Prevalence of Radiologic Superior Canal Dehiscence in Normal Ears and Ears with Chronic Otitis Media

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1 The Laryngoscope VC 2013 The American Laryngological, Rhinological and Otological Society, Inc. Prevalence of Radiologic Superior Canal Dehiscence in Normal Ears and Ears with Chronic Otitis Media Young W. Cho, MD; Byoung S. Shim, MD; Ji W. Kim, MD; Tae S. Kim, MD; Joong H. Ahn, MD; Jong W. Chung, MD; Kwang-Sun Lee, MD; Tae H. Yoon, MD; Hong J. Park, MD Objectives/Hypothesis: Although labyrinth fistulae are caused mostly by cholesteatoma, they can occur in longstanding chronic otitis media (COM) without cholesteatoma. We aimed to compare the prevalence of radiologic SCD on computed tomography (CT) between normal ears and contralateral COM ears in patients with unilateral COM and to assess the prevalence of superior canal dehiscence (SCD) according to the age. Study Design: Case series with comparison performed at a tertiary care academic referral center. Methods: We retrospectively reviewed consecutive temporal bone CT scans of 759 patients with unilateral COM between 2009 and The mean (6 standard deviation) age was 48 years (614 years). Images were independently evaluated by two otologists, and the bone overlying the superior canal was characterized as normal, suspicious, or definite SCD. Results: The prevalence (3.4%) of definite SCD in COM ears was significantly higher than that (0.3%) in normal ears. The prevalence (6.6%) of suspicious or definite SCD in COM ears was also higher than that (1.2%) in normal ears. There was no correlation between the prevalence of SCD and age in either normal or COM ears. All of the normal ears with suspicious or definite SCD also showed contralateral suspicious or definite SCD (bilateral involvement). Conclusions: Our present findings suggest that the COM is related to the presence of SCD. The roof of the temporal bone may become thin by the failure of postnatal bone development and susceptible to chronic brain pulsation and pressure exerted by the temporal lobe in COM ears. Key Words: Semicircular canals, dehiscence, chronic otitis media, radiology, computerized tomography. Level of Evidence: 4 Laryngoscope, 124: , 2014 INTRODUCTION Minor et al. first described superior canal dehiscence (SCD) syndrome, which is characterized by vertiginous symptoms induced by loud sounds and hyperacusis. 1 It is not clear whether SCD is a congenital or acquired condition, and it has been reported that developmental anomalies are a possible cause. 2,3 However, it has also been reported that the radiologic prevalence of SCD increases among older age groups, suggesting that SCD is an acquired condition. 3 Recently, it was reported that the mastoid air-cell volume in the SCD side was significantly smaller than the control From the Department of Otolaryngology (Y.W.C., J.W.K., J.H.A., J.W.C., K.-S.L. T.H.Y., H.J.P.), Asan Medical Center, University of Ulsan College of Medicine, Seoul; the Department of Otolaryngology (B.S.S.), Seogwipo Medical Center, Jeju; and the Department of Otolaryngology (T.S.K.), Kangwon National University, Chuncheon, Republic of Korea. Editor s Note: This Manuscript was accepted for publication June 6, This study was supported by a grant ( ) from the Asan Institute for Life Sciences, Seoul, Korea. The authors have no other funding, financial relationships, or conflicts of interest to disclose. Young Wook Cho, MD, and Byoung Soo Shim, MD, contributed equally to this work. Send correspondence to Hong Ju Park, MD, Department of Otolaryngology, Asan Medical Center, University of Ulsan College of Medicine, 86 Asanbyeongwon-gil, Songpa-gu, Seoul, Korea dzness@amc.seoul.kr DOI: /lary group, which suggests that the decreased mastoid pneumatization possibly related to the otitis media is closely related to the generation of SCD. 4 Although labyrinth fistulae are caused almost exclusively by cholesteatoma, they can sometimes occur as a complication of longstanding suppurative chronic otitis media (COM) without cholesteatoma. 5,6 Nevertheless, there have been no previous studies that have investigated the radiologic prevalence of SCD in ears with COM. The aim of our current study was to compare the prevalence of radiologic SCD on computed tomography (CT) between normal ears and ears with COM in patients with unilateral COM, and to assess the prevalence of SCD according to age. MATERIALS AND METHODS Patients We reviewed 924 consecutive cases of mastoidectomy between January 2009 and December All of the patients had COM with/without cholesteatoma and underwent mastoidectomy to eliminate inflammation in the mastoid or to remove cholesteatoma. Of these patients, 165 patients with COM in both ears were excluded, and 759 patients with unilateral COM were included in this study. Contralateral healthy ears showed a normal tympanic membrane, and there was no conductive hearing loss (air-bone gaps < 10 db). Temporal bone CT scans of the 759 patients with unilateral COM were reviewed retrospectively. The mean (6 standard deviations) age of the patients

