Effects of laserneedle stimulation in the external auditory meatus on brainstem and very early auditory evoked potentials in humans.
OBJECTIVE
For the first time, brainstem auditory evoked potentials (BAEP) and very early auditory evoked potentials (EAEP) were investigated in 23 volunteers (mean age: 26.5 +/- 3.6 years) under resting conditions and during continuous and frequency modulated (2 Hz) laser stimulation in the external auditory meatus.


METHODS
Using a new ear adapter, the outer region of the auditory canal was stimulated with laser light (685 nm, 4 x 30-40 mW, duration: 10 minutes).


RESULTS
The EAEPs were significantly changed during continuous (p=0.019), as well as frequency modulated (p=0.014) laser stimulation compared with control measurements.


CONCLUSIONS
Physiologic alterations of inner ear mechanism such as extra-cerebral changes in conductance or stimulation-dependent depolarization processes in extra-cerebral regions of the auditory system could be possible explanations for the significant difference in measurement parameters.
Litscher
G
G
Research Unit of Biomedical Engineering in Anesthesia and Intensive Care Medicine, Medical University Graz, Austria. gerhard.litscher@meduni-graz.at
D000328:Adult; D001300:Audiometry, Evoked Response / Q000379:methods; D001306:Auditory Pathways / Q000502:physiology*; D004307:Dose-Response Relationship, Radiation; D004424:Ear Canal / Q000294:innervation / Q000528:radiation effects*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000528:radiation effects*; D005260:Female; D006801:Humans; D007834:Lasers; D008297:Male; D011930:Reaction Time / Q000528:radiation effects