CHARLES NKURUNZIZA,MDUNIVERSITY OF RWANDADEPARTMENT OF ENT HEAD & NECK SURGERYENT DEPART ACADEMIC MEETING Wed 3rd DEC 2014*

IntroductionAnatomyPathophysiologyEpidemiologyPresentationWork up planManagement**

Disease of the bony otic capsule and is unique to humans

Results in fixation of the ossicular chain and CHL

May have SNHL component if the cochlea is involved

The most common cause of progressive CHL in adults

Genetically mediatedAutosomal dominant

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Osteodystrophy: abnormal development of the boneProcess of bone resorption of the petrous bone (spongiosis), followed by replacement with thick irregular sclerotic bone (sclerosis), often leading to hearing loss. The most commonly affected location is around the oval window, which can result in conductive hearing loss due to stapes footplate fixation (fenestral otosclerosis). In approximately 10% of the patients, otosclerotic foci will also affect the otic capsule (retrofenestral otosclerosis) resulting in cochlear otosclerosis accompanied by sensorineural hearing loss.*

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Otosclerosis occurs at certain sites of predilection within the temporal bone with the most common site being the area anterior to the oval window (80-95 percent of cases).3,4 [**** J Other sites of involvement in descending order of frequency are the round window niche (about 30percent), the apical medial wall of the cochlear labyrinth (about 15 percent), the stapes footplate (about 12 percent) and posterior to the oval window (5-10 percent).

Demineralised hypodense fenestral otosclerotic foci are best seen on axial HRCT because of the anteroposterior orientationof the oval window and stapes crura. Otic capsule: skeletal element enclosing the inner earThe cochlea is a snail-like tube that is divided along its length into three compartments: the scala vestibuli (top), the scala media (middle), and the scala tympani (bottom). Reissner's membrane separates the scala vestibuli from the scala media. The basilar membrane separates the scala media from the scala tympani. Perilymph, a fluid similar to extracellular fluid, fills the scala vestibuli and tympani, and endolymph, a fluid similar to intracellular fluid, fills the scala media. The scala media houses the organ of Corti.The otic capsule arises from mesenchyme surrounding the otic vesicle at 4 weeks. At 8 weeks, the cartilaginous framework is begun. At 16 weeks, endochondral bony replacement of this framework begins in 14 identifiable centers. In some people, complete bony replacement does not occur and leaves cartilage in certain locations.One of these regions, the fissula ante fenestram IS usually the last area of endochondral bone formation in the labyrinth.According to temporal bone studies, this region is affected in 80% to 90% of patients with OS.

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**Bone resorption of the petrous bone (spongiosis phase) Replacement with thick irregular sclerotic bone (sclerosis )Two types:Fenestral CHLRetrofenestral.SNHLLiberation of toxic metabolites into the inner ear Direct extension of lesions into the cochlea

Inciting event:HereditaryHormonalMeasles virus infectionAutoimmune

Process of bone resorption of the petrous bone (spongiosis), followed by replacement with thick irregular sclerotic bone (sclerosis), often leading to hearing loss. The most commonly affected location is around the oval window, which can result in conductive hearing loss due to stapes footplate fixation (fenestral otosclerosis).Support for this hypothesis comes fromultrastructural and immunohistochemical evidence ofmeasles-like structures and antigenicity in active otosclerotic lesions.

Choclear endosteumInvolvement area dictates the clinical presentation. The CHL is due to fixation of the stapes footplate, usually beginning at the fissula ante fenestram

Two phases of diseaseActive (otospongiosis phase)Osteocytes, histiocytes, osteoblastsActive resorption of boneDilation of vesselsSchwartzes sign

Mature (sclerotic phase)Depositionmechanism for the SNHL is possibly the of new bone (sclerotic and less dense than normal bone)The liberation of toxic metabolites into the inner ear with resultant injury to neuroepithelium, vascular compromise, or direct extension of lesions into the cochlea, causing disruption of electrolytes and changes in basilar membrane mechanics.

demineralised foci of spongy new bone typically occur in the region of the embryonic fissula ante fenestram, which is a cleft of fibrocartilagenous tissue between the inner and middle ear, just anterior to the oval window

The promontory, round window niche and tympanic segment of the facial nerve canal can also be involved

The disease gradually extends to involve the entire footplate of the stapes and may subsequently involve the cochlea. Heaped-up bony plaques formed in the healing phase typically cause narrowing of the oval and round windows

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Paul Merkus et al, 2011*Clinical otosclerosis is about 2%.Histological otosclerosis: 10%

Female to male ratio 2:1.

