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title: "Otosclerosis"
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pageDescription: "Otosclerosis"
pageKeywords: "Head and Neck, Diagnosis, Temporal Bone, Inner Ear, Infectious and Inflammatory Lesions, Otosclerosis"
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---
# KEY FACTS
- ## Terminology
- Synonym:**Otospongiosis**
- Types: Fenestral otosclerosis (FOto), cochlear otosclerosis (COto)
- Pathologic appearance of lytic, spongy bone foci in bony labyrinth of unknown cause
- Starts perifenestral (FOto), progresses to surround cochlea (FOto + COto)
- **Fissula ante fenestram**: Cleft of fibrocartilaginous tissue between inner & middle ears just anterior to oval window
- ## Imaging
- Best diagnostic clue: Temporal bone CT shows **lytic (otospongiotic) foci** involving bony labyrinth
- FOto: Starts at anterior margin of oval window (fissula ante fenestram)
- COto: Affects pericochlear bony labyrinth
- ## Top Differential Diagnoses
- Chronic otitis media with tympanosclerosis
- Temporal bone Paget disease
- Temporal bone fibrous dysplasia
- Temporal bone osteoradionecrosis
- Temporal bone osteogenesis imperfecta
- ## Pathology
- Enchondral layer of bony labyrinth displays spongy, vascular, decalcified, irregular bone formation
- ## Clinical Issues
- Bilateral progressive conductive (FOto) or mixed (FOto + COto) hearing loss in young adult
- ## Diagnostic Checklist
- Typical otospongiotic plaques of otosclerosis are **lytic** & affect **bony** labyrinth
# TERMINOLOGY
- ## Abbreviations
- Fenestral otosclerosis (FOto)
- Cochlear otosclerosis (COto)
- ## Synonyms
- Otospongiosis, fenestral otospongiosis, cochlear otospongiosis
- ## Definitions
- Pathologic appearance of **lytic, spongy bone foci** in bony labyrinth of unknown cause
- Starts perifenestral (FOto), progresses to surround cochlea (FOto + COto)
- **Fissula ante fenestram**: Cleft of fibrocartilaginous tissue between inner & middle ears just anterior to oval window
- Cochlear cleft is fatty marrow due to incomplete ossification that parallels cochlea rather than localizing to fissula antefenestram
- May be present in children & adults, should be differentiated from otosclerosis
# IMAGING
- ## General Features
- ### Best diagnostic clue
- Temporal bone CT: Lucent (otospongiotic) foci involving bony labyrinth
- Usually in context of normally aerated middle ear
- ### Location
- FOto: Starts at anterior margin of oval window (fissula ante fenestram)
- May involve any bony area along medial wall middle ear
- COto: Affects pericochlear bony labyrinth
- May involve any portion of bony labyrinth
- ### Size
- Millimeter punctate or linear foci; may become confluent
- ### Morphology
- FOto: Ovoid plaques most common
- COto: Ovoid to linear (confluent foci)
- ## CT Findings
- ### CECT
- No role for CECT in diagnosis of otosclerosis
- ### Bone CT
- **Early** temporal bone CT findings
- Begins as radiolucent focus at oval window anterior margin (FOto)
- Spreads to involve all margins of oval & round windows
- Abnormal thickening of otic capsule bone near oval window (> 2.3 mm) with bulging contour
- May spread to inner ear otic capsule (COto)
- Double ring sign or "halo" of radiolucency surrounds cochlea in severe COto
- Progressive disease may involve any portion of bony labyrinth, including internal auditory canal lateral walls
- **Late**, chronic (healing phase) temporal bone CT findings
- FOto: "Heaped up" new bone along oval & round window margins
- Healed plaque may occlude oval ± round window
- COto: Mixed radiolucent-radiodense foci present in bony labyrinth
- ## MR Findings
- ### T1WI
- Faint intermediate T1 signal of plaques
- ### T2WI
- Thin-section high-resolution T2 may not visualize otosclerosis, even when extensive
- Large plaques can show increased signal
