Djordje Sterio

Complications of deep brain stimulation surgery

Although technological advances have reduced device-related complications, DBS surgery still carries a significant risk of transient and permanent complications. We report our experience in 86 patients and 149 DBS implants. Patients with Parkinson’s disease, essential tremor and dystonia were treated. There were 8 perioperative, 8 postoperative, 9 hardware-related complications and 4 stimulation-induced side effects. Only 5 patients (6%) sustained some persistent neurological sequelae, however, 26 of the 86 patients undergoing 149 DBS implants in this series experienced some untoward event with the procedure. Although there were no fatalities or permanent severe disabilities encountered, it is important to extend the informed consent to include all potential complications.

Comparison of anatomic and neurophysiological methods for subthalamic nucleus targeting.

OBJECTIVE The subthalamic nucleus (STN) has recently become the surgical target of choice for the treatment of medically refractory idiopathic Parkinsons disease. A number of anatomic and physiological targeting methods have been used to localize the STN. We retrospectively reviewed the various anatomic targeting methods and compared them with the final physiological target in 15 patients who underwent simultaneous bilateral STN implantation of deep brain stimulators. METHODS The x, y, and z coordinates of our localizing techniques were analyzed for 30 STN targets. Our final targets, as determined by single-cell microelectrode recording, were compared with the following: 1) targets selected on coronal magnetic resonance inversion recovery and T2-weighted imaging sequences, 2) the center of the STN on a digitized scaled Schaltenbrand-Wahren stereotactic atlas, 3) targeting based on a point 13 mm lateral, 4 mm posterior, and 5 mm inferior to the midcommissural point, and 4) a composite target based on the above methods. RESULTS All anatomic methods yielded targets that were statistically significantly different (P < 0.001) from the final physiological targets. The average distance error between the final physiological targets and the magnetic resonance imaging-derived targets was 2.6 +/- 1.3 mm (mean +/- standard deviation), 1.7 +/- 1.1 mm for the atlas-based method, 1.5 +/- 0.8 mm for the indirect midcommissural method, and 1.3 +/- 1.1 mm for the composite method. Once the final microelectrode-refined target was determined on the first side, the final target for the contralateral side was 1.3 +/- 1.2 mm away from its mirror image. CONCLUSION Although all anatomic targeting methods provide accurate STN localization, a combination of the three methods offers the best correlation with the final physiological target. In our experience, direct magnetic resonance targeting was the least accurate method.

Neurophysiological refinement of subthalamic nucleus targeting.

OBJECTIVEAdvances in image-guided stereotactic surgery, microelectrode recording techniques, and stimulation technology have been the driving forces behind a resurgence in the use of functional neurosurgery for the treatment of movement disorders. Despite the dramatic effects of deep brain stimulation (DBS) techniques in ameliorating the symptoms of Parkinson’s disease, many critical questions related to the targeting, effects, and mechanisms of action of DBS remain unanswered. In this report, we describe the methods used to localize the subthalamic nucleus (STN) and we present the characteristics of encountered cells. METHODS Twenty-six patients with idiopathic Parkinson’s disease underwent simultaneous, bilateral, microelectrode-refined, DBS electrode implantation into the STN. Direct and indirect magnetic resonance imaging-based anatomic targeting was used. Cellular activity was analyzed for various neurophysiological parameters, including firing rates and interspike intervals. Physiological targeting confirmation was obtained by performing macrostimulation through the final DBS electrode. RESULTS The average microelectrode recording time for each trajectory was 20 minutes, with a mean of 5.2 trajectories/patient. Typical trajectories passed through the anterior thalamus, zona incerta/fields of Forel, STN, and substantia nigra-pars reticulata. Each structure exhibited a characteristic firing pattern. In particular, recordings from the STN exhibited an increase in background activity and an irregular firing pattern, with a mean rate of 47 Hz. The mean cell density was 5.6 cells/mm, with an average maximal trajectory length of 5.3 mm. Macrostimulation via the DBS electrode yielded mean sensory and motor thresholds of 4.2 and 5.7 V, respectively. CONCLUSION The principal objectives of microelectrode recording refinement of anatomic targeting are precise identification of the borders of the STN and thus determination of its maximal length. Microelectrode recording also allows identification of the longest and most lateral segment of the STN, which is our preferred target for STN DBS electrode implantation. Macrostimulation via the final DBS electrode is then used primarily to establish the side effect profile for postoperative stimulation. Microelectrode recording is a helpful targeting adjunct that will continue to facilitate our understanding of basal ganglion physiological features.

