The surgical anatomy for multiple-electrode extracochlear implant operations

Area of Science:

• Otorhinolaryngology
• Neurosurgery
• Biomedical Engineering

Background:

• Direct access to the entire cochlea via an endaural middle ear approach is crucial for precise electrode placement in cochlear implant surgery.
• Current surgical techniques face significant anatomical limitations, restricting the usable length of cochlear access.

Purpose of the Study:

• To evaluate the extent of cochlear access achievable through an endaural middle ear approach for extracochlear electrode insertion.
• To identify the anatomical structures that impede surgical access to the cochlea.

Main Methods:

• Surgical anatomical review focusing on the endaural middle ear approach.
• Analysis of anatomical restrictions including the middle cranial fossa, facial nerve, internal carotid artery, and temporomandibular joint.
• Assessment of cochlear position and axis relative to surgical entry points.

Main Results:

• The endaural approach provides access to approximately 10 mm of the cochlear turns, representing less than one-third of the total length.
• Anatomical structures like the middle cranial fossa, facial nerve, internal carotid artery, and temporomandibular joint significantly restrict surgical access.
• The cochlea's anterior position and axis limit the approach to a postero-lateral direction, though basal, middle, and apical turns remain partially accessible.

Conclusions:

• The endaural middle ear approach severely restricts access to the full length of the cochlea for electrode placement.
• Understanding these anatomical limitations is essential for optimizing surgical strategies and electrode design in cochlear implantation.