NeuroRehabilitation 23 (2008) 105–113 105 IOS Press Deep brain stimulation: Treating neurological and psychiatric disorders by modulating brain activity Mustafa Saad Siddiqui a,* , Thomas L. Ellis a , Stephen B. Tatter a and Michael S Okun b a Movement Disorders Section, Departments of Neurology and Neurosurgery, Wake Forest University School of Medicine, Winston-Salem, NC, USA b Movement Disorders Center, Department of Neurology, McKnight Brain Institute, University of Florida, Gainesville, FL, USA 1. Introduction Attempts to modulate brain activity for therapeutic purposes by stimulating various cortical and subcor- tical areas, have been made since the 19th century. Bartholow was one of the first to describe in detail, a case of brain stimulation in 1874 [13]. However, it was not until a century later, when in 1987, Benabid and Pollack proved that chronic high frequency deep brain stimulation (DBS) of thalamus could be used as a safe and effective way of treating the tremor of Parkinson’s disease (PD) [11,19]. A timeline of important mile- stones in the history of brain stimulation is shown in Fig. 1. In this article we will discuss the currently ap- proved and the experimental uses of DBS. In addition we will give a brief overview of the proposed mecha- nisms by which DBS is currently thought to modulate brain activity. Sometimes referred to as a ‘brain pacemaker’, DBS involves placement of intracranial electrodes (Fig. 2) which can be connected to a subcutaneously and sub- clavicularly implanted pulse generator (IPG). The IPG allows noninvasive adjustments of current amplitude, frequency, pulse width and polarity by means of a hand- * Address for correspondence: Mustafa Saad Siddiqui, MD, De- partment of Neurology, Medical Center Boulevard, Winston-Salem, NC 27012, USA. E-mail: mssiddiq@wfubmc.edu. held device. The implanted electrodes have four stimu- lation contacts which permits manipulation of the stim- ulation field. Since its inception in 1987, DBS has gained widespread popularity and is considered by many to be the surgical treatment of choice for a subgroup of patients with medically refractory symptoms of PD, es- sential tremor (ET) and more recently, dystonias and some neuropsychiatric disorders. DBS has many ad- vantages over the alternative treatment i. e ablation therapy. It is reversible, which allows for future thera- peutic options. Autopsy studies in DBS patients have shown to date no significant tissue changes [28,60]. The technology is adjustable, which allows optimiza- tion of the settings for improved efficacy and the min- imization of side effects. DBS allows bilateral pro- cedures to be done without resultant gait, speech and pseudobulbar side effects commonly seen with bilateral lesion therapy. The disadvantages of DBS include its expense when compared to lesions. Hardware related complications such as infection and device failure can also occur over the lifetime of the device. DBS requires more patient commitment for follow up care and may require a specialized center. Underdeveloped countries may not be able to offer DBS because of economic and social constraints. Long term follow up studies of patients with DBS have shown it has persistent efficacy [49]. Complica- ISSN 1053-8135/08/$17.00  2008 – IOS Press and the authors. All rights reserved