Use Of Microelectrode Recording Research Articles

A technique for minimally altering anatomically based subthalamic electrode targeting by microelectrode recording

Implantation of a subthalamic nucleus (STN) deep brain stimulation (DBS) electrode is increasingly recognized as an effective treatment for advanced Parkinson disease (PD). Despite widespread use of microelectrode recording (MER) to delineate the boundaries of the STN prior to stimulator implantation, it remains unclear to what extent MER improves the clinical efficacy of this procedure. In this report, the authors analyze a series of patients who were treated at one surgical center to determine to what degree final electrode placement was altered, based on readings obtained with MER, from the calculated anatomical target. Subthalamic DBS devices were placed bilaterally in nine patients with advanced PD. Frame-based volumetric magnetic resonance images were acquired and then transferred to a stereotactic workstation to determine the anterior and posterior commissure coordinates and plane. The initial anatomical target was 4 mm anterior, 4 mm deep, and 12 mm lateral to the midcommissural point. The MERs defined the STN boundaries along one or more parallel tracks, refining the final electrode placement by comparison of results with illustrations in a stereotactic atlas. In eight of 18 electrodes, the MER results did not prompt an alteration in the anatomically derived target. In another eight placements, MER altered the target by less than 1 mm and two of 18 electrode positions differed by less than 2 mm. The anterior-posterior difference was 0.53 +/- 0.65 mm, whereas the medial-lateral direction differed by 0.25 +/- 0.43 mm. The ventral boundary of the STN defined by MER was 2 +/- 0.72 mm below the calculated target (all values are the means +/- standard deviation). All patients attained clinical improvement, similar to previous reports. In this series of patients, microelectrode mapping of the STN altered the anatomically based target only slightly. Because it is not clear whether such minor adjustments improve clinical efficacy, a prospective clinical comparison of MER-refined and anatomical targeting may be warranted.

Lidocaine and muscimol microinjections in subthalamic nucleus reverse Parkinsonian symptoms.

Inactivation of neurones in the subthalamic nucleus (STN) of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine treated monkey model of Parkinson's disease has been shown to relieve parkinsonian motor symptoms. In patients with Parkinson's disease, neurones in the STN display hyperactive firing rates and rhythmic discharge activity such as tremor-related oscillations (3-8 Hz) and synchronous high-frequency oscillations (15-30 Hz). In this study, microinjections of lidocaine (n = 4) and muscimol, a GABA(A) receptor agonist (n = 2), were performed in the STN of six patients with Parkinson's disease to determine whether the focal suppression of STN neuronal activity can lead to an improvement in tremor, bradykinesia and rigidity. We also report the first use of microelectrode recording of the effects of microinjections on neuronal activity in the human brain (n = 2). Microinjections of 10-23 microl of lidocaine produced striking improvements in bradykinesia, limb tremor and rigidity in three out of three patients. These improvements were correlated with good therapeutic effects of subsequent STN deep brain stimulation performed in the same microelectrode trajectories as these injections. The most dramatic observation following lidocaine injections was the appearance of dyskinetic limb movements. In one patient, simultaneous microelectrode recording during an injection of 3.5 microl of lidocaine demonstrated a suppression of neuronal activity at distances of < 0.9 mm from the injection site, but no suppression was observed at > or = 1.2 mm from the injection site. Microinjections of 5-10 microl of muscimol in a region with tremor-related activity resulted in suppression of limb tremor in two out of two patients. Interestingly, in one of these patients, 4 Hz oscillatory activity was diminished in a neurone recorded 1.3 mm from the injection site, but there was no reduction in the mean firing rate or 20 Hz oscillatory activity. These results demonstrate that inactivation of neuronal activity in the STN of patients with Parkinson's disease improves motor symptoms. These findings also suggest that a focal block of the STN might alter the oscillatory activity of neurones located beyond the inhibited region.

Microelectrode Recording Technology

The historical development of the use of microelectrode recording to guide functional stereotactic procedures is briefly reviewed and the technique described in detail as used during pallidal or thalamic surgery for movement disorders.

Stereotactic pallidotomy and thalamotomy using individual variations of anatomic landmarks for localization.

The optimal choice of imaging and localization for stereotactic surgery for movement disorders remains uncertain, with controversy surrounding the use of microelectrode recording and the role of distortion of magnetic resonance imaging (MRI) scans in reducing the accuracy of lesion placement. We review our experience with 67 pallidotomies and 35 thalamotomies performed without microelectrode recording, using instead individual variations in anatomic landmarks. Computed tomography is used as the primary modality, with comparison with carefully angled MRI scans and the use of neural structures, such as the mamillary bodies and the vascular anatomy. Pallidal target sites are chosen immediately lateral and superior to the optic tract on a line bisecting the axis of the peduncle, with macrostimulation guiding the final adjustment of target position. Forty-seven patients undergoing unilateral pallidotomies were studied in the "off" state and the "on" state using a modified Unified Rating Scale for Parkinson's disease (URSP) score and a dyskinesia scale, preoperatively and postoperatively at 2 weeks, 2 months, 6 months, and 12 months. In the 31 patients undergoing thalamotomy, tremor was rated preoperatively and postoperatively as near-complete resolution, partial resolution, and failure. The "off" state Unified Rating Scale for Parkinson's disease motor score declined from 42.0 to 32.2 at 2 weeks after surgery (P < 0.0001, n = 42). The Unified Rating Scale for Parkinson's disease motor score was 34.2 at 2 months (P < 0.0001, n = 35), 29.4 at 6 months (P < 0.0001, n = 27), and 24.9 at 12 months (P = 0.005, n = 12), representing an overall improvement in "off" state motor function of approximately 25 to 40%. The "on" state dyskinesia score fell from 5.5 to 2.0 at 2 weeks (P < 0.0001) and persisted in the later visits. The dyskinesia score for the contralateral side fell from 2.5 preoperatively to 0.26 at 2 weeks, 0.28 at 2 months, 0.22 at 6 months, and 0.0 at 12 months. Of the patients undergoing thalamotomies, 65% experienced near-complete or complete tremor resolution, 23% experienced partial tremor relief, and 13% were considered treatment failures. Stereotactic procedures for movement disorders requiring high precision can be safely and successfully performed without the use of microelectrode recording techniques. Meticulous alignment of MRI and computed tomographic scans based on visualized anatomy allows precise lesion placement and avoids the distortion inherent in MRI scans.