- ### T1WI C+
- Enhancing punctate foci in medial wall of middle ear (FOto) ± pericochlear bony labyrinth (COto)
- Most obvious when FOto & COto combined
- Enhancing lesions may be seen anywhere in bony labyrinth in severe cases
- ## Imaging Recommendations
- ### Best imaging tool
- Temporal bone CT
- ### Protocol advice
- T1 C+ MR shows enhancing foci in active phase
- High-resolution T2 MR may miss otosclerosis
# DIFFERENTIAL DIAGNOSIS
- [Chronic Otitis Media With Tympanosclerosis](/document/chronic-otomastoiditis-with-tympan-/e8b91656-ad18-405d-bf67-b0b902f04265)
- Clinical: Obvious chronic middle ear-mastoid inflammatory disease
- Imaging: Postinflammatory new bone deposition is not limited to oval & round windows as with most FOto
- Seen in tympanic membrane (TM), middle ear, ossicles, & mastoids
- New bone deposition is irregular, not smooth, in oval window area
- [Temporal Bone Paget Disease](/document/temporal-bone-paget-disease/d0c7cbca-1489-488e-ae7d-1b9aee88467d)
- Clinical: Bone disease of old age (> 50 years)
- Imaging: Diffuse skull base involvement is rule
- Diffuse involvement of bony labyrinth, not confined to lateral wall
- Usually seen as diffuse temporal bone cotton wool appearance
- [Temporal Bone Fibrous Dysplasia](/document/temporal-bone-fibrous-dysplasia/e5b44f77-f666-4f32-8eb0-6ed2da7d9898)
- Clinical: Bone disease of young (age < 30 years)
- Imaging: Involves all parts of temporal bone
- Relative sparing of inner ear is rule
- Usually sclerotic, ground-glass in appearance
- [Temporal Bone Osteoradionecrosis](/document/temporal-bone-osteoradionecrosis/95475621-6d44-4bbd-a779-476154a5a2cc)
- Clinical: History of skull base or nasopharyngeal radiation therapy
- Imaging: CT shows diffuse, permeative lucencies of otic capsule
- [Temporal Bone Osteogenesis Imperfecta](/document/temporal-bone-osteogenesis-imperfe-/d819723f-660b-4067-9b47-f8aeec3ba0b8)
- Clinical: Blue sclera; patients with mild form develop deafness by 40 years of age
- Imaging: Looks like severe COto with more generalized demineralization of bony labyrinth
# PATHOLOGY
- ## General Features
- ### Etiology
- Unknown
- ### Genetics
- Sporadic or autosomal dominant gene transmission
- Bony otic capsule development: 3 layers
- Thin inner endosteal layer
- **Middle layer** of combined endochondral & intrachondral bone (**otosclerosis occurs here**)
- Outer periosteal layer
- Normal otosclerosis progression
- Begins at fissula ante fenestram (FOto)
- Disease spreads from fissula ante fenestram posteriorly along oval window margins to round window
- Continued active disease spreads to otic capsule (both FOto & COto present)
- Active **FOto fixes stapes footplate** in oval window niche
- This "donut" FOto ankyloses stapes footplate
- Pathophysiology of **conductive hearing loss**
- COto leads to sensorineural hearing loss
- Best hypothesis: Spiral ligament becomes compromised
- Secondary hypothesis: Toxic proteases affect cochlear nerve cells
- ## Staging, Grading, & Classification
- Symons/Fanning CT grading system of otosclerosis (2005) has high intra- & interobserver agreement
- Grade 1: Solely fenestral
- Grade 2: Patchy localized cochlear disease (± FOto)
- To basal cochlear turn (grade 2A)
- To middle/apical turns (grade 2B)
- Grade 3: Diffuse confluent cochlear involvement (± FOto)
- ## Gross Pathologic & Surgical Features
- Otoscopic vascular hue behind TM = **Schwartze sign**
- Active otosclerotic areas along margins of oval & round windows or beneath cochlear promontory
- Bony ankylosis of stapes footplate is reflected as stapes immobilization when pulled on by surgeon
- ## Microscopic Features
- Enchondral layer of bony labyrinth displays spongy, vascular, decalcified, irregular bone formation
- 3 pathologic phases of otosclerosis
- Acute phase: Deposition of islets of osteoid tissue
