Bone Conducting Hearing Bone Conducting Hearing Aid SolutionsAid Solutions

Dr Zeeshan AhmadM.S.(ENT,PGY1)

Department of ENT,NMCH,Patna.

27-09-2012

Hearing impairment is a common occurence.

Most patients have abnormality of cochlear function and can be treated by use of conventional hearing aid.

However, a significant number have conductive cause.

Many of these can also be treated by conventional hearing aid but a proportion do not tolerate mould or insert in ear canal, so alternative means must be considered.

What is Hearing aid? A hearing aid is a battery-powered, electronic device that makes listening easier for people with a hearing loss. A hearing aid consists of a microphone, an amplifier and a receiver. The microphone picks up sounds in your acoustic environment and turns them into electronic signals. The amplifier selectively amplifies the acoustic electronic signals. The receiver is a very small speaker that changes the electric signals back to sounds and delivers the sound to the ear.

Consideration in using Hearing aids

HistoryHistory1551- Bone conduction device consisting

of metal shaft or spear.1670- Sir Samual Moreland, England

invented a large speaking trumpet.

1892- first patent for electric hearing aid in the U.S.

1912- first volume control for a hearing aid.

History Contd….History Contd….1931- first electric hearing aid eyeglass

patent1937- first wearable vacuum tube HA in

US1953- first all-transistor hearing aid1987- first commercially available

implantable hearing aid system.1997- FDA approved BAHA®

Recently- Oticon implants

Basic Hearing Aid StructureBasic Hearing Aid Structure

MECHANISM of BONE MECHANISM of BONE CONDUCTION HEARINGCONDUCTION HEARING

Vibration of bone of skull is coupled to soft tissues of ear canal. More when ear canal is occluded.

Some of sound energy transmitted directly to ossicular chain.

Alternate compression and expansion of cochlear shell by vibratory forces on bone.

The BAHAThe BAHA®®

BAHA® is the trade namefor bone anchored hearing aid system available From CochlearTM.

BAHA system is comprised of three BAHA system is comprised of three parts:parts:

Titanium fixture(3)Connecting

abutment(4)Detachable sound

processor(6)

How does it Work?How does it Work?

The processor receives sound through the abutment and sends it to the functioning cochlea using the skull as a pathway to bypass the outer and middle ears

CandidatesCandidatesChronic otitis mediaCongenital aural

atresiaMicrotiaCholesteatomaMiddle ear

dysfunction or disease

Acoustic neuromaNeurologic

degenerative diseaseMeniere’s diseaseViral infectionTrauma

A photograph from NMCH OPDA photograph from NMCH OPD

PrerequisitesPrerequisitesMixed or conductive hearing loss Bone conduction pure-tone average in the

indicated ear is greater than or equal to 45 dB HL

Monosyllabic word discrimination score ≥ 60%For single sided DeafnessFor bilateral fittings – candidates must have

symmetrical bone conduction pure-tone averages between ears

Age > 5 years

To anticipate a "high success rate" To anticipate a "high success rate" with BAHAwith BAHA

Patients should have a PTA less than 45 dB, although improvements in hearing should still be expected for a PTA of up to 60 dB.

(Hakansson B, Tjellstrom A, Carlsson P:  Percutaneous vs. transcutaneous

transducers for hearing by direct bone conduction.   Otolaryngol Head Neck Surg  1990; 102:339-344.)

Operative TechniqueOperative Technique

A. Posterior-based skin flap is elevatedB. Flap is thinned until all hair follicles are removed from the flap centerC. Soft tissues beneath and adjacent to the flap are excised to create a smooth transition from surrounding tissue to the thin central skin flap

Operative TechniqueOperative Technique

D. 3- to 4-mm hole is drilled in mastoid or retromastoid cortex. E and F, A countersink creates a recessed surface for implant placement.

Operative TechniqueOperative Technique

G. The hole is tappedH. Titanium screw is implantedI. Titanium screw is tightened in place

Operative TechniqueOperative Technique

H/I. The titanium screw is tightened into placeK. The skin flap is replaced

Operative TechniqueOperative Technique

L/M. Metallic abutment for later attachment of the vibrating external hearing aid is attached to the screwN/O. A healing cap is placed to apply pressure to the skin flap

Perioperative Complications with the Perioperative Complications with the Bone-Anchored Hearing AidBone-Anchored Hearing Aid

Loss of Skin GraftLoss of Skin Graft

Growth of skin graft over the abutmentGrowth of skin graft over the abutment

Implant extrusionImplant extrusion

InfectionInfection

The most important factor in The most important factor in obtaining a trouble-free bone-obtaining a trouble-free bone-anchored hearing aid (BAHA) site is:anchored hearing aid (BAHA) site is:

A. Having thin, immobile, hairless skin around the A. Having thin, immobile, hairless skin around the

abutment abutment B. Using a 4-mm fixture flangeB. Using a 4-mm fixture flangeC. Using a longer abutment – The longest C. Using a longer abutment – The longest D. Performing surgery in two stagesD. Performing surgery in two stages

To Prevent Loss of Skin GraftTo Prevent Loss of Skin GraftHave thin, immobile, hairless skin around

the abutment - This allows for placement of the fixture in a tissue bed that has minimal local tissue reaction to the implant and thereby minimizes chance of skin graft loss, infection or extrusion

Ensure that the skin graft is firmly attached to the underlying periosteum

Ensure that the fixture and skin penetrating abutment are firmly secured

To prevent growth of skin graft To prevent growth of skin graft over the abutmentover the abutment

Use longest implant possibleObtain adequate removal of surrounding

soft tissueApproximate the surrounding skin edges

to the periosteum

To prevent implant extrusionTo prevent implant extrusionAllow patients with poor wound healing and

thin bones to have six months of osseointegration

Fix any coagulopathies that the patient may have pre-operatively

Maintain proper hemostasis to prevent hematoma formation

Use a 4-mm fixture if there is bone still present at the bottom after using a 4-mm drill guide

Patients with thin, brittle bone should have a two stage surgery

To prevent infectionTo prevent infection

Other complicationsOther complications

Penetration of sigmoid sinus – Insert bone wax or muscle plug

Brain abscess

OTICON PONTO HEARING AIDOTICON PONTO HEARING AID

SOPHONO ALPHA 1 SYSTEMSOPHONO ALPHA 1 SYSTEM

THANK THANK YOUYOU

for patient listeningfor patient listening