aim of the pilot study was to evaluate the effect of Vagus Nerve Stimulation (VNS) paired with sounds in chronic tinnitus patients. All participants were implanted and randomized to a paired VNS (n = 16) or control (n = 14) group. After 6 weeks of home therapy, all participants received paired VNS. The device was used on 96% of days with good compliance. After 6 weeks, the paired VNS group improved on the Tinnitus Handicap Inventory (THI) (p = 0.0012) compared to controls (p = 0.1561). The between-group difference was 10.3% (p = 0.3393). Fifty percent of the participants in the paired VNS group showed clinically meaningful improvements compared to 28% in controls. At one year, 50% of participants had a clinically meaningful response. The therapy had greater benefits for participants with tonal and non-blast induced tinnitus at the end of 6 (24.3% vs. 2%, p = 0.05) and 12 weeks (34% vs. 2%, p = 0.004) compared to controls with 80% and 70% responding at 6 months and 1 year, respectively. Adverse effects were mild and well-tolerated and the therapy had a similar safety profile to VNS for epilepsy. VNS paired with tones may be effective for a subgroup of tinnitus patients and provides impetus for a larger pivotal study.

Novel Therapeutic Targets Against Spreading Depression

Migraine is among the most prevalent and disabling neurological diseases in the world. Cortical spreading depression (SD) is an intense wave of neuronal and glial depolarization underlying migraine aura, and a headache trigger, which has been used as an experimental platform for drug screening in migraine. Here, we provide an overview of novel therapeutic targets that show promise to suppress SD, such as acid-sensing ion channels, casein kinase Iδ, P2X7-pannexin 1 complex, and neuromodulation, and outline the experimental models and essential quality measures for rigorous and reproducible efficacy testing.

Current and novel insights into the neurophysiology of migraine and its implications for therapeutics

Migraine headache and its associated symptoms have plagued humans for two millennia. It is manifest throughout the world, and affects more than 1/6 of the global population. It is the most common brain disorder, and is characterized by moderate to severe unilateral headache that is accompanied by vomiting, nausea, photophobia, phonophobia, and other hypersensitive symptoms of the senses. While there is still a clear lack of understanding of its neurophysiology, it is beginning to be understood, and it seems to suggest migraine is a disorder of brain sensory processing, characterized by a generalized neuronal hyperexcitability. The complex symptomatology of migraine indicates that multiple neuronal systems are involved, including brainstem and diencephalic systems, which function abnormally, resulting in premonitory symptoms, ultimately evolving to affect the dural trigeminovascular system, and the pain phase of migraine. The migraineur also seems to be particularly sensitive to fluctuations in homeostasis, such as sleep, feeding and stress, reflecting the abnormality of functioning in these brainstem and diencephalic systems. Implications for therapeutic development have grown out of our understanding of migraine neurophysiology, leading to major drug classes, such as triptans, calcitonin gene-related peptide receptor antagonists, and 5-HT1F receptor agonists, as well as neuromodulatory approaches, with the promise of more to come. The present review will discuss the current understanding of the neurophysiology of migraine, particularly migraine headache, and novel insights into the complex neural networks responsible for associated neurological symptoms, and how interaction of these networks with migraine pain pathways has implications for the development of novel therapeutics.

Pathophysiology of Migraine: A Disorder of Sensory Processing

Plaguing humans for more than two millennia, manifest on every continent studied, and with more than one billion patients having an attack in any year, migraine stands as the sixth most common cause of disability on the planet. The pathophysiology of migraine has emerged from a historical consideration of the "humors" through mid-20th century distraction of the now defunct Vascular Theory to a clear place as a neurological disorder. It could be said there are three questions: why, how, and when? Why: migraine is largely accepted to be an inherited tendency for the brain to lose control of its inputs. How: the now classical trigeminal durovascular afferent pathway has been explored in laboratory and clinic; interrogated with immunohistochemistry to functional brain imaging to offer a roadmap of the attack. When: migraine attacks emerge due to a disorder of brain sensory processing that itself likely cycles, influenced by genetics and the environment. In the first, premonitory, phase that precedes headache, brain stem and diencephalic systems modulating afferent signals, light-photophobia or sound-phonophobia, begin to dysfunction and eventually to evolve to the pain phase and with time the resolution or postdromal phase. Understanding the biology of migraine through careful bench-based research has led to major classes of therapeutics being identified: triptans, serotonin 5-HT1B/1D receptor agonists; gepants, calcitonin gene-related peptide (CGRP) receptor antagonists; ditans, 5-HT1F receptor agonists, CGRP mechanisms monoclonal antibodies; and glurants, mGlu5 modulators; with the promise of more to come. Investment in understanding migraine has been very successful and leaves us at a new dawn, able to transform its impact on a global scale, as well as understand fundamental aspects of human biology.

