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Otosclerosis ddc7b884-3c17-4834-9e96-d985c6b618a9
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07a2c087-6202-49e7-870b-7aa162d18f06 Bronwyn E. Hamilton, MD
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4b6589b0-9b8d-4467-8a90-01a0a59742fc Troy A. Hutchins, MD
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Head and Neck ece2b7f0-702e-40e6-908c-dd1ffa3be6e3 ca5797ec-4f56-46bd-b9d3-a583c34fa6fe 18 08/10/21 Otosclerosis Head and Neck, Diagnosis, Temporal Bone, Inner Ear, Infectious and Inflammatory Lesions, Otosclerosis Otosclerosis | STATdx Otosclerosis DX true
Head and Neck
Diagnosis
Temporal Bone
Inner Ear
Infectious and Inflammatory Lesions
Otosclerosis

title: "Otosclerosis" docid: "ddc7b884-3c17-4834-9e96-d985c6b618a9" authors:

  • key: "07a2c087-6202-49e7-870b-7aa162d18f06" value: "Bronwyn E. Hamilton, MD"
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  • "Head and Neck"
  • "Diagnosis"
  • "Temporal Bone"
  • "Inner Ear"
  • "Infectious and Inflammatory Lesions"
  • "Otosclerosis"

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
    • 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
    • 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
    • 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
    • Clinical: History of skull base or nasopharyngeal radiation therapy
    • Imaging: CT shows diffuse, permeative lucencies of otic capsule
  • Temporal Bone Osteogenesis Imperfecta
    • 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

