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The Laryngoscope C 2011 The American Laryngological, V Rhinological and Otological Society, Inc. Transmastoid Resurfacing of Superior Semicircular Canal Dehiscence Hosam A. Amoodi, MD; Fawaz M. Makki, MD; Michael McNeil, MD; Manohar Bance, MB, MSc, FRCSC Objectives/Hypothesis: To describe a new and fast surgical technique in treating superior semicircular canal dehiscence syndrome by resurfacing the canal defect via the transmastoid approach without retraction of the whole temporal lobe and to demonstrate the clinical and audiologic results of the superior canal dehiscence repair. Superior semicircular canal dehiscence syndrome is a well-described pathology. Surgical procedures through the middle fossa approach to resurface the superior canal and transmastoid plugging are considered the main surgical therapeutic options for patients with debilitating symptoms. Both have drawbacks; plugging is invasive to the inner ear, and resurfacing requires a middle fossa approach. Study Design: Retrospective review. Methods: Four patients presented with classic symptomatic semicircular canal dehiscence syndrome with radiographic confirmation of their dehiscence. The patients underwent the resurfacing procedure with a transmastoid approach. Results: All four patients reported resolution of their symptoms. Audiograms documented some improvement in three subjects. Conclusions: The transmastoid approach for resurfacing superior semicircular canal dehiscence is a safe and less-invasive technique than the standard middle fossa approach, which has many potential complications and requires much longer hospitalization. In our study, the surgeries were completed within 90 minutes, and patients stayed in the hospital only overnight. Key Words: Superior semicircular canal, dehiscence syndrome, resurfacing. Level of Evidence: 4. Laryngoscope, 121:1117–1123, 2011 INTRODUCTION Superior semicircular canal dehiscence (SCCD) syndrome (SCCDS) is a relatively new clinical condition, described by Minor et al. in 1998.1 Patients with this condition may experience episodic vertigo and disequilibrium in response to intense sound (Tullio phenomenon), to changes in pressure in the external ear canal (Hennebert’s sign), or to changes in intracranial or middle ear pressure, along with conductive hearing loss and autophony.2,3 The abnormal communication between the superior semicircular canal and the middle fossa exposes the vestibular system to variations in intracranial pressure and to bone-transmitted sound. This phenomenon results in a so-called ‘‘third window effect,’’ in which acoustic energy is lost and the vestibular system is abnormally stimulated.2,4,5 The incidence of symptomatic SCCD is unknown. Confirming the diagnosis of suspected superior SCCDS requires a combination of audiometric From the Division of Otolaryngology–Head and Neck Surgery, Dalhousie University, Halifax, Nova Scotia, Canada. Editor’s Note: This Manuscript was accepted for publication September 1, 2010. Presented at the 64th Annual Meeting of the Canadian Society of Otolaryngology–Head and Neck Surgery, Niagara Falls, Ontario, Canada, May 23–25, 2010. This work was carried out by all of the authors at Dalhousie University, Halifax, Nova Scotia, Canada. The authors have no funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Hosam A. Amoodi, MD, 10 Northtown Way, Apt 2401, Toronto, M2N 7L4, ON, Canada. E-mail: hosamamodi@ hotmail.com DOI: 10.1002/lary.21398 Laryngoscope 121: May 2011 evaluation, vestibular evoked myogenic potentials (VEMPs), and high-resolution (<1-mm slice thickness) computed tomography (CT) scanning to visualize the dehiscence. Audiometric evaluation in patients with SCCDS usually shows a low-frequency conductive hearing loss with a 5- to 10-db hearing level (HL) air-bone gap that affects two or more frequencies, and in some patients the bone conduction thresholds are lower than 0 db HL. Demonstrating the superior semicircular canal defect by means of high-resolution CT scanning (<1-mm cuts) is the key to diagnosis of this syndrome. Patients with SCCDS have larger VEMP amplitudes and reduced thresholds as compared with non-SCCDS controls,6,7 with both a sensitivity and a specificity of 80%.8 The management of superior SCCDS includes both conservative and surgical approaches. Ideal patients for the conservative approach would be asymptomatic patients or patients with a mild form of the disease who are not affected greatly by their symptoms. Bilateral dysfunction is a challenging clinical problem. In these cases, preservation of vestibular function is as important as hearing. Resurfacing, plugging, or capping of the dehisced canal is effective in alleviating the symptoms and signs associated with