Clin Exp Otorhinolaryngol.  2015 Dec;8(4):320-328. 10.3342/ceo.2015.8.4.320.

Anatomic Variants on Computed Tomography in Congenital Aural Atresia and Stenosis

• Qin FH
• Zhang TY
• Dai P
• Yang L

• KMID: 2128904
• DOI: http://doi.org/10.3342/ceo.2015.8.4.320

Abstract

OBJECTIVES
To quantitatively analyzing the anatomic variants on temporal computed tomography (CT) in congenital external auditory canal stenosis (EACS), congenital aural atresia (CAA), and normal ear structure.
METHODS
Through a retrospective study, we analyzed 142 temporal high-resolution CT studies performed in 71 microtia patients. The following 6 parameters were compared among the three groups: Marx classification, medial canal diameter, vertical facial nerve (VFN) anterior displacement, tegmen mastoideum position, tympanic cavity volume, and malleus-incus joint or malleus-incus complex (MIC) area.
RESULTS
The results showed that the microtia distributions in the Marx classification in these three groups were significantly different, as 86% (31 of 35) of ears with major microtia (third-degree dysplasia) had an atresia, and in 54.8% (23 of 42) of the minor microtic (first-degree or second-degree) ears, the bony or cartilaginous part of the external auditory canal was stenotic. Measurement data also showed that the potential medial canal diameter of the atresia group was obviously shorter than that of the stenosis group. The VFN anterior displacement and temporomandibular joint backward-shift together lead to medial canal diameters in ears with atresic canals that is smaller than those with stenotic canals. The tegmen mastoideum position was not significantly different between the three groups.
CONCLUSION
The mal-development of the external auditory canal is significantly associated with auricle and middle ear developmental anomalies. Compared with CAA ears, EACS have better development of the auricle, canal, tympanic cavity and MIC and relatively safer surgical operation except for the position of the tegmen mastoideum and the VFN.

Keyword

Conginital Microtia; Ear Canal; Congenital Aural Atresia; Multidetector Computed Tomography

MeSH Terms

Classification
Constriction, Pathologic*
Ear
Ear Canal
Ear, Middle
Facial Nerve
Humans
Joints
Multidetector Computed Tomography
Retrospective Studies
Temporomandibular Joint

Figure

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  Fig. 1 Microtia. Grades I, II, and III in Marx classification are shown separately in panels (A), (B), and (C).

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  Fig. 2 Medial canal diameter. Right normal ear (A), right stenosis ear (B), and right atresia ear (C). The white line shows the tangent through the most salient point of the bone posterior wall of temporomandibular joint; the white arrow shows the vertical facial nerve.

• 

  Fig. 3 Vertical facial nerve (VFN) position. The distance (dashed line) from the VFN to the coronal plane passing through the middle point of the foramen spinosum. Right normal ear (A, D, G), stenosis ear (B, E, H), right atresia ear (C, F, I). The line shows the horizontal line located in the coronal plane; the arrow shows stenosis of the canal in panel B and the starting point of the VFN in panels (D), (E), and (F); the dashed arrow shows the ending point of the VFN.

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  Fig. 4 Vertical facial nerve (VFN) antedisplacement. Computed tomography image at the level of the right round window niche (black arrow) shows an anteriorly displaced VFN (white arrow) which is normally positioned posterior to the round window niche (A, coronal plane; B, axial plane).

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  Fig. 5 The horizontal facial nerve (arrow) laterally displaces to the lateral wall of tympanic cavity in a left atretic ear. The ossicular is absent (A, axial plane; B, coronal plane).

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  Fig. 6 Tegmen mastoideum position. (A) shows a normal tegmen mastoideum (white arrow) in left atretic ear; (B) shows an inferiorly displaced tegmen mastoideum (white arrow) and an anteriorly displaced facial nerve (black arrow) in the area of the oval window niche in a left atretic ear.

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  Fig. 7 Malleus-incus complex or malleus-incus joint in the axial plane in a normal canal (A), stenosis canal (B), and atresia canal (C). White dashed arrow shows the horizontal facial nerve and white solid arrow shows the malleus-incus complex or malleus-incus joint.

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  Fig. 8 The microtia distribution in Marx classification in the three groups. N represent normal auricle. Grades I, II, and III represent different deformity of auricle in Marx classification. CAA, congenital aural atresia; EACS, external auditory canal stenosis.

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  Fig. 9 Three-dimensional reconstruction tympanic cavity in left normal ear (A), in left stenosis ear (B), in left atresia ear (C, D).

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  Fig. 10 Comparison results of different parameters. Data are the mean±SD. MCD, medial canal diameter; VFN-FS, distance from vertical facial nerve (VFN) to the coronal plane through the middle point of foramen spinosum; LSCC-TM, distance from the middle point of lateral semicircular canal caliber to the tangent through the lowest point of tegmen mastoideum; TCV, tympanic cavity volume; MIC, malleus-incus complex; CAA, congenital aural atresia; EACS, external auditory canal stenosis. *P<0.05, statistical significance in pair-wise comparison. †The starting point of VFN. ‡The ending point of VFN.

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