A Comprehensive Review of Vagus Nerve Stimulation for Depression.

OBJECTIVES: Vagus nerve stimulation (VNS) is reemerging as an exciting form of brain stimulation, due in part to the development of its noninvasive counterpart transcutaneous auricular VNS. As the field grows, it is important to understand where VNS emerged from, including its history and the studies that were conducted over the past four decades. Here, we offer a comprehensive review of the history of VNS in the treatment of major depression. MATERIALS AND METHODS: Using PubMed, we reviewed the history of VNS and aggregated the literature into a narrative review of four key VNS epochs: 1) early invention and development of VNS, 2) path to Food and Drug Administration (FDA) approval for depression, 3) refinement of VNS treatment parameters, and 4) neuroimaging of VNS. RESULTS: VNS was described in the literature in the early 1900s; however, gained traction in the 1980s as Zabara and colleagues developed an implantable neurocybernetic prosthesis to treat epilepsy. As epilepsy trials proceed in the 1990s, promising mood effects emerged and were studied, ultimately leading to the approval of VNS for depression in 2005. Since then, there have been advances in understanding the mechanism of action. Imaging techniques like functional magnetic resonance imaging and positron emission tomography further aid in understanding direct brain effects of VNS. CONCLUSIONS: The mood effects of VNS were discovered from clinical trials investigating the use of VNS for reducing seizures in epileptic patients. Since then, VNS has gone on to be FDA approved for depression. The field of VNS is growing, and as noninvasive VNS quickly advances, it is important to consider a historical perspective to develop future brain stimulation therapies.

The Effects of Focal Electrically Administered Seizure Therapy Compared With Ultrabrief Pulse Right Unilateral Electroconvulsive Therapy on Suicidal Ideation: A 2-Site Clinical Trial.

BACKGROUND: Preliminary data suggest that focal electrically administered seizure therapy (FEAST) has antidepressant effects and less adverse cognitive effects than traditional forms of electroconvulsive therapy (ECT). This study compared the impact of FEAST and ultrabrief pulse, right unilateral (UB-RUL) ECT on suicidal ideation. METHODS: At 2 sites, patients in a major depressive episode were treated openly with FEAST or UB-RUL ECT, depending on their preference. The primary outcome measure was scores on the Beck Scale for Suicide Ideation (SSI). Scores on the suicide item of the Hamilton Rating Scale for Depression (HRSD-SI) provided a secondary outcome measure. RESULTS: Thirty-nine patients were included in the intent-to-treat sample (FEAST, n = 20; UB-RUL ECT, n = 19). Scores on both the SSI and HRSD-SI were equivalently reduced with both interventions. Both responders and nonresponders to the interventions showed substantial reductions in SSI and HRSD-SI scores, although the magnitude of improvement was greater among treatment responders. CONCLUSIONS: Although limited by the open-label, nonrandomized design, FEAST showed comparable effects on suicidal ideation when compared with routine use of UB-RUL ECT. These results are encouraging and support the need for further research and a noninferiority trial.

Neuroversion: using electroconvulsive therapy as a bridge to deep brain stimulation implantation.

Parkinson's disease (PD) is a movement disorder with significant neuropsychiatric comorbidities. Electroconvulsive therapy (ECT) is effective in treating these neuropsychiatric symptoms; however, clinicians are reluctant to use ECT in patients with deep brain stimulation (DBS) implantations for fear of damaging the device, as well as potential cognitive side effects. Right unilateral ultra-brief pulse (RUL UBP) ECT has a more favorable cognitive side-effect profile yet has never been reported in PD patients with DBS implants. We present a case series of three patients with a history of PD that all presented with psychiatric decompensation immediately prior to planned DBS surgery. All three patients had DBS electrode(s) in place at the time and an acute course of ECT was utilized in a novel method to "bridge" these individuals to neurosurgery. The patients all experienced symptom resolution (psychosis and/or depression and/or anxiety) without apparent cognitive side effects. This case series not only illustrates that right unilateral ultra-brief pulse can be utilized in patients with DBS electrodes but also illustrates that this intervention can be utilized as a neuromodulatory "bridge", where nonoperative surgical candidates with unstable psychiatric symptoms can be converted to operative candidates in a manner similar to electrical cardioversion.

A Review of Parameter Settings for Invasive and Non-invasive Vagus Nerve Stimulation (VNS) Applied in Neurological and Psychiatric Disorders.

