Clinical Practice Guideline
Developed for the
Aerospace Medical Association
by their constituent organization
Overview: Otosclerosis is characterized by an abnormal deposition of bone at the footplate of the stapes. It is a disease of unknown etiology and appears to affect genetically predisposed individuals. This bony deposition leads to fixation of the stapes at the oval window preventing normal transmission of sound. It is the leading cause of conductive hearing loss in adults who do not have a middle ear effusion. Stapes fixation was first described by Valsalva in 1704 during an autopsy on a deaf patient, and in 1860 Toynbee first described the condition causing a hearing loss by fixation of the stapes. In 1894 Politzer first referred to the fixation of the stapes as otosclerosis. Successful surgery for this condition dates back to Holmgren who fathered the practice of fenestration surgery in 1923. Although the major concern with otosclerosis is conductive hearing loss, it can also cause a sensorineural hearing loss when it invades the otic capsule. Additionally an estimated 10-30% of patients will also present with vestibular symptoms or demonstrate abnormalities on vestibular testing.
The overall prevalence of histologic otosclerosis is about 10%. Around 10% of these are affected clinically making the overall prevalence of noticeable hearing loss secondary to otosclerosis approximately 1% in the US population. This disease is more common in Caucasians than in other races. Women more commonly seek medical attention for hearing loss secondary to otosclerosis; however, studies looking at histologic prevalence of otosclerosis show no difference in men versus women. However, pregnancy seems to hasten presentation. The incidence of otosclerosis also increases with age. The most common age group presenting with hearing loss from otosclerosis is 15-45 years; however, it has been reported to manifest as early as 7 years and as late as the mid 50s. Approximately 80% of patients will develop bilateral otosclerosis, though the progression of each ear may be different. Diagnosis is based on history and clinical exam. Clinical exam may show a reddish blush on the promontory mucosa (Schwartze’s sign—associated with active disease). Screening with 512-Hz and 256-Hz forks will often show a reverse Rinne test. Audiometric screening includes air conduction, bone conduction, acoustic reflexes and speech audiometry. Typically depending on how advanced the disease is, the audiogram will show varying degrees of conductive hearing loss. As mentioned above some advanced forms may cause a sensorineural hearing loss. Acoustic reflexes are absent due to stapes fixation. In recent years, imaging studies have played a greater role with high-resolution CT (HRCT) being the radiologic method of choice in the assessment of the labyrinthine windows and otic capsule. Recent estimates demonstrate the sensitivity of CT for the diagnosis of otosclerosis to be at least 90%1. The differential diagnosis for conductive hearing loss in patients without discernable ear pathology includes the following: congenital malleus/incus fixation, congenital stapes fixation, other congenital ossicular abnormalities (1st or 2nd arch syndromes), post-inflammatory ossicular fixation, ossicular discontinuity, osteogenesis imperfecta tarda, Paget’s disease, and osteopetrosis.
For many people with otosclerosis, no treatment is indicated initially. As the hearing loss progresses, the patient may opt to try hearing aids. Use of hearing aids in the cockpit environment may be a handicap as the aviator will be unable to tune out unwanted sounds and transmissions. In fact the phenomenon of “Paracusis of Willis” allows patients with otosclerosis to hear better in a noisy environment than in a quiet locations. Hearing aids work by essentially amplifying all sound transmitted to the ear, and even distorting the sound at times. However, modern hearing aids can offer a variety of noise filters for different listening environments. The currently popular surgical treatment for otosclerosis is stapedectomy, first performed by John Shea in 1956. This procedure is still commonly performed, with some modifications, by many ENT surgeons throughout the world. With increasing availability of good surgical care and of adequate screening tests, the average age of presenting patients has declined over the past fifty years (52 to 50) as has the number of years with noticeable hearing loss (18 to 11).
There are actually three surgical options for otosclerosis: total stapedectomy, partial stapedectomy, and stapedotomy. The different designations correspond to the amount of footplate removed. Partial stapedectomy involves removal of the posterior third of the footplate while stapedotomy involves drilling or lasering a hole in the stapes footplate, inserting a prosthesis through the hole to the oval window and anchoring it to the incus. The technique chosen depends on the degree of sclerosis and surgeon preference; most perform a stapedotomy. In experienced hands, the success rate of these procedures is in excess of 90% as measured by return of hearing to normal or near normal. Over time, a small percentage of patients have a return of hearing loss symptoms or develop complications such as dizziness, sensorineural hearing loss, distortion of sound or tympanic membrane complications. Depending on the cause, a revision procedure is often accomplished. Expected outcomes for these patients are not as good as with the primary procedure; successful hearing results range from 16% to 80% with a mean of 53%, with the variability in results due to the indication for the revision.
