An evaluation of per-scalar cochlear electrode implantation techniques

Abstract

The effects of infection and trauma on the organ of Corti and spiral ganglion cells following per-scalar cochlear electrode implantations in cats were evaluated. The incidence of infection with a per-scalar electrode inserted through an opening made directly into the apical and middle turns was low, provided the procedure was carried out aseptically with an antibiotic cover. Trauma could also be kept to a minimum by inserting the electrode into the scala tympani, taking care to insert the electrode without applying force and ensuring that the 1st insertion was the only one. The tip of the electrode should be blunt, and its diameter smaller than the width of the scala tympani. Damage to the organ of Corti, and loss of spiral ganglion cells only occurred as a local phenomenon, and its extent was related to the severity of the damage to the Reissner''s and basilar membranes. The insertion of an electrode through the round window and along the scala tympani was not free of risk, as infection which led to a marked loss of spiral ganglion cells occurred, particularly in the basal turn. When the size of the electrode was small in relation to the cross sectional area of the scala tympani, and it was not inserted far along the length of the basal turn, the evidence of trauma was minimal. Tissue reaction to the teflon-coated Pt electrode was also not observed.