SCCDS.1,9 Two main surgical approaches are currently used to address the superior canal bony defect: 1) from above via a middle fossa craniotomy and 2) via the transmastoid approach with direct access to the superior canal. The canal defect is either 1) plugged or occluded or 2) resurfaced. The transmastoid approaches described usually plug the canal, and the middle fossa approaches resurface, but Amoodi et al.: Superior Canal Transmastoid Resurfacing 1117 plugging can also be performed via the middle fossa approach. Canal plugging theoretically carries a higher risk of damage to the vestibular and cochlear structures, because it is more invasive to the labyrinth. On the other hand, resurfacing requires a more invasive and risky approach, via craniotomy and temporal lobe retraction, with the attendant risk of seizure. The transmastoid approach is more familiar to most otologists and has less of the potential major complications including cerebrospinal fluid leak, facial nerve injury, and major intracranial complications. Plugging of the involved canal entails packing the canal lumen with fascia and bone dust to eliminate the flow of endolymph in that canal. Plugging has been performed either through middle fossa3,9–11 or through transmastoid approaches.12 On the other hand, the resurfacing technique involves covering the defect with native tissue (fascia and/or a bone graft) to seal the communication between the labyrinth and brain. Resurfacing through the middle fossa approach has reportedly shown variable success.2,4 Very recently, transmastoid resurfacing similar to our approach has been described in two patients with good results but with short follow-up.13 We believe, however, that this recent report lacks one of the elements that we have found very useful, namely, direct visualization of the dehiscence with a mirror technique. Both plugging and resurfacing techniques have been reported to alleviate symptoms of superior canal dehiscence, in particular the sound- and pressure-induced vertigo. Some authors have suggested that the plugging technique achieves superior results and symptomatic control as compared with the resurfacing technique, but it does carry a higher risk of permanent loss of hearing.14 Canal plugging, through either a middle fossa approach or transmastoid approach, poses a small risk of global vestibular hypofunction in addition to a risk of sensorineural hearing loss.15 Brantberg et al. described transmastoid superior canal occlusion in two patients. Of the two patients, one developed sensorineural hearing loss after the procedure.6 Mikulec et al. described 10 patients who underwent an occlusion procedure of their dehiscence using bone wax; three had mild high-frequency sensorineural loss, and one had a temporary hearing loss that recovered with steroids.3 Minor reported a recurrence of symptoms in four of 11 patients who underwent resurfacing and in one of nine patients treated with canal plugging2 and hence recommended plugging. Friedland and Michel reported on two patients with superior SCCD who experienced a recurrence of their symptoms several months after resurfacing of their dehiscence with a calvarial bone graft and fascia.4 Other reports suggest that middle fossa repair of superior canal dehiscence, in patients who have undergone revision surgery and in those who have undergone previous stapes surgery, carries a higher risk of sensorineural hearing loss, regardless the technique used (resurfacing or plugging).14 Minor reported five cases of superior SCCD managed with either plugging or resurfacing through the middle fossa approach. Three patients who underwent Laryngoscope 121: May 2011 1118 TABLE I. Patient Demographics. Patient No. Age, yr Sex Operated Ear 1 39 Male Right/left 2 3 38 54 Male Female Right Right 4 51 Female Left plugging of the canal had relief of their symptoms. One patient developed a moderate sensorineural hearing loss, and another patient developed signs of generalized vestibular hypofunction with preserved hearing in the operated ear. Two patients underwent resurfacing of the canal with fascia and cortical bone, and one developed vestibular hypofunction after the procedure.9 We describe an approach that combines the advantages of both approaches, that is, fast direct exposure through the familiar transmastoid approach, but with accurate localization and direct visualization of the dehiscence, along with the less-invasive resurfacing rather than canal plugging. We report on four patients (five ears) with superior SCCDS treated with resurfacing of the dehiscence through a transmastoid approach; all patients recovered well, with resolution of their symptoms. All surgeries were completed within 90 minutes, and patients stayed in hospital just one night, mainly because