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Bilateral Oval and Round Window Atresia on CT Temporal Bone: a Rare Anomaly Clinically Mimicking Otosclerosis in an Adult

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Bilateral Oval and Round Window Atresia on CT Temporal Bone: a Rare Anomaly Clinically Mimicking Otosclerosis in an Adult Hindawi Case Reports in Radiology Volume 2019, Article ID 7457603, 5 pages https://doi.org/10.1155/2019/7457603 Case Report Bilateral Oval and Round Window Atresia on CT Temporal Bone: A Rare Anomaly Clinically Mimicking Otosclerosis in an Adult Manzoor Ahmed ,1 Yogesh Indrasen More,2 and Shaik Irfan Basha2 1Department of Radiology, Sheikh Khalifa Medical City, Abu Dhabi, UAE 2Department of ENT Surgery, Sheikh Khalifa Medical City, Abu Dhabi, UAE Correspondence should be addressed to Manzoor Ahmed; [email protected] Received 11 July 2019; Accepted 15 November 2019; Published 27 December 2019 Academic Editor: Daniel P. Link Copyright © 2019 Manzoor Ahmed et al. ­is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We present a rare adult case of bilateral oval and round window atresia. Clinical and audiologic ndings were suggestive of otosclerosis. High resolution CT Temporal bones showed unequivocal ndings of bilateral oval and round window atresia. Atresia of these windows is a rare temporal bone anomaly. Presentation as an adult can confound the clinicians and warranting a closer look on the CT for atretic windows and subtle signs of otosclerosis in patients with conductive hearing loss. 1. Introduction called subtle ndings warrant closer look and quality HR CT T-Bone study with standard reconstructions. Isolated oval window atresia (OWA) is a rare middle ear tem- Round window atresia (RWA) is even more rare than poral bone congenital anomaly. Multiple earlier reports have OWA with few case reports [7–10]. ­e nding can be even been surgical [1–3]. OWA can be conrmed on high resolution overlooked on surgery. Conductive hearing loss due to RWA (HR) CT temporal bone (CT T-Bone). Usually there are asso- is theoretically related to no pressure release mechanism for ciated middle ear ndings like inferio-medial course of the inner ear ¢uid displaced by the stapes footplate and even total facial nerve (covering the site of oval window) and malformed conductive hearing loss can be expected [10]. Isolated and or displaced incus and stapes [1, 4, 5]. About 40% of the cases nonsyndromic RWA is extremely rare with hearing tests are bilateral [6]. mimicking otosclerosis [9]. Unlike the oval window, normal ­e oval window is a small oval-shaped normal bony round window can be easily identied on routine angular defect or window designed for the stapes foot-plate at the reconstructed images of the HR CT T-Bone with a pocket or medial wall of the middle ear opening into the vestibule cave of air in the middle ear as a landmark for identication (Figure 1). ­e lateral adjacent important and reference struc- on axial images (Figure 1). tures include crura of the stapes and tympanic segment of the We report here a rare case of an adult, clinically presenting facial nerve. Ironically, presence and identication of this nor- as otosclerosis until HR CT T-Bone was performed showing bilateral both oval and round window atresia. ­is is an mal oval defect can be more subtle than vice versa. Atresia of the oval window can still be an easily over-looked nding on extremely rare case report [11] with unequivocal manifestation the CT T-Bone in a patient with conductive hearing loss. ­e of the bilateral OWA and RWA on HR CT T-Bone imaging. expected nding is a band of bone instead of a window. On the same lines, there are also few other subtle and signicant 2. Case Report not infrequently overlooked ndings on HR CT T-Bone e.g. Congenital or acquired bony dehiscence, Ossicular focal ero- A 30-year-old female was referred for hearing loss. She pre- sions like focal lenticular process uncal erosion, ante-fenestral sented with long-standing bilateral hearing loss. On further otosclerosis, anomalous facial nerve course, etc. All these so enquiry, the patient mentioned of having hearing loss since 2 Case Reports in Radiology (a) (b) (c) F§¨©ª« 1: High resolution CT Temporal bone axial ((a) and (b)) and coronal oblique (Pöschl’s view) imaging showing faintly visualized normal oval window defect (long arrow, (a)) with horse-shoe like stapedial crura visible in the vicinity (short arrow, (a)). Normal round window niche is marked by a small pocket of air (arrow, (b)). Both oval (long arrow, (c)) and round windows (short arrow, (c)) are well demonstrated in the same image on Pöschl’s view (c). 