Microelectrode-guided implantation of deep brain stimulators into the globus pallidus internus for dystonia: techniques, electrode locations, and outcomes.

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.

Thalamic deep brain stimulation for essential tremor: relation of lead location to outcome.

OBJECTIVE: Thalamic deep brain stimulation (DBS) is commonly used to treat essential tremor, but the optimal lead location within the thalamus has not been systematically evaluated. We examined the relation of lead location to clinical outcome in a series of essential tremor patients treated by thalamic DBS. METHODS: Fifty-seven leads in 37 patients were studied. Lead locations were measured by postoperative magnetic resonance imaging. Contralateral arm tremor was assessed in the DBS-on and DBS-off states using the Fahn-Tolosa-Marin tremor rating scale, with a mean follow-up of 26 months. Lead locations were statistically correlated, using analysis of variance, with percent improvement in tremor resulting from DBS activation. RESULTS: Improvement in tremor score was significantly correlated with lead location in both the anteroposterior and lateral dimensions. In the plane of the commissures, the optimal electrode location was determined statistically to be 6.3 mm anterior to the posterior commissure and 12.3 mm lateral to the midline, or 10.0 mm lateral to the third ventricle. CONCLUSION: Optimal electrode location for thalamic DBS in essential tremor corresponds to the anterior margin of the ventralis intermedius nucleus. Leads located greater than 2 mm (in the plane of the commissures) from the optimal coordinates are more likely to be associated with poor tremor control than leads within 2 mm of the optimal location. The incidence of true physiological tolerance to the antitremor effect of thalamic DBS (defined as poor tremor control in spite of lead location within 2 mm of the optimal site) was found to be 9%.

Hemorrhagic complications of microelectrode-guided deep brain stimulation.

BACKGROUND: The incidence of intracranial hemorrhage occurring during microelectrode-guided implantation of deep brain stimulators (DBS) for movement disorders has not been well defined. We report the incidence of hemorrhage in a large series of DBS implants into the subthalamic nucleus (STN), thalamus (VIM) and internal globus pallidus (GPi). METHODS: All DBS procedures performed by a single surgeon (P.A.S.) between June 1998 and April 2003 were included in this study. Patients had postoperative imaging (MRI or CT) 4-24 h following surgery, and all hematomas >0.2 cm(3) in volume were noted and scored as symptomatic (associated with any new neurologic deficit lasting >24 h) or asymptomatic. RESULTS: The total number of lead implants was 357. There were 5 symptomatic hematomas and 6 asymptomatic hematomas. The relative risk of hematoma (any type) per lead implant was 3.1%. The incidence of hematoma by target site was 2.5% per lead for STN-DBS, 6.7% for GPi-DBS and 0% for VIM-DBS. CONCLUSION: The overall risk of intraoperative or early postoperative symptomatic hemorrhage with microelectrode-guided DBS, over all targets, was 1.4% per lead implant. The brain target had a significant effect on the risk of hemorrhage.