Disclosure Congenital Anomalies of the Temporal Bone Author/editor: Elsevier Inc
Caroline D. Robson, MBChB
Department of Radiology Division of Neuroradiology Boston Children’s Hospital Harvard Medical School
Objectives Congenital anomalies of the temporal bone Anatomy Causes • Spectrum of congenital anomalies External auditory canal Environmental causes • Imaging techniques Middle ear space & contents Genetic mutations • Goals of imaging Inner ear structures Chromosomal causes Uncertain cause • Imaging findings & clinical relevance CEMEM: Congenital external & middle
• Highlight important syndromes ear malformation
Clinical Presentation MDCT Physical abnormality 0.625 mm axial images • Craniofacial malformation Reformats • Tags, pits, sinus tracts Axial parallel to hard palate (HP) Coronals perpendicular to HP Parallel to HP • Abnormal ear & ear canal Oblique reformats Short axis oblique • Ocular abnormalities Decreased patient dose Superior SCC • Nasal obstruction Cone beam units
• White forelock External & middle ear anomalies Perpendicular to HP • Other organ system malformations CHL or MHL Congenital cholesteatoma Vestibular aqueduct Hearing impairment SNHL • SNHL, CHL, MHL
MR (3T) Goals of imaging Brain screen • Identify structural causes of HL Axial & oblique sagittal 3D T2 e.g. 3D T2 SPACE • Provide syndromic diagnosis advanced shimming • Guide genetic testing techniques to ↓ artifact Non EPI DWI techniques • Information for parental counseling NO contrast! • Preoperative anatomy & surgical planning FN SVN SNHL (especially CI candidate) Anterior Posterior Is the patient a surgical candidate? CN IVN HL & neurological abnormality Which is the optimal side for CI? Inferior Are there anatomic risk factors?
CEMEM External auditory canal malformations External auditory canal Middle ear space & contents • EAC stenosis • Congenital cholesteatoma • EAC atresia • MEC hypoplasia/anomaly • EAC duplication • Ossicular malformations • EAC dermoid • Oval window stenosis/atresia • EAC 1st BCC • Round window stenosis/atresia • CN7 tympanic & mastoid segment anomalies
Normal EAC stenosis EAC atresia EAC duplication Dermoids
Paradoxical widening of stenotic EAC EAC anomalies
Bright on DWI trace & ADC Erosive EAC opacities Decreased ADC Hole in tympanic plate on DWI DDx cholesteatoma or keratosis obturans Dermoid mimicking BCC MR Interpreted as dermoid
Mural thickening on MR Decreased ADC Hair on exam Unilateral micrognathia Symmetric micrognathia Asymmetric micrognathia on DWI Cartilage on path e.g., HFM e.g., TCS e.g., BOR Dx: Duplicated EAC
Ossicles in congenital external & middle ear malformation Ossicular anomaly with CEMEM Normal IC cone 2 dots 2 dashes
Malformed Rotated Malformed Boomerang Rotated Fused to scutum
Descending CN 7 Normal ventrally displaced http://www.sickkids.ca/images/Research/auditory-science-lab/5123-ossicles.jpg
CEMEM: Windows & CN7 Normal Inner ear malformation
• “Microscopic malformations” • Enlarged vestibular aqueduct (EVA) • Cochlear & cochlear aperture malformations • Malformations of the vestibule • Malformations of the SCC Hypoplastic, opacified MEC; absent recesses • IAC malformations & CN 7 & 8 anomalies Low tegmen mastoideum Atretic oval window; hypoplastic round window Review the windows Anomalous tympanic CN7 along MEC floor & tympanic CN 7 Rudimentary or absent ossicles Enlarged vestibular aqueduct & IP-II anomaly
*
AJNR 2007 28: 1133-38
CONCLUSIONS: Measurements of the vestibular aqueduct can be performed reliably and accurately in the 45° oblique plane. The mean midpoint width was 0.5 mm, with a range of 0.3– 0.9 mm. These may be considered normal measurement values for the vestibular aqueduct midpoint width when measured in the 45° Enlarged vestibular aqueduct oblique plane. Deficient ISS between plump AJNR 2008 29:30-4 In contrast, the flared configuration of the normal vestibular middle & apical cochlear turns (IP-II) aqueduct at the external aperture creates difficulty with defining the Potential risk of Absent modiolus exact point at which a measurement there should be made, and it is * virtually impossible to determine a width perpendicular to the bony CSF leak at Widened cochlear aperture margins without a large degree of uncertainty and very limited cochleotomy Mildly enlarged vestibule & HSCC reproducibility. AJNR 2016 37:1331-37
Large endolymphatic sac on MR Enlarged vestibular aqueduct • Congenital lesion • Delayed onset SNHL • Fluctuating SNHL • Progressive SNHL • Post traumatic SNHL • Dysequilibrium • Familial cases
FN SVN SLC26A4 mutation Anterior Posterior ~27% to 40% CN IVN Pendred syndrome Inferior Non syndromic EVA (DFNB4) Normal Minimal CN hypoplasia Albert S, et al. (2006). "SLC26A4 gene is frequently involved in nonsyndromic hearing impairment with enlarged vestibular aqueduct in Caucasian populations." Eur J Hum Genet 14(6): 773-9.
