Impact of Imaging in Management of Otosclerosis

Key points

Disease overview

The pathophysiologic hallmark of the fenestral subtype of otosclerosis is remodeling of the temporal bone that is primarily taking place in the area of the oval window, specifically in its anterior part, the fissula ante fenestram, which is a groove between the oval window and the cochleariform process. During the active (otospongiotic) stage of the disease, hypodense foci of bone can be identified in this area.⁸ These foci will be replaced later by sclerotic bone in the nonactive

Fenestral and retro-fenestral otosclerosis: imaging diagnosis

The most common manifestation of fenestral otosclerosis, especially in its spongiotic active stage, is demineralization of the fissula ante fenestram, anterior to the oval window (Fig. 1). In the nonactive otosclerosis, this area becomes sclerotic and in advanced stages of the disease this sclerosis can thicken and obliterate the oval window. The former stage of the disease is usually easier to detect, whereas the later becomes detectable only when significant otosclerotic bone causes

Imaging-based grading systems for otosclerosis

Many types of grading systems were developed for otosclerosis based on surgical and histologic findings. Nonetheless, none of these systems are widely accepted. Several radiographic grading systems based on computed tomography were developed in order to describe the location and stage of otosclerosis and often the relationship of the disease radiographic stage and audiometric performance.9, 11, 12, 13, 14 Rotteveel and colleagues¹⁴ demonstrated a grading system based on the histologic

Imaging before referral for stapes surgery

The diagnosis of ORHL and the decision to refer patients for stapes surgery (ie, middle ear exploration with possible stapedectomy/stapedotomy or ossiculoplsty) as part of hearing rehabilitation alternatives have been traditionally defined when patients have a history of conductive or mixed hearing loss (with a significant conductive component) with absent stapedial reflexes (provided pure tone thresholds are still good enough to elicit stapedial reflex), a normal tympanic membrane on otoscopy,

Alternative diagnosis to otosclerosis demonstrated with imaging

Certain clinical situations might lead the clinician to suspect that a nonotosclerosis diagnoses is mimicking an ORHL and should call for imaging as additional foundation for verification of the underlying diagnoses.8, 10 Common examples are summarized in Box 1 and include mixed hearing loss, significant bilateral conductive or mixed hearing loss (in these cases the value of audiometric test might be limited because of the possible masking dilemma); sensorineural hearing loss; children with

The use of preoperative imaging in otosclerosis to avoid intraoperative complications

Preoperative imaging might also be used to avoid intraoperative complications during procedures for otosclerosis, which is the case with some inner-ear malformations that might jeopardize an outcome like enlarged vestibular aqueduct or X-linked mixed deafness, with accompanying defects in the fundus of the internal auditory canal (Fig. 5). These radiographic findings carry with them a significant risk of intraoperative perilymph gusher during stapes surgery and subsequent sensorineural hearing

Preoperative imaging assessment checklist

Meticulous and systematic assessment of available preoperative imaging can cover the domains that should be inspected during the diagnostic and surgical planning stage and help avoid the aforementioned misdiagnoses and possible intraoperative complications (Table 3).

Preoperative imaging in retro-fenestral (cochlear) otosclerosis

When retro-fenestral (cochlear) otosclerosis progresses and cochlear implantation is being considered, imaging (both HRCT and MRI) is of paramount importance. Both imaging modalities might be used to evaluate the patency of the cochlea in cases of far-advanced otosclerosis whereby the cochlear lumen may be obstructed (especially when implantation is delayed) and require drill-through or drill-out techniques. It has been demonstrated that these patients have higher numbers of partial electrode

MRI for evaluation of otosclerosis

Although HRCT is the modality of choice for most aspects of otosclerosis, additional imaging modalities might be useful for preoperative diagnosis and delineation of anatomy in otosclerosis. MRI will often be the first modality to assess patients with sensorineural or mixed hearing loss; hence, knowing to identify otosclerosis in this modality is important.³⁰ Although MRI is less useful for the demonstration of bony pathology and anatomy, it is very useful for the evaluation of the patency of

Single-photon emission computed tomography for evaluation of otosclerosis

Single-photon emission computed tomography (SPECT) using 99 technetium-diphosphonates (because diphosphonates are highly adsorbed by the immature hydroxyapatite of active otospongiotic foci).¹⁰ Scintigraphic examination using similar agents were tried but suffered from poor spatial orientation.¹⁰ Berrettini and colleagues¹⁰ suggested this option for diagnostic purposes in difficult cases and for medical treatment follow-up. In this study, SPECT exhibited high sensitivity and specificity (95.2%

Postoperative imaging in otosclerosis: complications and results assessment

Stapes surgery is a relatively safe procedure with a high rate of air-bone gap closure, and greater than 90% of patients report better hearing 1 year after the surgery.³⁴ Profound sensorineural hearing loss occurs in less than 1% of the cases, and worsening of the BC thresholds greater than 5 dB occur in about 5% of the cases.34, 35, 36 Incomplete closure of air-bone gap and a remaining conductive or mixed hearing loss occur in 6.5% to 27.0% of the cases.34, 37 Both sensorineural hearing loss

Summary

The use of imaging in otosclerosis for diagnosis, preoperative assessment, and follow-up gives the clinician an additional tier of validation and evaluation of patients’ diagnoses. This evaluation might help in offering the correct solution for hearing-impaired individuals whose type of hearing loss is likely to be ORHL. The use of imaging in otosclerosis is expected to reduce complication rates, failures, and disappointment. Imaging might be also used following an unsuccessful stapes procedure