Troubleshooting
*LH*
Lack of stimulus to the nerve; loss of all responses, peripheral response will be lost, no stimulus artifact, obligate waveforms will be absent but you will still average data that represents no response
Submaimal stimulus intensity, reduced amplitudes of all responses peripheral responses may be more greatly effected due to synaptic magnification, increased amplitude variability, cortical latencies may increase
High stimulator impedance, large stimulus artifact, impedances should not only be low but also matched, responses closest to the stimulator will be the greatest effected
60Hz noise contamination; response amplitudes ma be increased or decreased depending on where they fall relative to the 60Hz waveform; obligate peaks may appear shifted in latency; 60 Hz noise can be seen in the raw data, 3 cycles, 50 msec sample 6 cycles/100 msec sample
Non-cyclical noise, source EKG, EMG, surgical instruments electrical discharge, etc, response quality will be degraded and nosy, this noise can be seen in the raw data
Saturation of the amplifier, electrocautery can sometimes saturate the amplifier (overload it), sometimes causes some or all of the channels to be flat lines, sometimes artifacts such as EKG are amplified, can cause reduction in waveform amplitudes, may cause extra noise in some or all of the channels
Filter Problems, raising the cutoff of the locut or hicut filter will shorten the response latencies, lowering the cutoff of the locut or hicut filter will increase the response latencies, excessive filtering can reduce response amplitudes, to little filtering can make responses noisy
Recording Electrode is Out, high amplitude 60 Hz waveforms will be recorded, often artifact rejection stops averaging because the 60 Hz noise is so large, square waves can be seen 60 Hz noise clipped by the amplifier range
Troubleshooting Tips; always troubleshoot when placing your electrodes, in other words, check and double check all of your preps placements and connections, make sure your electrodes are taped well, eliminate all noise sources, keep your cords and cables away from power cords, never let them run parallel to power cords, braid or twist your electrodes, turn off unneeded sources of noise
Sources of cyclical noises; OR table not properly grounded, bair hugger, fluid warmer, infusion pumps, flat panel monitors, OR lights
Sources of Noncyclical noise, EMG artifact, EKG, electrostatic discharge from 2 metal surgical instruments touching (metalphonics) bovie, bipolar
Lack of stimulus to the nerve; loss of all responses, peripheral response will be lost, no stimulus artifact, obligate waveforms will be absent but you will still average data that represents no response
Submaimal stimulus intensity, reduced amplitudes of all responses peripheral responses may be more greatly effected due to synaptic magnification, increased amplitude variability, cortical latencies may increase
High stimulator impedance, large stimulus artifact, impedances should not only be low but also matched, responses closest to the stimulator will be the greatest effected
60Hz noise contamination; response amplitudes ma be increased or decreased depending on where they fall relative to the 60Hz waveform; obligate peaks may appear shifted in latency; 60 Hz noise can be seen in the raw data, 3 cycles, 50 msec sample 6 cycles/100 msec sample
Non-cyclical noise, source EKG, EMG, surgical instruments electrical discharge, etc, response quality will be degraded and nosy, this noise can be seen in the raw data
Saturation of the amplifier, electrocautery can sometimes saturate the amplifier (overload it), sometimes causes some or all of the channels to be flat lines, sometimes artifacts such as EKG are amplified, can cause reduction in waveform amplitudes, may cause extra noise in some or all of the channels
Filter Problems, raising the cutoff of the locut or hicut filter will shorten the response latencies, lowering the cutoff of the locut or hicut filter will increase the response latencies, excessive filtering can reduce response amplitudes, to little filtering can make responses noisy
Recording Electrode is Out, high amplitude 60 Hz waveforms will be recorded, often artifact rejection stops averaging because the 60 Hz noise is so large, square waves can be seen 60 Hz noise clipped by the amplifier range
Troubleshooting Tips; always troubleshoot when placing your electrodes, in other words, check and double check all of your preps placements and connections, make sure your electrodes are taped well, eliminate all noise sources, keep your cords and cables away from power cords, never let them run parallel to power cords, braid or twist your electrodes, turn off unneeded sources of noise
Sources of cyclical noises; OR table not properly grounded, bair hugger, fluid warmer, infusion pumps, flat panel monitors, OR lights
Sources of Noncyclical noise, EMG artifact, EKG, electrostatic discharge from 2 metal surgical instruments touching (metalphonics) bovie, bipolar