Burst Spinal Cord Stimulation Increases Peripheral Antineuroinflammatory Interleukin 10 Levels in Failed Back Surgery Syndrome Patients With Predominant Back Pain

OBJECTIVES

Burst spinal cord stimulation (SCS) has been reported to reduce back pain and improve functional capacity in Failed Back Surgery Syndrome (FBSS). However, its mechanism of action is not completely understood. Systemic circulating cytokines have been associated with the development of chronic back pain.

METHODS

This prospective, feasibility study enrolled 12 refractory FBSS patients with predominant back pain (70% of overall pain) suitable for Burst SCS. Back and leg pain intensity (back pain [VAS_B ]/leg pain [VAS_L ]), functional capacity (sleep quality [PSQI]), depressive symptoms (BDI), body weight, stimulation parameters, and plasma levels of pro-inflammatory (Il-1b; TNF; HMGB1)/anti-inflammatory (Il-10) cytokines were collected at baseline and after three months of Burst SCS and compared to healthy controls.

RESULTS

Pain intensity (pre VAS_B : 8.25 ± 0.75 vs. post 1.42 ± 1.24) and functional capacity (PSQI: pre 7.92 ± 3.92 vs. post 3.42 ± 1.24; BDI: pre 20.83 ± 3.56 vs. post 10.92 ± 0.75) significantly improved compared to baseline. Pro-inflammatory HMGB1 remained unchanged (preburst: 3.35 ± 3.25 vs. postburst: 3.78 ± 3.83 ng/mL; p = 0.27; W = -30) versus the HC group (2.53 ± 2.6 ng/mL; p = 0.47; U = 59), while anti-inflammatory IL-10 levels were significantly elevated after burst SCS as compared to baseline (preburst 12.54 ± 22.95 vs. postburst 43.16 ± 74.71 pg/mL; p = 0.03; W = -48) and HC group (HC: 7.03 ± 11.6 vs. postburst 43.16 ± 74.71 pg/mL; p = 0.03; W = -48; p = 0.04). Baseline preburst IL-10 values and preburst VAS_B significantly correlated (Spearman correlation r = -0.66; p = 0.05; 95 CI -0.86 to -0.24), while correlation was not significant between postburst IL-10 values and postburst VAS_B (Spearman correlation r = -0.49; p = 0.18; 95 CI -0.83 to -0.15). Postburst IL-10 values correlated significantly with postburst PSQI scores (Spearman correlation r = -0.66; p = 0.05; 95 CI -0.86 to -0.24), while no correlation was found between preburst and postburst changes related to the BDI.

CONCLUSIONS

Burst SCS increased systemic circulating anti-inflammatory IL-10, improved FBSS back pain and back pain associated co-morbidities like disrupted sleep architecture and depressive symptoms in FBSS patients. Thus, suggesting a possible relationship between burst SCS and burst-evoked modulation of peripheral anti-inflammatory cytokine IL-10 in chronic back pain.

