Cochlear Implantation in post-meningitic children – correlation between electrode impedances, implant charge and auditory results?

Introduction:

Bacterial meningitis can cause a labyrinthitis. Consequences often are intracochlear alterations like soft tissue or bone neoformation. Increased impedances and higher implant charge may result, which will complicate the rehabilitation with cochlear implants. This retrospective case-control-study aimed to find correlations between morphologic, electric and functional parameters.

Methods:

The study group included children, who lost hearing due to a bacterial meningitis (n = 35). Using preoperative computed tomography and intraoperative findings we grouped into 'unchanged cochleae', 'obliterated cochlea' and in 'ossified cochleae'. Control group children suffered from congenital deafness (n = 16) and presented with normal cochleae. Postoperatively we measured impedances and stimulation charge and performed hearing tests a various time points.

Results:

Control group patients showed a mean impedance of 6.3 kΩ and the mean charge applied was 19 nC. The study group averaged at 7.9 kΩ and 24.6 nC respectively. Patients with ossified cochleae had increased values of 8.6 kΩ and 29.7 nC. The control group reached a monosyllabic word understanding of 74% and the study group of 58%. Patients with ossified cochleae reached 36%.

Conclusions:

Higher impedances and increased charge in post-meningitic patients suggest ossified cochleae. Whether this is the only reason for a worse word understanding must be found out in further studies.

Publication History

Publication Date:
18 April 2018 (online)