Inner Ear Flashcards
Where is the inner ear?
Petrous part of temporal bone
What does the inner ear consist of?
Vestibule and semicircular canals
Cochlea
What is the function of the oval window?
Transmit vibrations from stapes into cochlea. This moves perilymph which causes hair cells on the tectorial membrane to vibrate at different frequencies and send impulses down CNVIII. The pressure change is compensated by the round window
What is the membranous labyrinth?
Labyrinth of endolymph that is surrounded by a bony labyrinth. It is suspended in perilymph
What is the difference between endolymph and perilymph?
Endolymph resembles intracellular fluid
Perilymph resembles CSF
How can the vestibular system be divided?
Semicircular canals
Utricle
Saccule
How do the semicircular canals exist with respect to one another? What do they detect?
3 canals all 90 degrees from one another
They detect rotatory movement
What to the utricle and saccule detect?
Linear motion
Utricle - point up - detect horizontal motion
Saccule - stick out to Side - verticle motion
How is balance maintained?
Input from vestibular system integrated centrally with proprioceptive and visual inputs
What is vertigo?
“Hallucination of movement” -symptom of dizziness associated with vestibular system
What central causes could lead to vertigo?
Stroke Migraine Neoplasms Demyelination Drugs
What are possible peripheral causes of vertigo?
BPPV
Meniere’s disease
Vestibular neuritis
What is BPPV?
Benign Paroxysmal Positional Vertigo
Vertigo associated with particular head movements that last a short time
What causes BPPV?
Otoliths (crystals) in the semicircular canals (commonly posterior) leading to abnormal stimulation of hair cells
How is BPPV described?
Spinning sensation upon moving head
Associated with nausea
Rapid onset, last 30s then stop
No vomiting, pain, tinnitus or hearing loss
How is BPPV diagnosed?
Dix-Hallpike test
How is BPPV treated?
Epley manoevre
Brandt Daroff exercises
What is Dix Hallpike test?
Patient lowered quickly to supine and neck extended to 30 degrees
If vertigo symptoms + nystagmus –> BPPV
What is epley manoevre?
Manoeuvring into various positions to treat BPPV by relocating particles in the semicircular canals
https://en.wikipedia.org/wiki/Epley_maneuver
What is the pathophysiology of Meniere’s disease?
Increased endolymph causes distention of membranous labyrinth which compress vestibular system
What are the clinical features of Meniere’s?
Tinnitus in affected ear
Episodic vertigo with N&V - last minutes to hours
Fluctuating sensorineural hearing loss which can become permanent
Aural fullness
Lasts minutes to hours
Well between attacks
How does Meniere’s disease progress?
Initially patients are well between attacks
As it progresses patients feel unsteady between attacks.
Reduced vestibular function and progressive sensorineural hearing loss
Over time, disease burn itself out so don’t get acute vertigo but still have reduced hearing and general unbalanced feeling
What are the 3 parts of management for Meniere’s disease?
Dietary changes
Medical intervention
Surgical intervention
Safety advice and support
What dietary changes are suggested for Meniere’s disease?
Reduce SACCC:
Salt Alcohol Chocolate Caffeine Chinese food
What medical interventions are used in Meniere’s disease?
Thiazides - bendroflumathiazide
Betahistine (antivertigo)
Antiemetic - prochlorperazine
What surgical interventions are used in Meniere’s disease?
Grommets Dexamethasone middle ear injection Endolymph sac decompression Vestibular destruction using middle ear gentamicin injection Surgical labyrinthectomy (rare)
How does vestibular neuritis/labyrinthitis cause vertigo?
Vestibular neuritis - herpes simplex affects the vestibular nerve
Labyrinthitis - inflammation of the membranous labyrinth due to prior URT infection
Inflammation of the middle ear cause severe incapacitating vertigo with N&V lasting several days
What would you see on examination of a patient suffering from vestibular neuritis?
Sudden, constant severe vertigo
Worse with head movement
Horizontal Nystagmus during attacks
Lasts for days
Hearing loss and tinnitus
How is an acute vestibular neuritis investigated?