Cochlear malformations Cochlear malformations • Complete labyrinthine aplasia • Cochlear aplasia • Common cavity malformation • Cochlear hypoplasia • Cystic cochleovestibular anomaly • Incomplete partition type I (IP-I) • Incomplete partition type II (IP-II) • Modiolar deficiency • Cochlear aperture stenosis or atresia CLA (Michel) C aplasia C hypoplasia Single turn IP-I Common cavity malformation & CCVM Cochlear hypoplasia Small, underdeveloped cochlea usually < 2 turns CH type I (small cochlear bud) No modiolus or ISS CH type II (small cystic cochlea) No modiolus or ISS
FN SVN CH type III (small cochlea, < 2 turns) Anterior Posterior CN IVN Shortened modiolus & ISS Inferior
Normal Cochlear nerve likely Cochlear nerve likely hypoplastic or absent hypoplastic or absent
Incomplete partition type I (IP-I) Incomplete partition type II (IP-II), EVA
Potential risk of CSF leak at cochleotomy Normal
Cochlear malformations IAC & cochlear nerve aperture in syndromes with HL • Wide IAC • Stenotic IAC (width < 2mm) Hypoplasia/aplasia CN VIII components • Wide cochlear aperture “Baseball cap” IP-II “Corkscrew” IP-III “Unwound” cochlea C, V, SCC hypo Deficient or absent modiolus & EVA Pendred XLMHL Branchio-oto-renal CHARGE • Stenotic/atretic cochlear aperture Oval window atresia Potential risk of CSF Hypoplasia/aplasia CN VIIIC leak at cochleotomy Anomalous course CN7 Large emissary veins Wide IAC IAC stenosis • NF1 dural ectasia • NF2 vestibular schwannoma • X-linked MHL (boys) • PHACES (unilateral) PHACES Wide cochlear aperture • Deficient or absent modiolus
Widened CNC IAC stenosis; separate CN7 canal
Cochlear aperture Vestibule & Semicircular Canals • Complete labyrinthine aplasia • Hypoplasia of the vestibule • Malformed or absent SCC • Globular vestibule & SCC
Widened CNC Atretic CNC CN aplasia CN aplasia
Vestibule & SCC “Baseball cap” cochlea & EVA/LES
Pendred syndrome Non syndromic EVA (DFNB4) Autosomal recessive SLC26A4 gene mutations, chr 7q22.3 FOXI1, KCNJ10 mutations < frequent
Hypoplastic V Glob SCC Small anlage Large anlage PSCC absent SCC small bone isl anomaly anomaly anomaly CHARGE Trisomy 21 Trisomy 21 Apert Waardenburg
“Corkscrew” cochlea + widened IAC “Unwound cochlea” hypoplastic middle & apical turns Branchio-oto-renal (BOR) syndrome X linked stapes gusher; DFNX2 Autosomal dominant, EYA1 gene, chr 8q13 Transcription factor POU3F4 mutation, chr Xq21.1
Hypoplastic vestibule & SCC Charge syndrome Autosomal dominant CHD7 chromodomain mutations, chr 7q21 Coloboma * Heart defects Atresia choanae * Retardation Genital Ear * * Major criteria
Small LSCC bone island & CNC Posterior SCC anomaly Trisomy 21 Waardenburg syndrome (IV) Alagille syndrome BOR Conclusion Conclusion • Reviewed CEMEM & inner ear malformations Deficiency of the cochlear modiolus • Pathognomonic syndromes • Risk of CSF leak cochleotomy Large vestibular aqueduct • IP-II cochlear anomaly + EVA/LES Flared EVA • X-linked mixed hearing loss PDS & DFNB4 Funnel shaped EVA Stenosis of CN canal BOR • Hypoplasia/absence of CN CHARGE • Failure of cochlear implantation • CHARGE syndrome, trisomy 21