Anatomy of the Ear & Hearing

Question 1

3 regions of the ear

Answer 1

Outer, middle and inner ear

Question 2

Purpose of the regions of the ear

Answer 2

Outer and middle ear transmit sound

Inner ear converts sound energy to fluid motion then electrical signal

Question 3

what is the Pinna

Answer 3

• The visible part of the external ear
• Acts as a tunnel to direct sound
• Cartilage, connective tissue and fat
• Collects sound
• Provides 5-6dB amplification

Question 4

Externa Ear Canal

Answer 4

Outer 1/3 cartilagionous: skin, hair, follicles, sebaceous & ceramunous glands
Inner 1/3 bony: thin skin over perioesteum

Question 5

Tympanic Membrane

Answer 5

Boundary between external and middle ear. Sound waves cause vibration

Question 6

Middle Ear

Answer 6

• Air filled cavity
• Bounded by temporal bone with ear drum laterally
• Communicates with nasopharynx via eustachian tube. Tube equalises pressure
• Contains the ossicles
• Oval and round windows on medial wall communicate with inner

Question 7

Ossicles

Answer 7

• Malleous, Incus, Stapes

- Transmit vibration from tympanic membrane to oval window of cochlea

Question 8

Inner Ear

Answer 8

Fluid filled sac within a bony chamber. Consists of cochlea and semi-circular canals

Question 9

Cochlea

Answer 9

• The organ of hearing
• Spiral shape containing coiled fluid filled channels
• Sound waves are converted into fluid motion then electrical impulses

Question 10

Conductive deafness

Answer 10

Disease of external or middle ear prevents sound wave from getting to cochlea

Question 11

Causes of conductive deafness

Answer 11

Ear wax (cerumen), osteomata, congenital absences of external ear canal, fluid in middle ear, problems with the ossicles

Question 12

Glue ear

Answer 12

When middle ear is filled with fluid instead of air. Common in children. Usually goes away on its own.

Question 13

Haemotympanum

Answer 13

Bleeding within the middle ear cavity with an intact tympanic membrane. Often caused by basal skull fracture.

Question 14

Problems with the ossicles

Answer 14

Dislocation and erosion

Question 15

Sensorineural deafness

Answer 15

Disease of middle ear or organ of hearing. Due to damage cochlea, cochlear nerve or central centres of hearing

Question 16

Causes of sensorineural deafness

Answer 16

Presbycusis, death of hear cells

Question 17

Presbycusis

Answer 17

Progressive, irreversible hearing loss of ageing

Question 18

How sensorineural deafness is treated

Answer 18

Hearing aids

Question 19

How is hearing assessed

Answer 19

Audiogram

Question 20

Tuning fork tests

Answer 20

• Useful bedside test
• Does not give absolute measure of hearing level
• Used to detect unilateral hearing loss and whether conductive or sensorineural
• Need a 512hz tuning fork

Question 21

Weber Test

Answer 21

A 512hz tuning fork is struck then placed on patients forehead. Sound energy is then transmitted into the skull and to each cochlea. Ask where sound is heard.

Question 22

Webers’ Test Result

Answer 22

• Normal: sound is heard equally in both ears
• Sensorineural deafness: sound is heard louder on the side of the intact ear
• Conductive deafness: sound is heard louder on the side of the affected ear

Question 23

Rinne Test

Answer 23

1. Bone conduction is first tested by holding fork on the tip of the mastoid bone. Tell patient to tell you when they can no longer hear the sound.
2. When no sound is hear, air conduction is then tested by holding fork near pinna.
3. Ask patient if they can hear the sound agan

Question 24

Rinne’s Test Result

Answer 24

Normal result: Air conduction > Bone conduction (Rinne’s positive)
Sensorineural deafness: Air conduction > Bone conduction (Rinne’s positive) – both air and bone conduction reduced equally
Conductive deafness: Bone conduction > Air conduction (Rinne’s negative)

Question 25

Tinnitus

Answer 25

An auditory sensation that occurs in the absence of any external stimulation. Can be subjective (heard only by patient) or objective) heard by examiner.

Question 26

Objective causes of Tinnitus

Answer 26

Vascular malformations
Arteriovenous fistula
Palatal myoclonus (spasms of the roof of the mouth muscles causing clicking or popping of the ear)

Question 27

Subjective causes of Tinnitus

Answer 27

Acoustic neuroma
Stroke
Multiple Sclerosis
Medication e.g. aspirin