Microelectrode recording during posteroventral pallidotomy: impact on target selection and complications.

OBJECTIVE To assess the practical usefulness of single-cell microelectrode recording (MER) when performing posteroventral pallidotomy. METHODS A retrospective comparison of the initial, magnetic resonance imaging-derived coordinates of the pallidotomy target to the final, MER-refined lesion coordinates in 132 consecutive pallidotomies was conducted. The time required to perform the procedure and the surgical complications are reported. RESULTS MER led to targeting changes in 98% of the cases. In 12%, the MER-refined target was more than 4 mm from the original, image-guided site, which is a targeting error that could adversely affect outcome. Although all components of targeting were affected by MER, laterality and depth were impacted most. The ventral border of the globus pallidus pars interna was located within 1 mm of the magnetic resonance imaging-selected target in only 40% of the cases. On average, only 2.2 MER trajectories were required to perform pallidotomy. During the last 3 years of our study, 85% of the procedures were performed with one or two trajectories. The mean operating time of the operations performed during the last 3 years was 2 hours and 12 minutes. The incidence of intracerebral hemorrhage in our series (1.5%) was no higher than that reported for other large series of stereotactic procedures. No patient suffered an optic tract injury. CONCLUSION MER provides important targeting information for performing pallidotomy. In particular, the micrometric delineation of the ventral border of the globus pallidus pars interna permits safe lesioning of the posteroventral region of the globus pallidus pars interna with little risk of visual field deficit. These data can be obtained efficiently and without increased surgical risk.

Success rate of motor evoked potentials for intraoperative neurophysiologic monitoring: effects of age, lesion location, and preoperative neurologic deficits.

Summary: Transcranial electrical stimulation with myogenic motor evoked potential (MEP) recording was used for intraoperative neurophysiologic monitoring in 341 consecutive “high-risk” neurosurgical or orthopedic procedures. Overall, the success rate for establishing reliable MEP response was 94.8% for upper extremities and 66.6% for lower extremities. The rate was only 39.1% for lower extremities in patients with preoperative motor deficit and up to 81% in neurologically intact adults. Further analysis demonstrated that extremes of age or the presence of a lesion in the spinal cord and motor deficit contributed to failure in obtaining reliable MEPs.

Electrical Stimulation of the Globus pallidus Preceding Stereotactic Posteroventral Pallidotomy

Physiological methods such as microelectrode recording of neuronal activity and electrical stimulation of target structures can improve the safety and efficacy of certain stereotactic surgeries. The globus pallidus (GP) was electrically stimulated in 136 patients with Parkinsons disease prior to unilateral posteroventral pallidotomy to identify functional areas and prevent deficits. We found that electrical stimulation of the GP elicited two principal responses: contractions of the contralateral hand and flashing lights. The mean voltage that evoked motor responses was 4.3 V (range 1.7-9.0 V), while higher intensity was necessary to elicit visual responses (mean 6.8 V; range 3.5-9.9 V). Contralateral tremor, speech impairment, paresthesias, and warm sensations were also elicited.

Pallidal Targeting with the COMPASS System

The authors describe their initial experience with the new pallidotomy targeting software for the COMPASS system. As COMPASS permits window and contrast settings to be changed at any time, multiple imaging modalities can be employed for targeting. This feature allowed the incorporation of fast-spin echo/inversion recovery (FSE/IR) magnetic resonance images (MRI) into the planning protocol. COMPASS has now been employed for 33 consecutive pallidotomies over the last year (July 96-June 97). A statistically significant reduction in the number of microelectrode recording trajectories required to physiologically localize sensorimotor globus pallidus interna (GPi) is noted in these cases as compared to the 41 cases performed in the previous year with a different computer planning system. The authors conclude that the COMPASS system accurately and efficiently targets the internal pallidum when FSE/IR MRI is employed. Nevertheless, pallidotomy should not be performed without neurophysiological localization.