Revision cochlear implant surgery in patients with suspected soft failures

To review our patient series who underwent revision cochlear implantation surgery, with special emphasis on the "soft failure" group.

Retrospective chart review of cochlear implant revision surgeries from 1979 to 2008. An extensive review of these patients' medical, audiologic, and radiographic histories was performed.

Two tertiary care hospitals and 1 academic cochlear implant center.

Explantation and reimplantation of cochlear implant, explanted device analysis, speech perception testing.

Postoperative speech performance.

Approximately 1,500 cochlear implant surgeries were performed from 1979 to 2008. Of these, 113 (7.53%) procedures in 98 patients were revision cases. The underlying reason for revision surgery was divided into 4 categories: 26 hard failures (23%), 31 medical failures (27.4%), 14 soft failures (12.4%), and 42 (37.2%) not classified/ambiguous cases. The last group was not categorized because of lack of available medical documentation or because of an ambiguous device failure analysis. The top 3 most common causes of hard failure were loss of hermiticity (8 patients [30.8%]), Vendor B defects (7 patients [26.9%]), and cracked casing (4 patients [15.4%]). The most common cause of medical failure was device extrusion (11 patients [35.5%]) followed by head trauma to the site of implantation (11 patients [35.5%]), and wound infection (5 patients [16.1%]). Fourteen patients (14.2%) were categorized as soft failures. All soft failure patients demonstrated a deterioration in pure-tone average and speech perception. Of the soft failure group, time to revision surgery was 4.7 years in contrast to 4.2 years for the hard failure group and 4.3 years for all revisions. An extensive review of patients' medical histories showed that 4 (28.5%) of the 14 patients had a previous diagnosis of meningitis. Two patients (14.3%) had evidence of inner ear malformations, and 2 patients (14.3%) had history of asthma.

Our cochlear revision series are comparable to what is reported in the literature. However, an unexpected relationship between meningitis was identified among our soft failure group. More than one-quarter carried a history of meningitis. Moreover, nearly one-half of all soft failures had some form of inflammatory derangement. We used the soft failure criteria established by the 2005 Consensus Development Conference for our population analysis. Although we agree that audiologic data often are essential for defining soft failure, multiple patients in our series experienced pain that was severe enough to prevent a complete audiometric evaluation, therefore not rigorously fulfilling the criteria set forth by the 2005 Consensus. However, because their symptoms resolved after reimplantation, and their speech performance restored, we propose modifications of the current definition of "soft failure" to include these patients.