Post-traumatic Malleo-Incudal Complex Dislocation

A 27-year-old man undergoes otolaryngologic evaluation for blunt head trauma suffered in a vehicular accident. With regards to the right ear, pertinent otologic findings include an ear canal laceration and a delayed-onset facial nerve paresis. Tuning fork testing reveals an abnormal Rinne test on t...

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Autor principal:	Nathaniel Yang
Formato:	article
Lenguaje:	EN
Publicado:	Philippine Society of Otolaryngology-Head and Neck Surgery, Inc. 2021
Materias:	temporal bone imaging ossicular chain trauma hearing loss Otorhinolaryngology RF1-547
Acceso en línea:	https://doaj.org/article/15da3846c18344e4910a437dd6ecf6a4
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id	oai:doaj.org-article:15da3846c18344e4910a437dd6ecf6a4
record_format	dspace
institution	DOAJ
collection	DOAJ
language	EN
topic	temporal bone imaging ossicular chain trauma hearing loss Otorhinolaryngology RF1-547
spellingShingle	temporal bone imaging ossicular chain trauma hearing loss Otorhinolaryngology RF1-547 Nathaniel Yang Post-traumatic Malleo-Incudal Complex Dislocation
description	A 27-year-old man undergoes otolaryngologic evaluation for blunt head trauma suffered in a vehicular accident. With regards to the right ear, pertinent otologic findings include an ear canal laceration and a delayed-onset facial nerve paresis. Tuning fork testing reveals an abnormal Rinne test on the right (AC<BC). The radiologist’s interpretation of the computerized tomographic imaging study of the temporal bone indicated the presence of a longitudinal fracture of the right temporal bone with no disruption of the ossicular chain. (Figure 1) However, careful examination of the anatomy of the malleo-incudal complex in relation to the other structures in the epitympanum actually reveals findings indicative of a malleo-incudal complex dislocation. How can this discrepancy in the radiologic interpretation be accounted for? By what objective parameters can the presence of a malleoincudal complex dislocation be identified? Meriot et al.1 described five types of traumatic ossicular dislocation injury: incudomalleolar joint separation, incudostapedial joint separation, stapediovestibular dislocation, incus dislocation, and malleo-incudal complex dislocation. Of these, incudomalleolar joint separation would probably be the most easily identified, as it would manifest as a disruption in the distinctive ice-cream cone appearance of the malleus head and the body and short process of the incus visualized on axial CT imaging of the temporal bone. (Figure 2) In contrast, malleo-incudal complex dislocation would involve movement of both ossicles en-bloc within the tympanic cavity (usually into the mesotympanum), without disruption of the incudomalleolar joint.1 As such, the ice-cream cone configuration may be preserved in this type of injury. Proper identification of this type of injury would be based on identifying any discrepancy in the positional relationship between the ossicular complex and the other structures within the confines of the tympanic cavity. The malleus head and the body and short process of the incus are located in the most superior portion of the tympanic cavity, the pneumatised area called the epitympanum. Also known as the attic or epitympanic recess, this region is bordered superiorly by the tegmen tympani and inferiorly by the mesotympanum. The epitympanum is divided into two compartments: the anterior epitympanic space or recess, and the much larger posterior epitympanum, which houses the epitympanic portions of the malleus and incus. This division is created by a thin bony plate known as the cog, which projects downwards from the tegmen tympani and is located anterior to the malleus head.2 In the axial plane, the malleo-incudal complex is normally centered within the posterior epitympanum with the short process of the incus pointing into the incudal fossa. The position of the malleo-incudal complex may sometimes be slightly lateral, but is never medial in the normal situation.1 Based on these broader anatomical relationships, it can be seen that in the imaging study under investigation (Figure 3), the malleo-incudal complex (the ice-cream cone) has actually shifted forward - the malleus head is located not posterior to the cog, but at the same level as the cog in the antero-posterior dimension. Additionally, the malleo-incudal complex is located more medially within the posterior epitympanum, and is much closer to the tympanic segment of the facial nerve than to the lateral bony margin (the scutum) of the epitympanum. These findings clearly and unequivocally demonstrate the presence of a malleo-incudal complex dislocation. In summary, one of the keys to the proper evaluation of post-traumatic ossicular injury is to look not only at the anatomical relationship between ossicles, but also at the relationship of the entire ossicular complex to the other structures that are also located within the confines of the tympanic cavity
format	article
author	Nathaniel Yang
author_facet	Nathaniel Yang
author_sort	Nathaniel Yang
title	Post-traumatic Malleo-Incudal Complex Dislocation
