------------------------------------------------------------------------------- TITLE: MALFORMATION OF THE EXTERNAL AND MIDDLE EARS SOURCE: Dept. of Otolaryngology, UTMB, Grand Rounds DATE: October 1, 1986 RESIDENT PHYSICIAN: William H. Rotzler, M.D. FACULTY: Byron J. Bailey, M.D., FACS DATABASE ADMINISTRATOR: Melinda McCracken, M.S. ------------------------------------------------------------------------------- "This material was prepared by resident physicians in partial fulfillment of educational requirements established for the Postgraduate Training Program of the UTMB Department of Otolaryngology/Head and Neck Surgery and was not intended for clinical use in its present form. It was prepared for the purpose of stimulating group discussion in a conference setting. No warranties, either express or implied, are made with respect to its accuracy, completeness, or timeliness. The material does not necessarily reflect the current or past opinions of members of the UTMB faculty and should not be used for purposes of diagnosis or treatment without consulting appropriate literature sources and informed professional opinion." MALFORMATION OF THE EXTERNAL AND MIDDLE EARS The external and middle ears are structures derived from the posterior elements of the first and second branchial arches. Although development is completely separate from that of the inner ear, up to 10% of atresia patients also have an inner ear malformation. The incidence of malformation approximates 1 in 10,000 to 1 in 20,000 live births, with the following patterns of predominance: 61% male, 57% right-sided, 71% unilateral. All can be considered a form of craniofacial microsomia, as all patients demonstrate some degree of change in mandibular structure. The etiology is unknown. I. EMBRYOLOGY A. Auricle - formed from mesenchyme flanking first branchial groove Week 6 6 hillocks develop on 1st, 2nd branchial arches Week 12 coalescence of hillocks into primitive auricle 1st arch gives rise to tragus and root of helix (15%) 2nd arch gives rise to remainder of auricle (85%) B. External Auditory Canal - between 1st and 2nd branchial arches, 1st branchial groove develops opposite corre- sponding 1st pharyngeal pouch Month 2 branchial groove deepens medially into funnel (represents outer 1/3 of EAC) Month 3 medial extremity of funnel produces solid core of epithelial cells which grows inward to meet epithelium of pharyngeal pouch (seam of connective tissue remains between layers which forms tunica propria of TM) Month 3 tympanic ring ossifies Month 7 after all other structures of inner, middle, and outer ear formed, solid core of cells splits, first deeply to form TM, then extending outward to join primitive meatus (forms medial 2/3 of EAC) C. Middle Ear 1. Middle ear space develops from 1st pharyngeal pouch Week 3: dorsal aspect of 1st pharyngeal pouch develops laterally toward 1st branchial groove forming tubotympanic recess Week 4-30:middle ear cavity formed, initially filled with mesenchyme; mesenchyme resorbs as endodermal lining develops Birth: middle ear, attic, and additus formed, but mastoid not yet pneumatized 2. Ossicles 1. 1st branchial arch (Meckel's cartilage) gives rise to head of malleus, body and short process of incus, mandible 2. 2nd branchial arch (Reichart's cartilage) gives rise to short process, handle of malleus, long process of incus, and stapes except vestibular portion of footplate 3. Ossification of malleus, incus progresses from 16th to 30th week, while the stapes ossifies during the 18th through 21st week, with further remodeling through the 38th week II. MALFORMATIONS OF THE EXTERNAL AND MIDDLE EAR A. General 1. Although there are no specific relationships between anomalies of the auricle, EAC, and middle ear, the degree of deformity of the auricle is generally proportional to the malformation of the middle ear. 2. Although more severe congenital auricular malformations are always associated with meatal atresia, meatal atresia may be seen with a normal auricle. 3. In congenital aural atresia, must carefully search for other abnormalities, as additional malformations can occur in 56% ; specific syndromes found in 15% . 4. In unilateral atresia, it is not uncommon for the other ear to show less severe malformation (narrow meatus, ossicular chain abnormality). 5. Positive family history can be elicited in 14% . 