![]() ![]() The facial nerve passes through the IAC’s anterosuperior compartment and into the temporal bone’s facial nerve canal. The internal auditory canal (IAC) is a channel in the petrous bone located between the porus acousticus (medial) and the fundus (lateral) (17). ![]() The osseous spiral lamina is a microanatomic structure that is faintly discernible on thin-section temporal CT images (16). However, the membranous labyrinth structures are not distinguishable on CT images (15). The otic capsule is the densest part of the temporal bone that surrounds the osseous labyrinth. These structures are well-delineated on CT images due to their sharp bony margins bordering on low fluid density within (14). The cochlea contains the end-organ for hearing, while the vestibule and semicircular canals are responsible for equilibrium. The inner ear within the petrous portion comprises the osseous labyrinth, including the cochlea, vestibule, and semicircular canals. If the tegmen exhibits abnormal downward bowing and contacts the malleus, there may be a resultant limitation of ossicular chain movement leading to conductive hearing loss (13). High-resolution CT is useful for the assessment of tegmen defects or fractures (12). The tegmen tympani is the middle ear’s roof, while the tegmen mastoideum is the roof of the mastoid. The tegmen refers to a thin bone plate that separates the middle cranial fossa’s dura from the middle ear and the mastoid cavity. The tympanic membrane attaches superiorly to the scutum, a sharp bony projection. This cavity contains the ossicular chain and is bounded by the tympanic membrane laterally, the inner ear structures medially, the tegmen tympani superiorly, and the jugular wall (floor) inferiorly (11). The middle ear is an air-filled cavity situated within the petrous portion of the temporal bone. Ī focal lobulated soft tissue opacity in the EAC (usually the inferior wall) with an erosion of the adjacent bony wall may represent an EAC cholesteatoma (a rare ear condition) (10). An increased density suggests myringosclerosis (calcification within the tympanic membrane) (9). If the membrane appears well-defined, it is likely thickened. The normal tympanic membrane is often faintly discernible on CT images. This membrane attaches to the tympanic annulus (fibrocartilage ligament) and measures approximately 10 mm in diameter (8). The EAC extends medially from the auricle to the tympanic membrane. The external ear includes the external auditory canal (EAC) and auricle. Several intrinsic fissures, intrinsic channels, and extrinsic sutures are often visible on CT images and can mimic fractures (pseudofractures) (7). The five osseous components of the temporal bone are the squamous, mastoid, petrous, tympanic, and styloid portions (6). The temporal bone consists of the lateral skull base, forming portions of the middle and posterior fossa (a hollow space in the skull, near the brainstem and cerebellum). It is helpful to examine the region and go through key structures in an organized and systematic fashion. There are several structures and disease entities in the temporal bone that one must be familiar with to interpret a CT imaging study. These tools provide a better demonstration of the intricate and minute temporal bone structures’ morphology, orientation, and inter-relationships in 3D space. Three-dimensional (3D) multiplanar reformatted or 3D volume-rendered CT images have recently become available to help demonstrate the temporal bone’s anatomy and pathology (5). Using intravenous contrast (iodine-based dye) to enhance the images is unnecessary for the indications (4). Images produced by the CT scan highlighting bone details are most useful for assessing and diagnosing conditions. This imaging method can visualize the temporal bone’s small and fine structures to the maximal detail. How Does a CT Scan of the Temporal Bone Work?Ī CT scan of the temporal bone is performed at a high-resolution and small field of view with thin imaging slices (0.5 mm) (3). Imaging data provided by CT scans of the temporal bone are fundamental to the diagnosis and treatment of chronic ear infections, temporal bone fractures, middle or inner ear disease, or conductive hearing loss (2). The cross-sectional images produced by the rotating X-ray beam help the radiologist determine any injury or bone abnormalities (1). The temporal bones are situated at the skull’s base and sides.ĬT scan allows the radiologist to view the different levels or slices of the skull bone’s temples or side. 3, Sigmoid sinus.Ĭomputed tomography or CT scan of the temporal bone uses X-ray technology and advanced computer software to generate detailed images of the head. CT Anatomy of temporal boneġ, Superior semicircular canal. ![]()
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