Fig. 6.

Histopathology of electrode array tracts. Typically, a thin fibrotic capsule (arrow) surrounds the electrode tract (asterisk), terminating adjacent to an superior semicircular canal (SSCC) crista (A). The electrode tract is seen traversing through the surgical fenestration into the SSCC ampulla (S). In B, the orientation of an horizontal semicircular (HSCC) electrode tract (asterisk) and its fibrous capsule (arrow) are seen in relation to other adjacent structures, including the HSCC ampulla (H), SSCC ampulla (S), facial nerve (FN), and Scarpa’s ganglion (SG). The close proximity of the HSCC electrode tract to the SSCC ampullary nerve is evident, demonstrating the anatomic basis for current spread between HSCC and SSCC ampullary nerves. In one monkey (C), osteoneogenesis (arrow) was found adjacent to an electrode tract (asterisk) in the HSCC ampulla (H). In another monkey (D), a vigorous fibrosis reaction (arrow) is seen adjacent to a posterior semicircular canal (P) electrode tract (asterisk). Osteoneogenesis and fibrosis may be due to electrode insertion or surgical placement of bone paté and/or fascia around labyrinthotomies during implantation. In all specimens, existent ampullary nerve innervation to crista was evident, even in cases that suffered surgical destruction of the crista during implantation (B). There was no evidence of granulomatous inflammation, hydrops, or extension of fibrosis into the vestibule in any specimens. H&E-stained images captured at ×2.5–×10 magnification under light microscopy. Specimens shown: M0603163RhO left ear (A and C), F32RhD right (B), and left (D) ears.