"Third Window" and "Single Window" Effects Impede Surgical Success: Analysis of Retrofenestral Otosclerosis Involving the Internal Auditory Canal or Round Window

Improved Bone Conduction Hearing After Middle Ear Surgery: Investigation of the Improvement Mechanism

OBJECTIVES

When performing middle ear operations, such as ossiculoplasty or stapes surgery, patients and surgeons expect an improvement in air conduction (AC) hearing, but generally not in bone conduction (BC). However, BC improvement has often been observed after surgery, and the present study investigated this phenomenon.

METHODS

We reviewed the preoperative and postoperative surgical outcomes of 583 patients who underwent middle ear surgery. BC improvement was defined as a BC threshold decrease of >15 dB at two or more frequencies. Subjects in group A underwent staged ossiculoplasty after canal wall up mastoidectomy (CWUM), group B underwent staged ossiculoplasty after canal wall down mastoidectomy (CWDM), group C underwent ossiculoplasty only (thus, they had no prior history of CWUM or CWDM), and group D received stapes surgery. We created a hypothetical circuit model to explain this phenomenon.

RESULTS

BC improvement was detected in 12.8% of group A, 9.1% of group B, and 8.5% of group C. The improvement was more pronounced in group D (27.0%). A larger gain in AC hearing was weakly correlated with greater BC improvement (Pearson's r=0.395 in group A, P<0.001; r=0.375 in group B, P<0.001; r=0.296 in group C, P<0.001; r=0.422 in group D, P=0.009). Notably, patients with otosclerosis even experienced postoperative BC improvements as large as 10.0 dB, from a mean value of 30.3 dB (standard error [SE], 3.2) preoperatively to 20.3 dB (SE, 3.2) postoperatively, at 1,000 Hz, as well as an improvement of 9.2 dB at 2,000 Hz, from 37.8 dB (SE, 2.6) to 28.6 dB (SE, 3.1).

CONCLUSION

BC improvement may be explained by a hypothetical circuit model applying the third window theory. Surgeons should keep in mind the possibility of BC improvement when making a management plan.

[A case of obliteration of a round window in otosclerosis]

The article presents a brief review of the literature on the anatomy and physiology of the round window (RW) niche, the causes of occlusion, the diagnosis of this pathology, the features of auditory disorders and tactics when it is detected in patients with otosclerosis (OS). A clinical case of diagnosis and effective surgical treatment for obliteration of RW in a patient with advanced OS, which occurred in 2019 in 0.7% of cases, is described. Removal of RW niche obliteration was carried out with a curette and microcresis by smoothing the canopy over RW until partial visualization of the secondary membrane. It was this stage of the operation that made it possible to restore the normal hydrodynamics of the inner ear fluids and contributed to a functional result. Thus, the diagnosis of RW obliteration in patients with OS is difficult, but possible when using computed tomography of the temporal bones and assessing the mobility of the RW membrane or analyzing changes in hearing at the end of the operation, if it is performed under local anesthesia. The simultaneous performance of stapedoplasty and the removal of bone obliteration of RW makes it possible to safely achieve functional rehabilitation in patients with OS.

Longitudinal analysis of surgical outcome in subjects with pulsatile tinnitus originating from the sigmoid sinus

A dominant sigmoid sinus with either diverticulum or dehiscence (SS-Div/SS-Deh) is a common cause of pulsatile tinnitus (PT). For PT originating from SS-Div/SS-Deh, an etiology-specific and secure reconstruction using firm materials is vital for optimal outcomes. As a follow-up to our previous reports on transmastoid SS resurfacing or reshaping for SS-Div/SS-Deh, this study aimed to evaluate the long-term results of transmastoid resurfacing/reshaping. We retrospectively reviewed 20 PT patients who were diagnosed with SS-Div/SS-Deh, underwent transmastoid resurfacing/reshaping, and were followed up for more than 1 year postoperatively. For PT, immediate and long-term changes (> 1 year) in loudness and annoyance were analyzed using the visual analog scale (VAS). Additionally, pre and postoperative objective measurements of PT using transcanal sound recording and spectro-temporal analysis (TSR-STA), imaging results, and audiological findings were comprehensively analyzed. Significant improvements in PT were sustained or enhanced for > 1 year (median follow-up period: 37 months, range: 12–54 months). On TSR-STA, both peak and root mean square amplitudes decreased after surgery. Also, the average pure-tone threshold at 250 Hz improved after surgery. Thus, our long-term follow-up data confirmed that the surgical management of PT originating from SS-Div/SS-Deh is successful with regard to both objective and subjective measures.