title_short	Post-traumatic Malleo-Incudal Complex Dislocation
title_full	Post-traumatic Malleo-Incudal Complex Dislocation
title_fullStr	Post-traumatic Malleo-Incudal Complex Dislocation
title_full_unstemmed	Post-traumatic Malleo-Incudal Complex Dislocation
title_sort	post-traumatic malleo-incudal complex dislocation
publisher	Philippine Society of Otolaryngology-Head and Neck Surgery, Inc.
publishDate	2021
url	https://doaj.org/article/15da3846c18344e4910a437dd6ecf6a4
work_keys_str_mv	AT nathanielyang posttraumaticmalleoincudalcomplexdislocation
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spelling	oai:doaj.org-article:15da3846c18344e4910a437dd6ecf6a42021-11-15T21:14:37ZPost-traumatic Malleo-Incudal Complex Dislocation1908-48892094-1501https://doaj.org/article/15da3846c18344e4910a437dd6ecf6a42021-11-01T00:00:00Zhttps://pjohns.pso-hns.org/index.php/pjohns/article/view/1819https://doaj.org/toc/1908-4889https://doaj.org/toc/2094-1501 A 27-year-old man undergoes otolaryngologic evaluation for blunt head trauma suffered in a vehicular accident. With regards to the right ear, pertinent otologic findings include an ear canal laceration and a delayed-onset facial nerve paresis. Tuning fork testing reveals an abnormal Rinne test on the right (AC<BC). The radiologist’s interpretation of the computerized tomographic imaging study of the temporal bone indicated the presence of a longitudinal fracture of the right temporal bone with no disruption of the ossicular chain. (Figure 1) However, careful examination of the anatomy of the malleo-incudal complex in relation to the other structures in the epitympanum actually reveals findings indicative of a malleo-incudal complex dislocation. How can this discrepancy in the radiologic interpretation be accounted for? By what objective parameters can the presence of a malleoincudal complex dislocation be identified? Meriot et al.1 described five types of traumatic ossicular dislocation injury: incudomalleolar joint separation, incudostapedial joint separation, stapediovestibular dislocation, incus dislocation, and malleo-incudal complex dislocation. Of these, incudomalleolar joint separation would probably be the most easily identified, as it would manifest as a disruption in the distinctive ice-cream cone appearance of the malleus head and the body and short process of the incus visualized on axial CT imaging of the temporal bone. (Figure 2) In contrast, malleo-incudal complex dislocation would involve movement of both ossicles en-bloc within the tympanic cavity (usually into the mesotympanum), without disruption of the incudomalleolar joint.1 As such, the ice-cream cone configuration may be preserved in this type of injury. Proper identification of this type of injury would be based on identifying any discrepancy in the positional relationship between the ossicular complex and the other structures within the confines of the tympanic cavity. The malleus head and the body and short process of the incus are located in the most superior portion of the tympanic cavity, the pneumatised area called the epitympanum. Also known as the attic or epitympanic recess, this region is bordered superiorly by the tegmen tympani and inferiorly by the mesotympanum. The epitympanum is divided into two compartments: the anterior epitympanic space or recess, and the much larger posterior epitympanum, which houses the epitympanic portions of the malleus and incus. This division is created by a thin bony plate known as the cog, which projects downwards from the tegmen tympani and is located anterior to the malleus head.2 In the axial plane, the malleo-incudal complex is normally centered within the posterior epitympanum with the short process of the incus pointing into the incudal fossa. The position of the malleo-incudal complex may sometimes be slightly lateral, but is never medial in the normal situation.1 Based on these broader anatomical relationships, it can be seen that in the imaging study under investigation (Figure 3), the malleo-incudal complex (the ice-cream cone) has actually shifted forward - the malleus head is located not posterior to the cog, but at the same level as the cog in the antero-posterior dimension. Additionally, the malleo-incudal complex is located more medially within the posterior epitympanum, and is much closer to the tympanic segment of the facial nerve than to the lateral bony margin (the scutum) of the epitympanum. These findings clearly and unequivocally demonstrate the presence of a malleo-incudal complex dislocation. In summary, one of the keys to the proper evaluation of post-traumatic ossicular injury is to look not only at the anatomical relationship between ossicles, but also at the relationship of the entire ossicular complex to the other structures that are also located within the confines of the tympanic cavity Nathaniel YangPhilippine Society of Otolaryngology-Head and Neck Surgery, Inc.articletemporal bone imagingossicular chain traumahearing lossOtorhinolaryngologyRF1-547ENPhilippine Journal of Otolaryngology Head and Neck Surgery, Vol 36, Iss 2 (2021)

Post-traumatic Malleo-Incudal Complex Dislocation

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