2 Fig. 1. Classification of the degrees of superior canal dehiscence (SCD) in three consecutive coronal computed tomography images. (A C) Normal: the bone overlying the superior canal is intact. (D F) Suspicious: SCD observed in only one section. (G I) Definite: SCD observed in two or more consecutive sections. Arrows indicate SCD. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] was 48 years (614 years), ranging from 2 to 81 years. The patients consisted of 303 males and 456 females. Temporal Bone CT and Detection of SCD High-resolution temporal bone CT scans were performed using a 64-row detector CT scanner (Siemens Medical Systems, Erlanger, Germany). Images were helically acquired without contrast and were reconstructed using a bone plus algorithm. The axial plane images were acquired using a 0.6-mm-section thickness at 200 ma and kv. The coronal reconstruction image was acquired using 0.4-mm interval reconstructions. All of the images were evaluated on a diagnostic Petavision (Emsoma, Seoul, Korea) picture archiving and communication system. Dehiscence was assessed using coronal interactive reconstruction. This study was reviewed and approved by the institutional review board of Asan Medical Center. All CT images were independently evaluated by two otologists, and the thickness of the bone overlying the superior canal was categorized as either normal, suspicious SCD, or definite SCD (Fig. 1). Normal was defined as having intact bone on the superior canal, suspicious SCD was defined as having suspicious dehiscence in only one coronal section, and definite SCD was defined as having suspicious dehiscence in two or more consecutive coronal sections. Any discrepancies were resolved by consensus. Statistical Analysis Data were analyzed using SAS statistical system version 9.1 (SAS Institute, Cary, NC). Statistical analysis comparing the observed counts between groups was performed using goodness of fit in a Fisher exact test. The radiologic prevalence of SCD was also assessed according to the patient s age. Age was categorized into four groups: 0 to 19 years, 20 to 39 years, 40 to 59 years, and 60 to 81 years. Log-linear regression models were used to estimate trends in prevalence ratios by age. The McNemar test was used to evaluate the association of SCD with contralateral involvement. RESULTS Of the 759 ears with COM analyzed in this study, 26 (3.4%) were identified as having definite SCD, and 747

3 TABLE I. Prevalence of SCD in Ears With COM and Normal Ears (N 5 759). 1 2 P * Definite SCD Ears with COM 26 (3.4%) 733 (96.6%) <.001 Normal ears 2 (0.3%) 757 (99.7%) Suspicious SCD Ears with COM 24 (3.2%) 735 (96.8%).003 Normal ears 7 (0.9%) 752 (99.1%) Definite or suspicious SCD Ears with COM 50 (6.6%) 709 (93.4%) <.001 Normal ears 9 (1.2%) 750 (98.8%) *Fisher exact test. COM 5 chronic otitis media; SCD 5 superior canal dehiscence. two ears (0.3%) out of 759 normal ears were identified as having definite SCD. The ears with COM had a significantly higher prevalence of definite SCD compared to normal ears (P <.001). Twenty-four (3.2%) out of 759 ears with COM were identified as having suspicious SCD, and seven (0.9%) of the 759 normal ears were characterized with suspicious SCD. Ears with COM also had a significantly higher prevalence of suspicious SCD than ears without COM (P 5.003). In terms of the summation of definite or suspicious SCD, the radiologic prevalence of definite or suspicious SCD in normal ears and ears with COM was 1.2% and 6.6%, respectively (P <.001, Table I). There was no discrepancy in determining normal SCD. There was discordance in determining the degrees of SCD in five (8%) of 59 ears with definite or suspicious SCD. Any discrepancies were resolved by consensus. Three patients who were finally decided to have definite SCD were assessed as having suspicious SCD by another examiner, and two patients who were finally decided to have suspicious SCD were assessed as having definite SCD by another examiner. The radiologic prevalence of suspicious or definite SCD was analyzed with respect to age. There was no correlation found between age and suspicious or definite SCD in both normal ears and in ears with COM (P >.05, Table II and Fig. 2). Interestingly, all of the normal ears with definite or suspicious SCD showed