Biomechanics of Third Window Syndrome

Third window syndrome describes a set of vestibular and auditory symptoms that arise when a pathological third mobile window is present in the bony labyrinth of the inner ear. The pathological mobile window (or windows) adds to the oval and round windows, disrupting normal auditory and vestibular function by altering biomechanics of the inner ear. The most commonly occurring third window syndrome arises from superior semicircular canal dehiscence (SSCD), where a section of bone overlying the superior semicircular canal is absent or thinned (near-dehiscence). The presentation of SSCD syndrome is well characterized by clinical audiological and vestibular tests. In this review, we describe how the third compliant window introduced by a SSCD alters the biomechanics of the inner ear and thereby leads to vestibular and auditory symptoms. Understanding the biomechanical origins of SSCD further provides insight into other third window syndromes and the potential of restoring function or reducing symptoms through surgical repair.

Pre-treatment Ongoing Cortical Oscillatory Activity Predicts Improvement of Tinnitus After Partial Peripheral Reafferentation With Hearing Aids

Although hearing aids (HAs) are sometimes efficacious in abating tinnitus, the precise mechanism underlying their effect is unclear and predictors of symptom improvement have not been determined. Here, we examined the correlation between the amount of tinnitus improvement and pre-HA quantitative electroencephalography (qEEG) findings to investigate cortical predictors of improvement after wearing HAs. QEEG data of thirty-three patients with debilitating tinnitus were retrospectively correlated with the percentage improvements in tinnitus handicap inventory and the numerical rating scale scores of tinnitus. Activation of brain areas involved in the default mode network (DMN; inferior parietal lobule, parahippocampus, and posterior cingulate cortex) were found to be a negative predictor of improvement in tinnitus-related distress after wearing HAs. In addition, higher pre-HA cortical power at the medial auditory processing system or higher functional connectivity of the lateral/medial auditory pathway to the DMN was found to serve as a positive prognostic indicator with regard to improvement of tinnitus-related distress. In addition, insufficient activity of the pre-treatment noise canceling system tended to be a negative predictor of tinnitus perception improvement after wearing HAs. The current study may serve as a milestone toward a pre-HAs prediction strategy for tinnitus improvements in subjects with hearing loss and severe tinnitus.

Vestibulocochlear Symptoms Caused by Vertebrobasilar Dolichoectasia

OBJECTIVES

Vertebrobasilar dolichoectasia (VBD), an elongation and distension of vertebrobasilar artery, may present with cranial nerve symptoms due to nerve root compression. The objectives of this study are to summarize vestibulocochlear manifestations in subjects with VBD through a case series and to discuss the needs of thorough oto-neurotologic evaluation in VBD subjects before selecting treatment modalities.

METHODS

Four VBD subjects with vestibulocochlear manifestations were reviewed retrospectively. VBD was confirmed by either brain or internal auditory canal magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA). Patient information, medical history, MRI/MRA findings, and audiometry or vestibular function tests were reviewed according to patient's specific symptom.

RESULTS

Of the four subjects, three presented with ipsilesional sensorineural hearing loss (SNHL), three with paroxysmal recurrent vertigo, and two with typewriter tinnitus. The MRI/MRA of the four subjects revealed unilateral VBD with neurovascular compression of cisternal segment or the brainstem causing displacement, angulation, or deformity of the cranial nerve VII or VIII that corresponded to the symptoms.

CONCLUSION

Vestibulocochlear symptoms such as SNHL, recurrent paroxysmal vertigo, or typewriter tinnitus can be precipitated from a neurovascular compression of the vestibulocochlear nerve by VBD. Because proper medical or surgical treatments may stop the disease progression or improve audio-vestibular symptoms in subjects with VBD, a high index of suspicion and meticulous radiologic evaluation are needed when vestibulocochlear symptoms are not otherwise explainable, and if VBD is confirmed to cause audiovestibular manifestation, a thorough oto-neurotologic evaluation should be performed before initial treatment.

Third Window Syndrome: Surgical Management of Cochlea-Facial Nerve Dehiscence

Objective: This communication is the first assessment of outcomes after surgical repair of cochlea-facial nerve dehiscence (CFD) in a series of patients. Pre- and post-operative quantitative measurement of validated survey instruments, symptoms, diagnostic findings and anonymous video descriptions of symptoms in a cohort of 16 patients with CFD and third window syndrome (TWS) symptoms were systematically studied. Study design: Observational analytic case-control study. Setting: Quaternary referral center. Patients: Group 1 had 8 patients (5 children and 3 adults) with CFD and TWS who underwent surgical management using a previously described round window reinforcement technique. Group 2 had 8 patients (2 children and 6 adults) with CFD who did not have surgical intervention. Interventions: The Dizziness Handicap Inventory (DHI) and Headache Impact Test (HIT-6) were administered pre-operatively and post-operatively. In addition, diagnostic findings of comprehensive audiometry, cervical vestibular evoked myogenic potential (cVEMP) thresholds and electrocochleography (ECoG) were studied. Symptoms before and after surgical intervention were compared. Main outcome measures: Pre- vs. post-operative DHI, HIT-6, and audiometric data were compared statistically. The thresholds and amplitudes for cVEMP in symptomatic ears, ears with cochlea-facial nerve dehiscence and ears without CFD were compared statistically. Results: There was a highly significant improvement in DHI and HIT-6 at pre- vs. post-operative (p < 0.0001 and p < 0.001, respectively). The age range was 12.8-52.9 years at the time of surgery (mean = 24.7 years). There were 6 females and 2 males. All 8 had a history of trauma before the onset of their symptoms. The mean cVEMP threshold was 75 dB nHL (SD 3.8) for the operated ear and 85.7 dB (SD 10.6) for the unoperated ear. In contrast to superior semicircular canal dehiscence, where most ears have abnormal ECoG findings suggestive of endolymphatic hydrops, only 1 of 8 operated CFD ears (1 of 16 ears) had an abnormal ECoG study. Conclusions: Overall there was a marked improvement in DHI, HIT-6 and symptoms post-operatively. Statistically significant reduction in cVEMP thresholds was observed in patients with radiographic evidence of CFD. Surgical management with round window reinforcement in patients with CFD was associated with improved symptoms and outcomes measures.

