The relation between human cochlear duct length and head size assessed by MRI and CBCT

The cochlea differs in length and shape among individuals and this might be due to the fact that it is affected by spatial constraints. The head size may restrict the cochlea which is located in the temporal bone, and individuals with smaller head sizes may have shorter cochlear duct lengths (CDL). On the other hand, normal-hearing participants with longer CDLs have an increase in low-frequency sensitivity. Therefore, not only the CDL but also auditory outcomes are thought to be significantly affected by cochlear structures and the factors affecting CDL may also affect outcomes of cochlear implantation. The head in which the cochlea is located and develops together, as well as, the body height in the human body are structures that continue to grow until certain periods after birth. Despite differences in the developmental process, the cochlea, head, and height may have a genetic makeup that is interconnected and affect one another. Hence, these growing parts of the body may influence the CDL during the development process. The present study was conducted with the aim of finding any relations between mentioned structures. It consisted of a study group that contained 112 postlingual-deafened adult participants who were cochlear implant users. Cone Beam Computed Tomography (CBCT) images of the cochlea and Magnetic Resonance (MR) images of the head were performed for each participant in the present study group. CDLs were determined via CBCT, head size measures were determined by 3D conversion via MRI, and the body height was completed. In terms of CDL, head size, and height: females had smaller averages than that males. The results of this study showed that CDL had not any significant correlation with head size but a weak correlation with height. Similar to the literature, the height and the head size showed statistically significant relationships with each other. Only CDL which was measured in the cochlea, may not be sufficient to demonstrate the effect of head size on the cochlea. Future studies might look at the links between the cochlear shape and its surroundings by using micro-CT.