contralateral SCD (bilateral involvement). There were two patients with definite SCD in their healthy ears; one patient had definite SCD in both ears, and the other patient had definite SCD in one healthy ear and suspicious SCD in the other ear with COM. In addition, there were seven patients with suspicious SCD in their healthy ears; three patients had definite SCD, and the other four patients had suspicious SCD in the ear with COM. Therefore, there was a significant association found between SCD in normal ears and bilateral involvement (P <.0001, McNemar test, Table II). Of 759 patients, 164 patients were diagnosed with cholesteatoma. Among them, 18 (11%) had lateral semicircular canal fistula, which was in direct contact with the matrix of cholesteatoma. In 595 patients without cholesteatoma, one (0.002%) had lateral semicircular canal fistula, which was associated with soft tissue tympanosclerosis. There was no posterior semicircular canal fistula in COM ears. There was no lateral or posterior semicircular canal fistula in healthy ears. DISCUSSION Ears with COM in our study showed a prevalence of definite SCD (3.4%) and suspicious SCD (3.2%), which was significantly higher than the prevalence (0.3% and 0.9%, respectively) seen in contralateral normal ears. Our present data demonstrate that the presence of COM increased the prevalence of SCD, suggesting that chronic inflammation of the bone may play a role in the generation of SCD in ears with COM. Although labyrinthine fistulae are usually caused by cholesteatoma, with the lateral semicircular canal being the most commonly affected site, fistula could arise in ears with COM without cholesteatoma. 5 7 This suggests that COM might have a role in the development of SCD. Chronic osteomyelitis induces inflammatory processes, leading to compromised vascular channels and the activation of osteoclast activity, which results in bony destruction. 8 However, COM does not seem to be a direct cause of SCD according to our study, because the dehiscence in the ears with COM was found on the roof of superior canal but not in other sites. Because the superior canal is the only site of dehiscence, the role of COM seems to make the roof of the temporal bone susceptible to chronic brain pulsation and pressure exerted by the temporal lobe on the middle cranial fossa. 2,9 There was a report that the radiologic prevalence of SCD among older age groups increases, suggesting that TABLE II. The Prevalence of SCD in Normal Ears and Ears With COM According to Age. Definite SCD Suspicious SCD Definite or Suspicious SCD Age Group, yr Normal Ears COM Ears Normal Ears COM Ears Normal Ears COM Ears 0 19, n (0%) 1 (2.2%) 1 (2.2%) 3 (6.7%) 1 (2.2%)/1 * 4 (8.9%)/1 * 20 39, n (0%) 3 (2.5%) 0 (0%) 3 (2.5%) 0 (0%) 6 (5%)/ , n (0.2%) 17 (3.7%) 5 (1.1%) 11 (2.4%) 6 (1.3%)/6 * 28 (6.1%)/6 * 60, n (0.7%) 5 (3.6%) 1 (0.7%) 7 (5.1%) 2 (1.4%)/2 * 12 (8.8%)/2 * *Number of patients with bilateral SCD. COM 5 chronic otitis media; SCD 5 superior canal dehiscence. 748

4 Fig. 2. The prevalence of definite or suspicious superior canal dehiscence (SCD) in normal ears and ears with chronic otitis media (COM) according to age. There was no correlation found between age and suspicious or definite SCD in either normal ears or ears with COM. SCD is more commonly an acquired rather than a congenital condition. 3 However, we found no significant relationship between the age and the prevalence of SCD, and there was a significant association between SCD in normal ears and bilateral involvement, which is consistent with a congenital or developmental theory. This discrepancy may come from racial differences, or the former study might have included many patients with COM, especially in the elderly. In this study, we investigated the prevalence of radiologic SCD on CT between normal ears and contralateral COM ears in patients with unilateral COM through the same radiologic criteria. How can our findings be used for understanding the relationship between SCD and COM? There has been a report that mastoid volumes of both lesioned and normal ears in patients with unilateral SCD syndrome were significantly smaller than those of controls, 4 suggesting bilateral involvement and the significance of reduced mastoid volume in the generation of SCD. Reduction of mastoid volume was reported in ears with a history of otitis media with or even without middle ear fluid, suggesting that the reduced mastoid volume is genetically programmed (congenital) or developmental by a history of otitis media. 