image-guided-convection-enhanced-delivery-into-agarose-gel-models

Image-guided Convection-enhanced Delivery into Agarose Gel Models of the Brain

Convection-enhanced delivery (CED) has been proposed as a treatment option for a wide range of neurological diseases. Neuroinfusion catheter CED allows ...

University of Tennessee Health Science Center

Semmes-Murphey Clinic

Device-related infection is a common complication of deep brain stimulator (DBS) implantation. We reviewed the incidence and management of early hardware-related infections in a large series.

Deep brain stimulator hardware-related infections: incidence and management in a large series.

Cluster headache is the most severe primary headache disorder known. Ten to 20% of cases are medically intractable. DBS of the posterior hypothalamic area has shown effectiveness for alleviation of cluster headache in many but not all of the 46 reported cases from European centers and the eight cases studied at the University of California, San Francisco. This surgical strategy was based on the finding of increased blood flow in the posterior hypothalamic area on H(2)(15)O PET scanning during spontaneous and nitroglycerin-induced cluster headache attacks. The target point used, 4-5 mm posterior to the mamillothalamic tract, is in the border zone between posterior hypothalamus, anterior periventricular gray matter, and inferior thalamus. Recently, occipital nerve stimulation has shown efficacy, calling in question the use of DBS as a first line surgical therapy. In this report, we review the indications, techniques, and outcomes of DBS for cluster headache.

Deep brain stimulation for medically intractable cluster headache.

Wir pr&auml;sentieren die Ans&auml;tze f&uuml;r die Verwendung von D&uuml;nnschicht-Polymeren Elektrode-Arrays f&uuml;r Anwendungen der minimal-invasiven neurologische &Uuml;berwachung. Die Flexibilit&auml;t und die einzigartige Oberfl&auml;cheneigenschaften von der D&uuml;nnschicht-Polyimid-Substrat in Kombination mit einem kompakten Ger&auml;t-Plattform machen sie zu einer Vielzahl von chirurgische Implantation Verfahren. Mit eine Rapid-Prototyping und Fertigung-Technik, k&ouml;nnen Arrays von verschiedenen Geometrien innerhalb einer Woche hergestellt werden. In diesem Papier testen wir zwei verschiedene Ans&auml;tze f&uuml;r die Bereitstellung von Elektrode Arrays durch kleine kraniale &Ouml;ffnungen.

Flexible D&uuml;nnschicht-Elektrode-Arrays f&uuml;r minimal-invasive neurologische &Uuml;berwachung.

Vi presentiamo gli approcci per l&#39;utilizzo di matrici polimeriche elettrodo a film sottile per applicazioni di monitoraggio neurologico minimamente invasiva. La flessibilit&agrave; e l&#39;unica propriet&agrave; di superficie del substrato sottile-pellicola poliimmide in combinazione con una piattaforma dispositivo compatto li rende suscettibili a una variet&agrave; di procedure chirurgiche di impianto. Utilizzando una tecnica di fabbricazione e di prototipazione rapida, matrici di varie geometrie possono essere realizzati entro una settimana. In questo libro ci prova due diversi approcci per la distribuzione di matrici elettrodo attraverso piccole aperture craniche.

Matrici di elettrodo flessibile a film sottile per monitoraggio neurologico minimamente invasivo.

Nous pr&#xE9;sentons des approches pour l&#x26;#39;utilisation de tableaux minces films d&#x26;#39;&#xE9;lectrodes polym&#xE8;res pour utilisation dans des applications de surveillance neurologique mini-invasive. La souplesse et des propri&#xE9;t&#xE9;s de surface unique du film mince de polyimide substrat en combinaison avec une plate-forme appareil compact rendre accessible &#xE0; une vari&#xE9;t&#xE9; de proc&#xE9;dures d&#x26;#39;implantation chirurgicale. En utilisant une technique de prototypage rapide et la fabrication, des tableaux de diff&#xE9;rentes g&#xE9;om&#xE9;tries peuvent &#xEA;tre fabriqu&#xE9;s dans une semaine. Dans cet article, nous testons deux approches diff&#xE9;rentes pour d&#xE9;ployer des r&#xE9;seaux d&#x26;#39;&#xE9;lectrodes &#xE0; travers de petites ouvertures du cr&#xE2;ne.

Mince et flexible r&#xE9;seaux d&#x26;#39;&#xE9;lectrodes de films pour la surveillance neurologique de mini-invasive

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We present approaches for using thin film polymeric electrode arrays for use in applications of minimally invasive neurological monitoring. The flexibility and unique surface properties of the thin-film polyimide substrate in combination with a compact device platform make them amenable to a variety of surgical implantation procedures. Using a rapid-prototyping and fabrication technique, arrays of various geometries can be fabricated within a week. In this paper we test two different approaches for deploying electrode arrays through small cranial openings.

Flexible thin film electrode arrays for minimally-invasive neurological monitoring.

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Se presentan los enfoques para el uso de finas matrices de pel&#xED;cula polim&#xE9;rica de electrodos para uso en aplicaciones de monitorizaci&#xF3;n neurol&#xF3;gica m&#xED;nimamente invasiva. La flexibilidad y las propiedades &#xFA;nicas de la superficie de la pel&#xED;cula delgada de poliimida sustrato en combinaci&#xF3;n con una plataforma dispositivo compacto hacerlas susceptibles a una variedad de procedimientos de implantaci&#xF3;n quir&#xFA;rgica. Usando una t&#xE9;cnica r&#xE1;pida de prototipos y la fabricaci&#xF3;n, las matrices de diversas geometr&#xED;as se pueden fabricar en una semana. En este trabajo se prueba dos enfoques diferentes para la implementaci&#xF3;n de gu&#xED;as de electrodos a trav&#xE9;s de peque&#xF1;as aberturas craneales.

