Electrocochleography in profoundly deaf children: comparison of promontory and round window techniques

It is important to be able to accurately assess residual cochlear function in profoundly deaf children. Profound hearing loss in children requires special consideration, because the choice between a cochlear implant and a hearing aid depends on accurate estimation of the residual hearing. Previous reports confirm that promontory (needle) electrocochleography (ECochG) is useful for evaluation of residual hearing in severely deaf children, but there were some limitations in assessing the lower audiometric frequencies and for assessing profound hearing loss. It is argued that accurate placement of a round window electrode (RW ECochG) provides better recordings. Round window ECochG testing is performed under general anesthesia in young children and gives an opportunity for inspection of the middle ear using an endoscope. This report describes a special "golf club" electrode that can be placed under direct vision into the round window niche, minimizing the risks of damaging an abnormal round window while providing the optimum extracochlear recordings. Round window ECochG gives better responses, especially in lower audiometric frequencies, than conventional promontory ECochG. In the Sydney children's cochlear implant program, RW ECochG has become an essential preoperative test.