Clin Exp Otorhinolaryngol.  2015 Dec;8(4):339-344. 10.3342/ceo.2015.8.4.339.

Anatomical Factors Influencing Pneumatization of the Petrous Apex

• Lee DH
• Kim MJ
• Lee S
• Choi H

• KMID: 2128907
• DOI: http://doi.org/10.3342/ceo.2015.8.4.339

Abstract

OBJECTIVES
Aim of the present study was to define the relationship between petrous apex pneumatization and the nearby major anatomical landmarks using temporal bone computed tomography (CT) images.
METHODS
This retrospective, Institutional Review Board-approved study analyzed CT images of 84 patients that showed normal findings bilaterally. Pneumatization of the petrous apex was classified using two methods. Eight parameters were as follows: angle between the posterior cranial fossa and internal auditory canal, Morimitsu classification of anterior epitympanic space, distance between the carotid canal and jugular bulb, distance between the cochlear modiolus and carotid canal, distance between the tympanic segment and jugular bulb, high jugular bulb, distance between the vertical segment and jugular bulb, and distance between the lateral semicircular canals and middle cranial fossa.
RESULTS
There was a significant difference in Morimitsu classification of the anterior epitympanic space between the two classification methods. Poorly pneumatic upper petrous apices were distributed uniformly in three types of Morimitsu classification, but more pneumatic upper petrous apices were found more often in anterior type. Lower petrous apex was well pneumatized regardless of the types of anterior epitympanic space, but the largest amount of pneumatization was found more frequently in the anterior type of anterior epitympanic space.
CONCLUSION
This study showed that there was no reliable anatomic marker to estimate petrous apex pneumatization and suggests that the pneumatization of the petrous apex may be an independent process from other part of the temporal bone, and may not be influenced by the nearby major anatomical structures in the temporal bone. In this study, the anterior type of anterior epitympanic space was found to be closely related to more well-pneumatized petrous apices, which implies that the anterior saccule of the saccus medius may be the main factor influencing pneumatization of the petrous apex.

Keyword

Petrous Bone; Temporal Bone; Growth and Development

MeSH Terms

Classification
Cranial Fossa, Middle
Cranial Fossa, Posterior
Growth and Development
Humans
Petrous Bone
Retrospective Studies
Saccule and Utricle
Semicircular Canals
Temporal Bone

Figure

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  Fig. 1 Examples of petrous apex pneumatization classification. Group 2 (A) and group 3 (B) classified using the labyrinth as the reference structure. Group 3 (C) and group 4 (D) classified using the carotid canal as the reference structure.

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  Fig. 2 Measurements of IAC-PCF angle (A) and CC-JB distance (B, C). IAC, internal auditory canal; PCF, posterior cranial fossa; CC, carotid canal; JB, jugular bulb.

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  Fig. 3 Measurements of CC-Co distance (A), FNtym-JB distance (B), FNver-JB distance (C), and LSCC-MCF distance (D). CC, carotid canal; Co, cochlea; FNtym, tympanic segment of the facial nerve; JB, jugular bulb; FNver, vertical (mastoid) segment of the facial nerve; LSCC, lateral semicircular canal; MCF, middle cranial fossa.

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  Fig. 4 Bar graphs showing significant differences in the types of anterior epitympanic spaces between both classification groups. (A) Poorly-pneumatic upper petrous apices of group 1 were distributed uniformly in the three types of anterior epitympanic space, but better-pneumatized upper petrous apices were found more often in the anterior type. (B) Lower petrous apices were well pneumatized regardless of the type of anterior epitympanic space, but the most pneumatization of group 4 was found more frequently in the anterior type of epitympanic space. AES, anterior epitympanic space.

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