ABSTRACT
The potential utility of otoacoustic emissions, especially distortion product ones (DPOAEs), has considerably expanded over the last two decades, from their initial goal, neonatal hearing screening, to new noninvasive methods for monitoring a variety of aspects of hearing relevant to clinical exploration. Because they are exquisitely sensitive to the amplifying capabilities of outer hair cells in the cochlea, DPOAE levels have been profitably used for tracking dangerous changes in cochlear blood flow during vestibular schwannoma resection surgery, or the detrimental effects of noise exposure. But DPOAEs are also ideally suited for probing minor changes in middle and inner-ear transfer functions produced by intracranial or intralabyrinthine pressure changes. Their sensitivity to pressure applies to two clinical domains, for patients with neurological conditions relating to disrupted homeostasis of cerebrospinal fluid, and with Menière symptoms in which endolymphatic pressure may vary abnormally. Both categories can benefit from a noninvasive, technically simple follow-up.
This chapter develops these two original applications of DPOAE detection, from the biophysical models that underpin how they physiologically relate 274to the tracked structures of interest, to the feasibility, performance, and shortcomings of the resulting methods in clinical settings.
