Cochlear Histopathology as Observed in Two Patients With a Cochlear Implant Electrode With Positioner

This study reports the cochlear histopathology of two patients who during life underwent cochlear implantation with a positioner.

A silastic positioner introduced by the Advanced Bionics Corporation in 1999 was designed to position the electrode of the cochlear implant close to the modiolus. The positioner was recalled in the United States in July 2002 because of an apparent higher incidence of bacterial meningitis in patients in whom the positioner had been placed.

Four celloidin-embedded temporal bones from two patients with cochlear implants with a positioner from the temporal bone collection of the Massachusetts Eye and Ear Infirmary were included in the study. In a previous study, we reported histopathologic findings in Patient 1, and in this report, we present the findings in a second case in a 94-year-old woman (Patient 2), and the similarities and differences between the two patients. All four specimens were prepared for histologic study by conventional techniques and 2-D reconstruction.

Evidence of insertion trauma was observed in all three implanted specimens. More significant trauma was found in Patient 2 than in Patient 1 including disruption of the osseous spiral lamina and the basilar membrane. In addition, there was more new fibrous tissue and bone in Patient 2 than in Patient 1. There was a large fluid space in all three implanted temporal bones around the electrode and positioner.

The findings observed in the two patients may help to explain the increased risk of meningitis in patients implanted with a positioner.