IMAGING OF

FAILURES AND COMPLICATIONS

AFTER SURGERY FOR OTOSCLEROSIS

 O NAGGARA*, MT WILLIAMS**, D AYACHE**, F HERAN**, JD PIEKARSKI**

*CH Sainte Anne, **Fondation Ophtalmologique A. de

Rothschild,

PARIS, FRANCE

Otosclerosis • Otosclerosis (OS) is a dysplasia of the otic

capsule located in most cases on the anterior margin of the oval window.

• OS is responsible for an ankylosis of the stapes footplate in the oval window, with subsequent conductive hearing loss (CHL).

• Stapes surgery is the only effective treatment of OS.

Principles of stapes surgery

The aim of surgical treatment of OS is to restore the transmission of sound vibrations to the labyrinthine fluids through the oval window.

Surgical procedures include

in all the cases:

- the removal of the stapedial arch

- the insertion of a prosthesis

(a.k.a. « piston »)

(M: malleus; I: incus; St: stapes)

Principles of stapes surgery: 3 main procedures

- Stapedectomy with graft interposition (A)

- Partial stapedectomy with graft interposition (B)

- Small fenestra stapedotomy (C)A B C

Surgical results

• The results of stapes surgery are excellent with a residual air-bone gap less than 10 dB in more than 90 % of the cases

• Failures: 8%• Complications: 2 % • Failures or complications = aetiologic

workup includes an imaging exploration (CT and/or MRI)

CT

• CT is the first line imaging technique in the work-up

of

unsuccessful stapes surgery. The purpose of CT

examination is to confirm OS and to detect

postoperative abnormalities

•TECHNIQUE:

- Acquisition in helical mode, bony reconstruction

algorithm

- Slice thickness: 0.5 to 1 millimeter

- Multiplanar reconstruction (MPR ) in high resolution

along the main axis of the prosthesis

Incremental acquisition without reconstructions is not

able to depict confidently abnormalities, such as a

slight displacement of the medial end of the piston

Multiplanar reconstruction (MPR )

Axial oblique MPR

Coronal oblique MPR

Reconstructions in patient without displacement

of the prosthesis

MRI • MR imaging may be useful in the exploration of labyrinthine complications, especially in those cases where CT is not contributive or not specific

• A possible displacement of non-ferromagnetic prostheses has been demonstrated in vitro; however, this displacement is clinically non-significant (1, 2)

• Technique: • use of a surface coil • inframillimetric (0.5-0.8 millimeters) strongly T2-weighted imaging• Precontrast and contrast-enhanced 2-millimeters thick T1-weighted images

(1) Syms MJ & al. Am J Otol 2000; 21: 494-498(2) Williams MD & al. Otol Neurotol 2001; 22: 158-161

Surgical failure • Surgical failure is defined as the persistence or the recurrence of CHL after stapes surgery by impairment of sound transmission mechanism• Failures accounts for # 80 % of surgical revisions • Most frequent causes of surgical failures:

Wiet 1997N = 1177

Sheer 1998N = 308

Lesinski 2002N = 279

Betsch 2003N = 73

45 % 24,4 % 81 % 37,1 %

23,6 % 14 % 31 % 8,5 %

Erosion of LPI - - 60 % -

10,5 % 4 % 13, 5 % 7,1 %

Fibrosis 2,9 % 13,6 % ? 32,8 %

Ankylosisdislocation

3,2% 0,8 % 8 % 10 %

Displacementof prosthesis

Osteonecrosis of LPI

Hypertrophic otosclerosis

Displacement of the prosthesis: 60 % of failures

Surgical failures related to the prosthesis

46-year-old man, sudden hearing loss after a trauma: complete dislocation of the prosthesis. (A) Oblique axial MPR; (B) Peroperative view

Surgical failures related to the

prosthesis

A

B

- Displacement of the medial end of the piston- loop of the piston dislocated from the long

process of the incus

- too short prosthesis

Persistant CHL 3 months after surgery in a 54-year-old woman: axial (A) and coronal (B) oblique MPRs show a gap between the oval window and the tip of the piston’s shaft, which has a correct orientation: too short prosthesis