125 250 500 1K 2K 4K 8K 125 250 500 1K 2K 4K 8K –10 –10 0 0 10 10 20 20 30 30 40 40 50 50 vel (dB HL) 60 vel (dB HL) 60 ing la 70 ing la 70 ar ar 80 80 He He 90 90 100 100 110 110 120 120 Frequency (Hz) 750 1.5K 3K 6K 12K Frequency (Hz) 750 1.5K 3K 6K 12K AC PTA 92 dB BC PTA 30 dB SII 0% AC PTA 88 dB BC PTA 28 dB SII 0% (a) (b) F§¨©ª« 2: Pure tone audiometry (PTA) of le¦ ear (a) and right ear (b) showing bilateral severe conductive hearing loss. Note bilateral intact unmasked bone conduction (BC) (marked by arrowheads) and profound ¢at air conduction (AC) loss (marked by X for le¦ and circle for right ear) across all frequencies resulting in signicant air-bone conduction (ABC) gap. childhood and has been regularly using hearing-aids. She did le¦. Tympanometry and stapedial re¢ex was within normal not have any signicant history of ear infections or ear trauma. limits for both ears. She denied any signicant past medical, surgical or family Based on clinical and audiology assessment, we suspected history. Clinical assessment shows bilateral normal ear canals, middle ear-ossicular chain pathology, most probably otoscle- both sides tympanic membranes were within normal limits. rosis given the chronologic age of the patient. Patient under- Hearing assessment performed in our department showed went High Resolution CT Temporal Bone (HR CT T-Bone) a conductive hearing loss in both ears. Bone conduction (BC) imaging mainly to conrm otosclerosis. CT showed the fol- in both ears almost normal with a dip at 2 KHz frequency. Air lowing ndings on both the right and le¦ temporal bones: conduction (AC) and air-bone gap was abnormal. ­ere was a large air-bone gap of 60 dB (AC 88 dB and BC 28 dB) in the (a) Absence of round windows (Figure 3(a), arrows) with right ear while 62 dB (AC 92 dB and BC 30 dB) in the le¦ ear sclerotic bone and adjacent posterior mesotympanic (Figure 2). Speech reception was 90 dB in right and 85 dB in dysmorphism with atretic sinus tympani. Case Reports in Radiology 3 (a) (b) (c) F§¨©ª« 3: (a) High resolution axial CT Temporal bone images at the level of round window (a), stapes and oval window (b), and tympanic facial nerve (c). Absence of bilateral round ((a), dark arrows) and oval windows ((b), dark arrows) with tympanic facial nerve covering the site of oval window (C, arrows). Stapedial anomalies present with aplastic crura on the right and nearly intact le¦ stapes except hypoplastic anterior crus (white arrows, (b)). Note skull base dysmorphism with abnormal orientation of internal auditory canal (IAC) and kissing carotid canals (marked as C in Figures 3(a)–3(c)). ­e patient has normal speech development while cur- rently her speech reception thresholds (SRT) are about 90 dB which is classied as profound hearing loss, this fact explains the progressive nature of this condition. Patient opted for hear- ing aids. Currently the patient is rehabilitated with high power hearing aids and coping well due to well preserved cochlea. F§¨©ª« 4: Coronal high resolution CT Temporal bone image showing bilateral dehiscent tympanic segments of facial nerve (arrows), 3. Discussion abutting the lateral wall of the bony labyrinth due to its inferio-medial anomalous course. We presented a rare adult case of bilateral oval and round window atresia presenting clinically as a case suggestive of otosclerosis. ­e case underscores the utility of HR CT T-Bone (b) Absence of oval window (Figure 3(b), dark arrows) as a crucial preoperative aid in identication of atretic oval with retained thick bony plate without a defect into window as well as the rarer coexisting nding of round win- the vestibule. Note aplastic crura of the stapes on the dow atresia. ­is case will fall under Class 4 congenital middle right and relatively well developed stapes on the le¦ ear anomalies. side except the hypoplastic anterior crus (Figure 3(b), A classication system was developed by Teunissen and white arrows). Cremers [12] to analyze the ndings. Class 1 comprises ears (c) Tympanic facial nerve anterio-medial positioning cov- with congenital isolated stapes ankylosis. Class 2 comprises ering the site of the oval window (Figure 3, arrows) as ears with congenital stapes ankylosis in combination with a well as showing dehiscence (Figure 4, arrows) congenital anomaly of the ossicular chain. Class 3 comprises (d) Skull base dysmorphism with near-sagittal orienta- ears with congenital anomalies of the ossicular chain and at tion of the internal auditory canal (IAC) and kissing least a mobile stapes footplate. Class 4 comprises ears with carotid canals (annotated with C in Figures 3(a)–3(c)). aplasia or severe dysplasia of the oval window or round (e) No HR-CT evidence of even subtle changes of the window. ­is warrants us to understand the embryologic basis ante-fenestral and or the peri-cochlear otosclerosis. of oval and round window atresia. 4 Case Reports in Radiology ­e embryologic development of the oval window is closely related to the development of the second branchial arch structures in about 5th–7th-week of development.
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