Modified occipital approach to the endolymphatic sac and cochlear aqueduct of the guinea pig

Obliteration of the endolymphatic sac reliably results in endolymphatic hydrops in some animal species. While this procedure is frequently utilized in the study of experimental Meniere's disease, additional information regarding inner ear fluid hydrodynamics can be obtained by obstructing the cochlear aqueduct to eliminate the influence of the cerebrospinal fluid on the perilymphatic compartment of the inner ear. This report describes a modified extradural occipital approach for surgical obliteration of the endolymphatic sac and obstruction of the cochlear aqueduct in the guinea pig. The extradural approach allows direct visualization of the cochlear aqueduct without manipulation or retraction of the dura, sigmoid sinus, or cerebellum. For experimental studies, which require obliteration of both the endolymphatic sac and cochlear aqueduct, this approach provides improved reliability with reduced morbidity and mortality.