Clin Exp Otorhinolaryngol.  2020 Aug;13(3):249-254. 10.21053/ceo.2019.01144.

A Retrospective Review of Temporal Bone Computed Tomography to Present Safe Guideline for Bone-Anchored Hearing Aids

• Kim S
• Cho YS
• Cho YS
• Moon IJ

• KMID: 2504919
• DOI: http://doi.org/10.21053/ceo.2019.01144

Abstract

Objectives
. Bone-anchored hearing device (BAHD) is contraindicated in patients younger than 5 years because their calvarial bones are not thick enough to be implanted site. However, it has not been studied in the Korean population. This study was not only to establish a safe guideline for depth of implant device in all age groups who undergo BAHD implant surgery, but also to investigate whether implantation of currently used BAHDs could be done safely in Korean children, especially those younger than 5.
Methods
. Two hundred eighty patients, who underwent high-resolution temporal bone computed tomography (TBCT) images between August 2010 and October 2018 were randomly enrolled in all ages. We retrospectively reviewed TBCT imaging to measure skull bone thickness at the recommended BAHD implant site.
Results
. The average skull bone thickness was 2.87 mm in patients younger than 5 years and 6.72 mm in patients older than 5 years, respectively, which conforms to the current guideline. The results indicate nearly 50% of calvarial bone thicknesses were less than 3 mm in patients under 5 years old, while 92.78% of the patients older than 5 years of age showed bone thickness greater than 4 mm. Of note, calvarial bone thickness was thicker than 3 mm in all patients who are older than 6 years.
Conclusion
. This study confirms that the currently approved BAHD implantation guideline is suitable in the Korean population. For safety, we suggest taking TBCTs prior to surgery, especially in pediatric patients. Besides, noninvasive applications are recommended for patients younger than 5.

Keyword

Bone Conduction; Hearing Aid; Acoustic stimulation; Hearing Loss; Computed Tomography; Pediatrics

Figure

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  Fig. 1. Axial slice of temporal bone by computed tomography and example of skull bone thickness is marked at the point of measurement. Measurement point is 1 cm posterior to the right sigmoid sinus posterior margin (black arrow), and 1 cm superior to the superior margin of the right external auditory canal.

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  Fig. 2. Average of skull bone thickness versus age.

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  Fig. 3. Proportion of skull bone thickness <3 mm to ≥3 mm in groups younger than 5 years of age.

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  Fig. 4. Skull bone thickness (mm) versus age (yr) with trend line. The bone thickness increases in general as patient age increases.

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  Fig. 5. One 16-month-old male patient’s temporal bone axial slice computed tomography. Fontanels had not been closed (white arrows) entirely when the temporal bone computed tomography was taken.

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