Temporal bone characterization and cochlear implant feasibility in the common marmoset (Callithrix jacchus)

• Published in: Hearing research 2012-08, Vol.290 (1-2), p.37-44
• Main Authors: Johnson, Luke A., Della Santina, Charles C., Wang, Xiaoqin
• Format: Article
• Language: English
• Subjects: Age Factors; Animals; Callithrix - anatomy & histology; Cochlear Implantation - instrumentation; Cochlear Implants; Feasibility Studies; Models, Animal; Ostomy; Prosthesis Design; Scala Tympani - anatomy & histology; Scala Tympani - diagnostic imaging; Scala Tympani - surgery; Temporal Bone - anatomy & histology; Temporal Bone - diagnostic imaging; X-Ray Microtomography
• ISSN: 0378-5955; 1878-5891
• DOI: 10.1016/j.heares.2012.05.002

The marmoset (Callithrix jacchus) is a valuable non-human primate model for studying behavioral and neural mechanisms related to vocal communication. It is also well suited for investigating neural mechanisms related to cochlear implants. The purpose of this study was to characterize marmoset temporal bone anatomy and investigate the feasibility of implanting a multi-channel intracochlear electrode into the marmoset scala tympani. Micro computed tomography (microCT) was used to create high-resolution images of marmoset temporal bones. Cochlear fluid spaces, middle ear ossicles, semicircular canals and the surrounding temporal bone were reconstructed in three-dimensional space. Our results show that the marmoset cochlea is ∼16.5 mm in length and has ∼2.8 turns. The cross-sectional area of the scala tympani is greatest (∼0.8 mm2) at ∼1.75 mm from the base of the scala, reduces to ∼0.4 mm2 at 5 mm from the base, and decreases at a constant rate for the remaining length. Interestingly, this length–area profile, when scaled 2.5 times, is similar to the scala tympani of the human cochlea. Given these dimensions, a compatible multi-channel implant electrode was identified. In a cadaveric specimen, this electrode was inserted ¾ turn into the scala tympani through a cochleostomy at ∼1 mm apical to the round window. The depth of the most apical electrode band was ∼8 mm. Our study provides detailed structural anatomy data for the middle and inner ear of the marmoset, and suggests the potential of the marmoset as a new non-human primate model for cochlear implant research. ► MicroCT was used to create high-resolution images of marmoset temporal bones. ► Cochlea, ossicles, and semicircular canals were reconstructed and characterized. ► The marmoset cochlea is ∼16.5 mm in length and has ∼2.8 turns. ► A multi-channel implant electrode can be inserted ¾ turn into the scala tympani. ► The marmoset is a promising primate model for cochlear implant research.