Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Contemporary workup of the air bone gap - inc.informa
Document related concepts
Transcript
Contemporary workup of the air bone gap Daniel J. Lee, MD, FACS Director, Pediatric Otology and Neurotology Department of Otology and Laryngology Massachusetts Eye and Ear Infirmary Harvard Medical School Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Overview • Case presentation • Diagnostic workup • Differential diagnosis Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Case Presentation • 9 year old male • presented for 2nd opinion for possible congenital stapes fixation • Hearing loss first discovered during school hearing screen Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 case report: 9 y/o otherwise healthy male with hearing loss Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Case Presentation • No history of head trauma • No otalgia, otorrhea, vertigo • BTE aid - left ear • Doing well in school and speaking English and German • Sister and parents hear normally Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Physical Exam • Normocephalic • Normal otoscopy • 512Hz forks - lateralize to left ear • Symmetric facial nerve function Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 • Left conductive HL • Right anacusis • Stable since April 2004 Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Audiologic Testing • LEFT – 96% word discrimination – present OAEs – present acoustic reflexes • RIGHT – anacusis – absent OAEs and reflexes • Normal tympanograms AU • VEMPs Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 VEMP Reflex Arc Inferior Vestibular Nucleus Inferior Vestibular Nerve Saccule Massachusetts Eye and Ear Infirmary Harvard Medical School Lateral (Deiter’s) Nucleus Lateral Vestibulospinal Tract Sternocleidomastoid DJL 2014 VEMP testing Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 VEMP testing • VEMP response requires a normal middle ear and intact saccule/inferior vestibular nerve • does NOT require sensorineural hearing as auditory nerve is bypassed • conditions where VEMP thresholds are elevated or absent: – otitis media – ossicular fixation / otosclerosis – Meniere’s Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 VEMP testing • our 9 year old patient – left - air-bone gap (nl tymps and reflexes) – right - anacusis – VEMP thresholds: left right 250Hz 70 55 Massachusetts Eye and Ear Infirmary Harvard Medical School 500Hz 65 60 1000Hz 70 75 DJL 2014 What is your differential diagnosis? Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Differential diagnosis of air bone gap • • • • • Otitis externa Otitis media TM retraction TM perforation Eustachian tube dysfunction Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Evaluation of air bone gap • • • • • Otoscopy Tuning forks Masked bone conduction Tympanometry Acoustic reflexes Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Differential diagnosis of air bone gap with NORMAL TM • Ossicular fixation – otosclerosis – malleus fixation • Temporal lobe encephalocele Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Temporal lobe encephalocele Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 What about the inner ear and conductive hearing loss? Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Large Vestibular Aqueduct Syndrome (LVAS) • Enlargement of bony canal connecting vestibule to posterior cranial fossa • Contains endolymphatic duct and sac • Normal diameter 0.4 – 1.0 mm – measured midway between external aperture and common crus • When A-P diameter is greater than 1.4 mm the VA is enlarged Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 normal Massachusetts Eye and Ear Infirmary Harvard Medical School LVAS DJL 2014 Features of LVAS • 55% - 94% of cases bilateral • Slight female predominance • < 1/3 have vestibular complaints Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Genetics of LVAS • autosomal recessive • Pendred syndrome gene (PDS) on 7q31 • PDS mutations cause syndromic and nonsyndromic SNHL • LVA seen branchio-oto-renal syndrome, distal renal tubular acidosis and others Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Hearing loss in LVAS • Varies from normal to profound SNHL • 50% have trauma-associated SNHL • Conductive hearing loss? – 17% to 59% Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 case report: 42 y/o female with progressive left-sided hearing loss Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 tymps-nl OAEs-absent (left) reflexes-nl Massachusetts Eye and Ear Infirmary Merchant et al, 2007 Harvard Medical School DJL 2014 Massachusetts Eye and Ear Infirmary Merchant et al, 2007 Harvard Medical School DJL 2014 case report: 29 y/o female with dizziness, hearing loss, and autophony Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Massachusetts Eye and Ear Infirmary Watters et al, 2007 Harvard Medical School DJL 2014 Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 preop Massachusetts Eye and Ear Infirmary Harvard Medical School postop DJL 2014 Superior canal dehiscence (SCD) • Minor, 1998 • Bony defect of superior semicircular canal Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Arcuate eminence defect Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 SCD: air-bone gap • Minor, 2005 • 60 SCD patients • 70% had air-bone gap > 10 dB Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Postoperative closure of AB gap seen in majority of SCD patients N=30 * = p<0.01 * * * Niesten, Lee et al, 2013 Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 “third window” • #1 - Oval window • #2 - Round window • “Third window” – Shunting of acoustic energy to a site of lower impedance Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Merchant et al, 2007 Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Left ear tympanotomy for conductive hearing loss Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Take home message • Not all air-bone gaps with normal otoscopy and normal tympanometry are due to ossicular fixation • Complete audiometric testing for air-bone gap is crucial to avoid unnecessary middle ear surgery • Don’t forget to check tymps and acoustic reflexes! Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 Take home message • CT can rule out a “third window” cause of airbone gap –LVAS –SCD • VEMP testing (if available) is a helpful tool to assess for ossicular mobility and “third window” Massachusetts Eye and Ear Infirmary Harvard Medical School DJL 2014 LVAS Superior Canal dehiscence Massachusetts Eye and Ear Infirmary Harvard Medical School Temporal lobe encephalocele DJL 2014
