Otosclerosis / Otospongiosis

Fossa antefenestrum

Oval window

Type AS

High-frequency audiometry is specifically for ototoxicity monitoring, comprises air conduction thresholds from 10,000 to 20,000 Hz.

 Most ototoxic hearing losses will first occur in that frequency region, which is higher than the speech range. 

Type A tympanograms have normal peak height and pressure.

Two variations of the Type A tympanogram also are normal in pressure, but may be shallow (AS), reflecting otosclerosis or middle ear effusion, or peaked very high (AD), reflecting ossicular discontinuity or a monomeric eardrum

• Otosclerosis is suggested by a positive family history, 
• a tendency toward onset at an earlier age, 
• the presence of conductive hearing loss, or
•  bilateral symmetric auditory impairment
• Treatment with a combination of sodium fluoride, calcium gluconate, and vitamin D may be effective. If not, surgical stapedectomy should be considered.

Endolymphatic hydrops i.e menieres disease leads to SNHL and not conductive hearing loss.

• 50% of patients of otosclerosis have positive family history.
• Females are more commonly affected than males. 
• Whites are affected more than negroes.
• Age = most common between 20-30 years and is rare before 10 and after 40 years.
• Deafness is increased by pregnancy, menopause, trauma and major operations.
• Viruses like measles virus have also been associated with it.

Ans. is a i.e. Oval window

Ans. is a i.e. Normal

Gene’s Test

This test was earlier done to confirm the presence of otospongiosis.

In this test, BC (bone conduction) is tested and at the same time Siegle’s speculum compresses the air in the meatus.

In normal individuals hearing is reduced after this; i.e. Gelles test is positive; but in stapes fixation, sound is not affected. i.e Gelles test is negative.

Carharts notch

• Bone conduction is normal in otosclerosis.
• In some cases there is a dip in bone conduction curve which is maximum at 2000 Hz / 2 KHZ called as Carharts notch.
• Carharts notch is seen only in bone conduction curve.
• It disappears after successful stapedectomy/stapedotomy.

• The reason why it disappears after successful surgery is that when the skull is vibrated by bone—conduction sound, the sound is detected by the cochlea via 3 routes:

–  Route (a)—is by direct vibration within the skull.

–  Route (b)—is by vibration of the ossicular chain which is suspended within the skull.

–  Route (c)—is by vibrations emanating into the external auditory canal as sound and being heard by the normal air-conduction route.

• In a conduction type of hearing loss (as in otosclerosis) the latter two routes are deficient but regained by successful reconstruction surgery. Hence bone conduction thresholds improve following surgery.

• In otosclerosis-50% cases have positive family history.
• Females are affected more than males.
• Bilateral conductive deafness seen in otosclerosis is not irreversible as it can be successfully treated by stapedectomy / Stapedotomy.
• Sensorineural hearing loss occurs when later in the course of time 
• osteosclerotic focus reaches the cochlear endosteum but actually most common hearing loss seen is conductive type.Q
• Carharts notch is seen in bone conduction curve at 2000 Hz.

Tuning Fork Tests in Otosclerosis

• Rinnes test-negative
• Webers test-lateralised to ear with greater conductive loss
• Absolute bone conduction-normal (It is decreased in cochlear otosclerosis)
• Pure tone audiometry-shows loss of air conduction more for lower frequency.

Ans. is a i.e. It inhibits osteoblastic activity

The most useful medication which prevents rapid progression of cochlear otoscierosis is sodium fluoride

Mechanism of Action

• It reduces osteoclastic bone resorption and increases osteoblastic bone formation, which promote recalcification and reduce bone remodelling in actively expanding osteolytic lesion.
• It also inhibits proteolytic enzymes that are cytotoxic to cochlea and lead to SNHL (Hence specially useful in cochlear otosclerosis). 
  • Current Otolaryngology 2nd/ed pg 678 

Ans. is a i.e. Teflon piston

The currently used prosthesis in otosclerosis surgery are:

• Teflon (M/C used)
• Stainless steel
• Platinum                       — All are MRI compatible
• Gold
• Titanium

The prosthesis is placed between the long process of incus and foot plate of stapes