of travel distances. If they had lived closer to the hospital, then they all could have been discharged the same day. MATERIALS AND METHODS This study is a retrospective review of patients who underwent superior SCCD resurfacing surgery with a technique developed at our institution between November 2005 and May 2008 by the senior author (M.B.). All patients underwent a comprehensive neurotologic evaluation, which included audiograms, VEMP testing, and high-resolution CT scanning. We describe four patients who had classic symptoms and findings of SCCDS (Table I shows patient demographics). VEMP testing showed hypersensitive responses in all involved ears (except in patient 3, described later). A high-resolution CT scan clearly confirmed the superior SCCD in all affected ears (bilateral dehiscences in patients 1 and 2). Patient 3 had concurrent middle ear disease. Her audiogram revealed bilateral mixed hearing loss with a 40dB air-bone gap, probably mostly due to her chronic suppurative otitis media. She was the only patient with absent responses on VEMP testing. Patient 4 had undergone previous surgical repair of the dehiscence through the middle fossa approach at a different institution. After 6 months of being symptom free, all her symptoms from before the repair manifested again. All patients underwent surgery to resurface the canal dehiscence via a transmastoid approach. Patient 1 underwent bilateral superior canal resurfacing in a staged procedure 4 months after the first procedure. Surgical Technique Cortical mastoidectomy through a postauricular approach was commenced; general anesthesia was used. In this procedure, after the horizontal semicircular canal has been identified, the otic capsule is outlined, and the origin of the superior semicircular canal from its anterior ampulla usually Amoodi et al.: Superior Canal Transmastoid Resurfacing Fig. 1. Buckingham mirror for lifting and visualizing the dehiscence. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] can be readily seen in these healthy mastoids. The tegmen dehiscence is usually apparent almost immediately on entering the mastoid antrum. The superior canal is gently outlined by drilling away the perilabyrinthine air cells. As attention is turned toward the tegmen, the dehiscence in the tegmen is usually readily and easily seen without the need for drilling on the tegmen, although this area may be clarified by drilling away any overhangs that prevent visualization. We usually try to avoid bone-dust accumulation in the middle ear by using copious irrigation. Once the tegmen dehiscence is identified (it might have to be slightly enlarged to allow access later), a Silastic (Dow Corning, Midland, MI) is placed on the dura, and the dura is lifted by pressure on the Silastic sheet. This action will lift the dura off the superior canal easily, and the sheet is then gently moved over the superior canal to keep the dura raised over this. The sheet allows for upward retraction of the dura with a sucker or elevator for the resurfacing and allows for visualization of the dehiscence. The next step is a key to effective resurfacing and diagnosis. A Buckingham mirror is pressed against the Silastic sheeting and used to raise the dura up, and it allows the defect in the superior canal to be seen easily as a slit. It also allows the extent of the dehiscence to be seen (Fig. 1). Fig. 2. (A) The mirror technique for lifting and visualizing the dehiscence. (B) A piece of fascia placed on top of the dehiscence. (C) A piece of tragal cartilage inserted between the dura and the fascia. (D) Tisseel applied over the repair. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] Laryngoscope 121: May 2011 Amoodi et al.: Superior Canal Transmastoid Resurfacing 1119 Fig. 3. Patient 1. (A) Preoperative audiograms of the right ear. (B) Postoperative audiograms of the right ear. (C) Preoperative audiograms of the left ear. (D) Postoperative audiograms of the left ear. In case 2, we used bone pate harvested previously and mixed with Tisseel (Baxter Biosciences, Vienna, Austria) to pack the lumen of the superior canal from above, without further drilling on the canal, with additional cortical bone chips placed above this. In cases 1 and 3, we used fascia to resurface the canal and then used tragal cartilage cut to a 0.4-mm thickness to cover this and keep the dura away from the canal dehiscence (Fig. 2). We have experimented with cortical calvarial bone, but the rigidity of the bone did not allow it to easily conform to the curved dura in the superior canal region. Once the defect is visualized, resurfacing can commence with either fascia, bone chips, or cartilage. We have moved toward a first layer of fascia, covered by tragal cartilage. The dura traps the fascia and tragal