Suri Imaging Handbook on Anatomy of Cochlea

1. Auflage 2024
ISBN: 978-93-95390-87-3
Verlag: Thieme
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 198 Seiten, ePub

The book Imaging Handbook on Anatomy of Cochlea is specially written from surgeon's perspective on radiology, which will help and guide the implant surgeon in reading images preoperatively. This book covers normal anatomy and anatomical variations in detail. It provides an insight into the minute detailed imaging of the cochlea and its related structures (facial nerve, cochlear aperture, IP-II, IP-III, common cavity, and internal auditory canal). It emphasizes on how a normal anatomy is different from anomalies and to what extent cochlear anomalies will impact surgeries and their outcomes. When ENT surgeons think of starting their own cochlear implant (CI) surgery journey, they rely on reports from radiologists. A lot can be missed, leading to complications intraoperatively. Hence, understanding not only the imaging of normal cochlea but also knowing the cochlear aperture, facial nerve, facial recess, and internal auditory canal, and placement of the facial nerve and cochlear nerve prior to the surgery is of utmost importance to the cochlear implant surgeon.Key featuresThis handbook will teach you about radiological imaging of cochlea, from fundamental structures to uncommon anatomical variances.Facial nerve in cochlea, cochlear aperture, IP-III, and cochlear hypoplasia are beautifully shown in this book.Easy to understand with labelled diagrams and chapters written keeping in mind the practical approach in cochlear implant surgeries. This print book includes complimentary access to a digital copy on https://medone.thieme.com.Publisher's Note: Products purchased from Third Party sellers are not guaranteed by the publisher for quality, authenticity, or access to any online entitlements included with the product.

Zielgruppe

Ärzte

Autoren/Hrsg.

Suri, Neeraj

Fachgebiete

• Medizin | Veterinärmedizin Medizin | Public Health | Pharmazie | Zahnmedizin Klinische und Innere Medizin HNO-Heilkunde, Phoniatrie, Audiologie

Inhaltsverzeichnis

1. Computed Tomography/Magnetic Resonance Imaging: A Surgeon's Perspective 2. Cochlear Implant Related Anatomy: Temporal Bone 3. Radiology of Normal Cochlea 4. Facial Nerve in Cochlear Implants 5. Cochlear Abnormalities 5a. Cochlear Implant in IP-III Malformation 6. Cochlear Hypoplasia 7. Cochlear Aperture: Bony Cochlear Nerve Canal 8. Vestibular and Cochlear Aqueduct 9. Cochlear Ossification 10. Internal Acoustic Meatus 11. Impact of Intra-Operative X-Ray in Cochlear Implant 12. Interesting Imaging 13. Difficult Cochlear Implant Cases