Displacement of the prosthesis

Surgical failures related

to the prosthesis

AB

Recurrence of CHL 12 months after stapes surgery in a 61-year-old woman: oblique axial (A) and coronal (B) MPRs show the « empty loop » of the desinserted prosthesis

Displacement of the prosthesisSurgical failures

related to the prosthesis

A

B

- Osteonecrosis of the long process of the incus (23 %) - Ankylosis of the ossicular chain in the epitympanum (5%)- Incudomalleolar dislocation (2%)

Surgical failures related to the ossicular chain

Ossicular chain: 30% of failures

Osteonecrosis of the long process of the incus: 23%

• Second cause of surgical failure • Erosion is almost constantly seen at revision surgery, but large osteonecrosis visible at CT is less frequent• Severity of bone necrosis greater with prostheses including a metallic loop• Slight erosions of the long process of the incus (LPI) are usually not detected on CT scans• In case of necrosis, MPRs show an abnormally short LPI often associated to a dislocation of the loop of the piston

Surgical failures related to the ossicular chain

Ankylosis of the ossicular chain: 5 %

• Ankylosis of the ossicular chain in the epitympanum may be due to:

• the ossification of the anterior malleolar ligament

• a congenital bony bridge between the head of the malleus and the anterior part of the tegmen tympani.

• IT IS EXTREMELY IMPORTANT TO DETECT THESE CASES, BECAUSE THE SURGICAL REVISION MAY DESERVE A SPECIFIC PROCEDURE

A B

Surgical failures related to the ossicular chain

Ankylosis of the ossicular chain: 5 %

Lack of postoperative hearing improvement in a 37-year-old patient.

(A) Axial CT scan shows a thickening and

an ossification of the anterior malleolar ligament (solid arrow) in left ear;

(B) Normal aspect of anterior malleolar ligament (arrowheads) in right ear

Surgical failures related to the ossicular chain

A

B

Ankylosis of the ossicular chain: 5 %

Absence of hearing improvement after stapes surgery: congenital bony bridge between the malleus head and the lateral attic wall (House syndrome)

A B

Surgical failures related to the ossicular chain

Incudomalleolar Dislocation: 2% This condition :

• may be a consequence of surgery• or is sometimes present prior to stapes surgery

Persistant CHL 3 months after stapes surgery in a 36-year-old woman: enlargement of incudomalleolar space visible on

oblique axial (A) and sagittal (B) MPRs

Surgical failures related to the ossicular chain

A

B

Fibrosis: - could be considered as a cofactor of surgical failure rather than its direct cause- is difficult to detect with CT, except for the cases in

which a soft tissue mass is present.

Oval window postoperative fibrosis: 30 %

Surgical failures related to fibrosis

Non calcified soft tissue mass obliterating the oval window recess around the shaft of the piston in two different patients : postoperative fibrosis

• The development of hypertrophic dysplastic bone around the piston is a rare postoperative condition

- Revision surgery is considered hazardous (increased risk of postoperative sensorineural hearing loss)

- CT shows a calcified mass in the oval window recess

Hypertrophic otosclerosis 8 %

Surgical failures related tohypertrophic OS focus

Recurrent CHL in a 58-year-old woman: slightly calcified tissue mass in the oval window recess around the piston’s shaft: Hypertrophic ostosclerotic focus

• Labyrinthine complications are fairly less frequent than failures, accounting for # 20 % of patients who have undergone surgical revision• Complications are suspected in patients presenting with vertigo, sensorineural hearing loss (SNHL) or tinnitus after stapes surgery. • The main causes of labyrinthine complications are summarized in table below:

Surgical complications

Wiet 1997N = 1177

Sheer 1998N = 308

Lesinski 2002N = 279

Betsch 2003N = 73

Fistula 10 % 2 % 5,4 % 5,7 %

Protrusion 0,4 % 0,8 % 2 % 5,7 %

Granuloma 2,3 % 0,4 % 5,7 %

Perilymphatic fistula

Intense postoperative vertigo with destructive nystagmus and complete

hearing loss in a 41-year-old man: Initial CT examination showed a pneumolabyrinth,

whichs persists on control CT scans 3 weeks later

Perilymphatic fistula• Perilymphatic fistula corresponds to a perilymphatic fluid leakage through the oval window • Treatment consists in clogging the fistula using a venous or an aponevrotic graft • CT inconstantly shows a pneumolabyrinth which is the only specific sign of perilymphatic fistula • A dependent fluid effusion in the tympanomastoid cavities is not specific in the early postoperative peroid