6. Classifications vary slightly among authors. B. Group I - minor variations in auricle secondary to later developmental stage abnormality 1. Pinna a. Protruding ear -normal shape and size except for: 1) antihelix, helix poorly formed, incompletely developed 2) excessive conchal cartilage 3) increased angle of protrusion -may be unilateral or bilateral -may be associated with hearing loss b. Cup ear 1) deep, concave, cup-shaped concha 2) deficient development of superior half of helix margin 3) decreased height c. Lop ear - 2 forms 1) downward folding of superior pole of pinna lies above Darwin's tubercle, making appearance shorter 2) downward folding occurs below Darwin's tubercle, allowing superior pole to droop over anterior conchal surface d. Macrotia - uncommon; usually well-formed pinna e. Accessory tags 1) occur along line from tragus to corner of mouth (corresponding to juncture of maxillary, mandibular segments) 2) treatment is simple excision f. Preauricular sinuses 1) pits superior to tragus, close to helix 2) usually bilateral 3) more prevalent in dark-skinned races 4) treatment is excision if symptomatic 2. EAC and TM may be normal or hypoplastic; TM is usually thickened and appears opaque 3. Middle ear space may be hypoplastic a. Handle of malleus is most often deformed and in abnormal position b. Incus may also be malformed 4. Inner ear rarely abnormal C. Group II - moderate external and middle ear malformations; represents the majority of ear deformities 1. Pinna - rarely normal a. Microtia of the pinna 1) auricle represented by rudimentary soft tissue, often in anterior, inferior position 2) classified according to degree of deformity a) Type I - different parts of rudimentary auricle still recognizable b) Type II - auricle represented by vertical curving ridge which includes some cartilage and resembles a primitive helix c) Type III - rudimentary soft tissue, usually in anterior, inferior position, no longer resembles any portion of the auricle b. Anotia - usually found in severe, Group III malformations 2. EAC a. Stenosis 1) bony, cartilaginous, or both 2) TM frequently present 3) middle ear usually well developed, but ossicles may be deformed b. Atresia 1) EAC present, but has failed to canalize (true atresia plate) 2) osseous atresia more common than membranous atresia, and is regularly associated with middle ear deformity 3) partial or complete - Cremers subclassifies these as IIA and IIB due to different prognosis 4) mandibular condyle in normal position c. Duplications 1) EAC is normal 2) fistula tract results from incomplete fusion of cleft between 1st and 2nd branchial arches 3) 2 types classified by Work a) Type I i) presents as cystic mass in retroauricular area ii) accessory tract passes anteriorly beneath concha, turning medially to parallel EAC iii) opens deep in bony canal or ME, or ends as a cul-de-sac at level of TM b) Type II i) fistula tract opens externally at angle of mandible ii) tract extends medially and superiorly to open into cartilaginous EAC 4) most significant concern is relationship of fistula tract to facial nerve - highly variable surgical excision must include ID of facial nerve 3. Middle ear a. cellular development of mastoid varies from normal to absent, but usually restricted b. differentiation of antrum directly related to degree of pneumatization c. ossicular malformations regularly encountered in Group II 1) malleus and incus frequently fused or are ankylosed to atresia plate and walls of epitympanic recess 2) wide variation in stapes abnormalities, including suprastructure and footplate d. facial nerve frequently has abnormal course, exiting ME anteriorly into glenoid fossa D. Group III - severe malformation of external, middle ear 1. Pinna - severely malformed or absent(anotia) 2. EAC - aplasia a. tympanic bone and cartilaginous canal fail to develop b. bony plate extends medial to normal position of TM displacing chorda tympani and facial nerve laterally c. mandible articulates with anterior wall of mastoid process d. facial nerve and TMJ are major surgical concerns 3. Middle ear a. mastoid process hypoplastic, little to no pneumatization b. middle ear and antrum may be absent or represented by slit-like lumen c. ossicles severely malformed or absent d. facial nerve anomalies the rule 4. Associated malformations of the inner ear more frequently found 5. Severe cranial malformations associated with this group III. SYNDROMES ASSOCIATED WITH EXTERNAL AND MIDDLE EAR MALFORMATIONS A. Mandibulofacial Dysostosis (Treacher-Collins syndrome) 1. Autosomal dominant inheritance 2. Bilateral, usually symmetrical deformities a. otologic abnormalities a prime feature, including microtia, EAC atresia, hypoplastic ME. Correlation between auricular deformity and middle ear malformation is poor (exception to the rule). b. lower eyelid colobomas, antimongoloid palpebral fissures c. hypoplasia of maxilla, mandible B. Acrofacial Dysostosis (Nager syndrome) 1. Autosomal recessive inheritance suggested 2. Otologic abnormalities similar to Treacher-Collins 3. Preaxial radial upper limb defects C. Hemifacial Microsomia 1. Spectrum of craniofacial malformations with considerable variation of expression 2. Assymetric facies with unilateral abnormalities 3. Malformed or absent auricle, atretic EAC 4. Mandibular hypoplasia, coloboma of upper eyelid D. Goldenhar's Syndrome 1. 