Cochlear otosclerosis: the current understanding

Role of Radiologic Imaging in Otosclerosis

Purpose of Review

To review the role of imaging in otosclerosis with an emphasis on pre- and post-operative imaging evaluation.

Recent Findings

Pre-operative CT imaging can help define the extent of bone involvement in otosclerosis and may help avoid surgical complications due to variant anatomy or unsuspected alternative causes of conductive hearing loss. In patients with recurrent hearing loss after surgery, CT imaging can clarify prosthesis position and re-assess anatomy.

Summary

CT imaging complements otologic exam and audiometry findings in patients with suspected otosclerosis, for pre-operative planning, and post-operative assessment for patients with recurrent symptoms.

Role of MRI as first-line modality in the detection of previously undiagnosed otosclerosis: a single tertiary institute experience

Background

Otosclerosis causes conductive, sensorineural and mixed hearing loss (CHL, SNHL, MHL) and tinnitus in young adults. It is best diagnosed on high-resolution CT (HRCT). Occasionally, patients presenting with SNHL and/or tinnitus may undergo temporal bone MRI as the first investigation. In this study, we have described the role of MRI as the first-line modality in the detection of previously undiagnosed otosclerosis.

Using search words ‘MRI otosclerosis’ we found 15 cases in the PACS of our institute, (University Hospitals, KU Leuven, Belgium) from 2003 to 2018. Of these, 2 were known cases of otosclerosis, hence excluded from the study. The remaining 13 patients underwent MRI as first-line investigation for unilateral SNHL (8/13), bilateral SNHL (3/13), unilateral MHL (1/13) and bilateral pulsatile tinnitus (1/13). All MRI studies were reported by the same senior radiologist.

Results

Of these 13 cases, 12 were reported as showing MRI features suspicious for otosclerosis. The typical positive findings in these cases were intermediate T1 signal and post-contrast enhancement in the perilabyrinthine/pericochlear regions. Out of 13 patients, 9 underwent subsequent HRCT, confirming otosclerosis in all. The single MRI which was reported as normal initially showed otosclerosis on HRCT. Retrospective evaluation of this MRI study showed subtle positive findings of otosclerosis.

Conclusion

The end point of this study was to validate the subtle findings of otosclerosis on MRI, by comparison to the gold-standard modality HRCT. Our hypothesis is that in the appropriate clinical setting, familiarity with MRI features of otosclerosis would increase the diagnostic ‘catch’ in the first ‘net’ itself i.e. first-line MRI.

Magnetic resonance imaging in the evaluation of clinical treatment of otospongiosis: a pilot study

OBJECTIVES

To evaluate the applicability of magnetic resonance imaging (MRI) as a method for monitoring the activity of otospongiotic lesions before and after clinical treatment.

STUDY DESIGN

Prospective, randomized, controlled, double-blind study.

SETTING

One single tertiary care institution in a large, cosmopolitan city.

METHODS

Twenty-six patients (n = 42 ears) with clinical, audiometric, and tomographic diagnosis of otosclerosis were enrolled. If computed tomography (CT) demonstrated active lesions, these patients underwent MRI to detect otospongiotic foci, seen as areas of gadolinium enhancement. Patients were divided into 3 groups and received treatment with placebo, sodium alendronate, or sodium fluoride for 6 months. After this period, clinical and audiometric evaluations and a second MRI were performed. Each MRI was evaluated by both a neuroradiologist and an otolaryngologist in a subjective (visual) and objective (using specific eFilm Workstation software) manner.

RESULTS

Otospongiosis was most predominantly identified in the region anterior to the oval window, and this site was reliable for comparing pre- and posttreatment scans. The patients in the alendronate and sodium fluoride groups had MRI findings that suggested a decrease in activity of otospongiotic lesions, more relevant in the alendronate group. These findings were statistically significant for both subjective and objective MRI evaluations.

CONCLUSIONS

MRI shows higher sensitivity than clinical or audiometric assessment for detecting reduction in activity of otospongiosis. The objective MRI evaluation based on software analysis was the most accurate method of monitoring clinical treatment response in otospongiosis.

Evolution of otosclerosis to cochlear implantation

INTRODUCTION

Otosclerosis is an osteodystrophy of the labyrinthine capsule producing conductive hearing loss. If the process invades the cochlea, a sensorineural hearing loss usually takes place. The cochlear implant is a good alternative in these patients.

OBJECTIVE

To ascertain the behaviour of cochlear implantation in otosclerosis.

MATERIAL AND METHODS

We reviewed a database of 250 patients that underwent cochlear implantation, performing a retrospective study of 13 patients with clinical, audiological and/or imaging findings of bilateral otosclerosis. The 26 ears were studied as to their natural history, previous surgeries, evolution to profound hearing loss, computed tomography images, complications and functional results.

RESULTS

Of the cases studied, 46% were female and 54% were men, with a mean age of 26 years at the onset of conductive hearing loss. Stapes surgery was performed in 19 ears (73%), with a mean patient age of 29 years, and 53% of them underwent cochlear implantation. Computed tomography results showed that there were signs of different degrees of radiological affectation in 54% of the ears. A total of 3 complications took place (23%): implant failure, overstimulation of the facial nerve and bilateral tinnitus were found. One year after implantation, the average percentages of correct 2-syllable words were 80% and 85% in open sentences.