3 days after surgery

Perilymphatic fistula

5 days after surgery

Early postoperative vertigo and sensorineural hearing loss in a 43-year-old woman. (A): Axial CT 3 days after procedure shows a pneumolabyrinth; (B): complete resolution of pneumolabyrinth on control CT scan 2 days

later, with dramatic improvement of clinical symptoms

A

B

Postoperative vertigo in a 34-year-old woman. Oblique axial (A) and coronal (B) MPRs show intravestibular penetration of the prosthesis superior to 1 mm.

Intravestibular protrusion of the prosthesis

Intravestibular penetration of the piston superior to 1 mm is considered abnormal only in patients presenting with labyrinthic symptoms

A

B

52-year-old patient with cophosis, vertigo and superficial suppuration. Obliteration of the intralabyrinthine fluids, with abnormal low signal of the labyrinthine cavities on T2-weighted images (A), associated to an extensive enhancement of the labyrinth (small arrows) on postcontrast T1- weighted images (B).MRI is able to depict regional complications: meningitis, sigmoid sinus thrombosis, abcess in the superficial soft tissues of the temporal region (solid arrow in B)

Suppurative labyrinthitis

A B

Intravestibular granuloma

Rapid postoperative onset of vertigo with nystagmus and SNHL in 53-year-old woman (A): non specific fluid effusion in the middle ear on CT scan (B): low signal intensy of posterior labyrinth on T2-weighted images associated with enhancement on postcontrast T1-weighted images (not shown) : granuloma

• May occur since the first week after stapes surgery • Postoperative inflammatory granuloma develops around the tip of the prothesis and extends into the labyrinth. • Surgical revision is urgent with withdrawal of the prothesis, of granulation tissue • CT usually shows a non specific soft tissue mass in the oval window • Diagnosis based upon MR imaging

A

B

« Floating footplate »

• Rare complication of surgery• The stapes footplate “falls” inside the vestibular cavity during the stapedectomy• CT shows a linear dense structure in the vestibule

- The prosthesis- The ossicular chain- The middle ear cavities

Conclusion

Helical CT scans with MPRs: Evaluation of:

Postoperative CHL

- Normal status of the prosthesis

- No pneumolabyrinth- Normal middle ear or non specific mass of middle ear

Conclusion

MRIHelical CT scans with

MPRs

Postoperative SNHL / vertigo

References•Nadol JB Jr. Histopathology of residual and recurrent conductive hearing loss after stapedectomy.Otol Neurotol. 2001 Mar;22(2):162-9.

•Williams MD, Antonelli PJ, Williams LS, Moorhead JE.Middle ear prosthesis displacement in high-strength magnetic fields. Otol Neurotol. 2001 Mar;22(2):158-61.

•Lesinski, S. Causes of conductive hearing loss after stapedectomy or stapedotomy: a prospective study of 279 consecutive surgical revisions. Otol Neurotol, 2002(23): p. 281-288

•Wiet RJ, Kubek DC, Lemberg P, Byskosh AT. A meta-analysis review of revision stapes surgery with argon laser: effectiveness and safety. Am J Otol., 1997. Mar;18(2): p.166-71

•Rangheard AS, Marsot-Dupuch K, Mark AS, Meyer B, Tubiana JM. Postoperative complications in otospongiosis: usefulness of MR imaging. AJNR Am J Neuroradiol, 2001(22): p. 1171-1178

•Hammerschlag PE, Fishman A., Scheer AA. A review of 308 cases of revision stapedectomy. Laryngoscope, 1998. Dec;108(12): p. 1794-800

•Betsch C, Ayache D, Decat M, Elbaz P, Gersdorff M. J Otolaryngol., 2003. Feb;32(1): p. 38-47.

•Williams MD, Antonelli PJ, Williams LS, Moorhead JE. Middle ear prosthesis displacement in high-strength magnetic fields. Otol Neurotol. 2001 Mar;22(2):158-61.