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

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>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.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>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.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>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 (&gt; 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.</jats:p></jats:sec>

Which patients with dystonia benefit from deep brain stimulation? A metaregression of individual patient outcomes

“…There are multiple reports of lead migration and lead fracture,4 5 8 22–26 and one group have proposed that this complication is more common among dystonia patients than other patients undergoing DBS 27. Other surgical adverse events do not seem to occur particularly more commonly in dystonia with only occasional reports of haemorrhage,26 infection4 8 13 22 28–33 and misplaced electrodes 26 34. Adverse effects specifically related to chronic GPi stimulation for dystonia include dysarthria25 30 33 35–37 and parkinsonism,7 38–40 both of which seem to be reversible but sometimes at the expense of inadequate dystonia relief.…”

Postoperative MRI localisation of electrodes and clinical efficacy of pallidal deep brain stimulation in cervical dystonia

“…For both the Medtronic electrode Models 3387 and 3389, the tip of the electrode is located 1.5 mm distal to the distal border of the first contact and 2.25 mm distal to the centre of the first contact. In this respect, it seems important to refer separately to the target point of the tip of the electrode and to the actual active point of stimulation as reported in previous studies 11 37…”

Long-term follow-up of pallidal deep brain stimulation in two cases of Huntington's disease

“…Patient 1 received generalised anaesthesia for the entire duration of the surgery (due to prominent chorea affecting the head/neck), and patient 2 received propofol for stereotactic headframe placement and MRI but underwent the surgery in an awake and alert state in order to allow microelectrode mapping 18. The methods of the surgical technique were similar to those previously described for Parkinson's disease19 and dystonia 20. The initial anatomical target was determined by stereotactic brain MRI using inversion recovery-fast spin echo images with direct visualisation of the GPi borders and optic tract.…”