Radiologic diagnosis of cochlear otosclerosis

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.

Involvement of the Internal Auditory Canal in Subjects With Cochlear Otosclerosis: A Less Acknowledged Third Window That Affects Surgical Outcome

OBJECTIVE

To investigate the effects of cavitating lesions involving the internal auditory canal (IAC) in subjects with cochlear otosclerosis with regard to poststapedotomy hearing outcome.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral center.

PATIENTS

A retrospective chart review of 134 subjects with otosclerosis treated from January 2011 to June 2017 at Seoul National University Bundang Hospital was conducted. Sixteen subjects (23 ears) with temporal bone computed tomography (TBCT)-confirmed cochlear otosclerosis who underwent stapedotomy were included in the study.

MAIN OUTCOME MEASURES

Pure tone audiometry (PTA) (i.e., air and bone conduction; AC and BC, respectively) thresholds and air-bone gap (ABG), measured at 6 months postoperatively were compared between cochlear otosclerosis with and without IAC involvement (IAC group and non-IAC group, respectively).

RESULTS

A total of 14 of 23 ears showed involvement of the IAC. There were no significant differences in age, side of otosclerosis, or preoperative hearing threshold between the two groups. The mean postoperative AC and BC thresholds and ABG of the IAC group were significantly poorer (45.7 dB, 33.8 dB, and 11.8 dB, respectively) than those of the nonIAC group (24.1 dB, 20.0 dB, and 4.1 dB, respectively).

CONCLUSIONS

Cochlear otosclerosis with cavitating lesions involving the IAC showed significantly poorer postoperative audiological outcomes than those without any cavitating lesion. Cavitation extending to the IAC may act as a third window providing a route for sound energy shunting, and thus precluding successful hearing outcome in some subjects with cavitating otosclerosis after stapedotomy.

Obliquity of the Stapes in Otosclerosis: A New Radiological Sign

Introduction Observing the obliquity of stapes by closely scrutinizing the HRCT temporal bone in otosclerosis revealed a reliable and consistent finding. This finding can add to the existing radiological criteria in diagnosis of otosclerosis.

Objective The objective of this study is to establish the obliquity of stapes in otosclerosis by radiological measurements using HRCT temporal bone by comparing: (a) the distance between the horizontal (tympanic) segment of facial nerve and stapes head in otosclerotic ears (study group) with non-otosclerotic ears (control group); and (b) the angle subtended by stapes with promontory in the study and control groups.

Methods This is a prospective study performed after the institutional Ethics Committee clearance (IEC 3/2013).

Results An increased mean distance between the horizontal segment of facial nerve and stapes head in otosclerotic patients (i.e., 2.49mm +/− 0.24mm SD), when compared with the non-otosclerotic patients (i.e., 1.46mm +/− 0.16mm SD) is noted. There is a change in angle (i.e., 64.550 +/− 7.190 SD) subtended by the stapes toward the promontory in otosclerotic ears when compared with that of controls (i.e., 99.700 +/− 40 SD). We applied the Mann-Whitney U non-parametric test and considered p value of < 0.0001 highly significant.

Conclusions Obliquity of stapes in otosclerosis referred to as a “Pisa” sign by the senior author has diagnostic value as a new radiological sign in imaging of otosclerosis. This obliquity explains the torsional effect of otosclerosis on the ossicular chain. The findings correlate with late complications and failures in stapes surgery.

Obliquity of the stapes in otosclerosis: intra-operative observations and implications in stapes surgery

OBJECTIVE

To establish the prevalence of stapes obliquity as observed in otosclerosis patients during stapes surgery by a simple method of intra-operative measurement.

DESIGN

Prospective observational study.

RESULTS

Intra-operative measurements showed that the mean distance (± standard deviation) between the horizontal segment of the facial nerve and stapes crura in 10 cases of otosclerosis was 0.74 mm (± 0.21 mm), whereas in 10 cases of non-otosclerosis the same distance was 0.20 mm (± 0.00). There was no gap (0 mm) between the stapes crura and inferior border of the oval window niche in otosclerotic ears, whereas in non-otosclerotic ears the same distance was 0.13 mm (± 0.05 mm). The differences were statistically significant (p < 0.0001).

CONCLUSION

Obliquity and downward displacement of the stapes occurs in otosclerosis. It has diagnostic value as a new clinical sign in otosclerosis. The findings correlate with late complications and failures in stapes surgery. Methods to avoid these have been suggested.

Meniere's Syndrome: An Approach to Therapy

There are patients with symptoms similar to those of Meniere's disease who do not have Meniere's disease and therefore do not respond to conventional medical or conservative surgical management. Some have subtle disorders of carbohydrate and lipid metabolism and inner ear otosclerosis, which are responsible for the production of their symptoms. The response to dietary therapy confirms that glucose tolerance levels which are not diabetic nor hypoglycemic may be sufficiently significant in relation to inner ear function to produce the symptoms like those of Meniere's Disease. Management of inner ear otosclerosis with supplemental sodium fluoride, calcium carbonate, and Vitamin D was also effective in controlling the symptoms in some patients.