Age predilection is 20-40 yearsYoungest: 6 years

Most common among white peopleUncommon among Asian people Extremely rare in black people.

The incidence of clinical otosclerosis in the general population is about 2%. *

*History:Age of onset Progression, fluctuation, or stability of the HLUnilateral versus bilateral hearing loss Family history of hearing loss and ear surgery History of events surrounding the onset of hearing loss (e.g. infection, trauma, pregnancy, measles)

Physical examination:Normal Tympanic membraneSchwartze sign TFTRinne test: NegWeber test:lateralizes to side with greater CHL

Excessive vascularity within the mucosa over an otosclerotic focus near the oval window and promontory is the histologic substrate for the red vascular blush seen at otoscopy' inpatients with active otosclerosis (Schwartze's sign). *

**1.Pure Tone AudiometryAkinori Kashio et al, 2011

audiological examination is the most important diagnostic tool Incidence of Carhart notch was almost identical among the stapes fixation, incudostapedial joint detachment, and malleus or incus fixation groups. Most useful audiometric test for otosclerosisa widening ABG that usually begins in the low frequenciesBone conduction may show a 20 dB loss at 2000 Hz ( Carharts notch)Decrease in bone conduction thresholds5 dB at 500 Hz10 dB at 1000 Hz15 dB at 2000 Hz5 dB at 4000 Hz*

2.Tympanometry**

3.Imaging: High-resolution CT scans**

Axial (a)andcoronal(b) HRCT images of the right temporal bone in an adult patient with right-sided CHL. A hypodense demineralised plaque(arrow) is noted in the region of the fissula ante fenestram in keeping with fenestral otosclerosisDemineralised hypodense fenestral otosclerotic foci are best seen on axial HRCT because of the anteroposterior orientation of the oval window and stapes crura.HRCT adequately demonstrates the demineralised foci in the otic capsule. The classical imaging appearance of cochlearotosclerosis on HRCT is a distinctive pericochlear hypodense double ring (which is also known as the 4th ring of Valvassori)Imaging plays an important role in the diagnosis and management of otosclerosis. High-resolution CT (HRCT) of the temporal bone using 1-mm (or less) thick sections is the modality of choice for assessment of the labyrinthine windows and cochlear capsules.fissula ante fenestram, which is a cleft of fibrocartilagenous tissue between the inner and middle ear, just anterior to the oval window (Fig. 1). Bilateral involvement is common (Fig. 2). The promontory, round window niche and tympanic segment of the facial nerve canal can alsobe involved *

**Ossicular discontinuity

2. Congenital stapes fixation3. Pagets disease4. Osteogenesis imperfecta

Paget disease (osteitis deformans) is a disease with diffuse bony involvement that is histologically similar to OS. In contrast to OS, Paget disease begins in the periosteal layer and involves the endochondral bone last. Temporal bone involvement can produce SNHL,but stapes involvement or fixation rarely occurs

Osteogenesis imperfecta (van der Hoeve-de-Kleyn syndrome) is an autosomal dominantdefect of osteoblast activity resulting in multiple fractures. Stapes fixation and uniqueblue sclera are also found in 40% to 60% of affected patients.*

**1.Stapes Surgery:

The aim of stapes surgery is to restore the vibration of uids within the cochlear canal. The basic surgical steps include disarticulatingthe incudostapedial joint, removal of stapes suprastructres and opening up the stapes footplate Disarticulating the incudostapedial joint Removal of stapes suprastructres Opening up the stapes footplateStapectomyVs Stapedotomy

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*Hasan Al-Husban, 2013

Outcome of Management of Otosclerosis by Stapedotomy Compared to Stapedectomy in a Jordanian Populationto a small hole in the stapes footplate, the stapedotomy. The aim of stapes surgery is to restorethe vibration of uids within the cochlear canal. *

*2.AmplificationHearing Aid

3.Cochlear Implant Uppal et al, 20104. MedicalSodium uoride Neutralises and inactivates the hydrolytic and proteolytic enzymes 20mg/day x6/12 and control hearingBisphosphonates Patient intolerant to sodium uoride therapyActive otospongiosis and positive Schwartz sign

alternative treatment to sodium uoride in cases where the patient is intolerant to sodium uoride therapy. (retrofenestral otosclerosis), resulting in cochlear otosclerosis with sensorineural hearing loss.In advanced otosclerosis, characterized by mixed hearing loss, hearing aids alone often do not result in optimal hearing rehabilitation, and surgery becomes an option. Nowadays, two surgical techniques are available: stapedotomy or CI. The decision for the appropriate treatment for each patient can be challenging given that both interventions differ in costs, risks, and success rate*

TAKE HOME MESSAGEMost common cause of progressive CHL in adultsPrevalence of OS is greater in womenPathologic changes begin as spongification of the bone of the otic capsuleGold standard for the diagnosis is surgeryManagement options include:Stapes surgeryHARarely:

Medical Cochlear implantation.Stapes surgery options include:Stapedotomy Total stapedectomyPartial stapedectomyComplications of stapes surgery include SNHL, vertigo, fistula, infection, TM perforation.

