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Surgical importance of the tympanic bone: multidetector computed tomography findings

  • Received : 2021.11.20
  • Accepted : 2022.04.19
  • Published : 2022.06.30

Abstract

Objectives: To measure tympanic bone thickness (anterior-superior, anterior-inferior, and inferior wall), external ear canal length, and tympanomandibular distance that can be useful in cases that undergo tympanic bone resection. Materials and Methods: The temporal computed tomography (CT) images of 349 patients were retrospectively evaluated. The anterior-inferior, anterior-superior, and inferior wall thicknesses; tympanomandibular distance; and external auditory canal (EAC) bone canal length were measured from the narrowest part of the canal. The shapes of the EAC in the coronal and sagittal planes were also examined. Results: The numbers of female and male patients were similar, and the mean age was 49.45±13.95 years. The anterior-superior, anterior-inferior, and inferior wall thicknesses were 1.92±0.60, 2.54±0.74, and 9.16±2.20 mm, respectively. The anterior-superior and anterior-inferior wall thicknesses and canal lengths were greater on the right side (P<0.001). All measurement values were higher in males, except right tympanomandibular distance (P<0.05). A non-significant negative correlation was found between the age of the participants and the left anterior-inferior wall and tympanomandibular distance on both sides. Intra-observer agreement was high for all measurements. We observed four main shapes in the external ear canal in the coronal plane: Type 3, Type 2, Type 1, and Type 4 in order of frequency on the right, and Type 2, Type 3, Type 1, and Type 4 on the left. In the sagittal plane, we detected three shapes: oval (74.4%), triangular (16.3%), and round (9.4%). Conclusion: The anterior wall thicknesses and tympanomandibular distance should be measured on preoperative temporal bone CT to safely perform tympanic bone anterior resection, which is required in some otological procedures, and also to prevent temporomandibular joint damage.

Keywords

References

  1. Isaacson B. Anatomy and surgical approach of the ear and temporal bone. Head Neck Pathol 2018;12:321-7. https://doi.org/10.1007/s12105-018-0926-2
  2. Lavy J, Fagan P. Canalplasty: review of 100 cases. J Laryngol Otol 2001;115:270-3. https://doi.org/10.1258/0022215011907424
  3. Selesnick SH, Carew JF, DiBartolomeo JR. Herniation of the temporomandibular joint into the external auditory canal: a complication of otologic surgery. Am J Otol 1995;16:751-7.
  4. Kim CW. Osteomyelitis of the temporomandibular joint following canal wall down mastoidectomy. J Craniofac Surg 2015;26:e351-3. https://doi.org/10.1097/SCS.0000000000001821
  5. Litton WB, Krause CJ, Anson BA, Cohen WN. The relationship of the facial canal to the annular sulcus. Laryngoscope 1969;79:1584-604. https://doi.org/10.1288/00005537-196909000-00005
  6. Williams BJ. The relationship of the facial nerve to the tympanic annulus and external auditory canal. J Otolaryngol Soc Aust 1988;6:95-6.
  7. Adad B, Rasgon BM, Ackerson L. Relationship of the facial nerve to the tympanic annulus: a direct anatomic examination. Laryngoscope 1999;109:1189-92. https://doi.org/10.1097/00005537-199908000-00002
  8. Rodrigues S, Fagan P, Doust B, Moffat K. A radiologic study of the tympanic bone: anatomy and surgery. Otol Neurotol 2003;24:796-9. https://doi.org/10.1097/00129492-200309000-00017
  9. Eckerdal O, Ahlqvist J. External bony auditory canal and the tympanic bone. Morphologic properties and influences on the tomographic reproduction. Acta Radiol Diagn (Stockh) 1980;21:425-31. https://doi.org/10.1177/028418518002100314
  10. Mancini F, Taibah AK, Falcioni M. Complications and their management in tympanomastoid surgery. Otolaryngol Clin North Am 1999;32:567-83. https://doi.org/10.1016/s0030-6665(05)70153-5