cartilage into place very securely once it is allowed to come back down. The dura is allowed to come back down slowly after removing the Silastic sheet. Finally, another layer of Tisseel is applied over the repair to hold the fascia and the cartilage in Laryngoscope 121: May 2011 1120 place. Layered skin closure is followed by placement of a pressure mastoid dressing. The procedure usually takes between 80 and 90 minutes, including the anesthesia time. RESULTS Follow-up times were 20 and 30 months for patients 1 and 2, respectively, and 4 years for patients 3 and 4. All four patients had almost complete resolution of their superior SCCD symptoms, with all describing greater than 90% improvement in their symptoms on the operated side. Postoperatively, they all had disequilibrium that resolved within a few days (except patient 2). None of them had evidence of sound- or pressure-induced nystagmus or autophony postoperatively. Amoodi et al.: Superior Canal Transmastoid Resurfacing Fig. 4. Patient 3. (A) Preoperative audiograms. (B) Postoperative audiograms. Patient 1 underwent repair of the second side 4 months after the first procedure. Postoperative audiogram showed minimal bilateral air-bone gap in both ears (Fig. 3). He remained asymptomatic at last followup, 20 months after the second procedure. Patient 3 underwent ipsilateral ossiculoplasty in addition to the superior resurfacing procedure. Her postoperative audiogram showed mild worsening of her airbone gap (Fig. 4), most likely from her concomitant middle ear surgery, but she remained asymptomatic for 4 years in regard to the SCCD symptoms. Interestingly, she presented 4 years later with drainage and otalgia, and her mastoid was explored. She was found to have cholesteatoma, which was removed. This is a sequela to her lifelong chronic suppurative otitis media. At this surgery, we were able to examine the superior canal repair, which looked intact and had healed well, in keeping with her lack of SCCD symptoms. Patient 2 had a more complicated postoperative course. He had very large dehiscences bilaterally. In this patient we used bone pate first, before fascia resurfacing; the size of his dehiscence allowed us to pack quite a lot of bone pate into the canal lumen, which was closer to the ampulla than the other dehiscences. Postoperatively, he was off balance and ataxic and developed tinnitus in the operated ear. An urgent audiogram was obtained that showed mild high-frequency sensorineural hearing loss (Fig. 5). This hearing loss recovered with oral steroids except at very high frequency (Fig 5C), but his tinnitus, although much diminished, persisted. He also was found to have complete loss of caloric function on vestibular testing in his right ear. He seemed to recover from his imbalance initially, but over the next year he developed persistent imbalance, which seemed to be related mostly to symptoms from his contralateral ear, with a large dehiscence there; he said it felt like the Laryngoscope 121: May 2011 world was moving with his heartbeat, on mild straining, and on sudden movements. Components of this imbalance are likely related to his unrepaired dehiscence in his left ear, because he is quite clear that he has no further autophony, pulsatile tinnitus, body conducted sound hypersensitivity, or Tullio in his repaired ear. However, he is understandably not keen to undergo surgery that may result in bilateral vestibular loss. It should be noted that this was the only patient who had bone pate used to resurface his canal, and very likely because of his large dehiscence, there would have been closer to a plugging of his canal as the pate entered the inner ear. Patient 4 had transmastoid resurfacing of the dehiscence after the middle fossa approach failed; we were able to salvage the repair. Pre- and postoperative audiograms were within normal limits (Fig. 6). The patient moved out of town, but she remains in regular email contact with the surgeon. She has remained asymptomatic for 4 years after surgery. She is illustrative in that we were clearly able to identify and repair the dehiscence even after a middle fossa approach had failed. DISCUSSION In this study, four patients (five ears) underwent resurfacing of their superior semicircular dehiscence through a transmastoid approach. All procedures were performed by the same surgeon (senior author, M.B.) and were completed within 90 minutes. It should be noted that for most otologists, this would be considered a relatively straightforward procedure, as compared with middle fossa resurfacing or with outlining, blue-lining, and opening the superior canal to plug it. The patients had mild unsteadiness after the procedure but were discharged from the hospital within 24 hours. In fact, most could have been