Conductive Hearing Loss CT Scan Findings
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imaging in transmissional hearing loss with normal tympanic membran
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Conductive Hearing Loss CT Scan Findings
- 2. Conductive hearing loss with normal tympanic membran § 4 different kinds of pathologies ú Otosclerosis ú Post traumatic ú Chronic otitis ú Malformations: minor aplasia, gusher syndrom
- 3. Diagnosis § Anamnesis and clinical findings § Personal and family medical history § Partial or bilateral hearing loss § Acquired, increasing hearing loss § Normal tympanic membran § Conductive or mixed hearing loss § Absence of stapedial reflex § IMAGING RECOMMANDATION: CT
- 4. CT SCAN § No injection, Bone CT § Thin sections // skull base, above the crystaline § // LSCC § Sections: 0,4mm, reconstructions 0,5mm § Coronal reconstructions perpendicular to LSCC § Oblique reconstructions perpendicular to the stapes footplate: « V » ossicular
- 5. CBCT: X Ray comptuted tomography § Sectional imaging, 3D reconstruction § Bone analysis § Less irradiation than CT scan (4 to 12 less) § Less artifacts
- 6. CBCT: X Ray comptuted tomography § 250 to 360 aquisitions § Isotopric voxel § Spatial resolution: 100μ
- 8. CT findings: the surgeon expectations Pre operative Ø Diagnosis Ø Diagnosis ⊕ > 90% Ø Différential diagnosis or other pathology associated Ø Surgical anatomical informations Ø Oval window niche size, position of VII, occlusion of the oval window, vascular variants Ø Prognosis evaluation: round window occlusion, cochlear otosclerosis, endosteum extension
- 9. Reading method § External auditory meatus: ú walls, content § Middle ear ú walls, content: size, shape, ossicular morphology, aeration of the tympanic cavity ú Fenestral: thickness, size of recess, thickness of the stapes footplate < 0,7 mm (axial ) ú Position of the facial nerve, especially up to the oval window
- 10. Reading method § Inner ear: ú Malformation of semi-circular canal or vestibular abnormality ú Fenestration of the LSCC ú Exclude a gusher syndrom: modiolus >2,7mm
- 11. Key points § Conductive hearing loss are not only secondary of middle ear or windows pathologies § Inner ear lesions can also be responsible as: ú Labyrinthine malformation ú Fixed stapes footplate
- 12. Pathologies § Malformation ú Fixation of the ossicular chain Fixation of the head of the malleus (Goodhill syndrom): calcified bridge between the head of the malleus and the lateral or the the anterior wall of the attic wall. Rare 1% Inflammatory or traumatic secondary ossification.
- 13. Pathologies § Malformation Fixation of the long process of the incus Absence of the long process of the incus Absence or distorsion of the stapes Agenesia of the round window
- 14. Pathologies § Malformatiion ú Gusher syndrom: inherited hearing loss X-linked Perilymphatic communication with sub arachnoid space. ú Geyser fluid through the stapes floot plate during surgical platinotomy with cophosis
- 15. Pathologies § Superior canal dehiscence (Minor’s syndrom) : Importance of the 2D reconstruction perpendicular to the axis of the canal
- 16. Temporal bone injury § Third leading cause of conductive hearing loss § CT scan: incudostapedial or incudomalleus discolation (55 - 60%) § Fracture of the stapes Diastasis > 1 mm
- 18. Pathologies § Otospongiosis ú Common ú Perifenestral bony labyrinth pathology where spongy bone foci appear ú Bilateral 2 /3, often asymmetrical ú 0,5 à 1% of caucasian population ú Women more often (sex ratio 2/1) from 15 to 45 years old. ú Very rare less than 10 years old
- 19. CT scan ú Lytic foci on anterior margin of oval window (Fissula antefenestram) ú Extension to the stapes footplate with fixation of the stapes ú Spreads to involve all margins of oval and round window CT CBCT
- 20. Otospongiosis: CT scan § Isolated lesion on the stapes footplate ú Unusual (0.02 %). ú Normal size of the stapes footplate < 0,3 mm on histological section ú Size on CT varies from 0,4 to 0,55. ú Physiological anterior thickening close to the anterior branch of the stapes ú Only an important thickening is available(> 0,7 mm ) to be significant.
- 22. Otospongiosis: CT scan § Hypertrophic Foci ú May result a fixation of the ossicular chain to the medial wall of the tympanic cavity (stapes, malleus and incus rarely) ú It can narrow the oval window: surgical difficulty
- 23. Otospongiosis: CT scan § Foci of the round window: poor postoperative results § Superior canal dehiscence
- 24. Otospongiosis: CT scan § Labyrinthine foci are rarely isolated, usually associated with anterior location. § Double ring appearance. § Posteriorlabyrinth lesions are unusual, most frequently seen around the lateral canal § Foci located to the internal auditory meatus are very rare.
- 25. Differential Diagnosis § Osteogenesis imperfecta § Phosphate metabolism disturbance § Paget disease
- 26. Pre operative staging § Superior canal dehiscence § Oval window’s size § Prolapsed facial nerve § Vascular variants § Enlarged modiolus
- 27. Failure and surgical complications imaging § Failure : Hearing loss persistence or recurrence: prothesis dysfunction § Complication : sensorineural hearing loss (vertigo): inner ear suffering
- 28. Failure and surgical complications imaging § Conductive hearing loss § CT ú Displacement or migration of prosthesis ú Erosion of incus ú Fibrosis ú Attic ankylosis ú Otosclerosis proliferation ú Prosthesis too short ú Incus dislocation § Sensorineural hearing loss § CT +/- MRI § Perilymphatic fistula § Intravestibular prosthesis § Inner ear infection § Granuloma around the oval window
- 30. CBCT
- 32. Intravestibular prosthesis § Intravestibular penetration>1 mm (WITH clinical inner ear symptoms)
- 33. Pneumolabyrinth § Air in inner ear cavities § Pathognomonic of a perilymphatic fistula § But it can be observed after stapedectomy without pejorative significance
- 34. No explanation on CT § No pneumolabyrinth § Airy middle ear cavity § Prosthesis well positioned § Non specific opacity in the middle ear cavity OR MRI
- 35. Perilymphatic fistula § Pneumolabyrinth: suggestive of PLF if seen afar surgery § Surgical revision if: Vertigo, nystagmus Conductive hearing loss
- 36. Infection
- 38. Conclusion § Imaging has a key role § CT scan or cone beam are the best imaging § Child conductive hearing loss : CT systematic § Adult conductive hearing loss : useful for the diagnosis § Systematic in pre-operative or if failure or complication before surgical revision