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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
  2. Akazawa Y et al: Measurement of stapes footplate thickness in otosclerosis by ultra-high-resolution computed tomography. Acta Otolaryngol. 140(11):899-903, 2020
  3. Kösling S et al: Imaging of otosclerosis. Rofo. 192(8):745-53, 2020
  4. 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
  5. Maxwell AK et al: Failure to close the gap: concomitant superior canal dehiscence in otosclerosis patients. Laryngoscope. 130(4):1023-7, 2020
  6. McClellan J et al: Stapes surgery outcomes in patients with concurrent otosclerosis and superior semicircular canal dehiscence. Otol Neurotol. 41(7):912-5, 2020
  7. Pucetaite M et al: The cochlear cleft: CT correlation with histopathology. Otol Neurotol. 41(6):745-9, 2020
  8. 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
  9. Andreu-Arasa VC et al: Otosclerosis and dysplasias of the temporal bone. Neuroimaging Clin N Am. 29(1):29-47, 2019
  10. 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
  11. Brown LA et al: Diagnostic protocol for detecting otosclerosis on high-resolution temporal bone CT. Ann Otol Rhinol Laryngol. 128(11):1054-60, 2019
  12. 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
  13. 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
  14. Yagi C et al: Otosclerosis: anatomical distribution of otosclerotic loci analyzed by high-resolution computed tomography. Eur Arch Otorhinolaryngol. 276(5):1335-40, 2019
  15. 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
  16. Puac P et al: Cavitary plaques in otospongiosis: CT findings and clinical implications. AJNR Am J Neuroradiol. 39(6):1135-9, 2018
  17. Quesnel AM et al: Otosclerosis: temporal bone pathology. Otolaryngol Clin North Am. 51(2):291-303, 2018
  18. 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
  19. Wolfovitz A et al: Impact of imaging in management of otosclerosis. Otolaryngol Clin North Am. 51(2):343-55, 2018
  20. 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
  21. Yamashita K et al: Additive value of "otosclerosis-weighted" images for the CT diagnosis of fenestral otosclerosis. Acta Radiol. 58(10):1215-21, 2017
  22. Anand V et al: Obliquity of the stapes in otosclerosis: a new radiological sign. Int Arch Otorhinolaryngol. 20(2):94-8, 2016
  23. Atan D et al: Relation of otosclerosis and osteoporosis: a bone mineral density study. Auris Nasus Larynx. 43(4):400-3, 2016
  24. Mukaida T et al: Magnetic resonance imaging evaluation of endolymphatic hydrops in cases with otosclerosis. Otol Neurotol. 36(7):1146-50, 2015
  25. 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
  26. 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
  27. Lee TC et al: CT grading of otosclerosis. AJNR Am J Neuroradiol. 30(7):1435-9, 2009
  28. 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
  29. Marshall AH et al: Cochlear implantation in cochlear otosclerosis. Laryngoscope. 115(10):1728-33, 2005
  30. Chadwell JB et al: The cochlear cleft. AJNR Am J Neuroradiol. 25(1):21-4, 2004
  31. 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
  32. Rondini-Gilli E et al: [Otosclerosis surgical techniques and results in 150 patients] Ann Otolaryngol Chir Cervicofac. 119(4):227-33, 2002
  33. 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
  34. Chole RA et al: Pathophysiology of otosclerosis. Otol Neurotol. 22(2):249-57, 2001
  35. Ruckenstein MJ et al: Management of far advanced otosclerosis in the era of cochlear implantation. Otol Neurotol. 22(4):471-4, 2001
  36. Shin YJ et al: Correlations between computed tomography findings and family history in otosclerotic patients. Otol Neurotol. 22(4):461-4, 2001
  37. Shin YJ et al: Sensorineural hearing loss and otosclerosis: a clinical and radiologic survey of 437 cases. Acta Otolaryngol. 121(2):200-4, 2001
  38. Veillon F et al: Imaging of the windows of the temporal bone. Semin Ultrasound CT MR. 22(3):271-80, 2001
  39. Niyazov D et al: Fenestration surgery for otosclerosis: CT findings of an old surgical procedure. AJNR Am J Neuroradiol. 21(9):1670-2, 2000
  40. Ziyeh S et al: MRI-visible pericochlear lesions in osteogenesis imperfecta type I. Eur Radiol. 10(10):1675-7, 2000
  41. Ziyeh S et al: MRI of active otosclerosis. Neuroradiology. 39(6):453-7, 1997
  42. Miura M et al: Computed tomographic image analysis of ears with otosclerosis. ORL J Otorhinolaryngol Relat Spec. 58(4):200-3, 1996
  43. Valvassori GE: Imaging of otosclerosis. Otolaryngol Clin North Am. 26(3):359-71, 1993
  44. Wilbrand HF: Radioanatomy of cochlear and stapedial otosclerosis. Scand Audiol Suppl. 30:181-3, 1988
  45. Mafee MF et al: Use of CT in stapedial otosclerosis. Radiology. 156(3):709-14, 1985
  46. Swartz JD et al: Fenestral and cochlear otosclerosis: computed tomographic evaluation. Am J Otol. 6(6):476-81, 1985

Images

Selected Images

Coronal graphic illustrates findings of fenestral otosclerosis with a "donut" otospongiotic plaque 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 "donut" otospongiotic plaque 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 "donut" otospongiotic plaque 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 "donut" otospongiotic plaque 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 , the typical appearance and location of an otospongiotic plaque of fenestral otosclerosis. Coronal right temporal bone CT shows a lytic focus anterior to the oval window , 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 "halo" around the cochlea with concurrent fenestral otosclerosis . Axial graphic demonstrates a classic example of cochlear otosclerosis. Note otospongiotic plaques in a "halo" around the cochlea with concurrent fenestral otosclerosis .

Axial left temporal bone CT shows cochlear otosclerosis as osteolytic foci surrounding the cochlea . Concurrent fenestral otosclerosis is noted as bony lucency along cochlear promontory extending from the fissula ante fenestram . Axial left temporal bone CT shows cochlear otosclerosis as osteolytic foci surrounding the cochlea . Concurrent fenestral otosclerosis is noted as bony lucency along cochlear promontory extending from the fissula ante fenestram .

