Otoslerosis

Otosclerosis can be familial, particularly  when it  is severe. It results  from fibrous ankylosis followed by bony overgrowth of the little ossicles of the middle car. A schwannoma typically  involves  the  eighth cranial nerve and results in  a  nerve  conduction form  of  deafness. Schwannomas are usually unilateral. although familial neurofibromatosis could result in the appearance of multiple schwannomas. A cholesteatoma is typically a unilateral process that complicates  chronic  otitis  media  in  a  child  or young adult otitis media by itself is usually self- limited and uncommon in an adult Chondrosarcomas may involve the skull in older adults but are rare and are solitary bulky masses in the region of the jaw.

Paracusis Willis refers to improved hearing with background noise. It is seen in patients with otosclerosis.

Hearing deficit typically becomes apparent when they reach a 25 -30dB loss where the patient has difficulty understanding speech.

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

The hallmark of bone conduction thresholds in otosclerosis is the Carhart notch.

This is characterized by the elevation of bone conduction thresholds of approximately 5, 10, and 15 dB at 500, 1000, and 2000 Hz, respectively.

The Carhart notch is thought to result from the disruption of normal ossicular resonance, which is approximately 2000 Hz.

It is therefore a mechanical phenomenon and not a true reflection of cochlear reserve

Otosclerosis is characterized by abnormal removal of mature dense otic capsule bone by osteoclasts, and replacement with the woven bone of greater thickness, cellularity, and vascularity.

When disease involves the annular ligament of the oval window and stapes footplate, a conductive hearing loss (CHL) occurs which is slowly progressive, usually bilateral and asymmetric. 

• 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.

• 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.

In Otosclerosis on Otoscopy

• Tympanic membrane is normal in appearance mostly, middle ear space is well pneumatized and malleus moves with pneumatic otoscopy (i.e. mobility is normal)
• Sometimes a reddish hue / Flammingo-pink may be seen on the promontory and oval window niche owing to the prominent vascularity associated with an otospongiotic focus. This is known as Schwartz sign.

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.

In otosclerosis – As type curve is seen which is a low compliance curve.

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.

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.