Hearing Outcomes of Transmastoid Plugging for Superior Canal Dehiscence Syndrome by Underwater Endoscopic Surgery: With Special Reference to Transient Bone Conduction Increase in Early Postoperative Period

Superior canal dehiscence syndrome: A review

Superior canal dehiscence syndrome (SCDS) is a vestibular disorder in which the presence of a pathological third window in the labyrinth causes several vestibular and cochlear symptoms. Herein, we review the diagnostic criteria and treatment of SCDS. The cause of SCDS is considered to be congenital or acquired; however, its etiology is not well known. Symptoms: Vertigo and/or oscillopsia induced by loud sounds (Tullio phenomenon) or stimuli that change the middle ear or intracranial pressure (fistula symptoms) with vestibular symptoms and hyperacusis and aural fullness with cochlear symptoms are characteristic clinical complaints of this syndrome. Neurological tests: Vertical-torsional eye movements can be observed when the Tullio phenomenon or fistula symptoms are induced. Conductive hearing loss with both a decrease in the bone conduction threshold at lower frequencies and an increase in the air conduction threshold at lower frequencies may be present on audiometry. Cervical and/or ocular vestibular evoked myogenic potentials are effective in strongly suspecting the presence of a pathologic third window in the labyrinth. Computed tomography (CT) imaging: High-resolution CT findings with multiplanar reconstruction in the plane of the superior semicircular canal consistent with dehiscence indicate SCDS. The Pöschl view along the plane of the superior semicircular canal and the Stenvers view perpendicular to it are recommended as CT imaging conditions. Findings from all three major diagnostic categories (symptoms, neurological tests, and/or CT imaging) are needed to diagnose SCDS. The surgical approaches for SCDS are as follows: the 1) middle cranial fossa approach, 2) transmastoid approach, and 3) round window and oval window reinforcement. Each technique has advantages and disadvantages.

Hearing Results after Transmastoid Superior Semicircular Canal Plugging for Superior Semicircular Canal Dehiscence: A Meta-Analysis

OBJECTIVE

The transmastoid plugging of a superior semicircular canal is considered a safe and effective technique for the management of superior semicircular canal dehiscence (SSCD). The aim of this meta-analysis is to assess the postoperative hearing outcomes after the transmastoid plugging of the superior semicircular canal. Search method and data sources: A systematic database search was performed on the following databases until 30 January 2023: MEDLINE, Embase, Cochrane Library, Web of Science, CINAHL, ICTRP, and clinicaltrials.gov. A systematic literature review and meta-analysis of the pooled data were conducted. We also included a consecutive case series with SCDS for those who underwent transmastoid plugging treatment at our clinic.

RESULTS

We identified 643 citations and examined 358 full abstracts and 88 full manuscripts. A total of 16 studies were eligible for the systematic review and 11 studies for the meta-analysis. Furthermore, 159 ears (152 patients) were included. The postoperative mean air conduction threshold remained unchanged (mean difference, 2.89 dB; 95% CI: -0.05, 5.84 dB, p = 0.58), while the mean bone conduction threshold was significantly worse (mean difference, -3.53 dB; 95% CI, -6.1, -0.95 dB, p = 0.9).

CONCLUSION

The transmastoid plugging technique for superior semicircular canal dehiscence syndrome, although minimally worsening the inner ear threshold, is a safe procedure in terms of hearing preservation and satisfactory symptom relief.

Analysis of postoperative effects of different semicircular canal surgical technique in patients with labyrinthine fistulas

Objective

Different semicircular canal surgery techniques have been used to treat patients with labyrinthine fistulas caused by middle ear cholesteatoma. This study evaluated postoperative hearing and vestibular function after various semicircular canal surgeries.

Materials and methods

In group 1, from January 2008 to December 2014, 29 patients with middle ear cholesteatoma complicated by labyrinthine fistulas were treated with surgery involving covering the fistulas with simple fascia. In group 2, from January 2015 to October 2021, 36 patients with middle ear cholesteatoma complicated by labyrinthine fistulas were included. Cholesteatomas on the surface of type I labyrinthine fistulas were cleaned using the “under water technique” and capped with a “sandwich” composed of fascia, bone meal, and fascia. Cholesteatomas on the surface of type II and III fistulas were cleaned using the “under water technique,” and the labyrinthine fistula was plugged with a “pie” composed of fascia, bone meal, and fascia, and then covered with bone wax.

Results

Some patients with labyrinthine fistulas in group 1 exhibited symptoms of vertigo after surgery. In group 2 Patients with type II labyrinthine fistulas experienced short-term vertigo after semicircular canal occlusion, but no cases of vertigo were reported during long-term follow-up. “sandwich.” In patients with type II labyrinthine fistulas, the semicircular canal occlusion influenced postoperative hearing improvement. However, postoperative patient hearing was still superior to preoperative hearing.

Conclusion

The surface of type I labyrinthine fistulas should be capped by a “sandwich” composed of fascia, bone meal, and fascia. Type II and III labyrinthine fistulas should be plugged with a “pie” composed of fascia, bone meal, and fascia, covered with bone wax.