Leseproben

2Cochlear Implant Related Anatomy: Temporal Bone Introduction A cochlear implant surgeon should have a thorough understanding of the intricate anatomy of the temporal bone. Possessing knowledge of the three-dimensional orientation of various structures and their inter-relationships helps in identifying intraoperative surgical landmarks while performing cochlear implant surgeries. It also helps to plan a rational surgical approach, especially in cases with middle ear as well as inner ear anomalies or abnormalities. External Ear The external ear has two parts, namely, the pinna and external auditory canal. Tympanic Membrane •It is 10 mm in diameter and attaches to the tympanic annulus (Fig. 2.1). Fig. 2.1 Axial high-resolution computed tomography (HRCT) of temporal bone showing tympanic membrane (white arrow). •It is faintly discerned on computed tomography (CT) images. •Lateral one-third is fibrocartilaginous. •Medial two-thirds is surrounded by the tympanic part of temporal bone. Middle Ear •It is an air-filled cavity within the petrous portion of the temporal bone. •It contains an ossicular channel which is bounded by the following: –Laterally by tympanic membrane. –Medially by inner ear structure. –Superiorly by tegmen. –Inferiorly by jugular bulb. •Scutum: A sharp bony projection to which the tympanic membrane is attached superiorly (Fig. 2.2). Fig. 2.2 High-resolution computed tomography (HRCT) of temporal bone coronal section showing scutum (white arrow). •Tegmen: It is a thin plate of bone separating middle cranial fossa from the mastoid cavity (Fig. 2.3). Fig. 2.3 High-resolution computed tomography (HRCT) of temporal bone axial section showing tegmen tympani (white arrow) and tegmen mastoideum (black arrow). •Roof of the middle ear cavity is formed by the tegmen tympani. •Roof of the mastoid cavity is formed by the tegmen mastoideum. •Posterior wall is formed by the facial recess also known as facial nerve recess. Pyramidal eminence overlies the stapedius muscle. •Subiculum separates the sinus tympani from the round window niche. •Lateral to the pyramidal eminence is the facial recess where lies the second genu of the facial nerve. •The facial recess is used by the surgeon to place cochlear implant electrode via round window (Fig. 2.4). Fig. 2.4 High-resolution computed tomography (HRCT) of temporal bone axial section showing pyramidal eminence (red star), sinus tympani (blue arrow), and facial recess (white arrow). •Prussak’s space also known as superior recess is bounded by the following: –Laterally by pars flaccida, scutum. –Superiorly by lateral malleal ligament. –Medially by neck of malleus. •Middle ear is subdivided into: –Epitympanum. –Mesotympanum. –Hypotympanum (opening of eustachian tube, internal carotid artery along its medial margin) (Fig. 2.5). Fig. 2.5 Subdivisions of the middle ear. •Mesotympanum consists of ossicular chain. –Malleus—head, neck, anterior process, lateral process, and manubrium. –Incus—body, short process, long process, lenticular process. –Stapes—head, anterior crus, posterior crus, foot plate. •The manubrium of the malleus is attached to the tympanic membrane, and the head of the malleus articulates with the body of the incus in the epitympanum forming incudomalleal joint (ice-cream cone appearance which is seen in axial section of high-resolution computed tomography [HRCT] of temporal bone). •The neck of the malleus anteriorly and the long process of the incus posteriorly give “two dots” appearance. •The manubrium of the malleus anteriorly and the long process of the incus posteriorly are seen as two parallel lines. •The lenticular process of the incus extends approximately at right angle from the long process of the incus. •The head of the stapes and the long process of the incus articulate together to form the incudostapedial joint. •The foot plate of the stapes attaches to the oval window of the vestibule. •There are four suspensory ossicular ligaments: –Superior malleal. –Lateral malleal. –Posterior malleal. –Posterior incudal. •The suspensory ossicular ligaments are seen on CT image as thin linear structures. •The lateral malleal ligament is the most commonly identified ligament among all suspensory ligaments. •The tensor tympani muscle arises from the cartilaginous part of the eustachian tube, and then turns sharply at cochleariformis process and attaches to the neck of the malleus (Fig. 2.6). •Epitympanum communicates with the mastoid via the aditus and antrum. Fig. 2.6 High-resolution computed tomography (HRCT) of temporal bone axial section showing tensor tympani (TT) muscle. •Mastoid is an air-filled cavity: –It is divided into numerous compartments by mastoid septations (Fig. 2.7). –Air cell sizes are variable. Fig. 2.7 High-resolution computed tomography (HRCT) of temporal bone axial section showing pneumatized mastoid (M) bone. •Korner’s septum: It is a bony structure (petrosquamous suture) separating mastoid air cells into two compartments. When thick may be confused with medial wall of the antrum by the surgeon. •Petromastoid canal is a channel passing between superior and lateral semicircular canal. –Commuting cranial cavity to mastoid antrum. –Measures 0.5 to 1 mm. –Contains subarcuate artery. –Potential channel for spread of infection to and from the mastoid antrum. –Not to be mistaken for fracture line. Inner Ear •It is situated in petrous part of temporal bone. •It comprises bony and membranous labyrinth. Cochlea •It is a snail-like structure. •It consists of basal turn, middle turn, and apical turn, which are separated by interscalar septae (Fig. 2.8a–c). Fig. 2.8 (a) Apical turn (AT), middle turn (MT), basal turn (BT), and internal auditory canal (IAC). (b) Axial high-resolution computed tomography (HRCT) of temporal bone showing apical, middle, and basal turn of cochlea (white arrow). (c) Coronal HRCT of temporal bone showing cochlea with its turns (white arrow). •The osseous spiral lamina is well appreciated on T2 magnetic resonance imaging (MRI). It parallels the interscalar septae. Cochlear Promontory •The bulge of cochlear promontory is prominently seen in the middle ear cavity as a dome (Fig. 2.9). •Nerve of Jacobson courses above the promontory. •Vestibule is ovoid shape, located superior and posterior to the cochlea. Fig. 2.9 High-resolution computed tomography (HRCT) of temporal bone axial section showing cochlear promontory (blue arrow). Semicircular Canals •They are three in number: –Superior. –Posterior. –Lateral semicircular canal. •They are placed at right angle to each other. •Each has ampulla at one end. •Posterior and superior semicircular canals have a common crus. •The lateral semicircular canal has two separate openings into the vestibule (Fig. 2.10a, b). Fig. 2.10 (a) High-resolution computed tomography (HRCT) axial section showing lateral semicircular canal (red dots and blue arrow). (b) HRCT coronal section showing superior (S-SCC) and lateral (L-SCC) semicircular canals. •The endolymphatic duct runs from the vestibule and ends in a blind pouch in the posterior cranial fossa. •Vestibular aqueduct: –Envelopes endolymphatic duct. –1 mm at mid-point and 2 mm at operculum. •Cochlear aqueduct is a narrow bony channel that surrounds perilymphatic duct and extends from the basal turn of the cochlea anterior (round window) to the subarachnoid space. –It measures 0.1 to 0.2 mm in the midportion. –It roughly runs parallel and immediately inferior to the internal auditory canal (approximately 6–7 mm). •Internal auditory...