![]() It has also been shown to change the functional connectivity of the default mode network in depressed patients. VNS may alter the functional connectivity in several brain regions and enhance synaptic plasticity to reduce excitatory activity involved in seizures. These neurotransmitters are involved in both epilepsy and other neuropsychiatric conditions such as depression and anxiety.Ĥ. VNS can change the activity of several neurotransmitter systems involving serotonin, norepinephrine and GABA. There is evidence that VNS has an anti-inflammatory effect through both peripheral and central mechanisms. Multiple lines of evidence suggest that inflammation plays a significant role in epilepsy as well as associated neurobehavioral comorbidities such as depression, autism spectrum disorder and cognitive impairment. This makes sense given that seizures consist of abnormal hypersynchronous activity in the brain.Ģ. There is evidence that VNS results in cortical desynchronization in epilepsy patients who had a favorable clinical response relative to those who did not. There are multiple potential mechanisms which may account for the efficacy of VNS in treating epilepsy and other conditions including:ġ. Afferents from the vagus nerve project to the nucleus tractus solitarii which subsequently communicates with other regions of the brain including the dorsal raphe nucleus, locus coeruleus, amygdala and other areas. It has the longest and widest distribution of all the cranial nerves and functions as a bidirectional link between the brain and peripheral organs. The vagus nerve is the tenth cranial nerve and arises from a series of rootlets in the medulla it carries both afferent (80%) and efferent (20%) fibers. Further sham-controlled studies over a longer observational period are desirable". A 2022 narrative review concluded that "The use of VNS is an approved, effective and well-tolerated long-term therapy for chronic and treatment-resistant depression. Depression Īs of 2017, the efficacy of VNS for TR-MDD is unclear. A number of predictors of a favorable clinical response have been identified including epilepsy onset > 12 years of age, generalized epilepsy type, non-lesional epilepsy, posttraumatic epilepsy and those who have less than a 10 year history of seizures. VNS has also been shown to reduce rates of sudden unexpected death in epilepsy (SUDEP) and to improve quality of life metrics. Approximately, 8% have total resolution of seizures. For instance, a study that followed 74 patients for 10-17 years found a seizure frequency reduction of 50-90% in 38.4%, 51.4%, 63.6% and 77.8% of patients at 1-, 2-, 10- and 17-years following implantation, respectively. Long term studies have shown that response to VNS increases over time. Approximately 50% of patients had an equal to or greater than 50% reduction in seizures at the time of last follow-up. Efficacy Epilepsy Ī meta-analysis of 74 clinical studies with 3321 patients found that VNS produced an average 51% reduction in seizures after 1 year of therapy. There are also reports of VNS being successfully utilized in patients with refractory and super-refractory status epilepticus. VNS may provide benefit for particular epilepsy syndromes and seizure types such as Lennox-Gastaut syndrome, tuberous sclerosis complex related epilepsy, refractory absence seizures and atonic seizures. Patients with comorbid depression have been found to have mood improvements with VNS therapy. Patients who have poor adherence or tolerance of anti-seizure medications may be good candidates for VNS. This is because epilepsy surgery is associated with a higher probability of resulting in seizure freedom. It is recommended that VNS is only pursued following an adequate trial of at least 2 appropriately chosen anti-seizure medications and that the patient is ineligible for epilepsy surgery. In the European Union, VNS is approved as an adjunctive therapy for patients with either generalized or focal onset seizures without any age restrictions. In the United States, VNS is approved as adjunctive therapy for those 4 years of age or older with refractory focal onset seizures. VNS devices are used to treat drug-resistant epilepsy and treatment-resistant major depressive disorder (TR-MDD). It is used as an add-on treatment for certain types of intractable epilepsy and treatment-resistant depression. ![]() ![]() Vagus nerve stimulation ( VNS) is a medical treatment that involves delivering electrical impulses to the vagus nerve.
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