Aeromedical Concerns: Loss of normal hearing capability is a concern in aircrew. Otosclerosis may progress to the point of hearing loss or more rarely vestibular symptoms significant enough to compromise flight safety. Most aircrew delay surgical intervention because of the Paracusis of Willis phenomenon. However, when the hearing begins to compromise communications, they will present for surgical or audiometric remediation. Surgery offers freedom from having to use amplification. Fortunately complications following surgery are rare, but may be significant. These include the following: acute otitis media, suppurative labyrinthitis and meningitis, vertigo, reparative granuloma, perilymph fistula, facial paralysis, fluctuating conductive hearing loss, persistent perforation of the tympanic membrane, taste disturbance and dry mouth, postoperative fibrosis, incus necrosis, and delayed sudden deafness. Vertigo may occur immediately after stapedectomy, or its onset may be delayed by weeks or years. Vertigo that is not resolved with treatment is incompatible with flying duties. Perilymph fistula postoperative risk is 0.34—9.0%, with symptoms similar to those of endolymphatic hydrops (hearing loss, vertigo, ear fullness, and tinnitus) and may be incompatible with flying duty if definitive treatment is not achieved. Facial nerve paralysis may cause dry eye which may present significant problems for aviators flying in dry cockpit conditions, or facial droop which may interfere with wear of aviator masks. Persistent perforation of one tympanic membrane could lead to alternobaric vertigo and is not compatible with flying duties.
Return to aviation duties following stapedectomy or stapedotomy has been controversial within the aeromedical community for the past forty years. In the 1960s and 1970s, concern with barometric pressure changes causing a perilymph fistula led to Air Force policy that prevented return to flying duties for aviators after these procedures. As more and more affected individuals had this procedure for a return to flying duties, pressure mounted on medical authorities to develop a more reasonable policy. Dr. Rayman’s proposed criteria in his 1972 paper led the way to a consistent and reasonable approach to these airmen. Revising policy has been a long process, but results so far have been very encouraging with the dreaded complication of a perilymph fistula being very rare in the carefully selected group of aviators.
Medical Work-up: Medical evaluation of an aviator with otosclerosis should include a complete history to include all hearing and vertiginous symptoms and impact on activities of daily living and aviation duties. There should also be discussion of all attempted treatments such as hearing aids. The exam need to include a complete audiologic exam to include air conduction threshold measurement; bone conduction threshold measurement (if indicated); speech reception threshold; speech discrimination testing; acoustic impedance testing and ENG if clinically indicated. Also, a complete report of the ENT exam is required as are any consultative reports from the ENT physician and audiologist. Finally, all surgical reports to include details of technique used, type of prosthesis and type of graft used are required.
Air Force: Otosclerosis and stapedectomy are not specifically mentioned in AFI 48-123, but it is noted that a history of surgery involving the middle ear is disqualifying. Also, hearing defects are well described as are conditions that interfere with auditory or vestibular functions.
If the otosclerosis results in hearing loss and/or vertigo, then waiver guidelines for those diagnoses should be followed as well. If the aviator undergoes successful surgical treatment, an evaluation at the USAF Aeromedical Consultation Service (ACS) is required for single seat high performance aircrew and FC I/IA candidates, and may be scheduled no earlier than 12 weeks postoperatively. Evaluation at the ACS will include evaluation by an otolaryngologist with review of all medical records, pre and post-operative testing, and surgical report. Diagnostic audiology including air conduction threshold measurement; bone conduction threshold measurement (if indicated); speech reception threshold; speech discrimination testing; acoustic impedance testing and ENG will be accomplished if indicated. An altitude chamber flight with a flight surgeon is required only for those who have had the traditional stapedectomy surgery, to test for perilymph fistula. For those who have undergone the newer stapedotomy surgery, an altitude chamber evaluation is not required. If a chamber flight is performed, it should include a rapid descent (5000 feet/min) from 10,000 feet. A rapid decompression is also required. Additional tests are done as clinically or aeromedically indicated. If ACS evaluation reveals no post-op sequelae, the aviator may be recommended for an unrestricted waiver.
Army: The inability to clearly hear cockpit radio transmissions and warning tones can have a significant impact on flight safety and this is the Army’s concern regarding this condition. Waivers will be considered depending on the degree of hearing loss and functional capability. Stapedectomies present problems because the operation creates an opening into the labyrinth, and involves the placement of a prosthesis in most cases. There is a risk of postoperative perilymph fistula, as well as subsequent shifting of the prosthesis, both of which can result in sudden attacks of vertigo. Bilateral stapedectomy is not waiverable. Initial flight applicants with a history of stapedectomy are considered disqualified, no exception to policy granted.
