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The Middle Ear and Ossicles

The Middle Ear and Ossicles

Disclosures

Difficult & • None : The Middle &

Benjamin Huang, MD,MPH University of North Carolina at Chapel Hill

Objectives Lecture Organization

By the end of this lecture, you should be • overview able to: • Ossicles • Name the compartments of the middle ear and • Muscles and tendons their contents • Facial • Describe the anatomy of the ossicles • Identify normal muscles and ligaments in the • Windows, spaces and recesses middle ear • Describe the tympanic course of the • Identify key anatomic windows and spaces associated with the middle ear

The The Tympanic Cavity

Epitympanum Epitympanum

Mesotympanum Aditus ad Antrum

Hypotympanum The Tympanic Cavity NPC Causing Mastoid Effusion

Protympanum

Mesotympanum

The Ossicles

• Malleus → • Transmit and amplify vibrations from tympanic membrane to • Mnemonic: “M I S O”

Top image: By Oreilleinterne.jpg: Marc GiaconeSVG version/translation: Angelito7 - Oreilleinterne.jpg, CC BY-SA 3.0, https://commons.wikimedia.org/ w/index.php?curid=59840795

Malleus Incus

Head Neck

Lat. Proc. Manubrium Suspensory Ligaments of the Incus Ossicles Suspensory Ligaments

Short Long • Anterior malleal Proc. Proc. • Lateral malleal • Superior malleal • Posterior incudal Sag. “Molar Tooth” View Manubrium

Lenticular Malleus Incus Proc.

Stapes Muscles in the Middle Ear

Two middle ear muscles: • Tensor tympani – Runs in canal along roof of bony Eustacian tube – Turns at cochleoriform process before inserting on malleus neck – Innervation: CN V3 • Stapedius – Smallest muscle in body – Located adjacent to FN in – Inserts on stapes neck – Innervation: CN VII

Tensor Tympani

Stapes neck

Incus lenticular process Stapedius tendon

Stapedius belly Facial Nerve Facial Nerve

Windows and Recesses

Windows • Oval window • Spaces & Recesses • Prussak’s space • Facial recess • Sinus tympani • Supratubal (anterior epitympanic) recess

Oval Window Fenestral otospongiosis Round Window Prussak’s Space

Left image courtesy of Dr Piotr Gołofit, Radiopaedia.org, rID: 43407

Epitympanic Facial Recess & Sinus Tympani

Pyramidal Eminence

Facial Sinus Recess Tympani

Anterior Epitympanic Summary (Supratubal) Recess • Middle ear compartments

Supratubal • Ossicular anatomy Recess Epitympanic – “M I S O” Cog • Muscles & tendons – Only 2: Tensor tympani & stapedius Epitympanum • Facial nerve • Windows, spaces & recesses – Put these in your checklist Geniculate CN7 - CROSS SECTIONAL ganglion Labyrinthine ANATOMY

Epitympanum REVIEW Additus ad antrum

Koerner septum Mastoid antrum

AXIAL CT ANATOMY AXIAL CT ANATOMY

Anterior malleal lig. Head of malleus Head of malleus Tensor Additus Incus body tympani ad antrum and short process

Mastoid CN7 – antrum tympanic segment

AXIAL CT ANATOMY AXIAL CT ANATOMY

Tensor tympani tendon Manubrium of malleus Neck of malleus Cochleoriform process Pro- Incudo- tympanum Incus long stapedial process

Oval Round window CN7 – window Facial descending (stapes footplate) recess (mastoid) segment

Stapes crura Pyramidal eminence Sinus tympani (CN7 & Stapedius) CORONAL CT ANATOMY CORONAL CT ANATOMY

Tegmen tympani Tegmen tympani CN7 – tympanic CN7 segment Head of malleus Incus body & long process Prussak’s Tensor space tympani tendon Scutum

Neck & lateral Incus - Lenticular Stapes entering process of malleus Process oval window

CORONAL CT ANATOMY CORONAL CT ANATOMY

Superior SCC

Lateral Incus SCC short Posterior process SCC

CN7 – Round mastoid window segment Internal jugular CN7 – tympanic segment

Stylomastoid foramen