Diagnosis of otosclerosis

• Otosclerosis is traditionally diagnosed by characteristic clinical findings, which include progressive conductive hearing loss, a normal tympanic membrane, and no evidence of middle ear inflammation.
• The cochlear promontory may have a faint pink tinge reflecting the vascularity of the lesion, referred to as the Schwartz sign.
• Conductive hearing loss is usually secondary to impingement of abnormal bone on the stapes footplate.
• This involvement of the oval window forms the basis of the name fenestral otosclerosis.
• The most common location of involvement of otosclerosis is the bone just anterior to the oval window at a small cleft known as the fissula ante fenestram.
• The fissula is a thin fold of connective tissue extending through the endochondral layer, approximately between the
  oval window and the cochleariform process, where the tensor tympani tendon turns laterally toward the malleus.

Hyperacusis is characterized by an over-sensitivity to certain frequency ranges of sound (a collapsed tolerance to normal environmental sound).

Hyperacusis can be acquired as a result of:

• The most common cause of hyperacusis is overexposure to excessively high decibel levels (or sound pressure levels).
• Migraine
• Severe head trauma
• Facial nerve dysfunction (to Stapedius)
• Tension Myositis Syndrome
• Adverse drug reaction
• Autism
• Bell’s palsy
• Meniere’s disease
• Asperger syndrome

In cochlear hyperacusis (the most common form of hyperacusis), the symptoms are ear pain, annoyance, and general intolerance to any sounds that most people don’t notice or consider unpleasant.

In vestibular hyperacusis, the sufferer may experience feelings of dizziness, nausea, or a loss of balance when certain pitched sounds are present.

Otosclerosis presents with hearing loss (bilateral and conductive type) and paracusis willisii (patient hears better in noisy environment).

FINDINGS IN OTOSCLEROSIS

Symptoms of otosclerosis

• Hearing loss :- Bilateral conductive deafness which is painless and progressive with insidious onset. In cochlear otosclerosis sensorineural hearing loss also occurs along with conductive deafness.
• Paracusis willissii :- An otosclerotic patient hears better in noisy than quiet surroundings.
• Tinnitus :- More common in cochlear otosclerosis.
• Speech :- Monotonous, well modulated soft speech.
• Vertigo :- is uncommon.

Signs in otosclerosis

• Tympanic membrane is quite normal and mobile.
• In 10% of cases flamingo – pink blush is seen through the tympanic membrane called as Schwartz sign. Various tests show conductive hearing loss.

Tuning fork tests in otosclerosis

• As otosclerotic patients have conductive deafness, the tuning fork tests results will be as follows :‑

1. Rinnes :- Negative
2. Webers :- Lateralized to the ear with greater conductive loss.
3. Absolute bone conduction (ABC) :- Normal (can be decreased in cochlear otosclerosis).
4. Gelles test :- No change in the hearing through bone conduction when air pressure of ear canal is increased by Siegle’s speculum.

Audiometry in otosclerosis

Audiometry is one of the important tools in evaluation of a patient of otosclerosis.Various audiometric tests are :‑

1) Pure tone audiometry

• Shows loss of air conduction, more for lower frequencies with characteristic rising pattern. Bone conduction is normal. However in some cases, there is a dip in bone conduction curve which is maximum at 2000 Hz (2 KHz) and is called the Carhart’s notch.

2) Impedance audiometry

• Impedance audiometry shows :-

i) Tympanometry

• Patient with early disease may show type A tympanogram (because middle ear areation is not affected) Progressive stapes fixation results in classical As type tympanogram.

ii) Acoustic (stapedial reflex)

It is one of the earliest sign of otosclerosis and precedes the development of airbone gap. In early stage, diphasic on-off pattern is seen in which there is a brief increase in compliance at the onset and at the termination, stimulus occurs. This is pathognomonic of otosclerosis. In later stage the reflex is absent.

Meniere’s disease is a disorder of the inner ear which is characterized by :-

i) Episodes of vertigo

ii) Tinnitus (ringing in the ears)

iii) Fluctuating sensorineural hearing loss

iv) Feeling of fullness or pressure in ear (aural fullness)