Ear

Swelling can block sound from entering the external acoustic meatus

Why can an auricular hematoma cause hearing loss?

Varicella zoster (shingles); dormant in the geniculate ganglion (CN VII)

What virus causes Ramsay Hunt syndrome, and where does it lie dormant?

CN VII makes a small sensory contribution to the external ear, so the shingles rash appears in that dermatome

Why does Ramsay Hunt syndrome affect the external ear?

Touching the external acoustic meatus/concha, which is supplied by a small CN X branch

What triggers the Arnold cough reflex?

Pars tensa: the taut majority; pars flaccida: the small, lax superior portion

Which part of the tympanic membrane is taut, and which is lax?

Anterior and inferior

Where does the cone of light point on a normal tympanic membrane?

The tip of the handle of the malleus, at the center (apex) of the cone-shaped tympanic membrane

What is the umbo?

Perforation of the tympanic membrane

Main risk of inserting objects (e.g., cotton swabs) into the ear canal

The tympanic portion of the temporal bone

What forms most of the bony external acoustic meatus?

Cochlea anterior, semicircular canals posterior, middle ear cavity lateral to both, beneath the tegmen tympani

Location of the ear structures on radiologic images

CN VII, in the facial canal

Which nerve runs along the medial wall of the middle ear?

The stapedius muscle

What does the pyramidal eminence enclose?

Posteriorly from the middle ear to the mastoid air cells (mastoid antrum)

Where does the aditus lead?

Stylomastoid foramen

Where does CN VII exit the skull after the facial canal?

Petrotympanic fissure

Where does the chorda tympani exit the skull?

Hiatus for the greater petrosal nerve

Where does the greater petrosal nerve emerge onto the middle cranial fossa floor?

Tympanic canaliculus

Through what opening does the tympanic nerve (Jacobson's n.) enter the middle ear?

The malleus (head = scoop) and incus (body = cone) seen together on CT

What is the "ice cream cone" on radiologic imaging?

In the oval window

Where does the base (footplate) of the stapes sit?

Sound -> tympanic membrane -> malleus -> incus -> stapes -> oval window -> cochlear fluid vibrations -> organ of Corti -> CN VIII action potentials

Full sound conduction pathway to CN VIII

Whether air conduction is stronger than bone conduction

What does the Rinne test check?

Sounds from chewing and loud noises

What kinds of loud sounds does the tensor tympani dampen?

Tensor and levator veli palatini open the pharyngotympanic tube, equalizing middle ear pressure

Why do your ears "pop" when you yawn or swallow on a plane?

Their pharyngotympanic tube is more horizontal, so the middle ear drains poorly

Why is otitis media more common in children?

Vestibular labyrinth (semicircular ducts, utricle, saccule) and cochlear labyrinth (cochlear duct)

2 parts of the membranous labyrinth

Utriculosaccular duct

What connects the utricle and saccule?

Ductus reuniens

What connects the cochlear duct to the saccule?

Suspended by delicate filaments within the bony labyrinth

How is the membranous labyrinth held in place?

Gravity and linear acceleration (utricle: horizontal plane; saccule: vertical plane)

What do the maculae of the utricle and saccule detect?

Rotational movement of the head

What do the semicircular ducts detect?

Helicotrema (at the apex of the cochlea)

Where do the scala vestibuli and scala tympani communicate?

Scala vestibuli begins at the oval window; scala tympani ends at the round window

Where does the scala vestibuli begin, and where does the scala tympani end?

Scala media

What is another name for the cochlear duct?

Vestibular membrane

What separates the cochlear duct from the scala vestibuli?

Basilar membrane

What separates the cochlear duct from the scala tympani?

On the basilar membrane, under the tectorial membrane

Where do the hair cells of the organ of Corti sit?

Spiral ligament

What lies on the lateral wall of the cochlear duct?

Runs in the vestibular aqueduct to end in the endolymphatic sac

Path of the endolymphatic duct

The perilymphatic space to the subarachnoid space (CSF)

What does the cochlear aqueduct connect?

Both the cochlear (tinnitus, hearing loss) and vestibular (vertigo) systems

Which systems does Ménière's disease affect?

Greater petrosal n., nerve to stapedius, chorda tympani

Branches of CN VII in/near the facial canal

Motor to the stapedius muscle

What does the nerve to stapedius supply?

Exits via the petrotympanic fissure, joins the lingual nerve (V3), and continues to the submandibular ganglion

Path of the chorda tympani after crossing the middle ear

Superior salivatory nucleus -> greater petrosal n. -> joins deep petrosal n. -> Vidian n. (pterygoid canal) -> pterygopalatine ganglion -> lacrimal gland and nasal/palatal mucosa

Greater petrosal parasympathetic pathway

The deep petrosal nerve (postganglionic sympathetic, from the internal carotid plexus)

What joins the greater petrosal nerve to form the Vidian nerve?