- Subacute phase: Spongiotic remodeling with osteoclasts causing focal bone resorption
- Chronic-sclerotic phase: Osteoblasts create new bone with irregular features resembling mosaic
- **Otospongiosis** better describes active disease process
- Chronic, healing phase appears truly **sclerotic**
- May be histologically indistinguishable from Paget disease
# CLINICAL ISSUES
- ## Presentation
- ### Most common signs/symptoms
- Bilateral progressive conductive (FOto) or mixed (FOto + COto) hearing loss
- ### Other signs/symptoms
- Tinnitus (ringing in ears)
- Otoscopy: Vascular hue behind TM = Schwartze sign
- ### Clinical profile
- Young adult presenting with unexplained **bilateral progressive** conductive or **mixed** **hearing loss**
- ## Demographics
- ### Age
- Appears in 2nd to 3rd decades of life
- ### Sex
- M:F = 1:2
- ### Epidemiology
- Occurs in 1% of population
- Most common type is **FOto alone (85%)**; COto in 15%
- **FOto** causes ~ **90%****conductive hearing loss in a****dults**
- ## Natural History & Prognosis
- FOto: Conductive hearing loss is progressive
- COto: Untreated, will evolve to profound hearing loss
- ## Treatment
- FOto: **Stapedectomy** with stapes prosthesis
- Results negatively impacted by concurrent COto
- If round window is obliterated, stapes prosthesis will fail
- If narrow oval window niche height (< 1.4 mm on coronal CT reformat), stapes surgery more challenging
- Cochlear implantation
- Used when severe FOto & COto present bilaterally, resulting in profound mixed hearing loss
- If round window obliteration present bilaterally, cochlear implantation may be more challenging
- **Fluoride** treatment if COto present
- Early treatment can arrest progression
# DIAGNOSTIC CHECKLIST
- ## Consider
- Always check oval window anterior margin for FOto in CT evaluation of conductive hearing loss
- Common blind spot; CT findings can be subtle
- If COto present, FOto also is present, so look for it
- MDCT sometimes shows normal fissula ante fenestram on pediatric temporal bone exams as focal radiolucency
- ## Image Interpretation Pearls
- Typical otospongiotic plaques of otosclerosis are lucent & affect bony labyrinth
- If bony fills in membranous labyrinth, diagnosis is **labyrinthine ossificans**, not COto
- ## Reporting Tips
- Assess oval & round window patency; narrowing or obliteration have important surgical implications
383a23f2-eea4-4589-bce6-050a80b7aac1
## References
# Selected References
1. [Fujima N et al: Utility of deep learning for the diagnosis of otosclerosis on temporal bone CT. Eur Radiol. 31(7):5206-11, 2021](http://www.ncbi.nlm.nih.gov/pubmed/?term=33409781%5Bpmid%5D)
1. [Akazawa Y et al: Measurement of stapes footplate thickness in otosclerosis by ultra-high-resolution computed tomography. Acta Otolaryngol. 140(11):899-903, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32700991%5Bpmid%5D)
1. [Kösling S et al: Imaging of otosclerosis. Rofo. 192(8):745-53, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32215901%5Bpmid%5D)
1. [Maxwell AK et al: Sensitivity of high-resolution computed tomography in otosclerosis patients undergoing primary stapedotomy. Ann Otol Rhinol Laryngol. 129(9):918-23, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32432485%5Bpmid%5D)
1. [Maxwell AK et al: Failure to close the gap: concomitant superior canal dehiscence in otosclerosis patients. Laryngoscope. 130(4):1023-7, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=31271445%5Bpmid%5D)
1. [McClellan J et al: Stapes surgery outcomes in patients with concurrent otosclerosis and superior semicircular canal dehiscence. Otol Neurotol. 41(7):912-5, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32472923%5Bpmid%5D)
1. [Pucetaite M et al: The cochlear cleft: CT correlation with histopathology. Otol Neurotol. 41(6):745-9, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32221113%5Bpmid%5D)