L-PGDS Mediates Vagus Nerve Stimulation-Induced Neuroprotection in a Rat Model of Ischemic Stroke by Suppressing the Apoptotic Response

The role of lipocalin prostaglandin D2 synthase (L-PGDS) in brain ischemia has not been fully clarified to date. Vagus nerve stimulation (VNS) protects against cerebral ischemia/reperfusion (I/R) injury, but the mechanisms involved need further exploration. This study investigated the role of L-PGDS in cerebral I/R and whether this process was involved in the mechanism of VNS-mediated neuroprotection. Male Sprague-Dawley rats were pretreated with a lentiviral vector (LV) through intracerebroventricular injection, followed by middle cerebral artery occlusion (MCAO) and VNS treatment. The expression of L-PGDS in the peri-infarct cortex was examined. The localization of L-PGDS was determined using double immunofluorescence staining. Neurologic scores, infarct volume and neuronal apoptosis were evaluated at 24 h after reperfusion. The expression of apoptosis-related molecules was measured by western blot analysis. The expression of L-PGDS in the peri-infarct cortex increased at 12 h, reached a peak at 24 h after reperfusion, and lasted up to 3 days. VNS treatment further enhanced the expression of L-PGDS following ischemic stroke. L-PGDS was mainly expressed in neurons in the peri-infarct cortex. I/R rats treated with VNS showed better neurological deficit scores, reduced infarct volume, and decreased neuronal apoptosis as indicated by the decreased levels of Bax and cleaved caspase-3 as well as increased levels of Bcl-2. Strikingly, the beneficial effects of VNS were weakened after L-PGDS down-regulation. In general, our results suggest that L-PGDS is a potential mediator of VNS-induced neuroprotection against I/R injury.

Chronic migraine headache prevention with noninvasive vagus nerve stimulation: The EVENT study

Objective:

To evaluate the feasibility, safety, and tolerability of noninvasive vagus nerve stimulation (nVNS) for the prevention of chronic migraine (CM) attacks.

Methods:

In this first prospective, multicenter, double-blind, sham-controlled pilot study of nVNS in CM prophylaxis, adults with CM (≥15 headache d/mo) entered the baseline phase (1 month) and were subsequently randomized to nVNS or sham treatment (2 months) before receiving open-label nVNS treatment (6 months). The primary endpoints were safety and tolerability. Efficacy endpoints in the intent-to-treat population included change in the number of headache days per 28 days and acute medication use.

Results:

Fifty-nine participants (mean age, 39.2 years; mean headache frequency, 21.5 d/mo) were enrolled. During the randomized phase, tolerability was similar for nVNS (n = 30) and sham treatment (n = 29). Most adverse events were mild/moderate and transient. Mean changes in the number of headache days were −1.4 (nVNS) and −0.2 (sham) (Δ = 1.2; p = 0.56). Twenty-seven participants completed the open-label phase. For the 15 completers initially assigned to nVNS, the mean change from baseline in headache days after 8 months of treatment was −7.9 (95% confidence interval −11.9 to −3.8; p < 0.01).

Conclusions:

Therapy with nVNS was well-tolerated with no safety issues. Persistent prophylactic use may reduce the number of headache days in CM; larger sham-controlled studies are needed.

ClinicalTrials.gov identifier:

NCT01667250.

Classification of evidence:

This study provides Class II evidence that for patients with CM, nVNS is safe, is well-tolerated, and did not significantly change the number of headache days. This pilot study lacked the precision to exclude important safety issues or benefits of nVNS.

Chronic migraine: risk factors, mechanisms and treatment

Chronic migraine has a great detrimental influence on a patient's life, with a severe impact on socioeconomic functioning and quality of life. Chronic migraine affects 1-2% of the general population, and about 8% of patients with migraine; it usually develops from episodic migraine at an annual conversion rate of about 3%. The chronification is reversible: about 26% of patients with chronic migraine go into remission within 2 years of chronification. The most important modifiable risk factors for chronic migraine include overuse of acute migraine medication, ineffective acute treatment, obesity, depression and stressful life events. Moreover, age, female sex and low educational status increase the risk of chronic migraine. The pathophysiology of migraine chronification can be understood as a threshold problem: certain predisposing factors, combined with frequent headache pain, lower the threshold of migraine attacks, thereby increasing the risk of chronic migraine. Treatment options include oral medications, nerve blockade with local anaesthetics or corticoids, and neuromodulation. Well-defined diagnostic criteria are crucial for the identification of chronic migraine. The International Headache Society classification of chronic migraine was recently updated, and now allows co-diagnosis of chronic migraine and medication overuse headache. This Review provides an up-to-date overview of the classification of chronic migraine, basic mechanisms and risk factors of migraine chronification, and the currently established treatment options.