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References1 .Cummings otolaryngology 5th edition.2.Scott Brown ENT 7th Edition3.Cunningham text review, Otolaryngology Prep and Practice4. International journal of Clinical Practice , March 2010, 64, 4, 5055105. Clayton AE, Mikulec AA, Mikulec KH, et al. Association between osteoporosis and otosclerosis in women. J Laryngol Otol 2004;118:617621.6. Paul M, et al. Decision Making in Advanced Otosclerosis: An Evidence-Based Strategy, the laryngoscope, 2011

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**OTOSCLEROSIS

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(a) The three normal routes of bone conduction of sound vibrations to the inner ear: route A: via the skull bone; route B: via the ossicular chain; and route C: via the external auditory canal. In a normal ear, when the skull is vibrated by bone-conduction, it not only vibrates the cochlea via route A, but it also vibrates the tympanic membrane and ossicular chain (route B) and the air in the external auditory canal (route C). (b) In the presence of a conductive defect, the osseous route A is the only route for sound vibrations to reach the inner ear. When there is a middle ear conductive defect, routes Band C are materially diminished in magnitude. Redrawn from Ref. 83, with permission. *

Osteodystrophy: abnormal development of the boneProcess of bone resorption of the petrous bone (spongiosis), followed by replacement with thick irregular sclerotic bone (sclerosis), often leading to hearing loss. The most commonly affected location is around the oval window, which can result in conductive hearing loss due to stapes footplate fixation (fenestral otosclerosis). In approximately 10% of the patients, otosclerotic foci will also affect the otic capsule (retrofenestral otosclerosis) resulting in cochlear otosclerosis accompanied by sensorineural hearing loss.*Otosclerosis occurs at certain sites of predilection within the temporal bone with the most common site being the area anterior to the oval window (80-95 percent of cases).3,4 [**** J Other sites of involvement in descending order of frequency are the round window niche (about 30percent), the apical medial wall of the cochlear labyrinth (about 15 percent), the stapes footplate (about 12 percent) and posterior to the oval window (5-10 percent).

Demineralised hypodense fenestral otosclerotic foci are best seen on axial HRCT because of the anteroposterior orientationof the oval window and stapes crura. Otic capsule: skeletal element enclosing the inner earThe cochlea is a snail-like tube that is divided along its length into three compartments: the scala vestibuli (top), the scala media (middle), and the scala tympani (bottom). Reissner's membrane separates the scala vestibuli from the scala media. The basilar membrane separates the scala media from the scala tympani. Perilymph, a fluid similar to extracellular fluid, fills the scala vestibuli and tympani, and endolymph, a fluid similar to intracellular fluid, fills the scala media. The scala media houses the organ of Corti.The otic capsule arises from mesenchyme surrounding the otic vesicle at 4 weeks. At 8 weeks, the cartilaginous framework is begun. At 16 weeks, endochondral bony replacement of this framework begins in 14 identifiable centers. In some people, complete bony replacement does not occur and leaves cartilage in certain locations.One of these regions, the fissula ante fenestram IS usually the last area of endochondral bone formation in the labyrinth.According to temporal bone studies, this region is affected in 80% to 90% of patients with OS.

*Process of bone resorption of the petrous bone (spongiosis), followed by replacement with thick irregular sclerotic bone (sclerosis), often leading to hearing loss. The most commonly affected location is around the oval window, which can result in conductive hearing loss due to stapes footplate fixation (fenestral otosclerosis).Support for this hypothesis comes fromultrastructural and immunohistochemical evidence ofmeasles-like structures and antigenicity in active otosclerotic lesions.

