Object. Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is a 
promising new procedure for the treatment of dystonia. The authors present their 
technical approach for placement of electrodes into the GPi in awake patients 
with dystonia, including the methodology used for electrophysiological mapping 
of the GPi in the dystonic state, clinical outcomes and complications, and the 
location of electrodes associated with optimal benefit. Methods. Twenty-three 
adult and pediatric patients who had various forms of dystonia were included in 
this study. Baseline neurological status and improvement in motor function 
resulting from DBS were measured using the Burke-Fahn-Marsden Dystonia Rating 
Scale (BFMDRS). Implantation of the DBS lead was performed using magnetic 
resonance (MR) imaging-based stereotaxy, single-cell microelectrode recording, 
and intraoperative test stimulation to determine thresholds for 
stimulation-induced adverse effects. Electrode locations were measured on 
computationally reformatted postoperative MR images according to a prospective 
protocol. Conclusions. Physiologically guided implantation of DBS electrodes in 
patients with dystonia is technically feasible in the awake state in most cases, 
with low morbidity rates. Spontaneous discharge rates of GPi neurons in dystonia 
are similar to those of globus pallidus externus neurons, such that the two 
nuclei must be distinguished by neuronal discharge patterns rather than by 
rates. Active electrode locations associated with robust improvement (> 50% 
decrease in BFMDRS score) were located near the intercommissural plane, at a 
mean distance of 3.7 mm from the pallidocapsular border. Patients with 
juvenile-onset primary dystonia and those with the tardive form benefited 
greatly from this procedure, whereas benefits for most secondary dystonias and 
the adult-onset craniocervical form of this disorder were more modest.