discharged the same day but for the fact that many had significant travel times to reach Amoodi et al.: Superior Canal Transmastoid Resurfacing 1121 Fig. 5. Patient 2. (A) Preoperative audiograms. (B) Postoperative audiograms. (C) Postoperative audiograms after a 1-week course of systemic steroids. their homes from our institution. All of our patients experienced almost complete resolution of their preoperative symptoms, and none has experienced a recurrence of their SCCD symptoms, despite follow-up of up to 4 years in two patients. No patient experienced a serious deterioration in bone-conduction thresholds as a result of the surgery, and all demonstrated improvement in air-conduction thresholds and at least partial closure of the air-bone gap. Patient 2 is instructive. Although there are many reasons why he might have developed vestibular loss and tinnitus, one factor that differentiated him from the other patients was that substantial amounts of bone pate were packed into the lumen, and the lumen in this case was close to the ampulla. Bone pate was used in this patient because of the (perhaps mistaken) belief that his large dehiscence and the severity of his symptoms required a hard and definitive repair, and bone pate was thought to be more likely to be effective than fascia. We do not currently use bone pate directly in the dehiscence. Laryngoscope 121: May 2011 1122 Otherwise, we feel our approach offers the benefits of resurfacing (no further drilling and opening of the otic capsule, no packing into the inner ear) along with the advantages of the transmastoid approach (no middle fossa craniotomy, no temporal lobe elevation, no risk of seizure, rapid surgical time with short hospital stay, positive identification of the defect). In particular, our use of the Buckingham mirror allows us to positively see the defect in the canal and to accurately resurface it. We feel this is a major and key piece of the surgical technique. In middle fossa surgery, there is the risk of movement of grafts when the temporal lobe is allowed to retract, and it may be difficult to positively identify the site of the defect. The use of the transmastoid dural elevation technique described will also allow plugging of the canal through the natural dehiscence, without drilling into the canal for plugging, as described by others. In the one patient in whom this technique was used, vestibular function was lost; for those who believe in plugging, however, this approach saves time blue-lining the canal, saves otic Amoodi et al.: Superior Canal Transmastoid Resurfacing Fig. 6. Patient 4. (A) Preoperative audiograms. (B) Postoperative audiograms. acoustic trauma from drilling on the canal, and allows actual visual confirmation of the bony dehiscence. The one caveat is that small dehiscences on the medial side of the superior canal may be difficult to visualize with the mirror. In place of the mirror, an endoscope may also be used. We have experimented with this method, but at our institution, the smallest endoscope diameter we had available was too large to fit into the crevice between the dura and the superior canal. CONCLUSION This small initial case series highlights an important clinical entity for which optimal treatment has not been established. We report an initial result with a new technique for resurfacing the superior SCCDS through a transmastoid approach, which is well known by all otologists dealing with mastoid diseases. The transmastoid approach is relatively safe and is a less-invasive technique than the standard middle fossa approach, which has many potential complications and requires longer hospitalization. The procedure offers the possibility of preserving the physiologic function of the canal, which is not the case with the occlusion technique. Long-term follow-up will be required to determine whether the improvement obtained remains effective in the long term. Further experience with the transmastoid approach will be needed to determine the pros and cons of this approach and to compare the result obtained with this approach with the results of the other surgical technique currently used. Laryngoscope 121: May 2011 BIBLIOGRAPHY 1. Minor LB, Solomon D, Zinreich JS, Zee DS. 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Outpatient repair of superior semicircular canal dehiscence via the transmastoid approach. Laryngoscope 2009;119:1765–1769. 14. Limb CJ, Carey JP, Srireddy S, Minor LB. Auditory function in patients with surgically treated superior semicircular canal dehiscence. Otol Neurotol 2006;27:969–980. 15. Carey JP, Migliaccio AA, Minor LB. Semicircular canal function before and after surgery for superior canal dehiscence. Otol Neurotol 2007;28: 356–364. Amoodi et al.: Superior Canal Transmastoid Resurfacing 1123