NIM® EMG ELECTRODE

Additional Manufacturer Narrative

MEDICAL SAFETY TEAM HAS REVIEWED THE EVENT AND ITS SEVERITY ARE KNOWN AND LABELED PER NIM VITAL PRA 10834094DOC, AND NIM VITAL IFU M 987224A001. MEDTRONIC SUBMITS THIS REPORT TO COMPLY WITH FDA REGULATIONS 21 CFR PARTS 4 AND 803. MEDTRONIC HAS MADE REASONABLE EFFORTS TO PROVIDE AS MUCH RELEVANT INFORMATION AS IS AVAILABLE TO THE COMPANY AS OF THE SUBMISSION DATE OF THIS REPORT. THIS REPORT DOES NOT CONSTITUTE AN ADMISSION OR A CONCLUSION BY FDA, MEDTRONIC, OR ITS EMPLOYEES THAT THE DEVICE, MEDTRONIC, OR ITS EMPLOYEE CAUSED OR CONTRIBUTED TO THE EVENT DESCRIBED IN THE REPORT. MEDTRONIC WILL SUBMIT A SUPPLEMENTAL REPORT IF ADDITIONAL RELEVANT INFORMATION BECOMES KNOWN.

Description of Event or Problem

IT WAS REPORTED THAT DURING PAROTID TUMOR SURGERY, A 4-CHANNEL FACIAL NERVE MONITOR WAS USED. THE RESPONSES WERE GOOD UNTIL PARTWAY THROUGH THE SURGERY, BUT WHEN OPERATING IN THE CH4 REGION, A WARNING TO "CHECK THE ELECTRODES" APPEARED SIMULTANEOUSLY FOR CH1 TO CH3. AT THIS POINT, THE MAIN TRUNK OF THE FACIAL NERVE (BEFORE IT BRANCHES) WAS STIMULATED, BUT THERE WAS NO RESPONSE IN CH1 (FOREHEAD), CH2 (UPPER EYELID), AND CH3 (NEAR THE UPPER LIP); ONLY CH4 (NEAR THE LOWER LIP) SHOWED A RESPONSE. VISUAL CONFIRMATION OF FACIAL MUSCLE MOVEMENT SHOWED THAT ONLY THE LOWER LIP MOVED. WHEN THE PERIPHERAL SIDE AFTER BRANCHING OF THE FACIAL NERVE WAS STIMULATED, CH1 TO CH3 SHOWED WEAK RESPONSES, WITH SOME MUSCLE MOVEMENT. ALTHOUGH CH4 WAS THE AREA BEING OPERATED ON, THE ISSUE OCCURRED WITH CH1 TO CH3, WHICH WAS CONFUSING. UPON REFLECTION, IT SEEMS THAT THE FACIAL NERVE TRUNK MAY HAVE BEEN DAMAGED BY THE ASSISTANT'S RETRACTION (AS THE ENTIRE PAROTID GLAND WAS BEING PULLED), RATHER THAN AN ACTUAL NERVE TRANSECTION. WHEN SPONTANEOUS NERVE DISCHARGES ARE HEARD, IT SUGGESTS THAT THE NERVE IS NOT BEING HANDLED GENTLY ENOUGH, BUT THIS DID NOT OCCUR DURING THE PROCEDURE. REBOOTED THE SYSTEM AND REPLACED THE NEEDLE ELECTRODES FOR CH1 TO CH3 WITH NEW ONES, BUT THE RESULTS REMAINED THE SAME. POST-OPERATIVELY, ALL REGIONS CORRESPONDING TO CH1 TO CH4 SHOWED INCOMPLETE PARALYSIS, WITH SOMEWHAT WEAKENED MOVEMENT. THE WEAKEST MOVEMENT WAS IN THE LOWER LIP, CORRESPONDING TO CH4. THIS DISCREPANCY BETWEEN THE NIM RESPONSES AND THE DEGREE OF POST-OPERATIVE PARALYSIS, ESPECIALLY WITH CH1 TO CH3 SHOWING NO RESPONSE ON THE NIM YET MILD PARALYSIS, WAS PUZZLING.