Choclear endosteumInvolvement area dictates the clinical presentation. The CHL is due to fixation of the stapes footplate, usually beginning at the fissula ante fenestram

Two phases of diseaseActive (otospongiosis phase)Osteocytes, histiocytes, osteoblastsActive resorption of boneDilation of vesselsSchwartzes sign

Mature (sclerotic phase)Depositionmechanism for the SNHL is possibly the of new bone (sclerotic and less dense than normal bone)The liberation of toxic metabolites into the inner ear with resultant injury to neuroepithelium, vascular compromise, or direct extension of lesions into the cochlea, causing disruption of electrolytes and changes in basilar membrane mechanics.

demineralised foci of spongy new bone typically occur in the region of the embryonic fissula ante fenestram, which is a cleft of fibrocartilagenous tissue between the inner and middle ear, just anterior to the oval window

The promontory, round window niche and tympanic segment of the facial nerve canal can also be involved

The disease gradually extends to involve the entire footplate of the stapes and may subsequently involve the cochlea. Heaped-up bony plaques formed in the healing phase typically cause narrowing of the oval and round windows

*The incidence of clinical otosclerosis in the general population is about 2%. *Excessive vascularity within the mucosa over an otosclerotic focus near the oval window and promontory is the histologic substrate for the red vascular blush seen at otoscopy' inpatients with active otosclerosis (Schwartze's sign). *audiological examination is the most important diagnostic tool Incidence of Carhart notch was almost identical among the stapes fixation, incudostapedial joint detachment, and malleus or incus fixation groups. Most useful audiometric test for otosclerosisa widening ABG that usually begins in the low frequenciesBone conduction may show a 20 dB loss at 2000 Hz ( Carharts notch)Decrease in bone conduction thresholds5 dB at 500 Hz10 dB at 1000 Hz15 dB at 2000 Hz5 dB at 4000 Hz*Axial (a)andcoronal(b) HRCT images of the right temporal bone in an adult patient with right-sided CHL. A hypodense demineralised plaque(arrow) is noted in the region of the fissula ante fenestram in keeping with fenestral otosclerosisDemineralised hypodense fenestral otosclerotic foci are best seen on axial HRCT because of the anteroposterior orientation of the oval window and stapes crura.HRCT adequately demonstrates the demineralised foci in the otic capsule. The classical imaging appearance of cochlearotosclerosis on HRCT is a distinctive pericochlear hypodense double ring (which is also known as the 4th ring of Valvassori)Imaging plays an important role in the diagnosis and management of otosclerosis. High-resolution CT (HRCT) of the temporal bone using 1-mm (or less) thick sections is the modality of choice for assessment of the labyrinthine windows and cochlear capsules.fissula ante fenestram, which is a cleft of fibrocartilagenous tissue between the inner and middle ear, just anterior to the oval window (Fig. 1). Bilateral involvement is common (Fig. 2). The promontory, round window niche and tympanic segment of the facial nerve canal can alsobe involved *Paget disease (osteitis deformans) is a disease with diffuse bony involvement that is histologically similar to OS. In contrast to OS, Paget disease begins in the periosteal layer and involves the endochondral bone last. Temporal bone involvement can produce SNHL,but stapes involvement or fixation rarely occurs

Osteogenesis imperfecta (van der Hoeve-de-Kleyn syndrome) is an autosomal dominantdefect of osteoblast activity resulting in multiple fractures. Stapes fixation and uniqueblue sclera are also found in 40% to 60% of affected patients.*The aim of stapes surgery is to restore the vibration of uids within the cochlear canal. The basic surgical steps include disarticulatingthe incudostapedial joint, removal of stapes suprastructres and opening up the stapes footplate Disarticulating the incudostapedial joint Removal of stapes suprastructres Opening up the stapes footplateStapectomyVs Stapedotomy

*Outcome of Management of Otosclerosis by Stapedotomy Compared to Stapedectomy in a Jordanian Populationto a small hole in the stapes footplate, the stapedotomy. The aim of stapes surgery is to restorethe vibration of uids within the cochlear canal. *alternative treatment to sodium uoride in cases where the patient is intolerant to sodium uoride therapy. (retrofenestral otosclerosis), resulting in cochlear otosclerosis with sensorineural hearing loss.In advanced otosclerosis, characterized by mixed hearing loss, hearing aids alone often do not result in optimal hearing rehabilitation, and surgery becomes an option. Nowadays, two surgical techniques are available: stapedotomy or CI. The decision for the appropriate treatment for each patient can be challenging given that both interventions differ in costs, risks, and success rate*

*(a) The three normal routes of bone conduction of sound vibrations to the inner ear: route A: via the skull bone; route B: via the ossicular chain; and route C: via the external auditory canal. In a normal ear, when the skull is vibrated by bone-conduction, it not only vibrates the cochlea via route A, but it also vibrates the tympanic membrane and ossicular chain (route B) and the air in the external auditory canal (route C). (b) In the presence of a conductive defect, the osseous route A is the only route for sound vibrations to reach the inner ear. When there is a middle ear conductive defect, routes Band C are materially diminished in magnitude. Redrawn from Ref. 83, with permission. *