CONCLUSIONS

Patients having profound bilateral sensorineural hearing loss secondary to otosclerosis obtain great benefit from cochlear implantation.

Imaging Evaluation in Otosclerosis: Single Photon Emission Computed Tomography and Computed Tomography

Objectives:

The aim of our study was to demonstrate the utility of diphosphonate bone single photon emission computed tomography (SPECT) in diagnosing otosclerosis and to correlate the findings from SPECT with age, gender, and sensorineural hearing loss. We also evaluated the ability of high-resolution computed tomography (HR-CT) in detecting otospongiotic and otosclerotic foci and correlated the HR-CT findings with the SPECT results.

Methods:

Seventy-three subjects with surgically confirmed otosclerosis underwent SPECT, and 45 of the 73 patients also underwent HR-CT of the petrous bones.

Results:

In the patient sample examined in this study, SPECT demonstrated a sensitivity of 95.2% and a specificity of about 96.7%. By correlating the SPECT findings, we found an inverse relationship between bone radioactivity and age (ie, greater disease activity in younger patients) and a direct relationship between bone radioactivity and the severity of sensorineural impairment in younger patients. In the 45 patients who also underwent HR-CT, the sensitivity of HR-CT (58%) was lower than that of SPECT, and the comparison between SPECT activity and the HR-CT findings (fenestral or retrofenestral type) demonstrated a statistically significant correlation between the morphological finding of bone demineralization (pericochlear foci) and a high uptake index.

Conclusions:

The use of SPECT seems to be highly effective in differentiating normal from pathological petrous bone. It also provides a quantitative evaluation of disease activity and shows a significant correlation with bone demineralization revealed by HR-CT.

Stimulation of the facial nerve by intracochlear electrodes in otosclerosis: a computer modeling study

HYPOTHESIS

The increased likelihood of facial nerve stimulation (FNS) with cochlear implantation in advanced cochlear otosclerosis is due to a lowering of the facial nerve excitation threshold with increasing bone demineralization.

BACKGROUND

Facial nerve stimulation can complicate cochlear implant fitting, often necessitating the deactivation of certain electrode contacts.

METHODS

High-resolution computed tomographic scans were used to estimate anatomic features of the cochlea and the facial nerve canal. These features were added to a detailed computational model of the implanted human cochlea to examine the consequences of increased conductivity of the bone of the otic capsule. The model took into account the electrode contact type (banded or otherwise) and position (perimodiolar or lateral wall) of the electrode array.

RESULTS

Contrary to the hypothesis, facial nerve thresholds were found to be slightly elevated with increased conductivity of the surrounding bone. However, the threshold and most comfortable loudness levels of the auditory nerve increase more rapidly owing to the reduced current density in the scala tympani as current leaks more easily out of the cochlea. Lateral wall electrodes were predicted to result in an increased likelihood of FNS. A progressively reduced probability of FNS was indicated for the full-band, half-band, and plated electrode arrays, respectively.

CONCLUSION

The clinical observation of increased FNS in cases of cochlear otosclerosis has been demonstrated in a computational model. Rather than decreased FN threshold, it is the increased levels for cochlear stimulation that is the main factor. Particularly, perimodiolar designs with more shielding against lateral spread of current could reduce the likelihood of FNS.

Relationship between CT densitometry with a slice thickness of 0.5 mm and audiometry in otosclerosis

The appropriate cutoff Hounsfield unit (HU) value for the diagnosis of otosclerosis was determined and the correlation between the bone conduction threshold and the findings of computed tomography (CT) densitometry investigated. CT images, 0.5-mm thick, were evaluated in 24 ears with otosclerosis and 19 control ears. Eight regions of interest were set around the otic capsule. The mean HU values in the area anterior to the oval window (A-OW) and anterior to the internal auditory canal (A-IAC) were significantly lower in otosclerosis than in controls. Based on receiver operating characteristic (ROC) analysis, the cutoff HU value in A-OW was determined to be 2,187.3 HU. The mean HU value in retrofenestral otosclerosis was significantly lower in the area A-OW, A-IAC and around the cochlea than in controls. Based on ROC analysis, the cutoff HU value in the latter was determined to be 2,045 HU. A statistically significant correlation was found between the density of the area A-OW and the hearing level at 500 and 1,000 Hz, and between the density of the area around the cochlea and the hearing level at most frequencies. These results suggest the semi-automated diagnosis of otosclerosis may be possible.

Audiovestibular disorders in patients with ankylosing spondylitis

OBJECTIVE

Audiovestibular disorders have been described in several autoimmune diseases but have not been studied in patients with ankylosing spondylitis (AS). The aim of this study was to evaluate the audiovestibular function in patients with AS.

METHODS

We prospectively evaluated 22 consecutive patients with AS. Clinical, radiologic, and immunogenetic features were analyzed. All patients underwent a complete ear, nose, and throat physical examination and audiologic evaluation that included pure-tone audiometry thresholds at octave frequencies of 250 to 8000 Hz, impedance audiometry (tympanogram, static compliance, acoustic reflexes, and reflex decay), and speech audiometry. Thirty-one healthy volunteers and 26 patients with rheumatoid arthritis (RA) were included as controls.

