Patrick D. Jenkins

Implantation of a closed-loop stimulation in the management of medically refractory focal epilepsy : A technical note

Open-loop stimulation studies have shown varying control of seizures with stimulation of different anatomical targets. A recent multi-institutional clinical study utilizing an external closed-loop stimulation system had promising results. A novel implantable closed-loop Responsive Neurostimulation System (RNS) (Neuropace, Inc., Mountainview, Calif., USA) consisting of a cranially implanted pulse generator, one or two quadripolar subdural strip or depth leads and a programmer is under testing in a prospective clinical trial. The RNS pulse generator continuously analyzes the patient’s electrocortigrams (ECoGs) and automatically triggers electrical stimulation when specific ECoG characteristics programmed by the clinician, as indicative of electrographic seizures or precursor of epileptiform activities, are detected. The pulse generator then stores diagnostic information detailing detections and stimulations, including multichannel stored ECoGs. The RNS programmer communicates transcutaneously with the implanted pulse generator when initiated by a clinician. The RNS programmer can download diagnostics and store ECoGs for review. The RNS programmer can then be used to program detection and stimulation parameters. In our current communication, we describe the selection criteria for implanting this system, the preparation of the surgical candidates as well as the surgical technique. We also present our preliminary results with 8 patients who had an RNS implanted. Seven patients (87.5%) had more than 45% decrease in their seizure frequency. The mean follow-up time in our series was 9.2 months. The implantation of a closed-loop stimulation system, in our experience, represents a safe and relatively simple surgical procedure. However, the efficacy of this new treatment modality remains to be determined in further multi-institutional, prospective clinical studies.

Closed-loop stimulation in the control of focal epilepsy of insular origin

Background: Previous studies have shown that closed-loop or responsive neurostimulation can abort induced or spontaneous epileptiform discharges. Objective: To assess the effectiveness of a programmable cranially implanted closed-loop neurostimulation system in the control of seizures originating from an area relatively inaccessible by open craniotomy. Method: A patient with drug-resistant partial epilepsy had previously undergone open resection of the left frontal opercular cortex and the underlying insular area. Although subdural-depth electrode ictal recordings had been nonlocalizing, depth electrode insular stimulation had produced the patient’s habitual aura. Postoperatively, there was a sustained 50% reduction in seizure frequency. The residual seizures were identical to the preoperative seizures. Repeat depth electrode monitoring revealed that the ictal focus was immediately posterior to the previously resected insular area. A closed-loop cranial internal pulse generator system including left anterior insular and posterior orbitofrontal depth electrodes was implanted. Result: There was an additional 60% reduction of seizures. Conclusion: Preliminary observation indicates that responsive neurostimulation may be an effective alternative to higher-risk resective epilepsy surgery.

Self-stimulatory behavior associated with deep brain stimulation in Parkinson's disease

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Magnetic source imaging guidance of gamma knife radiosurgery for the treatment of epilepsy

