CONDUCTIVEHEARINGLOSSWITHNORMALTYMPANICMEMBRAN

F.BENOUDIBA,JLSARRAZINServicedeNeuroradiologieCHUKremlinBicêtre

JFIMBarcelonanov1st2014

Conductivehearinglosswithnormaltympanicmembran§  4 different kinds of pathologies

ú  Otosclerosis ú  Post traumatic ú  Chronic otitis ú  Malformations: minor aplasia, gusher syndrom

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

CTSCAN

§  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

CBCT:XRaycomptutedtomography

§  Sectionalimaging,3Dreconstruction§  Boneanalysis§  LessirradiationthanCTscan(4to12less)§  Lessartifacts

CBCT:XRaycomptutedtomography§  250to360aquisitions§  Isotopricvoxel§  Spatialresolution:100μ

ANALYSECEPHALOMETRIQUETRIDIMENSIONNELLE(J.TREIL)

LogicielDolphin

3D

CTfindings:thesurgeonexpectations

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

Readingmethod

§  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

Readingmethod

§  Inner ear: ú  Malformation of semi-circular canal or

vestibular abnormality ú  Fenestration of the LSCC ú  Exclude a gusher syndrom: modiolus

>2,7mm

Keypoints

§  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

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.

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

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

Pathologies

§  Superior canal dehiscence (Minor’s syndrom) : Importance of the 2D reconstruction perpendicular to the axis of the canal

Temporalboneinjury

§  Third leading cause of conductive hearing loss

§  CT scan: incudostapedial or incudomalleus discolation (55 - 60%)

§  Fracture of the stapes Diastasis > 1 mm

Temporalboneinjury

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

CTscanú  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

Otospongiosis:CTscan §  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.

Otospongiosis:CTscan

§  Extensiontoendosteum

Otospongiosis:CTscan§  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

Otospongiosis:CTscan§  Foci of the round

window: poorpostoperativeresults

§  Superior canal dehiscence

Otospongiosis:CTscan§  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.

DifferentialDiagnosis

§  Osteogenesis imperfecta

§  Phosphate metabolism disturbance

§  Paget disease

Preoperativestaging§  Superior canal dehiscence §  Ovalwindow’ssize§  Prolapsedfacialnerve§  Vascularvariants§  Enlargedmodiolus

Failureandsurgicalcomplicationsimaging

§  Failure : Hearing loss persistence or recurrence: prothesis dysfunction

§  Complication : sensorineural hearing loss

(vertigo): inner ear suffering

Failureandsurgicalcomplicationsimaging

§  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

Prosthesisdisplacement

CBCT

Erosionofincus CBCT

CT

Intravestibularprosthesis

§  Intravestibular penetration>1 mm (WITH clinical inner ear symptoms)

Pneumolabyrinth§  Air in inner ear cavities §  Pathognomonic of a

perilymphatic fistula §  But it can be observed after

stapedectomy without pejorative significance

NoexplanationonCT

§  No pneumolabyrinth

§  Airy middle ear cavity §  Prosthesis well

positioned

§  Non specific opacity in the middle ear cavity

OR

MRI

Perilymphaticfistula

§  Pneumolabyrinth: suggestive of PLF if seen afar surgery

§  Surgical revision if: Vertigo, nystagmus Conductive hearing loss

Infection

Intra-labyrinthichemorrhage

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