Vagus nerve stimulation (VNS) is an established form of neuromodulation with a long history of promising applications. Earliest reports of VNS in the literature date to the late 1800's in experiments conducted by Dr. James Corning. Over the past century, both invasive and non-invasive VNS have demonstrated promise in treating a variety of disorders, including epilepsy, depression, and post-stroke motor rehabilitation. As VNS continues to rapidly grow in popularity and application, the field generally lacks a consensus on optimum stimulation parameters. Stimulation parameters have a significant impact on the efficacy of neuromodulation, and here we will describe the longitudinal evolution of VNS parameters in the following categorical progression: (1) animal models, (2) epilepsy, (3) treatment resistant depression, (4) neuroplasticity and rehabilitation, and (5) transcutaneous auricular VNS (taVNS). We additionally offer a historical perspective of the various applications and summarize the range and most commonly used parameters in over 130 implanted and non-invasive VNS studies over five applications.

Adaptive current-flow models of ECT: Explaining individual static impedance, dynamic impedance, and brain current density.

BACKGROUND: Improvements in electroconvulsive therapy (ECT) outcomes have followed refinement in device electrical output and electrode montage. The physical properties of the ECT stimulus, together with those of the patient's head, determine the impedances measured by the device and govern current delivery to the brain and ECT outcomes. OBJECTIVE: However, the precise relations among physical properties of the stimulus, patient head anatomy, and patient-specific impedance to the passage of current are long-standing questions in ECT research and practice. To this end, we develop a computational framework based on diverse clinical data sets. METHODS: We developed anatomical MRI-derived models of transcranial electrical stimulation (tES) that included changes in tissue conductivity due to local electrical current flow. These "adaptive" models simulate ECT both during therapeutic stimulation using high current (∼1 A) and when dynamic impedance is measured, as well as prior to stimulation when low current (∼1 mA) is used to measure static impedance. We modeled two scalp layers: a superficial scalp layer with adaptive conductivity that increases with electric field up to a subject-specific maximum (σSS¯), and a deep scalp layer with a subject-specific fixed conductivity (σDS). RESULTS: We demonstrated that variation in these scalp parameters may explain clinical data on subject-specific static impedance and dynamic impedance, their imperfect correlation across subjects, their relationships to seizure threshold, and the role of head anatomy. Adaptive tES models demonstrated that current flow changes local tissue conductivity which in turn shapes current delivery to the brain in a manner not accounted for in fixed tissue conductivity models. CONCLUSIONS: Our predictions that variation in individual skin properties, rather than other aspects of anatomy, largely govern the relationship between static impedance, dynamic impedance, and ECT current delivery to the brain, themselves depend on assumptions about tissue properties. Broadly, our novel modeling pipeline opens the door to explore how adaptive-scalp conductivity may impact transcutaneous electrical stimulation (tES).

Regional cerebral blood flow changes associated with focal electrically administered seizure therapy (FEAST).

INTRODUCTION: Use of electroconvulsive therapy (ECT) is limited by cognitive disturbance. Focal electrically-administered seizure therapy (FEAST) is designed to initiate focal seizures in the prefrontal cortex. To date, no studies have documented the effects of FEAST on regional cerebral blood flow (rCBF). METHODS: A 72 year old depressed man underwent three single photon emission computed tomography (SPECT) scans to capture the onset and resolution of seizures triggered with right unilateral FEAST. We used Bioimage Suite for within-subject statistical analyses of perfusion differences ictally and post-ictally compared with the baseline scan. RESULTS: Early ictal increases in regional cerebral blood flow (rCBF) were limited to the right prefrontal cortex. Post-ictally, perfusion was reduced in bilateral frontal and occipital cortices and increased in left motor and precuneus cortex. CONCLUSION: FEAST appears to triggers focal onsets of seizure activity in the right prefrontal cortex with subsequent generalization. Future studies are needed on a larger sample.

Treating the depressions with superficial brain stimulation methods.

Many, if not most, of the different superficial brain stimulation methods are being either used or investigated to treat the depressions. There are likely many reasons why there is this much interest and research involving brain stimulation treatments for depression, including that the depressions are common, there is dissatisfaction with other treatments, and some patients do not respond to medications or talking therapies. This is coupled with the fact that depressive episodes are a periodic or temporary state of the brain, and that when patients are no longer in that state they return to normal functioning. Additionally, the oldest brain stimulation method, electroconvulsive therapy (ECT), is also the most effective antidepressant available for the acute treatment of depression in patients who do not respond to medications. The newer brain stimulation methods have followed in the path blazed by ECT, showing that stimulation of key regions can cause a change in brain state and treat the depression. After almost 20 years of research, repeated daily repetitive transcranial magnetic stimulation (rTMS) of the prefrontal cortex for several weeks is now also an established clinical treatment for acute episodes. The data are less convincing for the other brain stimulation methods, but all are being investigated. Using brain stimulation (as opposed to medications or talking therapy) to treat depression is a rapidly expanding area of research with already established clear indications. Much more work is needed to understand best which methods should be used in any given patient, and in what order.