Delgado y flexible matrices de Cine de electrodos para monitorizaci&#xF3;n neurol&#xF3;gica m&#xED;nimamente invasiva

Objective:  Deep brain stimulation technology now allows a choice between constant current and constant voltage stimulation, yet clinical trials comparing the two are lacking. Impedance instability would theoretically favor constant current stimulation; however, few publications address this with long-term follow-up. In this report, we review our series for impedance change and discuss our findings and their implications for future study design. Materials and Methods:  A retrospective chart review was performed of all consecutive patients seen in the outpatient clinic for deep brain stimulation adjustments at the University of Wisconsin-Madison from February 2006 to May 2007. The following data were extracted: Quadrapolar contact selection, frequency, voltage, pulse width, and measured impedance at the therapeutic parameters. Patients were selected if consecutive measurements of therapeutic impedances for the same patient were performed with the same frequency, pulse width, voltage, and configuration of active contacts. Results:  A total of 63 patients with 110 electrodes had 301 documented programming visits. From these, 16 patients had 20 consecutive measurements with unchanged parameters in 19 electrodes at a median interval of 68 days and median follow-up of 549 days after implantation. No significant intra-patient intra-electrode therapeutic impedance variability was observed in this study (SD = 105.3 Ω, paired t-test, p= 0.312). In contrast, marked inter-patient variability in impedance was noted. This variability could not be explained by stimulation target, measurement interval, time since implantation, monopolar vs. bipolar stimulation, stimulation voltage, or stimulation frequency. Conclusions:  No significant change in the same electrode therapeutic impedance was identified. Given the assumption that stimulation current is the critical parameter influencing clinical outcomes, these findings would not disadvantage constant voltage stimulation. However, inter-patient variability suggests a possible advantage for constant current stimulation when generalizing experience and comparisons over multiple patients. Further study of the relationship of stimulation efficacy to stimulation mode and impedance change is warranted.

Long-term measurement of therapeutic electrode impedance in deep brain stimulation.

Detection of epileptiform activity is of interest for responsive stimulation and diagnostic or monitoring devices in epilepsy; some implantable systems use low-computational-complexity algorithms such as line length trending and half-wave detection. Broadband noise was added to recorded electrocorticographic signals in order to model the potential impact of factors such as electrode-tissue interface properties and distance from the epileptic focus on these detection tools. Simulation demonstrated that half-wave and line length tools can yield consistent results in the presence of moderate amounts of noise.

Robustness of implantable algorithms to detect epileptiform activity in the presence of broad-spectrum background noise.

Deep brain stimulation (DBS) efficacy is related to optimal electrode placement. Several authors have quantified brain shift related to surgical targeting; yet, few reports document and discuss the effects of brain shift after insertion. Objective: To quantify brain shift and electrode displacement after device insertion. Twelve patients were retrospectively reviewed, and one post-operative MRI and one time-delayed CT were obtained for each patient and their implanted electrodes modeled in 3D. Two competing methods were employed to measure the electrode tip location and deviation from the prototypical linear implant after the resolution of acute surgical changes, such as brain shift and pneumocephalus. In the interim between surgery and a pneumocephalus free postoperative scan, electrode deviation was documented in all patients and all electrodes. Significant shift of the electrode tip was identified in rostral, anterior, and medial directions (p < 0.05). Shift was greatest in the rostral direction, measuring an average of 1.41 mm. Brain shift and subsequent electrode displacement occurs in patients after DBS surgery with the reversal of intraoperative brain shift. Rostral displacement is on the order of the height of one DBS contact. Further investigation into the time course of intraoperative brain shift and its potential effects on procedures performed with rigid and non-rigid devices in supine and semi-sitting surgical positions is needed.

Perioperative brain shift and deep brain stimulating electrode deformation analysis: implications for rigid and non-rigid devices.

Long-term stability of the electrode-tissue interface may be required to maintain optimal neural recording with subdural and deep brain implants and to permit appropriate delivery of neuromodulation therapy. Although short-term changes in impedance at the electrode-tissue interface are known to occur, long-term changes in impedance have not previously been examined in detail in humans. To provide further information about short- and long-term impedance changes in chronically implanted electrodes, a dataset from 191 persons with medically intractable epilepsy participating in a trial of an investigational responsive neurostimulation device (the RNS(®) System, NeuroPace, Inc.) was reviewed. Monopolar impedance measurements were available for 391 depth and subdural leads containing a total of 1564 electrodes; measurements were available for median 802 days post-implant (range 28-1634). Although there were statistically significant short-term impedance changes, long-term impedance was stable after one year. Impedances for depth electrodes transiently increased during the third week after lead implantation and impedances for subdural electrodes increased over 12 weeks post-implant, then were stable over the subsequent long-term follow-up. Both depth and subdural electrode impedances demonstrated long-term stability, suggesting that the quality of long-term electrographic recordings (the data used to control responsive brain stimulation) can be maintained over time.

Karl A. Sillay

University of Tennessee Health Science Center

Image-guided Convection-enhanced Delivery into Agarose Gel Models of the Brain