10,11 It has been reported that temporal bone specimens from infants show uniformly thin bone over the superior canal in the middle fossa at birth, with gradual thickening until 3 years of age, 2 and that SCD is not due to cephalic displacement or abnormally rotated orientation of the labyrinth but may arise from the failure of postnatal bone development. 12 All of the patients who were diagnosed with unilateral SCD syndrome had a normal tympanic membrane but decreased mastoid volumes in both ears, 4 suggesting that active inflammation is not directly responsible for the development of SCD, but a history of otitis media can be related to the reduced mastoid volume and the development of SCD. 10,11,13 A histopathological study of a temporal bone in a patient with SCD syndrome reported no osteoclastic process within the otic capsule bone surrounding the dehiscence. 14 It can be assumed that the reduced pneumatization, caused by a history of otitis media in early childhood, caused the roof of the superior canal to be thin enough and susceptible to brain pulsation and pressure to allow SCD to develop in a few normal subjects (0.3% in this study), suggesting a developmental theory. However, there is also a possibility that the temporal bone is congenitally thin, and previous history of otitis media enhances bony susceptibility to brain pulsation and pressure, resulting in SCD in COM ears. CONCLUSION Our findings showed that the presence of COM is closely related to the development of SCD, possibly making the roof of the temporal bone thin and susceptible to chronic brain pulsation and pressure exerted by the temporal lobe. Currently, the pathomechanism of SCD syndrome has not been known. Our findings suggest a hypothesis that SCD syndrome may arise in a few patients with a history of otitis media in early childhood that renders the bone overlying the superior canal to be thin due to the failure of postnatal bone development, 2 which is accompanied by decreased mastoid volume 4,10,11 and is susceptible to brain pulsation or pressure, resulting in the generation of SCD. This is an additional hypothesis to the previous hypothesis that SCD syndrome may arise from a failure of postnatal bone development, and that minor trauma may disrupt thin bone or stable dura over the superior canal. 2 In patients with 749

5 SCD syndrome accompanied by reduced mastoid volume but without any trauma history, our hypothesis can help to explain how SCD develops. BIBLIOGRAPHY 1. Minor LB, Solomon D, Zinreich JS, Zee DS. Sound- and/or pressureinduced vertigo due to bone dehiscence of the superior semicircular canal. Arch Otolaryngol Head Neck Surg 1998;124: Carey JP, Minor LB, Nager GT. Dehiscence or thinning of bone overlying the superior semicircular canal in a temporal bone survey. Arch Otolaryngol Head Neck Surg 2000;126: Nadgir RN, Ozonoff A, Devaiah AK, Halderman AA, Sakai O. Superior semicircular canal dehiscence: congenital or acquired condition? AJNR Am J Neuroradiol 2011;32: Shim BS, Kim CH, Kim TS, et al. Superior canal dehiscence patients have smaller mastoid volume than age and sex-matched otosclerosis and temporal bone fracture patients. Korean J Audiol 2012;16: Grewal DS, Hathiram BT, Dwivedi A, Kumar L, Sheth K, Srivastava S. Labyrinthine fistula: a complication of chronic suppurative otitis media. J Laryngol Otol 2003;117: Jang CH, Merchant SN. Histopathology of labyrinthine fistulae in chronic otitis media with clinical implications. Am J Otol 1997;18: Chole RA. Osteoclasts in chronic otitis media, cholesteatoma, and otosclerosis. Ann Otol Rhinol Laryngol 1988;97: Marriott I, Miller JR, Sahraei M. Therapeutic strategies against inflammation and bone loss associated with osteomyelitis. Curr Opin Investig Drugs 2007;8: Sanna M, Fois P, Russo A, Falcioni M. Management of meningoencephalic herniation of the temporal bone: Personal experience and literature review. Laryngoscope 2009;119: Swarts JD, Foley S, Alper CM, Doyle WJ. Mastoid geometry in a crosssection of humans from infancy through early adulthood with a confirmed history of otitis media. Int J Pediatr Otorhinolaryngol 2012;76: Csakanyi Z, Katona G, Josvai E, Mohos F, Sziklai I. Volume and surface of the mastoid cell system in otitis media with effusion in children: a casecontrol study by three-dimensional reconstruction of computed tomographic images. Otol Neurotol 2011;32: Potyagaylo VL, Della Santina CC, Minor LB, Carey JP. Superior canal dehiscence is not due to cephalic displacement of the labyrinth. Ann N Y Acad Sci 2005;1039: Andreasson L. Correlation of tubal function and volume of mastoid and middle ear space as related to otitis media. Ann Otol Rhinol Laryngol 1976;85: Teixido M, Kung B, Rosowski JJ, Merchant SN. Histopathology of the temporal bone in a case of superior canal dehiscence syndrome. Ann Otol Rhinol Laryngol 2012;121: