Auditory Brainstem Response/ABR
ABR Technical Considerations: Auditory Brainstem Responses are obtained from each ear using Etymotic Research insert tube phones in conjunction with Cadwell Cascade evoked potential instrumentation.
2000 trials at 100, 80, 60, 40, 30 dB nHL using 100 microsecond square wave alternating rarefaction/condensation test signals.
Electrode placement: Fpz (non-inverting) and A1/A2 (inverting) scalp positions
ABR Results: Demonstrate reliable responses of prominent wave I, III and V within normal latency/amplitude limits bilaterally.
V-I latency differences (4.9ms) and inter ear wave V latency differences (0.1 ms) are reflective of normal brainsetem auditory fiber tract transmission times and age appropriate myelinazation of white matter tracts within mid-pontine structures.
normal peripheral sensitivity, hearing is a cognitive precept dependent on appropriate thalamocortical connections
(ABRs) were also recorded to monitor the status of both 8th cranial nerves and overall brain stem integrity. Each ear was tested separately using an electrode montage in which subdermal needle electrodes (inverting leads) were placed, respectively, within the ear canal ipsilateral to the ear that received stimulation (A1/A2). The non-inverting lead was also a subdermal electrode placed at vertex (Cz). One-hundred microsecond (100 us) square wave pulses produced alternating rarefaction and condensation clicks of 80 dB nHL and were presented at a rate of 11.3 stim/sec. Stimuli were presented alternately to each ear every 45 milliseconds. Averages were collected to at least 2000 individual trials. A needle electrode inserted into the right shoulder served as ground. ABRs/EMGs were amplified (gain=105) using differential amplifiers (Cadwell-Cascade), monitored and averages collected on a computer (Toshiba). Listed below is a summary of intraoperative activities pertinent to monitoring procedures.
2000 trials at 100, 80, 60, 40, 30 dB nHL using 100 microsecond square wave alternating rarefaction/condensation test signals.
Electrode placement: Fpz (non-inverting) and A1/A2 (inverting) scalp positions
ABR Results: Demonstrate reliable responses of prominent wave I, III and V within normal latency/amplitude limits bilaterally.
V-I latency differences (4.9ms) and inter ear wave V latency differences (0.1 ms) are reflective of normal brainsetem auditory fiber tract transmission times and age appropriate myelinazation of white matter tracts within mid-pontine structures.
normal peripheral sensitivity, hearing is a cognitive precept dependent on appropriate thalamocortical connections
(ABRs) were also recorded to monitor the status of both 8th cranial nerves and overall brain stem integrity. Each ear was tested separately using an electrode montage in which subdermal needle electrodes (inverting leads) were placed, respectively, within the ear canal ipsilateral to the ear that received stimulation (A1/A2). The non-inverting lead was also a subdermal electrode placed at vertex (Cz). One-hundred microsecond (100 us) square wave pulses produced alternating rarefaction and condensation clicks of 80 dB nHL and were presented at a rate of 11.3 stim/sec. Stimuli were presented alternately to each ear every 45 milliseconds. Averages were collected to at least 2000 individual trials. A needle electrode inserted into the right shoulder served as ground. ABRs/EMGs were amplified (gain=105) using differential amplifiers (Cadwell-Cascade), monitored and averages collected on a computer (Toshiba). Listed below is a summary of intraoperative activities pertinent to monitoring procedures.