1. [Purohit B et al: Role of MRI as first-line modality in the detection of previously undiagnosed otosclerosis: a single tertiary institute experience. Insights Imaging. 11(1):71, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32430577%5Bpmid%5D)
1. [Andreu-Arasa VC et al: Otosclerosis and dysplasias of the temporal bone. Neuroimaging Clin N Am. 29(1):29-47, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=30466643%5Bpmid%5D)
1. [Bae YJ et al: "Third window" and "single window" effects impede surgical success: analysis of retrofenestral otosclerosis involving the internal auditory canal or round window. J Clin Med. 8(8), 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=31394873%5Bpmid%5D)
1. [Brown LA et al: Diagnostic protocol for detecting otosclerosis on high-resolution temporal bone CT. Ann Otol Rhinol Laryngol. 128(11):1054-60, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=31288548%5Bpmid%5D)
1. [Nguyen T et al: Conductive hearing loss with a "dry middle ear cleft"-a comprehensive pictorial review with CT. Eur J Radiol. 110:74-80, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=30599877%5Bpmid%5D)
1. [Shim YJ et al: Involvement of the internal auditory canal in subjects with cochlear otosclerosis: a less acknowledged third window that affects surgical outcome. Otol Neurotol. 40(3):e186-90, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=30741893%5Bpmid%5D)
1. [Yagi C et al: Otosclerosis: anatomical distribution of otosclerotic loci analyzed by high-resolution computed tomography. Eur Arch Otorhinolaryngol. 276(5):1335-40, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=30887165%5Bpmid%5D)
1. [Berrettini S et al: 3D fluid attenuated inversion recovery (FLAIR) magnetic resonance imaging at different stages of otosclerosis. Eur Arch Otorhinolaryngol. 275(11):2643-52, 2018](http://www.ncbi.nlm.nih.gov/pubmed/?term=30191304%5Bpmid%5D)
1. [Puac P et al: Cavitary plaques in otospongiosis: CT findings and clinical implications. AJNR Am J Neuroradiol. 39(6):1135-9, 2018](http://www.ncbi.nlm.nih.gov/pubmed/?term=29622557%5Bpmid%5D)
1. [Quesnel AM et al: Otosclerosis: temporal bone pathology. Otolaryngol Clin North Am. 51(2):291-303, 2018](http://www.ncbi.nlm.nih.gov/pubmed/?term=29397947%5Bpmid%5D)
1. [Sanghan N et al: Retrospective review of otic capsule contour and thickness in patients with otosclerosis and individuals with normal hearing on CT. AJNR Am J Neuroradiol. 39(12):2350-5, 2018](http://www.ncbi.nlm.nih.gov/pubmed/?term=30467217%5Bpmid%5D)
1. [Wolfovitz A et al: Impact of imaging in management of otosclerosis. Otolaryngol Clin North Am. 51(2):343-55, 2018](http://www.ncbi.nlm.nih.gov/pubmed/?term=29502724%5Bpmid%5D)
1. [Dudau C et al: Diagnostic efficacy and therapeutic impact of computed tomography in the evaluation of clinically suspected otosclerosis. Eur Radiol. 27(3):1195-201, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=27364152%5Bpmid%5D)
1. [Yamashita K et al: Additive value of "otosclerosis-weighted" images for the CT diagnosis of fenestral otosclerosis. Acta Radiol. 58(10):1215-21, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=28090791%5Bpmid%5D)
1. [Anand V et al: Obliquity of the stapes in otosclerosis: a new radiological sign. Int Arch Otorhinolaryngol. 20(2):94-8, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=27096011%5Bpmid%5D)
1. [Atan D et al: Relation of otosclerosis and osteoporosis: a bone mineral density study. Auris Nasus Larynx. 43(4):400-3, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=26656733%5Bpmid%5D)
1. [Mukaida T et al: Magnetic resonance imaging evaluation of endolymphatic hydrops in cases with otosclerosis. Otol Neurotol. 36(7):1146-50, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=25522197%5Bpmid%5D)
