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. 2013 Oct;34(8):1421-8.
doi: 10.1097/MAO.0b013e318287efe6.

Near-dehiscence: clinical findings in patients with thin bone over the superior semicircular canal

Bryan K Ward  1 , Angela Wenzel, Eva K Ritzl, Sergio Gutierrez-Hernandez, Charles C Della Santina, Lloyd B Minor, John P Carey
Affiliations

Near-dehiscence: clinical findings in patients with thin bone over the superior semicircular canal

Bryan K Ward et al. Otol Neurotol. 2013 Oct.

Abstract

Objective: To determine whether patients with thin bone over the superior semicircular canal can develop signs or symptoms of superior canal dehiscence syndrome (SCDS).

Study design: Retrospective case series.

Setting: Tertiary referral center.

Patients: All patients from our institution found to have thin but not frankly dehiscent bone over the superior canal despite symptoms and signs of SCDS.

Main outcome measures: Preoperative CT imaging, symptoms, audiometry, vestibular evoked myogenic potentials (VEMP), and intraoperative electrocochleography (ECochG) results were reviewed. Symptoms were assessed at least 1 month postoperatively in all patients, and postoperative physiologic data are presented when available.

Results: Ten patients (11 ears) had thin bone over the superior semicircular canal at surgery. All presented with autophony or sound- and/or pressure-induced vertigo, in addition to at least 1 physiologic measure consistent with SCDS. CT imaging was read as showing either dehiscence (36%) or marked thinning of bone overlying the affected canal (64%). Preoperative median low-frequency air-bone gap (ABG) was elevated (10.9 dB; interquartile range [IQR], 8.8-12.5), with 4 patients demonstrating negative bone conduction thresholds. Patients had elevated oVEMP amplitude (median, 20.7; IQR, 6.7-22.1) μV and ECochG SP/AP ratios (median, 0.59; IQR, 0.54-0.67). Postoperative ABG and SP/AP ratio decreased significantly compared with preoperative values (p < 0.05), and all patients reported symptomatic improvement.

Conclusion: Symptoms typical of SCDS can occur in cases with thin but not dehiscent bone. Surgical plugging or resurfacing can reduce symptoms in such cases.

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Figures

Figure 1
Figure 1
Example of CT imaging and intraoperative findings of left near dehiscence (figure A) and case of overt 2-mm left superior canal dehiscence (figure B). CT images show reformation in plane parallel to the superior semicircular canal and orthogonal to it. Arrows point to location of thin bone or dehiscence. Intraoperative microscopic views of dehiscence or near dehiscence are shown in the right panels. Photoshop filtering used to adjust blue content of entire intraoperative picture of near dehiscence to accentuate the blue-lining seen by eye at surgery.
See this image and copyright information in PMC

References

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