Radiographically confirmed cochlear otospongiosis among the Chinese

A high-resolution computed tomography (HRCT) study on 55 patients with surgically confirmed clinical otosclerosis confirms the existence of cochlear otospongiosis among the Chinese. Positive radiographic results of cochlear otospongiosis (13 ears, 12%) were found in patients with mixed-type deafness but in none with conductive hearing loss. Although there is a positive correlation between audiologic and radiographic findings, the HRCT results showed a lower positive rate and less severity than anticipated from the audiologic results. However, compared with the occurrence and extension of radiographic findings in similar studies of white people, it would seem to support our previous contention that the disease is indeed milder in Chinese people. Cochlear otospongiosis with extensive labyrinthine demineralization was found in three young patients with rapidly progressive hearing loss. This is important evidence of the overlooked fact that cochlear otospongiosis may also be one of the causes of sensorineural hearing loss in the Chinese. Thus, a high index of suspicion of the existence of this inner ear disorder is of paramount importance, and in such cases an HRCT study should be performed and sodium fluoride given to prevent further hearing deterioration.

Computed tomography in the diagnosis of cochlear otosclerosis

Twelve patients with surgically proven otosclerosis and sensorineural hearing loss were studied with high-resolution computed tomography (CT). The purpose was to identify abnormal bony changes that could be diagnostic of cochlear otosclerosis. Of the 24 temporal bones thus studied, 10 showed positive findings. The findings in our study--as well as those of others--show a pericochlear zone of radiolucency. The precise origin of this is undetermined.

Otosclerosis-past and present

Images

Sensorineural impairment in unilateral otosclerosis

Audiometric findings were evaluated in a group of patients with clinical unilateral otosclerosis. A comparison was made between bone conduction threshold in the better hearing ear and the ear with the mixed hearing loss. Over 50% of the patients had a significant elevation in the bone conduction thresholds in the ear with clinical otosclerosis as compared to the uninvolved ear. A pair of temporal bones from a patient with unilateral otosclerosis and unilateral mixed hearing loss is presented.

Ten years experience with fluoride in otosclerotic (otospongiotic) patients

Moderate dosage of sodium fluoride (NaF) (40 to 60 mg daily) has been used for ten years in more than 4,000 patients with active otospongiosis of the cochlear capsule. Initially the indication for this therapy was a positive Schwartze sign in a patient with progressive sensorineural impairment after successful fenestration or stapes surgery. Beginning in 1965 positive polytomographic evidence of a demineralized focus in the cochlear capsule has been the indication. Of the more than 4,000 patients that have received this treatment half were in Chicago and half in Beziers, France, the treatment lasting from one to as long as eight years in a few cases. Stabilization of the sensorineural component of loss, recalcification of the focus by polytomography and fading of a positive Schwartze sign are evidences of a favorable result. The results in surgically confirmed stapedial fixation otospongiosis and in pure cochlear otospongiosis are fairly uniform and consistent in the patients treated in Beziers and those treated in Chicago. A few patients have experienced a slight but significant recovery of sensorineural hearing. About 80% show stabilization of the sensorineural component of loss, while the remainder continue to show slow progression in the sensorineural loss. A smaller control group of cases that for one reason or another did not receive the medication show that progression in the sensorineural loss occurred in a much higher percentage than in the treated cases. Of interest were cases initially stabilized after fluoride therapy with improved appearance of the cochlear capsule by polytomography. The fluoride was then stopped, with reactivation of the focus two to seven years later as demonstrated by polytomography, resumption of the sensorineural progression and in some cases a positive Schwartze sign. A maintenance dose of 20 mg daily is now advised the rest of the patient's life. Our current practice is to prescribe one 20 mg enteric coated tablet of NaF after breakfast and supper with a half gram of calcium gluconate chewed up before each of these meals, and one multivitamin tablet daily to supply 400 units of Vitamin D. This is continued for two years when polytomography is repeated, the Schwartze sign is determined and the hearing tested. If the process is not arrested, the fluoride is increased to 60 mg daily for two years. A bone survey at the onset of therapy is repeated every two years to detect any beginning skeletal fluorosis. A small number of patients do not tolerate the medication due to side effects. In another small group the process continues to progress despite therapy. Our conclusion is that moderate dosage NaF is effective in 80% of cases in stabilizing the sensorineural component of loss by causing a vascular spongy expanding focus to become mature, recalcified and inactive. The toxic enzymes liberated by the active focus appear to be the mechanism of the sensorineural deterioration. Sodium fluoride acts partly as an enzyme inhibitor and partly to decrease osteoclastic resorption and to increase calcification of the focus thus arresting its activity.