Human Otopathology of Cochlear Implant Drill-out Procedures

UMMS Affiliation

Department of Otolaryngology; School of Medicine; Senior Scholars Program

Faculty Mentor

Aaron Remenschneider

Publication Date


Document Type



Medical Education | Otolaryngology | Otorhinolaryngologic Diseases


OBJECTIVE: Human otopathology following drill-out procedures for cochlear implantation (CI) in cases with labyrinthitis ossificans (LO) has not been previously described. This study uses the high sensitivity of histopathology to (1) evaluate surgical drill-out technique with associated intracochlear findings and (2) quantify spiral ganglion neuron populations in a series of patients with LO who underwent CI.

STUDY DESIGN: Retrospective otopathology study.

SETTING: Otopathology laboratory.

SUBJECTS AND METHODS: Temporal bone (TB) specimens from cases with evidence of preoperative intracochlear fibroossification that required a drill-out procedure for CI electrode array insertion were included. All cases were histopathologically evaluated and 3-dimensional reconstructions of the cochleae were performed to interpret drilling paths and electrode trajectories.

RESULTS: Five TB specimens were identified, of which 4 underwent drill-out of the basal turn of the cochlea and 1 underwent a radical cochlear drill-out. In multiple TBs, drilling was imprecise with resultant damage to essential structures. Two TBs showed injury to the modiolus, which was associated with substantially decreased or even absent neuronal populations within these areas. In addition, 2 cases with inadequate drill-out or extensive LO of the basal turn resulted in extracochlear placement of electrode arrays into the vestibule due to persistent obstruction within the basal turn.

CONCLUSION: Otopathology highlights the challenges of drill-out procedures in cases of LO. Imprecise drilling paths, due to distortion of normal cochlear anatomy, risk injury to the modiolus and adjacent neurons as well as extracochlear placement of electrode arrays, both of which may contribute to poorer hearing outcomes.


cochlear implantation, labyrinthitis ossificans, otopathology

DOI of Published Version



Trakimas DR, Ishai R, Kozin ED, Nadol JB Jr, Remenschneider AK. Human Otopathology of Cochlear Implant Drill-out Procedures. Otolaryngol Head Neck Surg. 2019 Oct;161(4):658-665. doi: 10.1177/0194599819847636. Epub 2019 May 7. PMID: 31060442. Link to article on publisher's site

Journal/Book/Conference Title

Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery


Danielle Trakimas participated in this study as a medical student in the Senior Scholars research program at the University of Massachusetts Medical School

Related Resources

Link to Article in PubMed

PubMed ID