40 Otosclerosis Flashcards
Define otosclerosis.
Define otosclerosis.
Otosclerosis is derived from the Greek word “hardening of the ear.” In a broad sense it is defined as altered bony metabolism in the otic capsule with ongoing resorption and deposition of bone. This process results in fixation of the ossicular chain and resultant conductive hearing loss (CHL).
Describe the epidemiology of otosclerosis.
Describe the epidemiology of otosclerosis.
Otosclerosis most commonly occurs in Caucasians in the second to fifth decades of life, with a female to male preponderance of 2:1. Bilateral disease occurs in 80% of patients, and approximately 20% to 30% develop sensorineural hearing loss (SNHL).
What is the pathophysiology of otosclerosis?
What is the pathophysiology of otosclerosis?
Otosclerosis is a localized remodeling process of bone occurring in and around the otic capsule. In the normal state, endochondral calcification is usually complete in the otic capsule at one year of age with little remodeling thereafter. The disease process of otosclerosis is the result of abnormal prolonged remodeling of bone in and around the otic capsule by osteoblasts and osteoclasts. This process results in poorly organized bone that becomes metabolically active, well-vascularized bone (spongiotic), and/or densely mineralized (sclerotic) bone (Figure). The end result in classic otosclerosis is fixation of the stapes footplate, usually beginning anteriorly with posterior progression to complete footplate involvement.
Figure text: Multiple otosclerotic lesions around the cochlea and anterior to the stapes footplate.
What are the initial symptoms of otosclerosis?
What are the initial symptoms of otosclerosis?
The characteristic presentation of otosclerosis is adult-onset progressive unilateral or bilateral conductive hearing loss. Although less likely, otosclerosis can present with SNHL due to “cochlear otosclerosis.” Some patients report improved hearing in noisy environments, referred to as “paracusis of Willis.” The second most common complaint is tinnitus. Vestibular symptoms are rarely reported.
Does genetics play a role in the development of otosclerosis?
Does genetics play a role in the development of otosclerosis?
Studies of families with otosclerosis have supported an autosomal dominant pattern of inheritance with incomplete penetrance. Within these groups multiple genes have been implicated, although there is significant heterogeneity of the genetic pattern. Although genetic factors likely influence the development of otosclerosis, approximately half of all cases arise without a positive family history.
What other factors may be causative in the development of otosclerosis?
What other factors may be causative in the development of otosclerosis?
Although literature supporting various etiologies is limited, persistent measles infection, autoimmunity, multiple endocrine factors, and low fluoride consumption have been implicated in the development of otosclerosis.
What is the Schwartze sign?
What is the Schwartze sign?
Schwartze sign is a reddish hue seen though the tympanic membrane reflecting the increased vascularity of the bone over the promontory. Although this may be seen early in the disease process, this finding is not present in all cases.
What physical exam findings are expected in patients with otosclerosis?
What physical exam findings are expected in patients with otosclerosis?
Physical exam findings of patients with otosclerosis are limited. Most present with a normal external auditory canal and tympanic membrane with an occasional Schwartze sign. Rinne and Weber tuning fork exams will typically reveal bone conduction to be greater than air conduction, and lateralization to the affected side, respectively, although these findings are not specific for otosclerosis.
What are the expected audiogram findings of otosclerosis?
What are the expected audiogram findings of otosclerosis?
Audiometric studies typically show a CHL that is worse at low frequencies. The Carhart notch is characteristic of otosclerosis showing an apparent SNHL at 2000 Hz.
What is a Carhart notch?
What is a Carhart notch?
A Carhart notch (Figure) is a decrease in bone thresholds on an audiogram at 2000 Hz which can be seen in otosclerosis and other pathologies affecting the middle ear. It is thought to be caused by inertia of the ossicular chain. It is not sensitive or specific for otosclerosis.
Figure text: Pure-tone audiogram (PTA; A, preoperative PTA, B, postoperative PTA). There is preoperative conductive hearing loss as shown by a characteristic Carhart notch (black arrow), which implies bone conduction impairment at 2 kHz. After the ossicular chain was reconstructed using a total ossicular replacement prosthesis (TORP), postoperative audiometric evaluations done at a 6-month follow-up visit demonstrated closure of the air–bone gap and disappearance of the Carhart notch.
What role does acoustic immitance testing play in diagnosis of otosclerosis?
What role does acoustic immitance testing play in diagnosis of otosclerosis?
Tympanometry will typically show an As configuration reflecting normal middle ear pressure, but decreased amplitude indicative of some degree of ossicular chain fixation. The stapedial reflex may be present in early portions of the disease process, but may show abnormalities including biphasic reflexes. Reflexes become absent with progression of the disease to stapes fixation.
Does imaging play a role in otosclerosis?
Does imaging play a role in otosclerosis?
Imaging modalities in otosclerosis such as computed tomography (CT) and magnetic resonance imaging (MRI) are not routinely needed. However, recent studies have suggested high resolution CT, along with physical and audiometric data, to be highly sensitive in diagnosing otosclerosis. In addition to assisting in diagnosis, CT may also provide information helpful for surgical planning and prevention of complications.
Does medical treatment play a role in otosclerosis?
Does medical treatment play a role in otosclerosis?
Current medical therapy is aimed at decreasing bone remodeling, specifically targeting osteoclastic activity. Much of this theory has been based on success with treatment of osteoporosis. Possible medical therapies include bisphosphonates and sodium fluoride. Given the success of surgical treatment and unknown efficacy, no medical therapies are consistently recommended. Hearing aids offer a successful nonsurgical alternative for correction of hearing loss associated with otosclerosis.
Describe the surgical treatment of otosclerosis.
Describe the surgical treatment of otosclerosis.
There are currently multiple techniques in use for correction of otosclerosis. Regardless of variations in technique, current literature reports successful outcomes in greater than 90% of patients measured by closure of their preoperative air–bone gap.
In general, the goal of surgery is to allow transmission of sound from the tympanic membrane through the ossicular chain to the oval window while bypassing the fixed stapes footplate. This process typically involves some variation of removal of the arch of the stapes, fenestration or partial removal of the stapes footplate, and insertion of a prosthesis connecting the incus to the oval window (Figure 40-3). In cases of incus necrosis, a prosthesis connecting the malleus to the oval window can be used.
Figure text: tapes prosthesis from the incus into the stapedotomy fenestra after removal of the stapes suprastructure.
Are there any special considerations in patients with bilateral otosclerosis?
Are there any special considerations in patients with bilateral otosclerosis?
Bilateral otosclerosis occurs in approximately 70% of cases. When electing to operate on a patient with bilateral disease, the poorer hearing ear is generally operated on first, and followed by, if successful, the contralateral ear 6 months later.
