Micro-channels in the mastoid anatomy. Indications of a separate blood supply of the air cell system mucosa by micro-CT scanning

Abstract

channels in the mastoid anatomy. Indications of a separate blood supply of the air cell system mucosa by micro-CT scanning, 2013, Hearing Research, (301) Tel: +46 (0)13 286724.Fax: +46 (0)13 101902.Abbreviations: ME = middle ear; TM = tympanic membrane; 2 AbstractThe mastoid air cell system has traditionally been considered a passive role in gas exchange and pressure regulation of the middle ear possibly with some acoustic function. However, more evidence has focused on the mucosa of the mastoid, which may play a more active role in regulation of middle ear pressure.In this study we have applied micro-CT scanning on a series of three human temporal bones.This approach greatly enhances the resolution (40 to 60 µm), so that we have discovered anatomical details, which has not been reported earlier. Thus, qualitative analysis using volume rendering has demonstrated notable micro-channels connecting the surface of the compact bone directly to the mastoid air cells as well as forming a network of connections between the air cells. Quantitative analysis on 2D slices was employed to determine the average diameter of these micro-channels (158 µm; range = 40 to 440 µm) as well as their density at a localized area (average = 75 cm -2 ; range = 64 to 97 cm -2 ).These channels are hypothesized to contain a separate vascular supply for the mastoid mucosa. However, future studies of the histological structure of the micro-channels are warranted to confirm the hypothesis. Studies on the mastoid mucosa and its blood supply may improve our knowledge of its physiological properties, which may have important implications for our understanding of the pressure regulation of the middle ear.

Enhancement of micro-channels within the human mastoid bone based on local structure tensor analysis

“…The bone specimen was scanned in Ghent at the Department of Physics and Astronomy, Belgium. The procedure used for scanning the temporal bone was similar to [4] and resumed in a previous study [1]. The micro-CT scan was cropped from an original size of 1820 × 1820 × 1211 voxels down to a volume of 300 × 300 × 220 voxels.…”

“…The tympanum, part of the middle ear and in direct communication with the mastoid air cell system (MACS), is known to be the main structure involved in this regulatory process. However, more recent studies have indicated that the MACS also plays an important role in pressure regulation [1], [2]. To allow an efficient gas exchange, such as in the lungs, a large surface area of respiratory mucosa is needed in relation to the volume of air contained within the air cavities.…”

“…To allow an efficient gas exchange, such as in the lungs, a large surface area of respiratory mucosa is needed in relation to the volume of air contained within the air cavities. To investigate how large the surface area and the volume of the MACS are, eight human temporal bone specimens were scanned using x-ray micro-CT scanning [1]. Part of a right human temporal bone is visualized using volume rendering in Fig.…”

“…2. Further investigation of the micro-CT scan led to the discovery of micro-channels within the bony part of the mastoid between the MACS, visible as small dark features, notably at the vicinity of the ear canal [1], see Fig. 2.…”

“…2. Micro-channels observed between the surface of the temporal bone and its inner structures while modifying the transfer function of the volume rendering scheme [1]. Legend: (EC) ear canal, (MACS) mastoid air cell system, (OSS) ossicles, (TMG) tympanic membrane groove, (TS) trabecular spaces, (TYMP) tympanum.…”