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Cochlear orientation: pre-operative evaluation and intra-operative significance

  • S Sharma (a1), M Grover (a1), S N Singh (a1), T Kataria (a1) and R S Lakhawat (a1)...

Abstract

Objective

The study primarily aimed to calculate the orientation of the cochlea pre-operatively, using high-resolution computed tomography of the temporal bone, and predict the ease of electrode insertion.

Methods

Pre-operatively, high-resolution computed tomography scans were conducted on children scheduled for cochlear implantation, and two angles, α and β, were calculated. The values of α and β were then correlated with intra-operative difficulty in insertion of the electrode array.

Results

Ninety-six children were included in the study. Of the seven patients who had an α angle of less than 50 degrees, the surgeon experienced difficulties in electrode insertion. However, there were four patients with an α angle of more than 50 degrees for whom the surgeon also experienced difficulties in electrode insertion. In all these patients, the β angle was more than 20 degrees.

Conclusion

Calculation of cochlear orientation and its angle with the surgical axis (α and β) can aid the planning of surgery, particularly with regard to the cochleostomy site and preservation of residual hearing.

Copyright

Corresponding author

Address for correspondence: Dr Mohnish Grover, Department of Otorhinolaryngology and Head Neck Surgery, SMS Medical College and Hospital, Jaipur – 302004, Rajasthan, India E-mail: drmohnish_aiims@rediffmail.com

Footnotes

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Dr M Grover takes responsibility for the integrity of the content of the paper

Footnotes

References

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2Jeffery, N, Spoor, F. Prenatal growth and development of the modern human labyrinth. J Anat 2004;204:7192
3Lloyd, SK, Kasbekar, AV, Kenway, B, Prevost, T, Hockman, M, Beale, T et al. Developmental changes in cochlear orientation – implications for cochlear implantation. Otol Neurotol 2010;31:902–7
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5Li, PM, Wang, H, Northrop, C, Merchant, SN, Nadol, JB Jr. Anatomy of the round window and hook region of the cochlea with implications for cochlear implantation and other endocochlear surgical procedures. Otol Neurotol 2007;28:641–8
6Briggs, RJ, Tykocinski, M, Stidham, K, Roberson, JB. Cochleostomy site: implications for electrode placement and hearing preservation. Acta Otolaryngol 2005;125:870–6
7Adunka, O, Unkelbach, MH, Mack, M, Hambek, M, Gstoettner, W, Kiefer, J. Cochlear implantation via the round window membrane minimizes trauma to cochlear structures: a histologically controlled insertion study. Acta Otolaryngol 2004;124:807–12
8Balkany, TJ, Cohen, NL, Gantz, BJ. Surgical technique for the CLARION cochlear implant. Ann Otol Rhinol Laryngol Suppl 1999;177:2730

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