Superior semicircular canal dehiscence simulating otosclerosis

This is a report of a patient with an air-bone gap, thought 10 years ago to be a conductive hearing loss due to otosclerosis and treated with a stapedectomy. It now transpires that the patient actually had a conductive hearing gain due to superior semicircular canal dehiscence. In retrospect for as long as he could remember the patient had experienced cochlear hypersensitivity to bone-conducted sounds so that he could hear his own heart beat and joints move, as well as a tuning fork placed at his ankle. He also had vestibular hypersensitivity to air-conducted sounds with sound-induced eye movements (Tullio phenomenon), pressure-induced nystagmus and low-threshold, high-amplitude vestibular-evoked myogenic potentials. Furthermore some of his acoustic reflexes were preserved even after stapedectomy and two revisions. This case shows that if acoustic reflexes are preserved in a patient with an air-bone gap then the patient needs to be checked for sound- and pressure-induced nystagmus and needs to have vestibular-evoked myogenic potential testing. If there is sound- or pressure-induced nystagmus and if the vestibular-evoked myogenic potentials are also preserved, the problem is most likely in the floor of the middle fossa and not in the middle ear, and the patient needs a high-resolution spiral computed tomography (CT) of the temporal bones to show this.     

Surgical capping of superior semicircular canal dehiscence

Surgical plugging and resurfacing are well established treatments of superior semicircular canal dehiscence, while capping with hydroxyapatite cement has been little discussed in literature. The aim of this study was to prove the efficacy of the capping technique. Charts of patients diagnosed with superior semicircular canal dehiscence were reviewed retrospectively. All patients answered the dizziness handicap inventory, a survey analyzing the impact of their symptoms on their quality of life. Capping of the dehiscent canal was performed via the middle fossa approach in all cases. Ten out of 22 patients diagnosed with superior semicircular canal dehiscence were treated with surgical capping, nine of which were included in this study. No major perioperative complications occurred. In 8 out of 9 (89 %) patients, capping led to a satisfying reduction of the main symptoms. One patient underwent revision surgery 1 year after the initial intervention. Scores in the dizziness handicap inventory were lower in the surgically treated group than in the non-surgically treated group, but results were not statistically significant (P = 0.45). Overall, capping is a safe and efficient alternative to plugging and resurfacing of superior semicircular canal dehiscence.     

Operative management of superior semicircular canal dehiscence

OBJECTIVE: To assess the outcomes of patients undergoing surgical management of superior semicircular canal dehiscence (SSCD). STUDY DESIGN: Retrospective review. METHODS: The medical records of all patients undergoing surgical treatment for SSCD at our institution between 2000 and 2004 were reviewed. RESULTS: Eleven patients underwent unilateral operative management via a middle fossa approach. Ten patients were treated successfully by canal plugging and one unsuccessfully by canal re-roofing. Plugging of SSCD provided resolution of sound- and pressure-induced nystagmus, autophony, and conductive hearing loss (HL). One patient experienced a mild high-frequency sensorineural HL and two patients experienced both a mild high-frequency sensorineural HL and a reduction in vestibular function. Two additional patients underwent exploration for SSCD but were found to have a thin layer of bone overlying the canal. CONCLUSIONS: Plugging of the SSCD, while efficacious in alleviating the symptoms of the disease, may cause loss of labyrinthine function beyond the superior canal.     

上半规管裂综合征的诊断

目的探讨上半规管裂综合征的临床诊断学特点，提高对该病的认识。方法回顾性分析近期诊断的6例上半规管裂综合征患者，总结其临床症状、体征、听力学和影像学特点。结果6例患者中4例患耳表现为低频听力下降，声反射均能引出；1例合并有中耳炎表现为极重度感音神经性听力下降；另1例听力正常。2例次患者有明显的自声增强，不能耐受自己说话的声音。5例次患者有不同程度的眩晕，眩晕持续时间数小时不等，程度不一。2例次患者主诉不能耐受外界噪声。4例次患者利用强声能诱导眩晕。所有患者在强声刺激或增加中耳压力、捏鼻鼓气时能观察到慢相向健侧的垂直旋转性眼球运动，其中1例患者强声刺激能诱发头部运动。所有患者均行颞骨CT检查，并行上半规管重建显示上半规管表面不同程度的骨质缺损。2例患者全身麻醉下行上半规管裂填塞修补术，术后症状明显改善。结论上半规管裂隙综合征的诊断主要依据颞骨高分辨率CT提示上半规管表面覆盖的骨质缺损，同时患者具有相关的前庭耳蜗症状。     

