L19 - Hearing & Balance disorders Flashcards
1. Revise anatomy of inner ear, vestibular cochlea nerve 2. Learn about disease of the outer and middle ear. 3. Disorder of inner eat affecting hearing and balance 4. Understand CNS lesions rarely cause hearing loss 5. Describe common causes of lightheadedness and feeling faint 6. Describe common causes of low BP, disease vestibular apparatus, brain stem and cerebellar disease
Describe the External Ear?
Auricle (pinna)
External Acoustic Meatus - ends at tympanic membranes
What is the function of the auricle?
Capture and direct sound waves towards external acoustic meatus.
Describe the tympanic membrane?
- Connective tissue structure.
- Connected to surrounding temporal bone by a fibrocartilaginous ring.
- Translucent.
Describe the functions of inner ear?
- Convert mechanical signals from middle ear into electrical signals.
- Maintain balance by detecting position and motion.
Where is the inner ear located?
Within the petrous part of temporal bone.
What are the two main components of the inner ear?
- Bony Labyrinth
2. Membranous Labyrinth
Describe the bony labyrinth?
- Series of bony cavities within the petrous part of the temporal bone.
a. cochlea
b. vestibule
c. three semi circular canals. - Structures lined internally with periosteum.
- Contain perilymph
Describe the membranous labyrinth?
- Lies within bony labyrinth.
- Consists of :
a. cochlear duct
b. semi-circular ducts
c. utricle
d. saccule. - filled with endolymph
Describe the 3 semi-circular canals of the bony labyrinth?
Lateral
Superior
Posterior
Describe the role of the vestibule?
- how is it separated from middle ear?
- anterior communication?
- posterior communication?
- Contains part of balance system.
- Separated from middle ear by oval window.
- Communicates anteriorly with cochlea
- communicates posteriorly with semi-circular canals.
What parts of the membranous labyrinth are located inside the vestibule?
Saccule
Utricle
What are the roles of the saccule and utricle?
detects?
which is bigger?
- Organs of balance.
- Detects:
a) movement
b) acceleration of head in the vertical and horizontal planes, respectively. - Utricle larger > saccule
Describe the flow of endolymph?
- Drains from saccule and utricle into endolymphatic duct.
- Duct travels through the vestibular aqueduct to the posterior aspect of petrous part of temporal bone.
- Duct then expands to a sac where endolymph can be secreted and absorbed.
Describe the two systems involved in hearing?
- Conducting system
- external and middle ear - Perceiving system
- inner ear, central connections of brain
Describe the role of mastoid air cells?
- Protection of delicate structures of ear.
- regulate ear pressure
- possibly protect temporal bone during trauma.
What bones are housed in the middle ear?
- Malleus
- Incus
- Stapes
- conduct sound from tympanic membrane to inner ear.
Briefly describe the conduction system?
External Ear
- auricle: collects air borne sound waves, passed on to external auditory canal
- EAC transmits air borne sounds to TM
Middle ear
- T.M vibrates,
- sound waves converted to mechanical energy
- ossicles, transmit and amplify sound waves to cochlea.
Describe vertigo?
Illusion of movement of the patient or surroundings.
Explain what normal balance requires?
- Accurate sensory information from eyes, proprioceptive receptors and vestibular labyrinth with coordination of this information within brain.
- normal motor neural control by CNS of an intact MSK system.
How may vertigo arise?
- Peripheral vestibular disorders (labyrinthine).
- Middle ear infections spreading to the labyrinth.
- Central vestibular disorders (MS)
- External damage to vestibular system (trauma)
What is atresia?
Absence or abnormal narrowing of an opening or passage in body.
What is Meniere’s disease?
Idiopathic Endolymphatic hydrops
- disorder of endolymph control
- associated with dilation of the endolymphatic spaces of the membranous labyrinth
What are symptoms of Meniere’s disease?
- Produces attacks of violent paraoxysmal vertigo
- often rotatory, associated with deadness and tinnitus.
Give examples of diseases associated with the outer ear?
- Ear Wax build up
- Otitis externa
- Exostosis
Describe Otitis externa?
aka Swimmer’s ear
- inflammation of infection of the outer ear (pinna and ear canal)
Describe Otitis Media?
Middle ear inflammation.
Inflammation or infection of middle ear.
What is an acoustic neuroma?
A non-cancerous tumor that grows on the main vestibular nerve (inner ear to brain)
- hearing loss, vertigo, tinnitiis
What is cholesteatoma?
- Benign condition.
- Buildup of fibrous tissue within the middle ear and surrounding bones.
Describe staphylococcus aureus?
Gram positive.
Sphere-shaped (coccal)
Most dangerous of all of the many common staphylococcal bacteria.
- often cause skin infections.
Give an examples of a bacterium which can cause an ear infection?
Psuedomonas aeruginosa - gram negative
What is otomycosis?
fungal ear infection affecting outer ear canal .
- presence of greyish white thick debris and heaviness in ear.
What may cause otomycosis?
Asperigillus niger.
Asp. Flavus
Candida Albicans
What is labyrinthitis?
causes?
associated with?
- Infection or inflammation of inner ear
- causes dizziness and loss of balance.
- Often associated with upper respiratory infection such as flu.
State some examples of balance disorders?
- Labyrinthitis.
- Meiniere’s disease
- Vestibular neuronitis
- Benign paroxymal positional vertigo.
Describe vestibular neuronitis?
An inflammation of the vestibular nerve that can be caused by a virus, primarily causes vertigo.
State some examples of hearing disorders? (3)
- Tinnitus
- Hyperacusis
- Single sided deafness
Tinnitus
Ringing in the ear, effect of inner ear damage or impairment
Hyperacusis
Condition affecting how we perceive sounds.
- experiencing heightened sensitivity to particular sounds.
Describe squamous cell carcinoma?
- Affects squamous cells of the epidermis.
- Patients often develop, scaly. red patches, open sores, or warts on their skin.
What may cause instant hearing loss?
Tympanic membrane perforation.
What is haemotympanum?
Presence of blood in tympanic cavity of middle ear.
- often result of basilar skull fracture.
Where does a cholesteatoma develop?
- Middle section of ear.
- Develops as a sac like structure
- lined with keratinizing squamous epithelium.
What is a common cause of lightheadedness?
Orthostatic hypotension
- sudden drop in BP when patient stands.
In medicine what does suppurative mean?
Disease causing suppuration
- causing the production of pus.
What is hyperaemia?
Excess of blood in vessels supplying an organ or other part of the body.
Describe how balance control occurs?
- Vestibular part of inner ear which is stimulated by head movement.
- Vision
- Proprioceptors of muscles and joints
Describe sudden sensorineural hearing loss? SSHL
Type of hearing loss in which root cause lies in inner ear or sensory organ.
- occurs as a consequence of damaged or deficient cochlear hair cells.
Describe acoustic trauma to the inner ear?
e.g. listening to screamo
Damage to cochlea due to exposure to loud sounds.
What is benign paroxysmal positional vertigo? BPPV
due to?
- Common vestibular disorder that causes vertigo, dizziness and other symptoms
- due to debris that has collected within a part of the inner ear.
Give some examples of disorders of the vestibular nerve/
- Vestibular neuronitis.
- inflammation of VN probably viral infection.
- sudden severe vertigo that lasts for days. - Vestibular schwannoma
- benign tumour arising from sheath of VII nerve.
Define ototoxicity
Property of being toxic to the ear, esp. cochlea or auditory nerve and sometimes vestibular system.
Give examples of diseases of the brain that could result in central vertigo?
- Strokes
esp. cerebellum - Tumours
- Encephalitis (brain inflammation)
