Congenital Aural Atresia | Embryology PPT

January 11, 2013 | By | Reply More

Congenital Aural Atresia | Embryology PPT

Power point presentation | lecture slide

Size: 541 KB

 


 

Congenital Aural Atresia

www.neuronarc.com

Congenital Aural Atresia

Embryology

Classification

Evaluation

Surgical Repair

Results

Complications

Controversies

Congenital Aural Atresia

Definition:  “a birth defect that is characterized by hypoplasia of the external auditory canal, often in association with dysmorphic features of the auricle, middle ear and, occasionally, the inner ear structures”

–Harold F. Schuknecht, 1989

Congenital Aural Atresia

Incidence:  1 in 10,000-20,000

Unilateral 3-5x more common than Bilateral

Males > Females

Right > Left

Inheritance—sporadic

Autosomal recessive or dominant

Congenital Aural Atresia

Associations

Hydrocephalus

Posterior cranial hypoplasia

Hemifacial microsomia

Cleft palate

GU anomalies

Syndromes

Treacher-Collins

Goldenhar’s

Crouzon’s

Mobius’

Klippel-Feil

Fanconi’s

DiGeorge

Pierre Robin

VATER

CHARGE

 

Embryology

Auricle

4th week of gestation

1st and 2nd branchial arches

Hillocks of His

1—tragus

2—helical crus

3—helix

4—antihelix

5—antitragus

6—lobule

 

Embryology

External Auditory Canal

8th week of gestation

1st branchial groove

Medial migration of a solid core of epithelial cells

Recanalization during 6-7th months of gestation

 

Embryology

Ossicles

4th week of gestation

Meckel’s cartilage

Malleus head and neck

Incus body and short process

Reichert’s cartilage

Malleus handle

Incus long process

Stapes suprastructure

Embryology

Labyrinth

3rd week of gestation

Invagination of otic placode to form otic vesicle

Semicircular canals—6th week

Utricle and Saccule—8th week

Cochlea—7-12th weeks

 

Embryology

Facial Nerve

4-5 weeks of gestation

Classification

Altmann’s

Grade I

Hypoplastic EAC, temporal bone, TM; normal or slightly hypoplastic middle ear cleft; normal or slightly deformed ossicles

Grade II

Absent EAC; small middle ear cleft; osseous atresia plate; fixed and malformed ossicles

Grade III

Absent EAC; markedly hypoplastic or absent middle ear cleft; absent or severely deformed ossicles

De la Cruz

Minor

Normal mastoid pneumatization

Normal oval window

Reasonable oval window-facial nerve relationship

Normal inner ear

Major

Poor pneumatization

Absent or abnormal oval window

Abnormal horizontal facial nerve

Anomalous inner ear

Classification

Schuknecht

Type A

 

 

 

Type B

Type C

 

 

 

Type D

Classification

Jahrsdoerfer, 1992

Based on HRCT temporal bone findings

Score correlates to likelihood of successful surgery

Evaluation

History

Details of pregnancy

Family history

Physical Examination

Microtia

Severity of EAC stenosis

Craniofacial development

Evaluation

Audiologic Evaluation—ABR before leaving the hospital

Unilateral atresia

Auditory function of the “normal” ear

Bilateral atresia

Establish presence of cochlear function

FIT WITH BONE CONDUCTION AID

Evaluation

High Resolution CT Temporal Bone

Age 5-6 years

Axial and Coronal

Evaluate

Middle ear and mastoid pneumatization

Anatomy of ossicles

Inner ear morphology

Course of facial nerve

Surgical Repair

Candidacy

ABSOLUTE REQUIREMENTS

1.  Normal inner ear

2.  Normal cochlear function

HRCT Score

</= 5/10: poor

6/10: marginal

7/10: fair

8/10: good

9/10: very good

10/10: excellent

Surgical Repair

Timing

Microtia repair should be performed prior to undertaking atresia repair

5-6 years of age

Controversy:

Between Stages 2 and 3 of microtia repair

2 months after completion of microtia repair

Surgical Repair

Transmastoid Approach

Infrequently used

Advantages:

More familiar approach

Identification of sinodural angle and lateral SCC as landmarks

Disadvantages:

Creation of mastoid cavity

Larger defect to be skin grafted

Prolonged healing

Lifelong maintenance

Surgical Repair

Anterior Approach

Popularized by Jahrsdoerfer, most frequently utilized approach

Advantage:

Avoidance of mastoid cavity

Disadvantages:

Unfamiliar approach

Lack of landmarks

Surgical Repair

Video

American Academy of Otolaryngology—Head and Neck Surgery Foundation

Congenital Disorders—Volume #4

Harold F. Schuknecht, MD

Results

Difficult to interpret

Different classification of atresia

Different criteria for surgical candidacy

Different definition of “successful” outcome

Different periods of follow-up

 

Results

Stability of Hearing Levels

Lambert, 1998

Early postoperative period (<1yr)

60% 25dB or better

70% 30dB or better

Prolonged follow-up (1-7.5yrs)

46% 25dB or better

50% 30dB or better

Complications

EAC restenosis

Highly variable:  8-50%

Correlation to severity of atresia

TM lateralization

5-26% of cases

Easier to prevent than to correct

Chronic infection

Reconstructed EAC lacks normal keratin migration and cerumen production

Create wide meatus, fix restenosis, frequent follow-up with canal debridement

Complications

Facial Nerve Injury

1.0-1.5%

Vulnerability

Skin incision

Dissecting in the glenoid fossa

During canalplasty

Transposing the nerve

Dissecting preauricular soft tissue

Prevention

Preoperative evaluation of HRCT

Intraoperative facial nerve monitoring

Complications

Sensorineural Hearing Loss

Up to 15% of cases

4,000-8,000 Hz

Acoustic trauma to the inner ear

Transmission of drill energy

Drill injury to ossicles

Manipulation of ossicular chain

Avoidance—Meticulous technique

Controversies

Surgical Repair of Unilateral Atresia

Historically

One hearing ear = normal speech and language development

No indication for surgery

Recently

Unilateral hearing loss = auditory, linguistic and cognitive deficits

Improved preop evaluation, patient selection, surgical techniques, predictable results

Surgery indicated

Controversies

Timing of Unilateral Repair

Conclusion

Complex and Challenging Problem

Goals:

Restore functional hearing

Construct patent and infection-free EAC

Rewarding Surgery

 

Untitled-1

Tags: , , , , , , , , , ,

Category: Medical, Powerpoint

WARNING: Any unauthorised use or reproduction of  www.neuronarc.com content for commercial or any purposes is strictly prohibited and constitutes copyright infringement liable to legal action.