Clinical manifestations of superior semicircular canal dehiscence

OBJECTIVES/HYPOTHESES: To determine the symptoms, signs, and findings on diagnostic tests in patients with clinical manifestations of superior canal dehiscence. To investigate hypotheses about the effects of superior canal dehiscence. To analyze the outcomes in patients who underwent surgical repair of the dehiscence. STUDY DESIGN: Review and analysis of clinical data obtained as a part of the diagnosis and treatment of patients with superior canal dehiscence at a tertiary care referral center. METHODS: Clinical manifestations of superior semicircular canal dehiscence were studied in patients identified with this abnormality over the time period of May 1995 to July 2004. Criteria for inclusion in this series were identification of the dehiscence of bone overlying the superior canal confirmed with a high-resolution temporal bone computed tomography and the presence of at least one sign on physiologic testing indicative of superior canal dehiscence. There were 65 patients who qualified for inclusion in this study on the basis of these criteria. Vestibular manifestations were present in 60 and exclusively auditory manifestations without vestibular symptoms or signs were noted in 5 patients. RESULTS: For the 60 patients with vestibular manifestations, symptoms induced by loud sounds were noted in 54 patients and pressure-induced symptoms (coughing, sneezing, straining) were present in 44. An air-bone on audiometry in these patients with vestibular manifestations measured (mean +/- SD) 19 +/- 14 dB at 250 Hz; 15 +/- 11 dB at 500 Hz; 11 +/- 9 dB at 1,000 Hz; and 4 +/- 6 dB at 2,000 Hz. An air-bone gap 10 dB or greater was present in 70% of ears with superior canal dehiscence tested at 250 Hz, 68% at 500 Hz, 64% at 1,000 Hz, and 21% at 2,000 Hz. Similar audiometric findings were noted in the five patients with exclusively auditory manifestations of dehiscence. The threshold for eliciting vestibular-evoked myogenic potentials from affected ears was (mean +/- SD) 81 +/- 9 dB normal hearing level. The threshold for unaffected ears was 99 +/- 7 dB, and the threshold for control ears was 98 +/- 4 dB. The thresholds in the affected ear were significantly different from both the unaffected ear and normal control thresholds (P < .001 for both comparisons). There was no difference between thresholds in the unaffected ear and normal control (P = .2). There were 20 patients who were debilitated by their symptoms and underwent surgical repair of superior canal dehiscence through a middle cranial fossa approach. Canal plugging was performed in 9 and resurfacing of the canal without plugging of the lumen in 11 patients. Complete resolution of vestibular symptoms and signs was achieved in 8 of the 9 patients after canal plugging and in 7 of the 11 patients after resurfacing. CONCLUSIONS: Superior canal dehiscence causes vestibular and auditory symptoms and signs as a consequence of the third mobile window in the inner ear created by the dehiscence. Surgical repair of the dehiscence can achieve control of the symptoms and signs. Canal plugging achieves long-term control more often than does resurfacing.     

上半规管裂隙综合征一例

MINOR等[1]在1998年首先报道了8例上半规管裂隙综合征患者,是由于上半规管位于中颅窝部位缺乏骨质覆盖。我科最近诊治1例上半规管裂隙综合征患者,报道如下。患者女,54岁,因反复发作眩晕伴左耳听力下降半年于2004年12月就诊。患者半年前因突发眩晕、左耳听力下降在外院诊断为“左耳突发性聋”,行高压氧治疗2个疗程,病情无缓解。患者仍反复发作眩晕,被诊断为梅尼埃病,继续对症治疗,病情仍无缓解,来我科求诊。经仔细询问病史,患者主诉听到高频强声、马路上的助动车声、用力屏气时均可导致眩晕发作,持续时间为30MIN到2H不等。体检发现患者用…     

