Intracochlear Inflammatory Response to Cochlear Implant Electrodes in Humans

Abstract

Hypothesis This study evaluates the types and degree of tissue response adjacent to the electrode of multichannel cochlear implants. Background cochlear implant electrodes have been classified as biocompatible prostheses. Nevertheless, in some reports, electrode extrusion, chronic inflammation and even soft failure of the implant system have been attributed to a tissue response to the electrode. Methods All celloidin embedded temporal bones with multichannel cochlear implants from the temporal bone collection of the Massachusetts Eye and Ear Infirmary were included in the study. A total of 28 temporal bones from 21 subjects were identified and processed for histology. The severity of cellular response including eosinophil and lymphocytic infiltration, giant cell reaction, new bone formation and fibrosis were scored on a scale from 0 to 3 at three 1mm-segments along the electrode: 1- first 1mm at the cochleostomy, last 1mm from the tip of electrode, and midway between these proximal and distal segments. The values were compared using the Wilcoxon test. Results A granulomatous reaction to the electrode was observed in 27 (96.4%) temporal bones. Eosinophil infiltration was observed in 7 (25%) temporal bones, suggesting an allergic reaction. The Inflammatory response to the electrode was significantly greater at the basal turn of cochlea close to the cochleostomy (p< 0.05) than distal to it. Conclusion An Inflammatory response is common after cochlear implantation and it is more robust at the cochleostomy than distal to it, suggesting the role of trauma of insertion as a contributing factor.

Histopathology of the Human Inner Ear in a Patient With Sensorineural Hearing Loss Caused by a Variant in DFNA5

“…The observed histopathology did not offer a morphologic reason for this decrement. The histopathological findings in the implanted ear were similar to those of previous reports in other causes of deafness (21,22).…”

Effects of a dexamethasone-releasing implant on cochleae: A functional, morphological and pharmacokinetic study

“…The present histological evaluation focused on the inflammatory response and TNF-alpha positive staining in the inferior cochlear turn after electrode insertion. The formation of fibrosis and bony tissue around the electrode postoperatively was consistent with previous temporal bone studies (Huang et al, 2007;Somdas et al, 2007;Seyyedi et al, 2014). The present study did not find significant differences in the area of new fibrous tissue between the control group and the DEXA group, likely because of the limited number of sections that were evaluated (five H&E-stained sections containing the modiolus).…”

The pattern and degree of capsular fibrous sheaths surrounding cochlear electrode arrays

“…The causes for this chronic local inflammation might be a delayed hypersensitivity or a local tissue reaction to the CI electrode array (Beruleit et al, 1999; Ho et al, 2003; Puri et al, 2005; Kunda et al, 2006; Nadol et al, 2008; Lim et al, 2011; Neilan et al, 2012; Bennatti et al, 2013). Several temporal bone studies have demonstrated fibrosis and new bone formation adjacent to the electrode track (Nadol and Eddington, 2004; li et al, 2007; Somdas et al, 2007; Seyyedi and Nadol, 2014; Kamakura and Nadol, 2016), and have shown that this local inflammatory response is quite common. (Nadol and Eddington, 2004; Seyyedi and Nadol, 2014; Kamakura and Nadol, 2016).…”

“…Several temporal bone studies have demonstrated fibrosis and new bone formation adjacent to the electrode track (Nadol and Eddington, 2004; li et al, 2007; Somdas et al, 2007; Seyyedi and Nadol, 2014; Kamakura and Nadol, 2016), and have shown that this local inflammatory response is quite common. (Nadol and Eddington, 2004; Seyyedi and Nadol, 2014; Kamakura and Nadol, 2016). Seyyedi and Nadol (2014) demonstrated evidence of a chronic inflammatory reaction including inflammatory mediator cells, fibrous tissue and new bone formation in twenty-eight specimens (100%), from patients who during life underwent cochlear implantation.…”