1. [Whetstone J et al: Surgical and clinical confirmation of temporal bone CT findings in patients with otosclerosis with failed stapes surgery. AJNR Am J Neuroradiol. 35(6):1195-201, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24481328%5Bpmid%5D)
1. [Ukkola-Pons E et al: Oval window niche height: quantitative evaluation with CT before stapes surgery for otosclerosis. AJNR Am J Neuroradiol. 34(5):1082-5, 2013](http://www.ncbi.nlm.nih.gov/pubmed/?term=23179652%5Bpmid%5D)
1. [Lee TC et al: CT grading of otosclerosis. AJNR Am J Neuroradiol. 30(7):1435-9, 2009](http://www.ncbi.nlm.nih.gov/pubmed/?term=19321627%5Bpmid%5D)
1. [Moser T et al: The hypodense focus in the petrous apex: a potential pitfall on multidetector CT imaging of the temporal bone. AJNR Am J Neuroradiol. 29(1):35-9, 2008](http://www.ncbi.nlm.nih.gov/pubmed/?term=17925374%5Bpmid%5D)
1. [Marshall AH et al: Cochlear implantation in cochlear otosclerosis. Laryngoscope. 115(10):1728-33, 2005](http://www.ncbi.nlm.nih.gov/pubmed/?term=16222185%5Bpmid%5D)
1. [Chadwell JB et al: The cochlear cleft. AJNR Am J Neuroradiol. 25(1):21-4, 2004](http://www.ncbi.nlm.nih.gov/pubmed/?term=14729522%5Bpmid%5D)
1. [Pekkola J et al: Localized pericochlear hypoattenuating foci at temporal-bone thin-section CT in pediatric patients: nonpathologic differential diagnostic entity? Radiology. 230(1):88-92, 2004](http://www.ncbi.nlm.nih.gov/pubmed/?term=14617763%5Bpmid%5D)
1. [Rondini-Gilli E et al: [Otosclerosis surgical techniques and results in 150 patients] Ann Otolaryngol Chir Cervicofac. 119(4):227-33, 2002](http://www.ncbi.nlm.nih.gov/pubmed/?term=12410119%5Bpmid%5D)
1. [Stimmer H et al: Magnetic resonance imaging and high-resolution computed tomography in the otospongiotic phase of otosclerosis. ORL J Otorhinolaryngol Relat Spec. 64(6):451-3, 2002](http://www.ncbi.nlm.nih.gov/pubmed/?term=12499773%5Bpmid%5D)
1. [Chole RA et al: Pathophysiology of otosclerosis. Otol Neurotol. 22(2):249-57, 2001](http://www.ncbi.nlm.nih.gov/pubmed/?term=11300278%5Bpmid%5D)
1. [Ruckenstein MJ et al: Management of far advanced otosclerosis in the era of cochlear implantation. Otol Neurotol. 22(4):471-4, 2001](http://www.ncbi.nlm.nih.gov/pubmed/?term=11449102%5Bpmid%5D)
1. [Shin YJ et al: Correlations between computed tomography findings and family history in otosclerotic patients. Otol Neurotol. 22(4):461-4, 2001](http://www.ncbi.nlm.nih.gov/pubmed/?term=11449100%5Bpmid%5D)
1. [Shin YJ et al: Sensorineural hearing loss and otosclerosis: a clinical and radiologic survey of 437 cases. Acta Otolaryngol. 121(2):200-4, 2001](http://www.ncbi.nlm.nih.gov/pubmed/?term=11349779%5Bpmid%5D)
1. [Veillon F et al: Imaging of the windows of the temporal bone. Semin Ultrasound CT MR. 22(3):271-80, 2001](http://www.ncbi.nlm.nih.gov/pubmed/?term=11451100%5Bpmid%5D)
1. [Niyazov D et al: Fenestration surgery for otosclerosis: CT findings of an old surgical procedure. AJNR Am J Neuroradiol. 21(9):1670-2, 2000](http://www.ncbi.nlm.nih.gov/pubmed/?term=11039348%5Bpmid%5D)
1. [Ziyeh S et al: MRI-visible pericochlear lesions in osteogenesis imperfecta type I. Eur Radiol. 10(10):1675-7, 2000](http://www.ncbi.nlm.nih.gov/pubmed/?term=11044947%5Bpmid%5D)
1. [Ziyeh S et al: MRI of active otosclerosis. Neuroradiology. 39(6):453-7, 1997](http://www.ncbi.nlm.nih.gov/pubmed/?term=9225330%5Bpmid%5D)
1. [Miura M et al: Computed tomographic image analysis of ears with otosclerosis. ORL J Otorhinolaryngol Relat Spec. 58(4):200-3, 1996](http://www.ncbi.nlm.nih.gov/pubmed/?term=8883105%5Bpmid%5D)
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1. [Mafee MF et al: Use of CT in stapedial otosclerosis. Radiology. 156(3):709-14, 1985](http://www.ncbi.nlm.nih.gov/pubmed/?term=4023230%5Bpmid%5D)
1. [Swartz JD et al: Fenestral and cochlear otosclerosis: computed tomographic evaluation. Am J Otol. 6(6):476-81, 1985](http://www.ncbi.nlm.nih.gov/pubmed/?term=4073255%5Bpmid%5D)
