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No device was returned for evaluation.Once nuvasive was notified of the issue, a third party neuromonitoring company was asked to export the system logs and send them to nuvasive software development engineering for evaluation.Review of the system logs was able to confirm the reported low stimulation readings.The system logs also identified free run electromyography (emg) activity prior to stimulation; however, a root cause for the low stimulation readings could not be conclusively determined.Based on the information obtained the root cause of the reported event is unknown, but may have been the result of the system perceiving noisy free run emg signals as emg stimulation response.Labeling review: "warnings, cautions and precautions.While the pulse system is designed to assist in the electromyographic location of spinal nerves in proximity to the surgical site, it is not intended to take the place of thorough knowledge of spinal anatomy and appropriate surgical technique, nor should the information provided by the system be construed as definitive indicators of nerve location.Such factors as the distance from the nerve, the position and placement of electrodes, individual muscle and/or nerve responses, the proximity and strength of sources of electrical interference, and other patient and environmental factors, may influence the operation.If, in the judgment of the clinician, this resistance is sufficient to preclude proper placement of instruments, the procedure should be suspended." ".The pulse system is to be used only as an adjunct to medical judgment and appropriate surgical practices.Dilator insertion and advancement should be conducted only after careful analysis of radiographic images of the operative target area.While a positive emg detection by the pulse system can be associated with a high level of certainty that a nerve is in close proximity to the dilator tip, the absence of such an emg detection cannot be construed as a certain indication that no nerves are close to the dilator tip.Do not advance dilator probes until all available data have been considered." ".Movement of the patient during stimulation can cause excessive electrical ¿noise¿ and/or false emg (noise) artifacts." ".The pulse system will not be able to reliably detect emg impulses on channels degraded by noise.If an impedance test error occurs, immediate attention should be directed toward correcting the problem by checking the electrode placement, securing the electrodes with tape, and eliminating any other sources of the noise.If excessive ambient noise persists or if a noise error message appears, check the position of all leads and electrodes, and position them as far away from other electronic equipment as possible.Observe the emg signals using the free run, or evoked potentials display to determine the nature of the noise.Poor electrode impedance may create susceptibility to electrical interference, which can adversely affect system performance.".
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