MRI to exclude acoustic neuroma
What is labyrinthitis?
Inflammatory disorder of the membranous labyrinth that effects the cochlear and vestibular end organs
Describe the process of sound transmission to hearing in the cochlea
Stapes articulate with oval window with pass vibrations into Scala vestibuli
Movement of perilymph and pressure changes (compensated by round window)
Vibrations transmit endolymph to tectorial membrane
Movement of tectorial membrane move hair cells
Inner hair cells move in response to endolymph to detect sound, Outer stereocilia amplify sound
What risk factors are associated with Menieres disease?
Genetics
Allergy
Autoimmune
How is vestibular neuritis managed?
Urgent ENT referral if sudden onset unilateral hearing loss
Encourage to be as active as possible
Antiemetic - prochlorperazine
What is an acoustic neuroma?
Tumour of vestibular cochlear nerve arising from Schwann cells
What risk factors are associated with acoustic neuromas?
Neurofibromatosis
High dose head/neck radiation
How does acoustic neuroma present?
Unilateral progressive hearing loss
Fluctuations in hearing
Balance disturbance
Tinnitus
How are acoustic neuromas managed?
Wait and see if it grows
Surgery
Targeted radiation
What is the Unterberger Test?
Patient walk on spot with eyes shut - rotate head to side of labyrinth lesion
What is Romberg’s test?
Feel together, eyes closed
Taken away sight leaves only vestibular and proprioception. If dysfunction in one of these then likely to become unbalanced - e.g. dorsal columns issue or vestibular issue
How is degree of hearing loss characterised?
Mild - 20-40dB - can’t hear whispers
Moderate - 40-70dB - can’t hear conversation
Severe 70-90dB - can’t hear shouting
Profound - >95dB - can’t hear sounds that would normally be painful
What key questions may you ask if someone has hearing loss?
How well do you cope with background noise
How well do you hear someone sat next to you
Secondary symptoms
Past ear history
Ototoxic drugs
Exposure to noisy environments
What conductive causes may there be for hearing loss??
External canal - obstruction (painless), growths, infection
TM - rupture (painful), tympanosclerosis
Middle ear - cholesteatoma (progressive), otosclerosis (painless, progressive), infection
Other - adenoids (painless, bilateral), TMJ syndrome (pain in ears, jaw, neck and head)
What sensorineural causes may lead to hearing loss?
Presbyacusis
Noise induced
Ototoxic - aminoglyocsies, cisplatin, salicylates, quinine,
loop diuretics
Autoimmune - present like menieres
Idiopathic
Perilymph fistula
Systemic - meningitis, diabetes, MS, MD
What pattern of hearing loss is seen with noise induced?
Bilateral gradual
or Acute with tinnitus
What pattern of hearing loss is seen with ototoxic drug induced?
Gradual
Fullness
Tinnitus
Balance problems
How does autoimmune sensorineural hearing loss present?
Like Menieres disease
How does idiopathic hearing loss present?
Sudden onset, unilateral
Tinnitus
Fullness
Vertigo
When should hearing loss be referred?
Sudden onset unilateral - ENT
50-80 no underlying pathology - hearing aids
Slight hearing difficulty and unwilling to have hearing aid - watchful waiting
Tinnitus >5mins - audiology
Mix of problems or under 50 - ENT
What characterises sudden onset hearing loss?
> 30dB in 72 hours
What may idiopathic sudden onset hearing loss be associated with?
Vertigo
Aural fullness
Tinnitus
Diagnosis of exclusion but don’t delay management with investigations
How is idiopathic sudden onset hearing loss managed?
14 days oral prednisolone
If it doesn’t work then refer for intratympanic steroids
50% get hearing back within 2 weeks
What are the red flags for sudden onset hearing loss?
Concurrent head trauma
Neurological signs
Unilateral middle ear effusion
How is sudden onset hearing loss investigated?
Examine - lymph nodes, cranial nerves, otoscope, tuning fork
Pure tone audiometry
Tympanometry
Flexible nasoendoscopy
MRI
