The Middle Ear and Ossicles
Disclosures
Difficult Head & Neck • None Anatomy: The Middle Ear & Ossicles
Benjamin Huang, MD,MPH University of North Carolina at Chapel Hill
Objectives Lecture Organization
By the end of this lecture, you should be • Middle ear overview able to: • Ossicles • Name the compartments of the middle ear and • Muscles and tendons their contents • Facial nerve • 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 facial nerve • Identify key anatomic windows and spaces associated with the middle ear
The Tympanic Cavity The Tympanic Cavity
Epitympanum Epitympanum
Mesotympanum Aditus ad Antrum
Hypotympanum Mastoid Antrum The Tympanic Cavity NPC Causing Mastoid Effusion
Protympanum
Mesotympanum
The Ossicles Malleus
• Malleus → Incus → Stapes • Transmit and amplify sound vibrations from tympanic membrane to oval window • 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 human body – Located adjacent to FN in pyramidal eminence – Inserts on stapes neck – Innervation: CN VII
Tensor Tympani Stapedius Muscle
Stapes neck
Incus lenticular process Stapedius tendon
Stapedius belly Facial Nerve Facial Nerve
Windows and Recesses
Windows • Oval window • Round 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 Cholesteatoma 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 joint
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 – vein tympanic segment
Stylomastoid foramen