Intraoperativ nevrofysiologisk monitorering har fått økende betydning ved operasjoner som innebærer risiko for skade på nervesystemet. Vi ønsker å gi en oversikt over muligheter og begrensninger ved bruk av intraoperative nevrofysiologiske metoder.
Monitorering av nervebaner under operasjon - av hvem og hvordan?
Monitorering anses å være et viktig hjelpemiddel for å kunne gjennomføre en best mulig operasjon, samt redusere postoperative nevrologiske utfall. Nevrologiske utfall kan eksempelvis være redusert kraft, lammelse eller nummenhet.
To provide a summary of the intraoperative monitoring of muscle motor evoked potentials (MEPs) based on the presence–absence concept during neurosurgical operations along the spinal cord.
This review discusses the physiologic and pharmacologic factors (including newer anesthetic agents and adjuncts) that influence sensory evoked potentials (SEPs), focussing on SSEPs, BAEPs, and VEPs.
Intraoperative neurophysiologic monitoring (INM) using somatosensory and motor evoked potentials (MEPs) has become popular to reduce neural risk and to improve intraoperative surgical decision making. Intraoperative neurophysiologic monitoring is affected by the choice and management of the anesthetic agents chosen. Because inhalational and intravenous anesthetic agents have effects on neural synaptic and axonal functional activities, the anesthetic effect on any given response will depend on the pathway affected and the mechanism of action of the anesthetic agent (i.e., direct inhibition or indirect effects based on changes in the balance of inhibitory or excitatory inputs).
Hironobu Hayashi and Masahiko Kawaguchi
In neurosurgical procedures that may cause visual impairment in the intraoperative period, the monitoring of flash visual
evoked potential (VEP) is clinically used to evaluate visual function. Patients are unconscious during surgery under
general anesthesia, making flash VEP monitoring useful as it can objectively evaluate visual function. The flash stimulus
input to the retina is transmitted to the optic nerve, optic chiasm, optic tract, lateral geniculate body, optic radiation (geniculocalcarine tract), and visual cortical area, and the VEP waveform is recorded from the occipital region.
Intraoperative flash VEP monitoring allows detection of dysfunction arising anywhere in the optic pathway, from the retina to the visual cortex. Particularly important steps to obtain reproducible intraoperative flash VEP waveforms under general
anesthesia are total intravenous anesthesia with propofol, use of retinal flash stimulation devices using high-intensity
light-emitting diodes, and a combination of electroretinography to confirm that the flash stimulus has reached the retina.
Relatively major postoperative visual impairment can be detected by intraoperative decreases in the flash VEP amplitude.