SS06: ACTIVE MIDDLE EAR IMPLANTS AND MHL

COCHLEAR WINDOWS POSITIONING OF THE VIBRANT SOUNDBRIDGE: RESULTS FROM MERAN

Giarbini N, Costanzo S, Streitberger C

ENT and Head-Neck Surgery Department, Hospital of Meran, Italy

Introduction:  One of the most challenging issues in middle-ear reconstructive surgery is to gain satisfactory long term functional results.

The development of middle ear implantable hearing devices during the last three decades, has offered a new surgical option in the treatment of conductive and mixed hearing loss. Different devices and sites of application have been tried out in different middle-ear conditions, but an agreement on positioning-choice is still missing.

Aim: Middle-ear reconstructive surgery needs to guarantee satisfactory long term functional results. The aim of this presentation is to describe the audiological results obtained for round and oval window positioning of the Vibrant Soundbridge’s (VSB) Floating Mass Transducer (FMT) and to discuss the device’s effectiveness on the bases of results obtained.

Subjects and Methods:  Of the 43 cases treated with Vibrant Soundbridge (VSB) during the last 4 years, the results obtained in 28 cases suffering from mixed hearing loss of different etiologies who received a VSB either on the round window (15 patients) or on the oval one (13 patients) will be described. The surgical approach was adapted case by case for all subjects and was alternatively: revision of radical cavities (CWU and CWD), transmastoid with posterior tympanotomy, transmeatal, or combined transmeatal-transmastoid.
For the round window placement, the niche was adapted for the FMT and positioning was in contact to the round window membrane, with or without interposition of autologues fascia.

For the oval window placement, the FMT was positioned in direct contact with the stapes footplate in 9 cases, on stapes supra-structure in 3 cases, and directly on oval window after stapedectomy in 1 case.

Results: No major surgical complications occurred and no significant worsening of bone conduction was observed post-operatively for all patients. Improvement of speech understanding at VSB activation when comparing aided with unaided condition was observed in all subjects.

The results obtained after a minimum of six months post-surgery were evaluated in terms of aided threshold improvement and functional gain.

For round window placement, data from 9 cases showed unaided mean pure tone average PTA4 at 78 dB HL (s.d.=17.38) with mean speech recognition threshold (SRT) of 85 dB HL. At 6 months from VSB activation mean PTA4 was 38.75 dB HL (s.d.=11.26) with mean SRT of 53 dB.

For oval window placement, data from 8 cases showed unaided mean pure tone average PTA4 at 76.94 dB HL (s.d.=18.08) with mean SRT of 84 dB HL. At 6 months from VSB activation mean PTA4 was 36.88 dB HL (s.d.=10.05) with mean SRT of 53 dB.

Results were maintained with a slight improvement over time in subjects with a longer period of observation.

Indications and results of all cases will be discussed for the two different placements.

Conclusions: In our opinion, the cochlear windows’ placement of the VSB has shown satisfactory functional results and the choice to direct drive the inner ear through the oval or the round window should be done on the base of imaging and intra-operative findings, aiming the best possible transfer of vibratory energy to the inner ear.