RESULTS

Patients with AS had a median age of 45.5 years (interquartile range [IQR] 38-54) and a median disease duration of 20 years (IQR 12.5-26.2). Otosclerosis was observed in 2 patients with AS (9.1%), 3 patients with RA (11.5%), but not in any healthy controls (P = not significant). Sensorineural hearing loss (SNHL) was observed in 13 patients with AS (59%), 17 patients with RA (65.4%), and 13 healthy controls (41.9%) without statistically significant differences. Because age can influence audiometric results, patients and controls were divided into 4 age groups. A higher frequency of SNHL was observed in patients with AS from 45 to 59 years compared with healthy controls and patients with RA (87% versus 20%, P = 0.03, versus 70%, P = not significant, respectively).

CONCLUSION

Middle-aged patients with AS had a significantly higher frequency of SNHL compared with controls. SNHL should be considered as a possible complication of AS as well as of RA and other autoimmune diseases. Possible toxic effect of nonsteroidal antiinflammatory drugs should also be considered in such patients.

Cochlear implantation in 53 patients with otosclerosis: demographics, computed tomographic scanning, surgery, and complications

OBJECTIVES

To collect data from a large number of cochlear implant recipients with otosclerosis and to make an assessment of these patients' clinical characteristics, computed tomographic scans, surgical findings, and complications, and to quantify the occurrence of postoperative facial nerve stimulation.

STUDY DESIGN

Retrospective multicenter study.

PATIENTS

Fifty-three patients with otosclerosis from four cochlear implant centers in the United Kingdom and The Netherlands were reviewed. Sixty surgical procedures were performed in these patients: 57 devices were placed in 56 ears.

RESULTS

The computed tomographic imaging demonstrated retrofenestral (cochlear) otosclerotic lesions in the majority of patients. Although not statistically significant, the extent of otosclerotic lesions on the computed tomographic scan as categorized in three types tends to be greater in patients with rapidly progressive hearing loss, in patients in whom there is surgically problematic insertion of the electrode array, and in patients with facial nerve stimulation. In four patients, revision surgery had to be performed. Twenty of 53 (38%) patients experienced facial nerve stimulation at various periods postoperatively.

CONCLUSION

Cochlear implant surgery in patients with otosclerosis can be challenging, with a relatively high number of partial insertions and misplacements of the electrode array demanding revision surgery. A very high proportion of patients experienced facial nerve stimulation mainly caused by the distal electrodes. This must be discussed with patients preoperatively.

Otospongiose cochléaire et pseudo-quatrième tour de cochlée

OBJECTIVE

To describe different sequences on magnetic resonance imaging (MRI) in otosclerosis with peri-cochlear involvement.

METHOD

MRI T1 and T2 sequences with T1 gadolinium injection and computed tomography (CT) scans with millimetric slices on axial and coronal views were obtained. The diagnosis of bilateral otosclerosis was confirmed by surgical exploration.

RESULTS

On the CT scan, there was a fourth turn of the cochlea which appeared on the MRI T1 sequence with an intermediate signal and on the T2 sequences with a high intensity signal. After gadolinium injection, there was signal enhancement, suggestive of active otospongiosis. On the CT scan, there was another lesion in front of the cochlea with endosteal involvement. This was no however visible on the MRI, even after gadolinium infusion, in accordance with inactive otospongiosis.

DISCUSSION

We reviewed the literature concerning MRI and results in otosclerosis.

CONCLUSION

MRI of the labyrinth with T1 sequences and gadolinium injection can be contributive to the diagnosis of otosclerosis to differentiate inactive from inactive otospongiosis. However, prospective studies must be conducted to confirm this hypothesis.

[Possible benefits of calcitonin in the treatment of otosclerosis]

This study shows the results obtained after treatment with intranasal calcitonin in 23 patients (36 ears) suffering from otosclerosis. 19.4% showed a hearing improvement upper of 10 dB. The gain was 32 dB in air conduction thresholds and 23 dB. In bone conduction. Tinnitus disappeared in 25% of cases suffering from tinnitus. Calcitonin tolerance was good, 8.7% of patients reported migraine. Authors recommended additional studies in order to evaluate the efficacy of this drug in the treatment of otosclerosis.

MRI of cochlear otosclerosis

Cochlear otosclerosis is an uncommon cause of mixed and sensorineural hearing loss. This has a characteristic appearance on CT, producing a distinctive pericochlear hypodense double ring. However, its appearance on MRI is not as readily appreciated, producing a ring of intermediate signal in the pericochlear and perilabyrinthine regions on T(1) weighted images, demonstrating mild to moderate enhancement after gadolinium administration. Increased signal on T(2) weighted images may also be seen. Recognition of these MRI features is important as MRI may be the first modality of investigation, especially when patients present with symptoms indicative of sensorineural hearing loss. We review four patients who presented with sensoineural hearing loss, and who were imaged with MRI as the first line of investigation.