Extension of the Clinical Significance of the “Cog”

Abstract

Objective: To study the clinical anatomy of the epitympanum, the attic, and its medial wall, to try to discover a new clinical operation-related anatomical landmark, and to investigate the adjacent anatomical relationship with this landmark. Materials and Methods: Eight donor temporal bone specimens were dissected endoscopically. For 29 healthy persons (17 males and 12 females), CT images of the temporal bone (57 ears) were taken, 3-dimensional (3-D) reconstruction and multidimensional plane reconstruction were performed, and identification and assessment of 3-D spatial relationships between any 2 of these complex structures were done. Results: 3-D images of the temporal bone structures including the facial nerve, the cochlea, the semicircular canal, and the brain plate were reconstructed and shown in detail. We discovered a new clinical surgery-related anatomical landmark (the “cog” tangent and the trailing edge of the cog). Based on the tangent and the trailing edge of the cog, we quantified the anatomical relationship between it and its neighboring important structures. Conclusion: Based on endoscopic anatomy and the temporal bone spiral CT 3-D structure reconstruction of the epitympanum, the attic, and the adjacent structures, we found an extension of the clinical significance the cog. Quantification of the adjacent anatomical relationship of this landmark is very important for otology microsurgical operation.

Distribution of different morphological types of anterior epitympanic plate “cog” and Köerner’s septum in CT images of cholesteatomatous and non-cholesteatomatous CSOM: is it really significant?

“…The anterior epitympanic recess (AER) is frequently involved in chronic infections and represents a common location of the more common pars flaccida growth [8,25]. The complexity of the anatomical architecture of epi-tympanum necessitates accurate and deep knowledge of the surgeon about the spatial relationships present at this site, thus avoiding misguided procedure and inadvertent injury of vital structures [8,26,27]. HRCT has a crucial role in the preoperative detailed anatomical information [9,28].…”

“…Regarding its location, pars flaccida variety is the commonest developing just lateral to the ossicles in the Prüssak's space (subcomponent of epi-tympanum). Pars tensa variety is much less common and often develops in hidden areas such as facial recess or sinus tympani, thus verifying the need for better assessment [5].. Owing to the fact that the epi-tympanum is considered one of the most frequent sites for primary and recurrent cholesteatoma, a sufficient awareness of the surgery-related details about anatomical construction of the epitympanum, the attic, and its adjacent structures is very valuable for the surgeon [6][7][8].…”

“…Surgeons are also blinded with subtle details of anatomical variations of the temporal bone prior to surgery [14][15][16][17]. Providing excellent spatial resolution, the high-resolution CT scanning offered an indispensable tool in confirmation of disease extension, identification of anatomical details, and detection of asymptomatic complications [5,8,9,18,19]. As a matter of fact, HRCT provides a clear roadmap for surgeons to plane the appropriate approach, especially for extensive cases and revision or second look surgery [20,21].…”