## Images
### Selected Images
![Coronal graphic illustrates findings of fenestral otosclerosis with a &quot;donut&quot; otospongiotic plaque <img src='img/arrows/WS.png'/> surrounding the stapes footplate in the oval window. The crisp margins of the oval window are obscured by plaque.](images/app.statdx.com_image_thumbnail_edf1b230-ca36-4909-9a2a-20b76cd87b30_annotated_true_size_900_quality_90_c1c8225a7c580f8738035e33ba9f30b58cd3c704.jpg)
*Coronal graphic illustrates findings of fenestral otosclerosis with a &quot;donut&quot; otospongiotic plaque <img src='img/arrows/WS.png'/> surrounding the stapes footplate in the oval window. The crisp margins of the oval window are obscured by plaque.*
![Coronal graphic illustrates findings of fenestral otosclerosis with a &quot;donut&quot; otospongiotic plaque <img src='img/arrows/WS.png'/> surrounding the stapes footplate in the oval window. The crisp margins of the oval window are obscured by plaque.](images/app.statdx.com_image_thumbnail_edf1b230-ca36-4909-9a2a-20b76cd87b30_size_174_quality_85_3544281237a14ad55265220ad49af5019da70cec.jpg)
*Coronal graphic illustrates findings of fenestral otosclerosis with a &quot;donut&quot; otospongiotic plaque <img src='img/arrows/WS.png'/> surrounding the stapes footplate in the oval window. The crisp margins of the oval window are obscured by plaque.*
![Coronal right temporal bone CT shows a lytic focus anterior to the oval window <img src='img/arrows/WC.png'/>, the typical appearance and location of an otospongiotic plaque of fenestral otosclerosis.](images/app.statdx.com_image_thumbnail_ebbe8d39-b2ce-4561-b322-aa06dbac9bdb_annotated_true_size_900_quality_90_2dd54fdaee91c1cc85708d804c7967bcf499649c.jpg)
*Coronal right temporal bone CT shows a lytic focus anterior to the oval window <img src='img/arrows/WC.png'/>, the typical appearance and location of an otospongiotic plaque of fenestral otosclerosis.*
![Axial graphic demonstrates a classic example of cochlear otosclerosis. Note otospongiotic plaques in a &quot;halo&quot; around the cochlea <img src='img/arrows/BS.png'/> with concurrent fenestral otosclerosis <img src='img/arrows/BO.png'/>.](images/app.statdx.com_image_thumbnail_4b2dd1e6-40ef-4071-8547-ad0ced2a33ed_annotated_true_size_900_quality_90_8217ff25c5054d3a65590e5f2e60edd6a3627047.jpg)
*Axial graphic demonstrates a classic example of cochlear otosclerosis. Note otospongiotic plaques in a &quot;halo&quot; around the cochlea <img src='img/arrows/BS.png'/> with concurrent fenestral otosclerosis <img src='img/arrows/BO.png'/>.*
![Axial left temporal bone CT shows cochlear otosclerosis as osteolytic foci surrounding the cochlea <img src='img/arrows/BS.png'/>. Concurrent fenestral otosclerosis is noted as bony lucency along cochlear promontory extending from the fissula ante fenestram <img src='img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_1f23931f-1264-4ee9-9a09-aeeca44df50f_annotated_true_size_900_quality_90_b611357d0335923c661eac1e7e64bea2aaa0fa7e.jpg)
*Axial left temporal bone CT shows cochlear otosclerosis as osteolytic foci surrounding the cochlea <img src='img/arrows/BS.png'/>. Concurrent fenestral otosclerosis is noted as bony lucency along cochlear promontory extending from the fissula ante fenestram <img src='img/arrows/WO.png'/>.*
![Axial bone CT shows a thick, lucent otosclerotic plaque anterior to the oval window <img src='img/arrows/WS.png'/> in the expected location of the fissula ante fenestram. An abnormal bulging convex contour is also noted due to the thickened bone. Stapes prosthesis is noted in the oval window <img src='img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_345b431a-5485-4d04-8d15-35a5084443e6_annotated_true_size_900_quality_90_f93b16581f39eb64b4e0ce65a626ed4488475b53.jpg)
