On the anatomy of the 'hook' region of the human cochlea and how it relates to cochlear implantation.
BACKGROUND
The optimal insertion route for an electrode array in hearing preservation cochlear implantation (CI) surgery is still tentative. Both cochleostomy (CO) and round window (RW) techniques are used today. In the present study we analyzed size variations and topographic anatomy of the 'hook' region of the human cochlea to better comprehend the Testo effects of various electric array insertion modes.


METHODS
Size variations of the cochlear 'hook' region were assessed in 23 human, microdissected temporal bones by measuring the distances between the oval and round windows, also outlining the spiral ligament/spiral lamina. Influence of size variations on spiral ligament position and fundamentals for different surgical approaches were evaluated in a subset of 'small' and 'large' cochleae performing different types of CO. In addition, the relationship between the microdissected accessory canal housing the inferior cochlear vein and the RW was analyzed.


RESULTS
The lateral vestibular wall and the cochlear 'hook' displayed large anatomic variations that greatly influenced the size of the potential surgical area. RESULTS showed that only very inferiorly located CO entered the scala tympani without causing trauma to the spiral ligament and spiral lamina. An inferior approach may challenge the inferior cochlear vein.


CONCLUSIONS
Preoperative assessment of the distance between the round and oval windows may direct the surgeon before CI hearing-preservation surgery. CO techniques, especially in 'small' ears, may lead to frequent damage to the inner ear structures. In those cases with substantial residual hearing, CI surgery may be better performed through a RW approach.
Department of Mental Health and Sensory Organs, Otorhinolaryngologic Unit, Medicine and Psychology, Sapienza University of Rome, Sapienza, Rome, Italy.
Francesca
F
Atturo
Maurizio
M
Barbara
Helge
H
Rask-Andersen
D003051:Cochlea / Q000033:anatomy & histology* / Q000601:surgery; D019929:Cochlear Implantation / Q000379:methods*; D003054:Cochlear Implants; D006801:Humans; D008953:Models, Anatomic; D013701:Temporal Bone / Q000033:anatomy & histology* / Q000601:surgery