Wideband acoustic immittance in superior semicircular canal dehiscence

ObjectiveThe apparent effect of superior semicircular canal dehiscence (SSCD) on middle ear- and cochlear impedance has led researchers to investigate the use of wideband acoustic immittance as a screening tool when SSCD is suspected. The purpose of the study was to describe the absorbance characteristics and tympanometric values of ears with confirmed SSCD measured at tympanometric peak pressure (TPP) and at ambient pressure.MethodsWideband Acoustic Immittance was performed at ambient pressure and at TPP on ten participants (12 ears) with confirmed SSCD, as well as on an age- and gender matched control group (12 ears). Inferential statistics were used to determine whether statistical differences existed for the absorbance values at each of the averaged frequencies, the resonance frequency (RF) and tympanometric data between the SSCD and control groups.ResultsThe mean absorbance of the SSCD group reached a maximum at 890.9 Hz and a minimum at 6349.6 Hz. When testing absorbance at TPP, a statistically significant increase/peak in the absorbance values of the SSCD group (compared to those of the control group) was found from 630 to 890.9 Hz and a decrease from 4489.8 to 6349.6 Hz. Similar patterns were observed for absorbance at ambient pressure. A lower mean RF for ears with SSCD as well as an increased mean admittance magnitude (AM) value at RF was found compared to those of the control group.ConclusionThe use of SSCD as a screening tool when SSCD is suspected was strengthened by results similar to those of previous studies. As a result of the significant difference in RF of SSCD ears compared to the RF of the control group, the potential value of measuring the RF of the middle ear to differentiate between mass-and stiffness dominated pathologies, was also illustrated.     

多平面重组技术评价上半规管裂综合征

上明确显示骨壁缺损的分别只有7个和8个,敏感度依次为77.8%和88.9%.另外9个健侧的上半规管在MPR图像上均显示骨壁连续完整,但在横断位和冠状位图像上均有2个显示为骨壁缺损,其特异性均为77.8%.结论 高分辨率CT扫描后行MPR技术的图像在上半规管裂综合征的诊断中较常规的横断位和冠状位图像具有更大的价值.     

An evidenced-based diagnostic tool for superior semicircular canal dehiscence syndrome

Purpose: To construct a symptoms-based prediction tool to assess the likelihood of superior canal dehiscence(SSCD) on high-resolution CT.Materials and methods: Mathematical modeling was employed to predict radiologic evidence of SSCD at a tertiary neurotology referral center.Results: A total of 168 patients were included, of which 118 had imaging-confirmed SSCD. On univariate analysis significant predictors of SSCD presence were: sound/pressure-induced vertigo(p = 0.006),disequilibrium(p = 0.008...     

多平面重组技术评价上半规管裂综合征

上明确显示骨壁缺损的分别只有7个和8个,敏感度依次为77.8%和88.9%.另外9个健侧的上半规管在MPR图像上均显示骨壁连续完整,但在横断位和冠状位图像上均有2个显示为骨壁缺损,其特异性均为77.8%.结论 高分辨率CT扫描后行MPR技术的图像在上半规管裂综合征的诊断中较常规的横断位和冠状位图像具有更大的价值.     

The effect of superior semicircular canal dehiscence on intracochlear sound pressures

Semicircular canal dehiscence (SCD) is a pathological opening in the bony wall of the inner ear that can result in conductive hearing loss. The hearing loss is variable across patients, and the precise mechanism and source of variability are not fully understood. Simultaneous measurements of basal intracochlear sound pressures in scala vestibuli (SV) and scala tympani (ST) enable quantification of the differential pressure across the cochlear partition, the stimulus that excites the cochlear partition. We used intracochlear sound pressure measurements in cadaveric preparations to study the effects of SCD size. Sound-induced pressures in SV and ST, as well as stapes velocity and ear canal pressure were measured simultaneously for various sizes of SCD followed by SCD patching. Our results showed that at low frequencies (<600 Hz), SCD decreased the pressure in both SV and ST, as well as differential pressure, and these effects became more pronounced as dehiscence size was increased. Near 100 Hz, SV decreased by about 10 dB for a 0.5-mm dehiscence and by 20 dB for a 2-mm dehiscence, while ST decreased by about 8 dB for a 0.5-mm dehiscence and by 18 dB for a 2-mm dehiscence. Differential pressure decreased by about 10 dB for a 0.5-mm dehiscence and by about 20 dB for a 2-mm dehiscence at 100 Hz. In some ears, for frequencies above 1 kHz, the smallest pinpoint dehiscence had bigger effects on the differential pressure (10-dB decrease) than larger dehiscences (less than 10-dB decrease), suggesting larger hearing losses in this frequency range. These effects due to SCD were reversible by patching the dehiscence. We also showed that under certain circumstances such as SCD, stapes velocity is not related to how the ear can transduce sound across the cochlear partition because it is not directly related to the differential pressure, emphasizing that certain pathologies cannot be fully assessed by measurements such as stapes velocity.