Superior salivatory nucleus -> chorda tympani -> lingual n. (V3) -> submandibular ganglion -> submandibular and sublingual glands

Chorda tympani parasympathetic pathway

Hyperacusis (stapedius paralysis)

CN VII lesion proximal to the nerve to stapedius causes:

Loss of taste (anterior 2/3 tongue) and reduced submandibular/sublingual salivation

CN VII lesion proximal to the chorda tympani causes:

Reduced lacrimation (dry eye), plus the chorda tympani and stapedius deficits

CN VII lesion proximal to the greater petrosal nerve causes:

Proximal to the greater petrosal nerve (at or before the geniculate ganglion)

Bell's palsy with hyperacusis, loss of taste, and dry eye: where is the lesion?

To avoid the chorda tympani (which crosses superiorly) and to allow better drainage

2 reasons myringotomy tubes are placed inferiorly

It involves loss of cochlear hair cells, which don't regrow

Why doesn't sensorineural hearing loss recover?

Canal blockage, middle ear fluid, tympanic membrane or ossicle problems, impaired oval/round window movement

Examples of conductive hearing loss causes

Sensorineural: cochlea or cochlear nerve; conductive: external or middle ear (sound never reaches the cochlea properly)

Sensorineural vs. conductive hearing loss: site of the problem

The external ear, middle ear, and organ of Corti; it stimulates the cochlear branch of CN VIII directly

What does a cochlear implant bypass?

External

Middle

Inner

The ear has three parts:

Equilibrium (balance)

Hearing

2 main functions of the ear

cochlear system

system within the ear in charge of hearing:

vestibular system

system within the ear in charge of balance:

Auricle

Identify the structure

External acoustic meatus

Identify the structure

external ear

the ear auricle is part of the:

external ear

the external acoustic meatus is part of the:

Auricle (pinna)

What is the irregular shaped cartilage plate covered by thin skin?

lobule

what part of the ear auricle does not have cartilage?

Helix

Identify the structure at #1

Antihelix

Identify the structure at #2

Antitragus

Identify the structure at #3

Lobule

Identify the structure at #4

Tragus

Identify the structure at #5

External acoustic meatus

Identify the structure at #6

auricular hematoma

patient is a wrestler and presents as such. What is the pathology?

Cauliflower ear

If a patient has a persistent auricular hematoma and it is not drained, it can lead to...

auriculotemporal n. (V3)

sensory innervation for the external ear over the anterior helix and tragus:

lesser occipital n. (C2)

great auricular n. (C2-3)

sensory innervation for the external ear over the posterior helix and anti-tragus:

Small sensory contributions from CN VII (blue circles) and X (red triangles)

What do the triangles and circles represent?

CN X

What cranial nerve is involved with the arnold cough reflex?

CN VII

What cranial nerve is involved with Ramsay-Hunt Syndrome?

CN VII

somatic motor innervation to the ear is done by:

Auriculotemporal n. (V3)

Identify the structure at #1

Lesser occipital n. (cervical plexus)

Identify the structure at #2

Greater auricular n. (cervical plexus)

Identify the structure at #3

Motor branches of CN VII

Auricular muscles are innervated by what nerve?

Posterior auricular branch of CN VII

Identify the structure at #1

Posterior auricular m.

Identify the structure at #2

Superior auricular m.

Identify the structure at #3

Anterior auricular m.

Identify the structure at #4

Temporal branch of CN VII

Identify the structure at #5

Cartilaginous portion of the external acoustic meatus

Identify the structure at #1

Bony portion of the external acoustic meatus

Identify the structure at #2

- About 1 inch long: Slightly sigmoid (S-shaped)

- Lined with skin containing sebaceous and ceruminous glands which produce ear wax

Characteristics of the external acoustic meatus (canal)

perforation of the tympanic membrane

identify the trauma:

perforation of the tympanic membrane

identify the trauma:

tympanic membrane

what is the medial boundary of the external ear?

tympanic membrane

what structure separates external and middle ear?

A sulcus of the temporal bone

What is the tympanic membrane set in?

Oriented laterally, anteriorly and inferiorly

How is the tympanic membrane oriented?

Tympanic membrane

What is a cone shaped with apex attached to the handle of the malleus at the umbo?

capture changes in air pressure (sound) and transfer to the bones of the middle ear

What is the function of the tympanic membrane?

malleus

the tympanic membrane is attached to which ossicle?