The purpose of this paper was to note a potential source of error in magnetic resonance (MR) imaging. Magnetic resonance images were acquired for stereotactic planning for GKS of a vestibular schwannoma in a female patient. The images were acquired using three-dimensional sequence, which has been shown to produce minimal distortion effects. The images were transferred to the planning workstation, but the coronal images were rejected. By examination of the raw data and reconstruction of sagittal images through the localizer side plate, it was clearly seen that the image of the square localizer system was grossly distorted. The patient was returned to the MR imager for further studies and a metal clasp on her brassiere was identified as the cause of the distortion.A-60-year-old man with medically intractable left-sided maxillary division trigeminal neuralgia had severe cardiac disease, was dependent on an internal defibrillator and could not undergo magnetic resonance imaging. The patient was successfully treated using computerized tomography (CT) cisternography and gamma knife radiosurgery. The patient was pain free 2 months after GKS. Contrast cisternography with CT scanning is an excellent alternative imaging modality for the treatment of patients with intractable trigeminal neuralgia who are unable to undergo MR imaging.The authors describe acute deterioration in facial and acoustic neuropathies following radiosurgery for acoustic neuromas. In May 1995, a 26-year-old man, who had no evidence of neurofibromatosis Type 2, was treated with gamma knife radiosurgery (GKS; maximum dose 20 Gy and margin dose 14 Gy) for a right-sided intracanalicular acoustic tumor. Two days after the treatment, he developed headache, vomiting, right-sided facial weakness, tinnitus, and right hearing loss. There was a deterioration of facial nerve function and hearing function from pretreatment values. The facial function worsened from House-Brackmann Grade 1 to 3. Hearing deteriorated from Grade 1 to 5. Magnetic resonance (MR) images, obtained at the same time revealed an obvious decrease in contrast enhancement of the tumor without any change in tumor size or peritumoral edema. Facial nerve function improved gradually and increased to House-Brackmann Grade 2 by 8 months post-GKS. The tumor has been unchanged in size for 5 years, and facial nerve function has also been maintained at Grade 2 with unchanged deafness. This is the first detailed report of immediate facial neuropathy after GKS for acoustic neuroma and MR imaging revealing early possibly toxic changes. Potential explanations for this phenomenon are presented.In clinical follow-up studies after radiosurgery, imaging modalities such as computerized tomography (CT) and magnetic resonance (MR) imaging are used. Accurate determination of the residual lesion volume is necessary for realistic assessment of the effects of treatment. Usually, the diameters rather than the volume of the lesion are measured. To determine the lesion volume without using stereotactically defined images, the software program VOLUMESERIES has been developed. VOLUMESERIES is a personal computer-based image analysis tool. Acquired DICOM CT scans and MR image series can be visualized. The region of interest is contoured with the help of the mouse, and then the system calculates the volume of the contoured region and the total volume is given in cubic centimeters. The defined volume is also displayed in reconstructed sagittal and coronal slices. In addition, distance measurements can be performed to measure tumor extent. The accuracy of VOLUMESERIES was checked against stereotactically defined images in the Leksell GammaPlan treatment planning program. A discrepancy in target volumes of approximately 8% was observed between the two methods. This discrepancy is of lesser interest because the method is used to determine the course of the target volume over time, rather than the absolute volume. Moreover, it could be shown that the method was more sensitive than the tumor diameter measurements currently in use. VOLUMESERIES appears to be a valuable tool for assessing residual lesion volume on follow-up images after gamma knife radiosurgery while avoiding the need for stereotactic definition.This study was conducted to evaluate the geometric distortion of angiographic images created from a commonly used digital x-ray imaging system and the performance of a commercially available distortion-correction computer program. A 12 x 12 x 12-cm wood phantom was constructed. Lead shots, 2 mm in diameter, were attached to the surfaces of the phantom. The phantom was then placed inside the angiographic localizer. Cut films (frontal and lateral analog films) of the phantom were obtained. The films were analyzed using GammaPlan target series 4.12. The same procedure was repeated with a digital x-ray imaging system equipped with a computer program to correct the geometric distortion. The distortion of the two sets of digital images was evaluated using the coordinates of the lead shots from the cut films as references. The coordinates of all lead shots obtained from digital images and corrected by the computer program coincided within 0.5 mm of those obtained from cut films. The average difference is 0.28 mm with a standard deviation of 0.01 mm. On the other hand, the coordinates obtained from digital images with and without correction can differ by as much as 3.4 mm. The average difference is 1.53 mm, with a standard deviation of 0.67 mm. The investigated computer program can reduce the geometric distortion of digital images from a commonly used x-ray imaging system to less than 0.5 mm. Therefore, they are suitable for the localization of arteriovenous malformations and other vascular targets in gamma knife radiosurgery.

Nonhabitual Seizures in Patients with Implanted Subdural Electrodes

The implantation of subdural electrodes has been widely employed in the invasive monitoring of patients with medically refractory epilepsy. The use of subdural electrodes, though, has been associated with rare but occasionally troublesome complications. We report the occurrence of nonhabitual seizures after implanting subdural grid electrodes. Among 57 patients diagnosed with medically refractory epilepsy who were evaluated in our department over a 12-month period, 21 patients underwent craniotomy for subdural grid/strip electrode implantation. Subdural grids and strips (AdTech, Racine, Wisc., USA) were used for continuous video EEG monitoring. In 3 patients, during subdural monitoring, consistent nonhabitual seizure activity was recorded. This was both clinically and electrographically different than the patients’ habitual seizures. The patients’ nonhabitual seizures disappeared postoperatively after removing the implanted electrodes. The occurrence of nonhabitual seizures, though quite rare, could lead to mislocalization of an epileptogenic focus. This complication might be the result of direct mechanical cortical irritation or chemical irritation caused by blood breakdown products. The occurrence of nonhabitual seizures comes to add itself to the existing list of complications associated with employment of subdural electrodes for invasive monitoring.

A 13-Year Experience with Epilepsy Surgery

Between 1985 and 1997, 563 therapeutic craniotomies were performed: 311 anterior temporal (ATL) and 158 extramesial temporal (XMT) resections, 67 callosotomies, 20 hemispherectomies and 7 multiple subpial transections. Sixty-seven percent of nonlesional ATL cases were seizure free (SF), and 76% of nonlesional ATL cases ≤18 years old were SF. Seventy-eight percent of lesional ATL cases with complete resection were SF. Seventy-three percent of lesional cases ≤18 were SF. Thirty-seven percent of nonlesional XMT cases were SF. Seventy percent of XMT lesional cases with complete resection were SF, and 82% of lesional XMT cases ≤18 were SF. Of the anterior callosotomy cases, there was a ≥90% decrease in generalized tonic-clonic seizures in 50% of patients, and in tonic seizures, drop attacks, absence and myoclonic seizures in approximately 60–70% of patients. Of 20 hemispherectomies, 65% were SF. Of 7 multiple subpial transections, 29% were SF.

