Utilization of impedance measurements in pallidotomy using a monopolar electrode.

OBJECT: This study was performed to evaluate the reliability and utility of using monopolar impedance monitoring for estimation of the location of the thermocouple electrode during a pallidotomy procedure. METHODS: In 26 patients, impedance profiles were measured at 2-mm intervals and anatomical boundaries were marked on postoperative MRI studies in 19 patients. The pattern of change in impedance as the electrode was towards the target coordinates in the globus pallidus was studied empirically in relation to MRI-defined anatomy and by electrical stimulations. The pattern of impedance change was of greater reliability than absolute impedance values. A drop in impedance was noted in 10 cases where the electrode entered the putamen or globus pallidus upon exiting the internal capsule, and in 9 of these this drop was measured before or at the distal boundary of the internal capsule. A variable pattern in the region of the base of the globus pallidus was observed, with 10 of 19 cases demonstrating a decrease and 8 cases an increase, consistent with the proximity of a CSF cistern in the former and the ansa lenticularis and optic tract in the latter. Simulations showed that the monopolar electrode was more sensitive to the approach of a boundary than the bipolar electrode. CONCLUSION: Our measurements and simulations suggest that a monopolar electrode could predict a nearby region of high or low impedance before penetrating it and a trend of decreasing impedance as the distal edge of the globus pallidus is approached.

Medical electronic link (MEL): providing telemedicine on the World Wide Web.

Many tertiary care centers in the USA have attempted to implement interactive television (IATV) or dynamic telemedicine systems. The advantage these systems provide is real-time interaction. The biggest disadvantage is cost: expensive hardware, band-width and personnel. An alternative to IATV is Medical Electronic Link (MEL); a low cost, store-forward, internet-based physician consultation system. MEL allows physicians in remote locations to consult physicians at the Dartmouth Hitchcock Medical Center in Lebanon, New Hampshire by using the World Wide Web. The Benefits of MEL are low hardware and band-width costs, accessibility, a self-explanatory interface, convenience, and its use of the case record. This system has been implemented at a family practice clinic in Manchester, NH and at the Tribhuvan University Teaching Hospital in Kathmandu, Nepal.