Dmitry M. Arbuck, MD President and Medical Director Indiana Polyclinic Carmel, Indiana
Ali A. Farooqui, MD Integrative Psychiatry, PLLC Clinical Faculty Department of Psychiatry University of Louisville School of Medicine Louisville, Kentucky
Rif S. El-Mallakh, MD Professor and Director, Mood Disorders Research Program Department of Psychiatry and Behavioral Sciences University of Louisville School of Medicine Louisville, Kentucky
Disclosures Dr. Farooqui is a speaker for AbbVie and BioXcel. Dr. El-Mallakh is a speaker for Axsome, Idorsia, Intra-Cellular Therapies, Janssen, Lundbeck, Myriad, Noven, Otsuka, and Teva, and has received research support from Sunovion. Dr. El-Mallakh is Current Psychiatry’s Section Editor, Clinical Neuroscience. Dr. Arbuck reports no financial relationships with any companies whose products are mentioned in this article, or with manufacturers or competing products.
Therapeutic noninvasive brain stimulation technology is plausible due to the relative lack of adverse effects and ease of administration. In transcranial direct current stimulation (tDCS), a low-intensity, constant electric current is delivered to stimulate the brain via electrodes attached to the scalp. tDCS modulates spontaneous neuronal network activity40,41 and induces polarization of resting membrane potential at the neuronal level,42 though the exact mechanism is yet to be proven. N-methyl-D-aspartate-glutamatergic receptors are involved in inhibitory and facilitatory plasticity induced by tDCS.43
tDCS has been suggested as a treatment for various psychiatric and medical conditions. However, the small sample sizes and experimental design of published studies have limited tDCS from being clinically recommended.30 No recommendation of Level A (definite efficacy) for its use was found for any indication. Level B recommendation (probable efficacy) was proposed for fibromyalgia, MDD episode without drug resistance, and addiction/craving. Level C recommendation (possible efficacy) is proposed for chronic lower limb neuropathic pain secondary to spinal cord lesion. tDCS was found to be probably ineffective as a treatment for tinnitus and drug-resistant MDD.30 Some research has suggested that tDCS targeting the DLPFC is associated with cognitive improvements in healthy individuals as well as those with schizophrenia.44 tDCS treatment remains experimental and investigational.
Deep brain stimulation
DBS is a neurosurgical procedure that uses electrical current to directly modulate specific areas of the CNS. In terms of accurate, site-specific anatomical targeting, there can be little doubt of the superiority of DBS. DBS involves the placement of leads into the brain parenchyma. Image guidance techniques are used for accurate placement. DBS is a mainstay for the symptomatic treatment of treatment-resistant movement disorders such as Parkinson disease, essential tremor, and some dystonic disorders. It also has been studied as a potential treatment for chronic pain, cluster headache, Huntington disease, and Tourette syndrome.
For treating depression, researched targets include the subgenual cingulate gyrus (SCG), ventral striatum, nucleus accumbens, inferior thalamic peduncle, medial forebrain bundle, and the red nucleus.45 In systematic reviews, improvement of depression is greatest when DBS targets the subgenual cingulate cortex and the medial forebrain bundle.46
The major limitation of DBS for treating depression is the invasive nature of the procedure. Deep TMS can achieve noninvasive stimulation of the SCG and may be associated with fewer risks, fewer adverse events, and less collateral damage. However, given the evolving concept of abnormal neurologic circuits in depression, as our understanding of circuitry in pathological psychiatric processes increases, DBS may be an attractive option for personalized targeting of symptoms in some patients.
DBS may also be beneficial for severe, treatment-resistant OCD. Electrode implantation in the region of the internal capsule/ventral striatum, including the nucleus accumbens, is used47; there is little difference in placement as a treatment for OCD vs for movement disorders.48
