Study on the clinical application of pulsed DC magnetic technology for tracking of intraoperative head motion during frameless stereotaxy

BACKGROUND: Tracking of post-registration head motion is one of the major problems in frameless stereotaxy. Various attempts in detecting and compensating for this phenomenon rely on a fixed reference device rigidly attached to the patient's head. However, most of such reference tools are either based on an invasive fixation technique or have physical limitations which allow mobility of the head only in a restricted range of motion after completion of the registration procedure. METHODS: A new sensor-based reference tool, the so-called Dynamic Reference Frame (DRF) which is designed to allow an unrestricted, 360° range of motion for the intraoperative use in pulsed DC magnetic navigation was tested in 40 patients. Different methods of non-invasive attachment dependent on the clinical need and type of procedure, as well as the resulting accuracies in the clinical application have been analyzed. RESULTS: Apart from conventional, completely rigid immobilization of the head (type A), four additional modes of head fixation and attachment of the DRF were distinguished on clinical grounds: type B1 = pin fixation plus oral DRF attachment; type B2 = pin fixation plus retroauricular DRF attachment; type C1 = free head positioning with oral DRF; and type C2 = free head positioning with retroauricular DRF. Mean fiducial registration errors (FRE) were as follows: type A interventions = 1.51 mm, B1 = 1.56 mm, B2 = 1.54 mm, C1 = 1.73 mm, and C2 = 1.75 mm. The mean position errors determined at the end of the intervention as a measure of application accuracy were: 1.45 mm in type A interventions, 1.26 mm in type B1, 1.44 mm in type B2, 1.86 mm in type C1, and 1.68 mm in type C2. CONCLUSION: Rigid head immobilization guarantees most reliable accuracy in various types of frameless stereotaxy. The use of an additional DRF, however, increases the application scope of frameless stereotaxy to include e.g. procedures in which rigid pin fixation of the cranium is not required or desired. Thus, continuous tracking of head motion allows highly flexible variation of the surgical strategy including intraoperative repositioning of the patient without impairment of navigational accuracy as it ensures automatic correction of spatial distortion. With a dental cast for oral attachment and the alternative option of non-invasive retroauricular attachment, flexibility in the clinical use of the DRF is ensured

Pharmacological Stimulation of Edar Signaling in the Adult Enhances Sebaceous Gland Size and Function

Impaired ectodysplasin A (EDA) receptor (EDAR) signaling affects ectodermally derived structures including teeth, hair follicles, and cutaneous glands. The X-linked hypohidrotic ectodermal dysplasia (XLHED), resulting from EDA deficiency, can be rescued with lifelong benefits in animal models by stimulation of ectodermal appendage development with EDAR agonists. Treatments initiated later in the developmental period restore progressively fewer of the affected structures. It is unknown whether EDAR stimulation in adults with XLHED might have beneficial effects. In adult Eda mutant mice treated for several weeks with agonist anti-EDAR antibodies, we find that sebaceous gland size and function can be restored to wild-type levels. This effect is maintained upon chronic treatment but reverses slowly upon cessation of treatment. Sebaceous glands in all skin regions respond to treatment, although to varying degrees, and this is accompanied in both Eda mutant and wild-type mice by sebum secretion to levels higher than those observed in untreated controls. Edar is expressed at the periphery of the glands, suggesting a direct homeostatic effect of Edar stimulation on the sebaceous gland. Sebaceous gland size and sebum production may serve as biomarkers for EDAR stimulation, and EDAR agonists may improve skin dryness and eczema frequently observed in XLHED

Magnetfreies Cochlear Implant - eine Alternative in besonderen Fällen

Einleitung: Die Fixierung des Headsets eines Cochlear Implants (CI) wird in der Regel über eine magnetische Verbindung zum Implantat sichergestellt. Ferromagnetische Materialien stellen relative Kontraindikationen zur Durchführung einer MRT dar. Im Falle spezieller Komorbiditäten ist eine MRT-Diagnostik unumgänglich, weshalb hier ein magnetfreies CI eine interessante Möglichkeit darstellt. Material und Methoden: Wir berichten über einen Patienten, der im Rahmen eines Cogan-Syndroms ertaubt und ein magnetfreies Clarion-Implantat der Fa. Advanced Bionics erhalten hatte, da wegen einer ebenfalls bestehenden Enzephalitis disseminata die Notwendigkeit postoperativer MRT-Untersuchungen bestand. Zur Verbesserung seiner kommunikativen Fähigkeiten wünschte er eine bilaterale Versorgung. Ergebnisse: Der Patient bevorzugte aufgrund seiner Vorerfahrungen ein HiRes® 90K Implant der Fa. Advanced Bionics. Wegen der oben geschilderten Umstände wurde beschlossen, den Magneten gegen einen nicht ferromagnetischen Platzhalter bereits bei der Implantation einzusetzen. Das Problem der Befestigung wurde mit Hilfe eines speziell für den Patienten angefertigten Ohrpassstückes mit Drahtbügel gelöst. Um ein möglichst geringes Drehmoment auf das Ohrpassstück zu haben, wurde die Lage des Implantates untypisch weit nach anterior und die Längsachse nach cranial orientiert. Die Implantation und der postoperative Verlauf gestalteten sich unauffällig. Die Anpassung des Sprachprozessors gelang ohne Probleme bei ergonomisch günstigem Sitz des Headsets. Schlussfolgerung: Das Fallbeispiel demonstriert die Machbarkeit der magnetfreien CI-Versorgung spezieller Fälle. Auf eine geeignete intraoperative Implantatlage ist zu achten