The Forgotten Second Window: A Pictorial Review of Round Window Pathologies

The round window serves to decompress acoustic energy that enters the cochlea via stapes movement against the oval window. Any inward motion of the oval window via stapes vibration leads to outward motion of the round window. Occlusion of the round window is a cause of conductive hearing loss because it increases the resistance to sound energy and consequently dampens energy propagation. Because the round window niche is not adequately evaluated by otoscopy and may be incompletely exposed during an operation, otologic surgeons may not always correctly identify associated pathology. Thus, radiologists play an essential role in the identification and classification of diseases affecting the round window. The purpose of this review is to highlight the developmental, acquired, neoplastic, and iatrogenic range of pathologies that can be encountered in round window dysfunction.

Beware of a Fragile Footplate: Lessons from Ossiculoplasty in Patients with Ossicular Anomalies Related to Second Pharyngeal Arch Defects

Background and objectives: We review the intraoperative findings and postoperative outcomes of ossiculoplasty in subjects with second pharyngeal arch (SPA)-derived ossicular anomalies. We summarize potential intraoperative complications and recommend precautions that may reduce the risk of fracture. Materials and Methods: Twenty-four patients with SPA-derived ossicular anomalies were included, and pre- and postoperative audiometric results were compared. Results: The mean air conduction threshold (56.0 ± 12.4 dB HL) was significantly improved 1 month (27.6 ± 10.1 dB HL) and 6 months (23.8 ± 13.2 dB HL) after surgery (p < 0.001). The preoperative air–bone gap (ABG) (40.4 ± 7.4 dB HL) was significantly decreased at 1 month (15.1 ± 5.9 dB HL) and 6 months (11.3 ± 8.9 dB HL) postoperation. ABG closure was successful (<20 dB HL) in 21 (87.5%) patients 6 months after surgery. Intraoperative footplate fractures occurred in 3 of 24 patients. The fractures were managed successfully, and the ABG closure was successful in all cases. Conclusions: The stapes footplate is likely to be relatively thin in subjects with SPA-derived ossicular anomalies because the footplate is partially or totally derived from the SPA. Thus, a fragile footplate should be expected, and care is needed when handling the footplate. However, when complications are overcome, the audiological outcomes are excellent in most cases.

Changes in the Resting-State Cortical Oscillatory Activity 6 Months After Modified Tinnitus Retraining Therapy

Although tinnitus retraining therapy (TRT) based on Jastreboff’s classical neurophysiological model is efficacious in most patients, its effects on the cortical activity changes responsible for the improvement of tinnitus are still unclear. In this study, we compared pre- and post-TRT resting-state quantitative electroencephalography (rs-qEEG) findings to identify power changes that could explain TRT-induced improvements. Thirty-seven patients with severe tinnitus were enrolled in the study, and rs-qEEG data recorded before the initial TRT sessions and 6 months after TRT were compared. In addition, associations between the changes in qEEG and percentage improvements in Tinnitus Handicap Inventory (THI) scores and numeric rating scale (NRS) scores of tinnitus loudness and tinnitus perception were examined. The mean THI score decreased significantly 6 months after the initial TRT session. Also, significant improvements were observed 6 months after the initial TRT session compared with the pre-treatment scores in NRS loudness, distress, and perception. As compared with the pre-TRT status, post-TRT 6 months status showed significantly decreased powers in the left primary and secondary auditory cortices for the gamma frequency band. Changes in the alpha 1 frequency band power in the right insula and orbitofrontal cortex (OFC) appeared to be positively correlated with the percentage changes in NRS distress. These results suggested that TRT improved tinnitus-related distress by reducing the power of the top-down autonomic response modulator or peripheral physiological responses to emotional experiences. That is, TRT induced habituation via modulation of functional connections between the auditory system and the limbic and autonomic nervous systems. Our results confer additional basis for understanding the neurophysiological model and the newly suggested integrative model of tinnitus by De Ridder et al. (2014) in the context of the long-term efficacy of TRT.