*Axial bone CT shows a thick, lucent otosclerotic plaque anterior to the oval window <img src='img/arrows/WS.png'/> in the expected location of the fissula ante fenestram. An abnormal bulging convex contour is also noted due to the thickened bone. Stapes prosthesis is noted in the oval window <img src='img/arrows/WC.png'/>.*
![Coronal right temporal bone CT in a patient with mixed hearing loss shows a &quot;halo&quot; of radiolucency surrounding the cochlea <img src='img/arrows/BS.png'/>, representing cochlear otosclerosis. Also note the associated fenestral otosclerosis <img src='img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_5b695628-d6da-434c-8068-f8c29006e516_annotated_true_size_900_quality_90_9d04d2017b15bb7775c5460da7af92a0c333b564.jpg)
*Coronal right temporal bone CT in a patient with mixed hearing loss shows a &quot;halo&quot; of radiolucency surrounding the cochlea <img src='img/arrows/BS.png'/>, representing cochlear otosclerosis. Also note the associated fenestral otosclerosis <img src='img/arrows/WO.png'/>.*
![Axial bone CT shows a small lucent plaque of fenestral otosclerosis <img src='img/arrows/WS.png'/> thickening the otic capsule bone immediately anterior to the oval window. Note the stapes visualized within the oval window <img src='img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_0deddff0-28f6-4bb1-a157-339122e7497f_annotated_true_size_900_quality_90_286c485dc3367f02e0b5fa32afbf6815dffd354c.jpg)
*Axial bone CT shows a small lucent plaque of fenestral otosclerosis <img src='img/arrows/WS.png'/> thickening the otic capsule bone immediately anterior to the oval window. Note the stapes visualized within the oval window <img src='img/arrows/WC.png'/>.*
![Axial left temporal bone CT demonstrates mixed lucent and sclerotic otospongiotic plaque obstructing the round window <img src='img/arrows/BS.png'/>. This predisposes to stapes prosthesis failure and makes cochlear implantation more challenging.](images/app.statdx.com_image_thumbnail_3fd79262-9e87-4e80-bcf2-3e4472d01276_annotated_true_size_900_quality_90_2036a6d59cb24997b65bc3d21ffdd2705b8624d3.jpg)
*Axial left temporal bone CT demonstrates mixed lucent and sclerotic otospongiotic plaque obstructing the round window <img src='img/arrows/BS.png'/>. This predisposes to stapes prosthesis failure and makes cochlear implantation more challenging.*
![Axial left temporal bone CT shows typical lytic plaques of combined fenestral <img src='img/arrows/WS.png'/> and cochlear otosclerosis <img src='img/arrows/WO.png'/>. The patient has undergone stapedectomy with insertion of a stapes prosthesis. Note the metallic density stapes prosthesis <img src='img/arrows/WC.png'/> at the oval window.](images/app.statdx.com_image_thumbnail_2aa90aa0-7e1b-478e-a95c-75e4be032029_annotated_true_size_900_quality_90_7c98fe22d21fd2c02bd3f6d42d5cd27bbb0471a3.jpg)
*Axial left temporal bone CT shows typical lytic plaques of combined fenestral <img src='img/arrows/WS.png'/> and cochlear otosclerosis <img src='img/arrows/WO.png'/>. The patient has undergone stapedectomy with insertion of a stapes prosthesis. Note the metallic density stapes prosthesis <img src='img/arrows/WC.png'/> at the oval window.*
![Axial T1WI C+ FS MR in the same patient reveals enhancement anterior to the oval window (fissula ante fenestram) <img src='img/arrows/WO.png'/> and surrounding the cochlea <img src='img/arrows/WS.png'/>, representing active fenestral and cochlear otosclerosis, respectively.](d233ee57-32fd-42a9-8c1a-1dd7895eaf65)
*Axial T1WI C+ FS MR in the same patient reveals enhancement anterior to the oval window (fissula ante fenestram) <img src='img/arrows/WO.png'/> and surrounding the cochlea <img src='img/arrows/WS.png'/>, representing active fenestral and cochlear otosclerosis, respectively.*
### Additional Images
![Axial bone CT shows an extensive pericochlear lucent &quot;halo&quot; <img src='img/arrows/WS.png'/> of cochlear otosclerosis.](69398b59-d88b-4d2a-b993-9dc1e3d83288)