Intracranial stimulation study of lateralization of affect

As part of their evaluation for epilepsy surgery, 53 patients underwent stimulation of depth or subdural electrodes. Responses obtained from depth stimulation included motor responses at 34 sites, sensory responses at 114 sites, language alterations at 6 sites, and affective responses at 22 sites. Responses obtained from subdural stimulation included motor responses at 19 sites, sensory responses at 31 sites, speech alterations at 10 sites, and affective responses at 1 site. Of 23 affective responses, 21 were dysphoric responses of fear, a sense of dying, or unpleasantness with or without some type of experiential phenomenon. Dysphoric responses were statistically associated (P=0.01) with right-sided stimulation (N=18) as compared with left-sided stimulation (N=3) of mesial frontal, orbitofrontal, mesial temporal, and insular stimulation sites. Two euphoric responses occurred, one with left-sided and one with right-sided stimulation. No affective responses were obtained with convexity or neocortical stimulation.

MR-based stereotactic mesencephalic tractotomy.

Introduction: Medically refractory pain related to cancer is a major indication for pain surgery. Stereotactic mesencephalic tractotomy (SMT) constitutes a widely accepted procedure in treating unilateral head and neck cancer pain. Material and Method: We report a case of a MRI-based right-sided SMT for treating intractable craniofacial pain, in a 38-year-old patient, related to a previously resected adenocystic carcinoma of the parotid gland. The patient had undergone an implantation of an intrathecal morphine/clonidine pump and subsequent radiofrequency cingulotomy with only temporary improvement. Prior to SMT the patient developed left-sided chest wall pain, secondary to metastasis, in addition to her left-sided facial, dysesthetic pain. The MRI-based SMT was performed with the assistance of a side-extruding monopolar electrode (Leibinger GmbH, Freiburg, Germany) for intraoperative, topographic mapping of the spinothalamic tract. Two lesions were made at 8 and 5 mm off the midline on the right side at the level of the superior colliculus at 70°C for 90 s with a 2 × 4 mm radiofrequency bipolar electrode (Leibinger GmbH). Results: The patient developed intraoperatively left-sided facial, bodily and extremity thermoanalgesia. She had an unremarkable postoperative course. No early proprioceptive or gaze deficits were noted. Her facial and truncal pain was well controlled with intrathecal morphine and clonidine at the preoperative dosology for 17 months. Left-sided upper extremity dysesthesia developed 15 months after the procedure. The patient expired 18 months after this procedure due to an extensive metastatic disease. Conclusions: The use of high-resolution MRI (MPRAGE) and side-extruding electrode represent technical maneuvers that could decrease the morbidity and further improve the long-term outcome of SMT in treating patients with chronic, medically refractory cancer pain, who have a likely survival time in the order of 1 year ± 6 months.

A 10-Year Experience with Magnetic Source Imaging in the Guidance of Epilepsy Surgery

Magnetic source imaging (MSI) of interictal epileptiform dipoles was studied in 100 epilepsy surgery candidates. Sixty underwent surgery. MSI epileptiform data were classified as focal, regional, multifocal, scattered or none. Resections of MSI epileptiform foci were classified as extensive (EXT) versus partial or none (P/N). MSI interictal epileptiform dipoles were found in 22 of 27 anterior temporal (ATL) cases, and in 31 of 33 extratemporal (XMT) cases. Of 10 EXT ATL cases, 5 (50%) were seizure free (SF). Of 12 P/N ATL cases, 7 (58%) were SF. Of 10 nonlesional EXT XMT resections, 8 (80%) were SF. Of 10 nonlesional P/N XMT resections, 1 (10%) was SF. Neither focality of MSI data or spatial agreement of electrographic and MSI data significantly affected outcomes.

Avoidance of Electrode Related MRI Artifact during Staged Deep Brain Stimulator Implantation

BACKGROUND Centers implanting deep brain stimulator (DBS) electrodes on different days often protect the first electrode tip with a protective cap, tunnel it under the scalp, and connect it to the generator at a later procedure. If magnetic resonance imaging (MRI) is used for planning during the second implantation, MRI artifacts from the protective cap could potentially corrupt the stereotactic coordinates. The importance of this problem may increase if emerging MRI safety data lead to more frequent use of MRI for these purposes. OBJECTIVE To describe an MRI artifact arising from the use of the standard protective DBS cap that corrupts stereotactic planning and to describe a way to avoid the artifact. METHODS After noting the artifact during a staged DBS procedure, a nonmetallic silastic sleeve contained in the existing DBS implantation kit was used in nine subsequent patients. Two caps with standard metallic screws were also tested with MRI phantoms. RESULTS The silastic sleeve protected the DBS electrode but did not produce MRI artifact. The phantom studies demonstrated significant artifact from caps containing screws. CONCLUSION A silastic sleeve provides adequate protection of the DBS electrode during staged implantation and avoids the MRI artifact associated with protective caps with screws.