Radiological evaluation of a new straight electrode array compared to its precursors

Area of Science:

• Otolaryngology
• Biomedical Engineering
• Neurosurgery

Background:

• Cochlear implant electrode array insertion is crucial for hearing restoration.
• Understanding electrode array position and dislocation is vital for surgical outcomes.
• Variations in electrode array length may influence cochlear coverage and intra-cochlear placement.

Purpose of the Study:

• To evaluate electrode array coverage, scalar position, and dislocation rates in straight electrode arrays.
• To specifically assess a new 26mm straight electrode array (MED-EL Flex 26) in comparison to other lengths.

Main Methods:

• Retrospective analysis of 201 cochlear implant surgeries performed between 2013 and 2019.
• Comparative analysis of lateral wall electrode arrays: 24mm (F24), 26mm (F26), 28mm (F28), and 31.5mm (F31.5).
• Cone beam computed tomography (CBCT) used to determine scalar position (scala tympani vs. scala vestibuli), dislocation, and insertion angles.

Main Results:

• No significant differences in cochlear size across study groups.
• The 24mm array (F24) had significantly shorter insertion angles than longer arrays.
• The 26mm array (F26) demonstrated no scalar dislocation or scala vestibuli insertion.
• The longest array (F31.5) had the highest rate of scala tympani dislocations (26.3%), while the F28 had the highest rate of scala vestibuli insertions (5.75%).
• Most dislocations occurred between 320° and 360°.

Conclusions:

• Shorter electrode arrays (24mm and 26mm) exhibit fewer scalar dislocations compared to longer arrays (28mm and 31.5mm).
• Cochlear coverage increases with electrode array length, but this is associated with a higher risk of scalar dislocation.
• Intracochlear dislocations predominantly occur in the apical cochlear region for lateral wall electrode arrays.