Lehmann et al. Journal of Medical Case Reports 2011, 5:47 http://www.jmedicalcasereports.com/content/5/1/47 C A S E R E P O R T JOURNAL OF MEDICAL CASE REPORTS Open Access Superior canal dehiscence in a patient with three failed stapedectomy operations for otosclerosis: a case report Martin Lehmann, Jörg Ebmeyer, Tahwinder Upile, Holger H Sudhoff* Abstract Introduction: This case illustrates that superior semicircular canal dehiscence syndrome can be associated with a “pseudo"-conductive hearing loss, a symptom that overlaps with the clinical appearance of otosclerosis. Case presentation: We present the case of a 48-year-old German Caucasian woman presenting with hearing loss on the left side and vertigo. She had undergone three previous stapedectomies for hearing improvement. Reformatted high-resolution computed tomographic scanning and the patient’s history confirmed the diagnosis of concurrent canal dehiscence syndrome. Conclusion: Failure of hearing improvement after otosclerosis surgery may indicate an alternative underlying diagnosis which should be explored by further appropriate evaluation. Introduction Superior semicircular canal dehiscence is an abnormal exposure of the vestibular membranous labyrinth in the middle cranial fossa. Superior semicircular canal dehis- cence syndrome (SCD) occurs when a loss of the bone normally covering the superior semicircular canal in the middle cranial fossa produces one or more of the fol- lowing symptoms: conductive hearing loss, acute pres- sure- and sound-evoked vestibular symptoms and chronic dysequilibrium [1]. The correlation between these symptoms and bony dehiscence of the superior semicircular canal in the floor of the middle cranial fossa was first recognized and described by Minor [2]. Case presentation We present the case of a 48-year-old German Caucasian woman who presented with hearing loss on the left side and vertigo. The patient had a history of three previous stapedectomy operations carried out elsewhere to improve her hearing loss (Figure 1). The first operation was performed for the diagnosis of otosclerosis. The next two operations were performed to improve her persistent hearing loss and vertigo. * Correspondence: holger.sudhoff@rub.de Department of Otolaryngology, Head and Neck Surgery, Bielefeld Academic Teaching Hospital, Münster University, Münster, Germany After the third operation, the patient came to our unit with persistent amblyacousia as well as severe vertigo and headache. Pure tone audiometry showed a maximal conductive hearing loss. The patient located in her left ear the sound of a tuning fork pressed on the right ankle. This phenomenon suggested SCD. Further high- resolution computed tomographic (CT) scans and audiometery were performed. A CT scan revealed super- ior semicircular canal dehiscence (Figure 2). Discussion We hypothesize that the otosclerotic focus in the oval window prevented the development of symptoms from this patient’s SCD. Surgical stapedectomy created a third window and resulted in immediate postoperative imbalance and auditory symptoms. SCD is one of the best documented and most investigated third-window lesions of the inner ear. We posit that patients with persistent audiovestibular symptoms after stapes sur- gery should be examined for the presence of SCD [3]. A combination of high-resolution CT scans and audiometry is recommended for diagnosis. The audio- metric signs of SCD are conductive hearing loss with low-frequency bone conduction threshold better than 0dB(HL) and normal tympanometry with intact acoustic reflexes. © 2011 Lehmann et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.