A feasibility study of a new method for electrically producing seizures in man: focal electrically administered seizure therapy [FEAST].

BACKGROUND: Electroconvulsive therapy (ECT) remains the most effective acute treatment for severe major depression, but with significant risk of adverse cognitive effects. Unidirectional electrical stimulation with a novel electrode placement and geometry (Focal Electrically Administered Seizure Therapy (FEAST)) has been proposed as a means to initiate seizures in prefrontal cortex prior to secondary generalization. As such, it may have fewer cognitive side effects than traditional ECT. We report on its first human clinical application. METHOD: Seventeen unmedicated depressed adults (5 men; 3 bipolar disorder; age 53 ± 16 years) were recruited after being referred for ECT. Open-label FEAST was administered with a modified spECTrum 5000Q device and a traditional ECT dosing regimen until patients clinically responded. Clinical and cognitive assessments were obtained at baseline, and end of course. Time to orientation recovery, a predictor of long-term amnestic effects, was assessed at each treatment. Nonresponders to FEAST were transitioned to conventional ECT. RESULTS: One patient withdrew from the study after a single titration session. After the course of FEAST (median 10 sessions), there was a 46.1 ± 35.5% improvement in Hamilton Rating Scale for Depression (HRSD24) scores compared to baseline (33.1 ± 6.8, 16.8 ± 10.9; P < 0.0001). Eight of 16 patients met response criteria (50% decrease in HRSD24) and 5/16 met remission criteria (HRSD24 ≤ 10). Patients achieved full re-orientation (4 of 5 items) in 5.5 ± 6.4 min (median = 3.6), timed from when their eyes first opened after treatment. CONCLUSION: In this feasibility study, FEAST produced clinically meaningful antidepressant improvement, with relatively short time to reorientation. Our preliminary work first in primates and now depressed adults demonstrates that FEAST is feasible, safe, well-tolerated and, if efficacy can be optimized, has potential to replace traditional ECT.

Ten sessions of adjunctive left prefrontal rTMS significantly reduces fibromyalgia pain: a randomized, controlled pilot study.

Transcranial magnetic stimulation (TMS) of the prefrontal cortex can cause changes in acute pain perception. Several weeks of daily left prefrontal TMS has been shown to treat depression. We recruited 20 patients with fibromyalgia, defined by American College of Rheumatology criteria, and randomized them to receive 4000 pulses at 10 Hz TMS (n=10), or sham TMS (n=10) treatment for 10 sessions over 2 weeks along with their standard medications, which were fixed and stable for at least 4 weeks before starting sessions. Subjects recorded daily pain, mood, and activity. Blinded raters assessed pain, mood, functional status, and tender points weekly with the Brief Pain Inventory, Hamilton Depression Rating Scale, and Fibromyalgia Impact Questionnaire. No statistically significant differences between groups were observed. Patients who received active TMS had a mean 29% (statistically significant) reduction in pain symptoms in comparison to their baseline pain. Sham TMS participants had a 4% nonsignificant change in daily pain from their baseline pain. At 2 weeks after treatment, there was a significant improvement in depression symptoms in the active group compared to baseline. Pain reduction preceded antidepressant effects. TMS was well tolerated, with few side effects. Further studies that address study limitations are needed to determine whether daily prefrontal TMS may be an effective, durable, and clinically useful treatment for fibromyalgia symptoms.

Non-invasive brain stimulation approaches to fibromyalgia pain.

Fibromyalgia is a poorly understood disorder that likely involves central nervous system sensory hypersensitivity. There are a host of genetic, neuroendocrine and environmental abnormalities associated with the disease, and recent research findings suggest enhanced sensory processing, and abnormalities in central monoamines and cytokines expression in patients with fibromyalgia. The morbidity and financial costs associated with fibromyalgia are quite high despite conventional treatments with antidepressants, anticonvulsants, low-impact aerobic exercise and psychotherapy. Noninvasive brain stimulation techniques, such as transcranial direct current stimulation, transcranial magnetic stimulation, and electroconvulsive therapy are beginning to be studied as possible treatments for fibromyalgia pain. Early studies appear promising but more work is needed. Future directions in clinical care may include innovative combinations of noninvasive brain stimulation, pharmacological augmentation, and behavior therapies.

Vagus nerve stimulation (VNS) for depression: what do we know now and what should be done next?

Vagus nerve stimulation (VNS) therapy is the first US Food and Drug Administration-approved somatic clinical intervention for treatment-resistant depression (TRD). Long-term open data suggest a sustainable antidepressant response over time. Here we review the clinical data that exist so far and their limitations. We also discuss guidelines that may inform the clinical utilization of this procedure. Further clinical studies, in addition to prospective cost utilization and health economic investigations, are needed to better understand VNS therapy and the impact it holds on TRD care.