The symptoms of the patients varied between individuals and included autophony, disequilibrium, ear fullness, hearing loss, oscillopsia, pulsatile tinnitus, tinnitus, and vertigo. Among these symptoms, pulsatile tinnitus (8/10), autophony (7/10), and vertigo (6/10) were the most frequent, followed by hearing loss (5/10) and disequilibrium (5/10) [Table 1]. In addition, the Tüllio phenomenon and Hennebert sign were found in 6 patients. Moreover, an air-bone gap of 10 dB or greater was found in 80% (8/10) of patients by PTA. Normal tympanometry was found in 17 ears, except 3 ears with type Ad by tympanometry (including the left ear in patient No. 1 and two ears in patient No. 5). In addition, VEMP test outcomes were found in nine patient medical records (not found in the record of patient No. 8). There was a significant difference in the VEMP threshold between the affected ears (12 ears) and normal ears (6 ears) (P = 0.005 < 0.05, Mann–Whitney U-test), but not in VEMP amplitude (P = 0.454 > 0.05, Mann–Whitney U-test), indicating that the VEMP threshold in affected ears was lower than that in normal ears, but the VEMP amplitude between them was not significantly different. A similar situation was found in the VEMP threshold (P = 0.042 < 0.05, Mann–Whitney U-test) and amplitude (P = 0.489 > 0.05, normal distribution and equal variance, t-test) of patients with unilateral SSCD.
Unilateral surgery was performed in all of the patients, including 3 patients with bilateral SSCD. In patients with bilateral SSCD, surgery was performed on the side with more severe symptoms which showing lower threshold and greater amplitude in VEMP outcomes; for example, surgery was performed on the left ear in patient No. 3 and the right ear in patient No. 7, but the left ear in patient No. 1 was excluded because of trauma in that ear. After surgery, all of the patients received regular follow-up for 9–56 months [Table 2]. Most of the patients showed complete resolution (4/10) or partial resolution (5/10), except for 1 patient with aggravated bilateral SSCD (patient No. 3; Table 2). In the 5 patients with partial resolution, residual symptoms included mild disequilibrium (3/5), autophony (1/5), and hearing loss (1/5). At the same time, the Tüllio phenomenon and Hennebert sign disappeared in most of the patients except patients No. 3 (both existed) and No. 4 (the Tüllio phenomenon existed).
In addition, there were 5 patients with hearing improvement [Figure 3]. Furthermore, no one had serious complications due to the surgery such as sensorineural hearing loss, facial paralysis, cerebrospinal fluid leakage, and intracranial hypertension.
In the present study, 10 patients underwent the unilateral transmastoid approach for resurfacing the canal defect using the temporalis fascia and autologous bone powders. In addition, most (9/10) of them had complete or partial resolution and avoided pulsatile tinnitus, autophony, vertigo, hearing loss, and severe disequilibrium [Figure 4]. Furthermore, hearing improved in 5 patients after surgery, and none had serious complications. Therefore, the transmastoid approach was proven to be effective and safe for patients with SSCD.
The transmastoid approach for resurfacing the canal defect was applied based on its lower invasiveness and risk of infection compared to the middle cranial fossa approach, and its higher stability and endurance compared to the transcanal approach. In previous studies, the temporalis fascia, tragal cartilage, tragal perichondrium, cortical bone graft, and silicone elastomer were used to resurface the canal defect with most satisfactory outcomes. Here, we first applied a dumpling structure made using autologous bone powder to fill in the middle of the temporalis fascia. In addition, the bone powders were shaped with a medical adhesive to fit the area surrounding the bone dehiscence. This structure had several advantages such as better flexibility than tragal cartilage to prevent shifting, better anti-resorption than tragal perichondrium, and better biocompatibility than silicone elastomer and hydroxyapatite cement.
All of the patients with unilateral SSCD (7/10) had satisfactory outcomes because all or most of the symptoms disappeared after surgery. One patient (patient No. 3) with bilateral SSCD had worsened symptoms after surgery, including autophony, vertigo, pulsatile tinnitus, and tinnitus, but the two other patients with the same condition had good outcomes (patient No. 1 had complete disappearance of symptoms, patient No. 7 had partial disappearance except hearing loss which possibly caused by injury of the inner ear from head trauma). We presumed that the outcomes in patient No. 3 may have been related to the effect of the contralateral SSCD, as well as possible shifting of the dumpling structure or its incorrect application; however, the precise reason remains unknown. Therefore, these results revealed that the surgery was effective for patients with unilateral SSCD while some interfering factors may reduce the effect for those with bilateral SSCD.
The VEMP threshold in the affected ear was lower than that in the normal ear in either all of the patients or those with unilateral SSCD based on statistics, which were in accordance with those from previous studies. However, the VEMP amplitude did not seem to be statistically greater in the affected ear than in the normal ear, possibly affected by muscle tension, head position, age and sample size, although a low VEMP threshold likely indicated SSCD.
The symptoms of SSCD can be classified into vestibular symptoms and hearing function disorders. The former includes vertigo, disequilibrium, oscillopsia, nystagmus, the Tüllio phenomenon, and the Hennebert sign; the latter comprises autophony, hearing loss, pulsatile tinnitus, tinnitus, and ear fullness. In our study, there were 8 patients with both vestibular symptoms and hearing function disorders, excluding 2 patients with only hearing function disorders. Regarding the incidence of symptoms, pulsatile tinnitus (8/10) occurred the most frequently in this group, followed by autophony (7/10), and vertigo (6/10). These results are not in accordance with those from previous studies, and to some extent, demonstrates the various manifestations of SSCD.
One limitation of this study is that we did not know the precise reasons underlying the aggravated symptoms that occurred in 1 patient after resurfacing of the canal defect, because the patient refused further examination. In addition, this retrospective study was only performed in one hospital, which limits the level of evidence. Therefore, a multi-center study on the effect of this surgical technique should be considered in the future.
In conclusion, there are two main manifestations of SSCD, vestibular symptoms and hearing function disorders, but the symptoms are variable. VEMP and computed tomography may help in diagnosing this syndrome. The transmastoid approach for resurfacing the canal defect using the dumpling structure was proven to be effective and safe for patients with unilateral SSCD. However, further studies are needed in those with bilateral SSCD.
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Edited by: Li-Min Chen
Source of Support: This work was supported by the grants from the National Science and Technology Pillar Program during the Twelfth Five-year Plan Period of China (No. 2012BA112B05), from the National Natural Science Foundation of China (No. 81171311), from the Beijing Municipal Commission of Education (No. KZ20110025029), from Capital Medical University of China (No. 13JL03), and from the Research Special Fund for Public Welfare Industry of Health (No. 201202001).
Conflict of Interest: None declared.
Keywords:© 2015 Chinese Medical Association
Autophony; Pulsatile Tinnitus; Resurfacing; Superior Semicircular Canal Dehiscence; Surgical Treatment; Transmastoid Approach; Vestibular Evoked Myogenic Potential