Spreading Depolarizations: A Therapeutic Target Against Delayed Cerebral Ischemia After Subarachnoid Hemorrhage

Delayed cerebral ischemia is the most feared cause of secondary injury progression after subarachnoid hemorrhage. Initially thought to be a direct consequence of large artery spasm and territorial ischemia, recent data suggests that delayed cerebral ischemia represents multiple concurrent and synergistic mechanisms, including microcirculatory dysfunction, inflammation, and microthrombosis. Among these mechanisms, spreading depolarizations (SDs) are arguably the most elusive and underappreciated in the clinical setting. Although SDs have been experimentally detected and examined since the late 1970s, their widespread occurrence in human brain was not unequivocally demonstrated until relatively recently. We now know that SDs occur with very high incidence in human brain after ischemic or hemorrhagic stroke and trauma, and worsen outcomes by increasing metabolic demand, decreasing blood supply, predisposing to seizure activity, and possibly worsening brain edema. In this review, we discuss the causes and consequences of SDs in injured brain. Although much of our mechanistic knowledge comes from experimental models of focal cerebral ischemia, clinical data suggest that the same principles apply regardless of the mode of injury (i.e., ischemia, hemorrhage, or trauma). The hope is that a better fundamental understanding of SDs will lead to novel therapeutic interventions to prevent SD occurrence and its adverse consequences contributing to injury progression in subarachnoid hemorrhage and other forms of acute brain injury.

Cervical non-invasive vagus nerve stimulation (nVNS) for preventive and acute treatment of episodic and chronic migraine and migraine-associated sleep disturbance: a prospective observational cohort study

Background

The debilitating nature of migraine and challenges associated with treatment-refractory migraine have a profound impact on patients. With the need for alternatives to pharmacologic agents, vagus nerve stimulation has demonstrated efficacy in treatment-refractory primary headache disorders. We investigated the use of cervical non-invasive vagus nerve stimulation (nVNS) for the acute treatment and prevention of migraine attacks in treatment-refractory episodic and chronic migraine (EM and CM) and evaluated the impact of nVNS on migraine-associated sleep disturbance, disability, and depressive symptoms.

Methods

Twenty patients with treatment-refractory migraine were enrolled in this 3-month, open-label, prospective observational study. Patients administered nVNS prophylactically twice daily at prespecified times and acutely as adjunctive therapy for migraine attacks. The following parameters were evaluated: pain intensity (visual analogue scale [VAS]); number of headache days per month and number of migraine attacks per month; number of acutely treated attacks; sleep quality (Pittsburgh Sleep Quality Index [PSQI]); migraine disability assessment (MIDAS); depressive symptoms (Beck Depression Inventory® [BDI]); and adverse events (AEs).

Results

Of the 20 enrolled patients, 10 patients each had been diagnosed with EM and CM. Prophylaxis with nVNS was associated with significant overall reductions in patient-perceived pain intensity; median (interquartile range) VAS scores at baseline versus 3 months were 8.0 (7.5, 8.0) versus 4.0 (3.5, 5.0) points (p < 0.001). Baseline versus 3-month values (mean ± standard error of the mean) were 14.7 ± 0.9 versus 8.9 ± 0.8 (p < 0.001) for the number of headache days per month and 7.3 ± 0.9 versus 4.5 ± 0.6 (p < 0.001) for the number of attacks per month. Significant improvements were also noted in MIDAS (p < 0.001), BDI (p < 0.001), and PSQI global (p < 0.001) scores. No severe or serious AEs occurred.

Conclusion

In this study, treatment with nVNS was safe and provided clinically meaningful decreases in the frequency and intensity of migraine attacks in patients with treatment-refractory migraine. Improvements in migraine-associated disability, depression, and sleep quality were also noted.