Axial bone CT shows a thick, lucent otosclerotic plaque anterior to the oval window 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 . Axial bone CT shows a thick, lucent otosclerotic plaque anterior to the oval window 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 .

Coronal right temporal bone CT in a patient with mixed hearing loss shows a "halo" of radiolucency surrounding the cochlea , representing cochlear otosclerosis. Also note the associated fenestral otosclerosis . Coronal right temporal bone CT in a patient with mixed hearing loss shows a "halo" of radiolucency surrounding the cochlea , representing cochlear otosclerosis. Also note the associated fenestral otosclerosis .

Axial bone CT shows a small lucent plaque of fenestral otosclerosis thickening the otic capsule bone immediately anterior to the oval window. Note the stapes visualized within the oval window . Axial bone CT shows a small lucent plaque of fenestral otosclerosis thickening the otic capsule bone immediately anterior to the oval window. Note the stapes visualized within the oval window .

Axial left temporal bone CT demonstrates mixed lucent and sclerotic otospongiotic plaque obstructing the round window . This predisposes to stapes prosthesis failure and makes cochlear implantation more challenging. Axial left temporal bone CT demonstrates mixed lucent and sclerotic otospongiotic plaque obstructing the round window . This predisposes to stapes prosthesis failure and makes cochlear implantation more challenging.

Axial left temporal bone CT shows typical lytic plaques of combined fenestral and cochlear otosclerosis . The patient has undergone stapedectomy with insertion of a stapes prosthesis. Note the metallic density stapes prosthesis at the oval window. Axial left temporal bone CT shows typical lytic plaques of combined fenestral and cochlear otosclerosis . The patient has undergone stapedectomy with insertion of a stapes prosthesis. Note the metallic density stapes prosthesis at the oval window.

Axial T1WI C+ FS MR in the same patient reveals enhancement anterior to the oval window (fissula ante fenestram) and surrounding the cochlea , representing active fenestral and cochlear otosclerosis, respectively. Axial T1WI C+ FS MR in the same patient reveals enhancement anterior to the oval window (fissula ante fenestram) and surrounding the cochlea , representing active fenestral and cochlear otosclerosis, respectively.

Additional Images

Axial bone CT shows an extensive pericochlear lucent "halo" of cochlear otosclerosis. Axial bone CT shows an extensive pericochlear lucent "halo" of cochlear otosclerosis.

Axial thin T2 MR in the same patient shows multifocal otic capsule hyperintensities that corresponded to plaques on CT. Axial thin T2 MR in the same patient shows multifocal otic capsule hyperintensities that corresponded to plaques on CT.

Coronal right temporal bone CT shows fenestral otosclerosis involving all the margins of the oval window . The net effect is to create a blurring and disappearance of the oval window niche. Coronal right temporal bone CT shows fenestral otosclerosis involving all the margins of the oval window . The net effect is to create a blurring and disappearance of the oval window niche.

Axial temporal bone CT demonstrates a classic otospongiotic plaque as extra lucent foci on the anterior margin of the oval window (fissula ante fenestram location). The otic capsule is otherwise spared. Axial temporal bone CT demonstrates a classic otospongiotic plaque 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 . 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 .

Axial bone CT demonstrates a severe case of combined fenestral and cochlear otosclerosis. The Schwartze sign was clearly seen on otoscopic examination. Axial bone CT demonstrates a severe case of combined fenestral and cochlear 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 and cochlear otosclerosis with enhancement signifying active disease is shown. Less avid enhancement in the vestibule and cochlea represents endolymphatic hydrops, which is sometimes associated with otosclerosis. Axial T1WI C+ FS MR of the right temporal bone in a severe case of combined fenestral and cochlear otosclerosis with enhancement signifying active disease is shown. Less avid enhancement in the vestibule and cochlea 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 in the expected location anterior to the oval window. Coronal left temporal bone CT in the same patient again demonstrates the lytic otospongiotic plaque of fenestral otosclerosis in the expected location anterior to the oval window.

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