*Axial bone CT shows an extensive pericochlear lucent &quot;halo&quot; <img src='img/arrows/WS.png'/> of cochlear otosclerosis.*
![Axial thin T2 MR in the same patient shows multifocal otic capsule hyperintensities <img src='img/arrows/WS.png'/> that corresponded to plaques on CT.](b77b2e89-f579-4b0d-b9a8-420125c30337)
*Axial thin T2 MR in the same patient shows multifocal otic capsule hyperintensities <img src='img/arrows/WS.png'/> that corresponded to plaques on CT.*
![Coronal right temporal bone CT shows fenestral otosclerosis involving all the margins of the oval window <img src='img/arrows/BS.png'/>. The net effect is to create a blurring and disappearance of the oval window niche.](ef834334-0bb6-4abc-a6c9-87fc765210b2)
*Coronal right temporal bone CT shows fenestral otosclerosis involving all the margins of the oval window <img src='img/arrows/BS.png'/>. The net effect is to create a blurring and disappearance of the oval window niche.*
![Axial temporal bone CT demonstrates a classic otospongiotic plaque <img src='img/arrows/WS.png'/> as extra lucent foci on the anterior margin of the oval window (fissula ante fenestram location). The otic capsule is otherwise spared.](edb8cf6c-80bd-4e2d-b216-e9ae77986446)
*Axial temporal bone CT demonstrates a classic otospongiotic plaque <img src='img/arrows/WS.png'/> as extra lucent foci on the anterior margin of the oval window (fissula ante fenestram location). The otic capsule is otherwise spared.*
![Coronal bone CT in a patient who has undergone stapedectomy for fenestral otosclerosis shows metallic stapes prosthesis. Also note otospongiotic plaque just anterior to the oval window <img src='img/arrows/WS.png'/>.](dbfe0708-d68d-49a6-a792-08a826b3afec)
*Coronal bone CT in a patient who has undergone stapedectomy for fenestral otosclerosis shows metallic stapes prosthesis. Also note otospongiotic plaque just anterior to the oval window <img src='img/arrows/WS.png'/>.*
![Axial bone CT demonstrates a severe case of combined fenestral <img src='img/arrows/WS.png'/> and cochlear <img src='img/arrows/BO.png'/> otosclerosis. The Schwartze sign was clearly seen on otoscopic examination.](9e6c9a4d-03c3-40c9-b3fe-009302402be2)
*Axial bone CT demonstrates a severe case of combined fenestral <img src='img/arrows/WS.png'/> and cochlear <img src='img/arrows/BO.png'/> otosclerosis. The Schwartze sign was clearly seen on otoscopic examination.*
![Axial T1WI C+ FS MR of the right temporal bone in a severe case of combined fenestral <img src='img/arrows/WC.png'/> and cochlear <img src='img/arrows/BS.png'/> otosclerosis with enhancement signifying active disease is shown. Less avid enhancement in the vestibule <img src='img/arrows/WS.png'/> and cochlea <img src='img/arrows/WO.png'/> represents endolymphatic hydrops, which is sometimes associated with otosclerosis.](a8ed8660-79fd-4178-a3ad-9c64ff31b838)
*Axial T1WI C+ FS MR of the right temporal bone in a severe case of combined fenestral <img src='img/arrows/WC.png'/> and cochlear <img src='img/arrows/BS.png'/> otosclerosis with enhancement signifying active disease is shown. Less avid enhancement in the vestibule <img src='img/arrows/WS.png'/> and cochlea <img src='img/arrows/WO.png'/> represents endolymphatic hydrops, which is sometimes associated with otosclerosis.*
![Coronal left temporal bone CT in the same patient again demonstrates the lytic otospongiotic plaque of fenestral otosclerosis <img src='img/arrows/WC.png'/> in the expected location anterior to the oval window.](921cb3c2-e839-4f75-8729-4709f9f3498e)
*Coronal left temporal bone CT in the same patient again demonstrates the lytic otospongiotic plaque of fenestral otosclerosis <img src='img/arrows/WC.png'/> in the expected location anterior to the oval window.*