4) transcutaneous Vagus Nerve Stimulation (tVNS)
is a very new and exciting treatment for medical and psychiatric conditions.
Before transcutaneous Vagus Nerve Stimulation (tVNS)
there was a Surgical Vagus Nerve Stimulation (VNS).
In 1997 the FDA cleared the surgical implantation of a vagus nerve stimulator (pacemaker) for the treatment of Seizures (epilepsy). Then it was cleared for depression in 2005 and for weight loss in 2015.
The non-surgical (transcutaneous) version takes advantage of the fact that a small area of skin on the outer ear is innervated by the vagus nerve. Gentle stimulation of that skin has been shown to produce similar fMRI brain activity changes (Kraus 2007, Dietrich 2008) as the surgical version.
2017 saw two tVNS devices cleared for use in the US. One for headaches (GammaCore) and one for opiate withdrawal (Bridge NSS-2).
In Europe three tVNS devices have been cleared for use - for Epilepsy (seizures) in 2010 and Pain in 2012 (CerboMed-Nemos), another device for headaches (GammaCore) and a third device for ringing in the ears - tinnitus (SaluStim).
GammaCore is also approved for the acute and prophylactic treatment of primary headaches (cluster headache, migraine, hemicrania continua), and reactive airway disease (asthma, exercise- induced bronchospasm, COPD), as well as adjunctive therapy for epilepsy prevention and reducing the symptoms of certain anxiety/depression conditions (eg, panic disorder, posttraumatic stress disorder, major depressive disorder, obsessive- compulsive disorder), gastric mobility disorders, and irritable bowel syndrome
(Grazzi L, Usai S, Bussone G.. Gammacore device for treatment of migraine attack: 2014:G12.
Gaul C, Diener H, Solbach K, et al.. Non-invasive vagus nerve stimulation using gammacoreVR for prevention and acute treatment of chronic cluster headache: Report from the randomized phase of the preva study; 2014:I7. )
OTHER USES of Transcutaneous Vagus Nerve Stimulation (tVNS):
It is used off label and being investigated (and appears to be effective and safe) for many conditions including:
Atrial Fibrillation (Stavrakis 2015, Yu 2013)
Depression (Hein 2013, Aaronson 2013)
Dementia (Polak 2006)
Diabetes (Huang 2014, Li 2015)
Endotoxemia (Huston 2007, Schmidt 2008)
Memory (Jacobs 2014 2015)
Myocardial Infarction (Wang 2015)
Pain (Laqua 2014, Busch 2013)
Postoperative Cognitive Dysfunction (POCD) (Xiong 2009)
Chronic Pelvic Pain (Napadow 2012)
Tinnitus (Li 2015, Hyvarinen 2015, Kreuzer 2014, Kreuzer 2015)
Schizophrenia (Hasan 2015)
Stroke (Cai 2014)
In our experience, it is effective for Anxiety (Generalized Anxiety, Panic Disorder, PTSD and Social Anxiety) and Insomnia.
How transcutaneous Vagus Nerve Stimulation Works (Mechanism of Action)
1) stimulating the skin of the ear,
2) stimulates the Auricular Branch of the Vagus Nerve
3) the stimulation goes to a nucleus (cluster of nerve cells) called the Nucleus Tractus Solitarius (NTS)
4) the NTS receives information from the body (heart, lungs, intestines, immune system) and
5) sends output to several structures including the Locus coeruleus and indirectly to the Dorsal raphe nucleus.
6) Locus Ceruleus is the brain's primary source of norepinephrine (aka noradrenaline)
7) Dorsal Raphe nucleus is the brain's primary source of serotonin
8) so those two structures influence alertness/energy (norepinephrine) and confidence (serotonin)
9) those two then send those chemicals (neurotransmitters) to the whole brain, especially parts for thinking and feeling. Serotonin (Calm Confidence) & Norepinephrine (Relaxed Energy) - are sent more to the thinking, deliberate, newer Prefrontal Cortex, and less to the Amygdala (Hippocampus and Anterior Thalamus). This reduces anxiety and panic (fight or flight response).
• How Does tVNS Work?
Fig. 6: The vagus nerve sends afferents to the nucleus tractus solitarius (NTS), which in turn projects to the locus coeruleus .... Vagus nerve stimulation (VNS) facilitates the excitatory pathway of neurons in the locus coeruleus more than the inhibitory one. The locus coeruleus then modifies the firing rate of serotonin (5-HT) neurons in the dorsal raphe nucleus. Therefore, VNS is believed to change the locus coeruleus activity, and then indirectly the serotoninergic neurons in the dorsal raphe nucleus. It leads to a change of norepinephrine (NE) and serotonin (5-HT) transmission. (after Manta 2009 Enhancement of the Function of rat serotonin and norepinephrine neurons by sustained vagus nerve stimulation)
••How Does tVNS Work?
2) BETTER RELATIONSHIP WITH SELF & LESS RUMINATION- Transcutaneous vagus nerve stimulation increases the functional connectivity (the way parts of the brain connect and communicate) of the default mode network (DMN) structures. The DMN is a set of brain areas that are more active when you are not focused on outside things or activities, awake and at rest, like when the mind wanders. The DMN is related to our relationship with ourself, our thoughts about our feelings, and emotion control (Connolly 2013, Berman 2011 & Nejad 2013). People who are depressed tend to have more self-focus and sensitivity to stress (Rodriguez 2012). Part of the DMN (medial) is activated during focus on self and part (Lateral) is activated when the focus is on others. tVNS shifts the focus (Fang 2015) "The Functional Connectivity between the DMN and anterior insula and parahippocampus decreased; the FC between the DMN and precuneus and orbital prefrontal cortex increased" (see below).
Figure 3. Yellow indicates brain regions that showed significant functional connectivity increase with default mode network in the transcutaneous vagus nerve stimulation group as compared with sham transcutaneous vagus nerve stimulation. Blue indicates brain regions whose default mode network functional connectivity changes (posttreatment minus pretreatment) were negatively correlated with the corresponding Hamilton Depression Rating Scale score changes across all subjects. L, left; OPFC, orbital prefrontal cortex; Precu, precuneus; rACC, rostral anterior cingulate cortex. (Fang 2016 transcutaneous vagus nerve stimulation Modulates Default Mode Network in Major Depressive Disorder. )