Tecnico Radiologo

Neuroimag Clin N Am 14 (2004) 721 – 760

Imaging of the temporal bone
H. Christian Davidson, MD
Department of Radiology, Veterans Affairs Salt Lake City Health Care System, University of Utah, 500 South Foothill Drive, Salt Lake City, UT 84148, USA

Normal anatomy Osseous components Classical descriptions of the temporal bone are based on its five embryologically distinct osseouscomponents: the petrous, mastoid, tympanic, squamous, and styloid portions. Petrous portion The petrous portion is a pyramid-shaped wedge of bone that forms the medial aspect of the temporal bone. The apex of the pyramid points medially and rests adjacent to the clivus, which relationship defines the petrooccipital fissure. The bsidesQ of the pyramid are made up of three surfaces: an anterior surface, aposterior surface, and an inferior surface. The dense bone of the otic capsule lies within the center of the petrous bone and contains the structures of the inner ear. The tympanic cavity is a complex space that lies laterally within the petrous bone and constitutes the middle ear. Mastoid portion The mastoid portion comprises the bulbous posterolateral portion of the temporal bone and includes theinferiorly projecting mastoid process. The medial margin of the mastoid is intracranial and forms part of the border of transverse sinus. The mastoid contains multiple aerated cells, which communicate with the middle ear. The mastoid process is not ossified at birth.

Tympanic portion The tympanic portion is a U-shaped bony plate that forms the bulk of the bony external auditory canal (EAC)andthe posterior (nonarticular)part of the mandibular fossa. The fissures that are formed by the junctions of the tympanic and other portions of the temporal bone are of anatomic interest and are discussed at length in other works dedicated to the study of the temporal bone [1].

Squamous portion The squamous portion is composed of a flat bony plate that forms the lateral wall of the middle cranialfossa and medial wall of the high masticator space. This portion contributes the posterior segment of the zygomatic arch and also forms the anterior (articular) part of the mandibular fossa.

Styloid portion The styloid portion is a thin fingerlike bony projection that extends inferiorly from the posterolateral aspect of the inferior surface of the petrous bone. The base of the styloid process islocated at the anterior margin of the stylomastoid foramen. Like the mastoid process, the styloid process is not ossified at birth.

Functional anatomic classification The anatomic classification used in this discussion defines six functional regions of the temporal bone, shown in Table 1. This organization groups together lesions that share common clinical, imaging, and therapeuticconsiderations.

This article was originally published in Magnetic Resonance Imaging Clinics of North America 10:4, 2002. E-mail address: h.christian.davidson@hsc.utah.edu

1052-5149/04/$ – see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.nic.2004.07.008

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H.C. Davidson / Neuroimag Clin N Am 14 (2004) 721 – 760

Table 1 Temporal bone functional anatomic regions RegionInternal auditory canal Inner ear (labyrinth) Intratemporal facial nerve Petrous bone Middle ear and mastoid External ear Contents Intracanalicular cistern, cerebellopontine angle cistern cranial nerves VII, VIII Cochlea; vestibule; semicircular canals Endolymphatic duct and sac. Labyrinthine, geniculate, tympanic, and mastoid segments excludes intracranial, intracanalicular, and intraparotidsegments. Petrous apex, pneumatized cells; carotid canal petrous bone proper except for otic capsule and tympanic cavity. Epitympanum; mesotympanum; hypotympanum tympanic mebrane; ossicular chain; round and oval windows mastoid bone, mastoid antrum and additus. Bony, cartilaginous, and soft-tissue external canal. Pinna and associated cutis.

Internal auditory canal The internal auditory canal (IAC)...