Octylcyanoacrylate: a new medical-grade adhesive for otologic surgery.

Hypothesis: The adhesive octylcyanoacrylate is not associated with significant inner ear toxicity in a guinea pig model.

Background: Many cyanoacrylate adhesives have been investigated for use in otologic surgery, but variable ototoxicity has been reported. Octylcyanoacrylate is a medical-grade adhesive with many properties that make it ideal for use in the ear. It is free of contaminants; it forms a strong, flexible bond; and it inhibits the growth of gram-positive organisms in culture. This is the first study to assess the ototoxicity of this new adhesive.

Methods: Fourteen adult guinea pigs were used. Preoperative auditory brainstem responses (ABRs) were determined. Bilateral antrotomies were performed, and the ears were randomized to adhesive and control (saline) groups. In the adhesive ears. 0.5 or 0.1 mL of octylcyanoacrylate was instilled into the middle ear. Eight weeks later, postoperative ABRs were determined, the animals were killed, and the temporal bones were removed. Middle ear changes were noted, and the ossicular chain was assessed. Cochlear hair cell analyses were performed. Histologic assessment of the middle ear mucosa was performed.

Results: There was a higher incidence of conductive hearing loss in the adhesive group secondary to fixation of the ossicular chain, but there was no significant difference in bone conduction thresholds. The median postoperative bone conduction thresholds (dB peak sound pressure level) was 15.0 in the control group and 17.5 in the adhesive group, p = 0.89. There was also no significant difference in inner hair cell counts (0.4% vs. 0.5% median hair cell loss, p = 0.72) or outer hair cell counts (3.7% vs. 3.0% median hair cell loss, p = 0.23) for the adhesive and control groups, respectively. Histopathologic analysis of the middle ear mucosa demonstrated variable mild to moderate foreign body reaction with no evidence of mucosal ulceration or necrosis.

Conclusions: A large amount of octylcyanoacrylate placed in the middle ear of the guinea pig did not cause any morphologic or functional evidence of inner ear toxicity. This new adhesive is a promising tool for otologic surgery.