Biasing of the Summating Potentials

Electrocochleographic findings in superior canal dehiscence syndrome

“…In endolymphatic hydrops, a relative increase in endolymphatic fluid pressure causes hydromechanical changes within the scala media and subsequent displacement of the basilar membrane toward the scala tympani. SP elevation is known to reflect these changes Durrant and Gans, 1975;Ferraro et al, 1985). In addition, perilymph fistula is also thought to have the same mechanism as secondary endolymphatic hydrops, and exhibits endolymphatic hydrops histologically and increased SP/AP in animal models (Campbell and Savage, 1992) and in man (Arenberg et al, 1988).…”

Electrocochleography as a Diagnostic and Intraoperative Adjunct in Superior Semicircular Canal Dehiscence Syndrome

“…An increase in the SP amplitude relative to the AP amplitude is widely thought to be the most useful ECoG measure for identifying ELH. Significant increases in SP amplitude result from experimental displacement of the basilar membrane toward the scala tympani, either by increasing hydrostatic pressure above the basilar membrane (19) or by low-frequency biasing (20). Clinical SP elevation may reflect hydromechanical changes within the scala media caused by a relative increase in endolymphatic fluid pressure (17), explaining the elevated SP/AP observed in two-thirds of patients with Ménière's disease (21) and in animal models of hydrops (22).…”

A Diagnostic Test for Ménière's Disease and Cochlear Hydrops: Impaired High-Pass Noise Masking of Auditory Brainstem Responses

“…Other investigators focused on the SP alone, rather than the ratio (6)(7)(8)11). Unfortunately, a number of variables can significantly affect the results and diagnostic value of the SP, as well as the SP/AP ratio measures; in particular, hearing loss (8,17).…”

“…Thus, various measures of evoked electrical activity, particularly electrocochleography studies, have focused on amplitude measures of the summating potential (SP) alone or on the ratio of the SP amplitude to compound action potential (AP) of the VIIIth cranial nerve (5)(6)(7)(8)(9)(10)(11). The SP/AP ratio has been studied for a number of years and the results have varied greatly.…”