Stimulatory methods in treatment of depression: the use of nerve vagus stimulation (VNS) and deep brain stimulation (DBS)
Abstract
High number of treatment-resistant patients with depression poses a clinical problem. In addition to pharmacotherapy, reversible invasive stimulation methods, vagus nerve stimulation (VNS) and deep brain stimulation (DBS), have been introduced into the management of treatment-resistant depression (TRD).
The paper reviews principles, neurobiology, and available clinical evidence of VNS and DBS in TRD. The basis of VNS is a stimulation of the left cervical vagus nerve with a programmable neurostimulator.
Efficacy of VNS was examined in four clinical trials with 355 patients. VNS demonstrated steadily increasing improvement with full benefit after 6-12 months, sustained up to 2 years.
Patients who responded best had a low-to-moderate antidepressant resistance. However, the primary results of the only controlled trial were negative.
DBS involves stereotactical implantation of electrodes powered by a pulse generator into the specific brain regions. For depression, targeted areas are subthalamic nucleus, internal globus pallidus, ventral internal capsule/ventral striatum, the subgenual cingulated region, and nucleus accumbens.
Antidepressant effects of DBS were examined in case series with the total number of 50 TRD patients. Stimulation of different brain regions resulted in rapid reduction of depressive symptoms.
The clinical data on the use of VNS and DBS in TRD are encouraging. The major contribution of the methods is a novel approach that allows for precise targeting of the specific brain areas, nuclei and circuits implicated in etiopathogenesis of neuropsychiatric disorders.
However, more controlled data are needed and potential impact of placebo effect has to be ruled out. Relatively high incidence of suicidal behavioral in DBS warrants caution.
For clinical practice, patients who may benefit from VNS or DBS best should be identified