1st and 2nd branchial arch abnormality with epibulbar dermoids 2. Preauricular pits or fistulae with mixed or conductive hearing loss 3. Abnormality of vertebral column (hemi-vertebrae) E. Craniofacial Dysostosis (Crouzon's syndrome) 1. Ocular hypertelorism, midface hypoplasia secondary to premature fusion of cranial sutures 2. Associated with severe otologic malformations IV. MANAGEMENT A. General 1. Early determination of cochlear function is the most important consideration as auditory amplification and training should begin as soon as possible (no later than 6 months in a child) 2. Evaluation of all family members important B. Diagnostics 1. Auditory function a. newborn - ABR b. adult - pure tone audiogram, ABR 2. Radiographic anatomy - may postpone until age 2-4 a. mastoid films for aeration, TMJ position b. AP, lateral tomograms c. high resolution CT scan 1) course of facial nerve more easily traced 2) stapes better visualized 3) 105 coronal, 30 axial cuts 3. Delineation of any associated abnormalities C. Surgery 1. Reconstructive surgery indicated only when there is a high probability of lasting success 2. Goal is to give the patient serviceable hearing, with an SRT no greater than 30-35 db 3. Criteria for surgical intervention a. radiographic evidence of a inner ear b. audiometric evidence of cochlear function 4. Surgery is generally reserved for children age 4-6 years with bilateral atresia and above criteria 5. With unilateral atresia, surgery is usually postponed until adulthood, at which time patient can make own decision. Some carefully selected atresia patients are operated on in childhood: a. adequate mastoid pneumatization b. ossicles present c. normal inner ear 6. Pinna vs. middle ear reconstruction priority still debated. Generally individualized to each patient. 7. Technique a. Group I 1) endaural incision with enlargement of EAC 2) establish free mobility of ossicular chain; ossicular repositioning may be needed 3) fenestration may be necessary if oval window not developed b. Group II 1) numerous similar approaches with goal of constructing sound conducting mechanism with impedance matching 2) two approaches to atresia surgery a) antrotomy, delineation of sinodural angle, working anteriorly to identify lateral canal, ossicular mass, oval window; mastoid cavity results b) Jahrsdoerfer uses postauricular incision to identify tympanic bone remnant, then drilling medially through this to identify middle ear. i) incus usually first landmark to ME ii) malleus neck usually fused to atretic plate iii) TM is constructed 1 1/2 times normal size by thinning atretic plate, gently fracturing and removing bony remnants and periosteum iv) assessment of facial nerve, oval and round windows, ossicular mass v) tympanoplasty performed to obtain mobile ossicular chain; facial nerve not displaced unless absolutely necessary; homografts don't work well in atresia surgery vi) if oval window absent, may fenestrate or withdraw vii) temporalis graft fashioned to 1.5x2.0 cm for new TM viii) STSG from abdomen(0.010 in) to line new EAC with center hole to allow migration of thin new layer of squame over fascia for new TM ix) silastic over fascia to prevent blunting, followed by packing which is removed one week postop; no further stenting 3) Results vary, but carefully selected patients with moderate malformation have a reasonably good chance of regaining serviceable hearing. a) Cremers notes a great disparity between results of his Group IIA and IIB atresia patients i) Group IIA: 72% success ii) Group IIB: 22% success b) may support subdivision of this group of patients for surgical selection 4) Complications a) facial nerve paralysis: 2% b) sensorineural hearing loss: 1-2% c) restenosis: 1-2% d) otorrhea: 10-30% e) TMJ injury: 1% c. Group III 1) operative intervention rarely undertaken because of low level of tegmen, lack of mastoid development, anterior lateral sinus, middle ear hypoplasia 2) most authors advocate amplification ------------------------------------------------------------------------- BIBLIOGRAPHY 1. English, G. Otolaryngology Philadelphia, 1985. Harper and Row Volumes 2,4 2. Paparella, M.; Shumrick, O. Otolaryngology Philadelphia, 1980. W.B. Saunders Co. Volume II, pages 1303-1344 3. Congenital Aural Malformations: Diagnosis and Treatment. Otolaryngologic Clinics of North America. Volume 14, No. 1, Feb 1981: pages 83-124 4. Anson, Donaldson. Surgical Anatomy of the Temporal Bone and Ear. 2nd edition, 1973; pages 32-41 5. Cremers, CW, et al. Congenital Aural Atresia. A New Subclassification and Surgical Management. Clin Otolaryngol 1984 Apr; 9(2):119-27 6. Marres, EH, Cremers, CW. Surgical Treatment of Congenital Aural Atresia. Am J Otol 1985 May;6(3):247-9 7. Jahrsdoerfer, RA, et al. High-resolution CT scanning and Auditory Brainstem Response in Congenital Aural Atresia: Patient Selection and Surgical Correlation. Otolaryngol Head Neck Surg 1985 Jun;93(3):292-8 8. Zalzal GH, Cotton, RT, et al. Value of CT scan in the Diagnosis of Temporal Bone Diseases in Children. Laryngoscope 1986 Jan;96(1):27-32 -------------------------------END----------------------------------------