Navy: Stapedectomy done to treat otosclerosis is considered disqualifying (CD) and requires a waiver. Designated aviators are grounded for three months following stapedectomy, before waiver being recommended to SG1 (pilot). For Naval Flight Officer (NFO) and other Class II (non-pilot) personnel, a waiver is also considered for duty involving flying after three months. Waiver criteria include being asymptomatic, passing a current flight physical, and that the prosthesis used was not a wire loop/gelfoam (a piston prosthesis and tissue graft is preferred versus a blood seal). No waiver will be recommended if there are signs of vestibular dysfunction, spontaneous nystagmus, or sudden/progressive neurosensory hearing loss. Bilateral stapedectomy is not waived. Applicants with a history of stapedectomy are CD, no waiver. Information required for waiver includes ENT consult, audiology consult (must include speech reception thresholds and speech discrimination scores), and surgical report.
Civilian: In the US civilian sector as long as one can clear their ears and does not have any vertigo they can fly. To pass the FAA's hearing standards one must only pass one of three different tests. The most commonly performed test is the Conversational Voice Test where the airman must be able to repeat what the Aviation Medical Examiner (AME) says while they are standing 6 feet from the AME facing the opposite direction. The next test that can be given is the standard Audiometry exam with a better ear worse ear standard, The Better ear being: 500 hz: 35 db, 1000 hz: 30 db, 2000 hz: 30 db ,3000 hz: 40 db; Worse ear: 500 hz: 35 db, 1000 hz: 50, 2000 hz: 50, 3000 hz: 60. The last test is the Speech discrimination test where the airman must hear at least 70% in one ear at 65 db. The airman may take any of these tests wearing hearing aids and if they pass with the aids they are given a medical certificate with the restriction MUST WEAR HEARING AMPLIFICATION. The airman can also attempt to pass the hearing test taking a medical flight test in which case they will be issued a Statement of Demonstrated Ability.
Air Force: A review of AIMWTS revealed a total of 29 cases submitted for a waiver with the diagnosis of otosclerosis. This total included one FC I case, 19 FC II cases, and nine FC III cases, all receiving a waiver. In ten of the cases, the airman had surgery, which was a stapedectomy in each case and there were four cases where it was stated the airman was wearing a hearing aid. There were a total of six females in the database.
Army: Otosclerosis with or without stapedectomy has been an uncommon diagnosis in this population. Of the 16,852 rated aircrew with a current flight physical in 2010, none carried the diagnosis of otosclerosis or had undergone stapedectomy. Historically, going back to 1987, there have been 15 cases of otosclerosis among rated US Army aircrew, all of whom were retained except for one.
Navy: Not available at this time.
Civilian: As of May 31, 2011 there were 52 first-class, 44 second-class and 113 third-class airmen currently issued with this condition.
ICD 9 codes for Otosclerosis and Stapedectomy
Vicente AO, Yamashita HK, Albernz PLM, and Penido NO. Computed tomography in the diagnosis of otosclerosis. Otolaryngol Head Neck Surg, 2006; 134:685-92.
Isaacson JE and Vora NM. Differential Diagnosis and Treatment of Hearing Loss. Am Fam Physician, 2003; 68:1125-32.
Muller C and Gadre A. Otosclerosis – Grand Rounds Presentation at UTMB Dept. of Otolaryngology, 4 June 2003.
House JW and Cunningham CD. Otosclerosis, Ch. 156 in Cummings: Otolaryngology: Head and Neck Surgery, 4th edition, 2005.
Saim L and Nadol JB. Vestibular Symptoms in Otosclerosis – Correlation of Otosclerotic Involvement of Vestibular Apparatus and Scarpa’s Ganglion Cell Count. Am J Otology, 1996; 17:263-70.
Jahn, AF and Vernick D. Otosclerosis: Diagnosis and Treatment, AAOHNS SIPAC, 1986; Pg 1-78.
Rayman RB, Hastings JD, Kruyer WB, et al. Clinical Aviation Medicine, 4th ed. New York; Professional Publishing Group, Ltd. 2006, 138-40.
Lippy WH, Berenholz LP and Burkey JM. Otosclerosis in the 1960s, 1970s, 1980s, and 1990s. The Laryngoscope, 1999; 109:1307-09.
Quaranta N, Besozzi G, Fallacara RA, and Quaranta A. Air and Bone Conduction After Stapedotomy and Partial Stapedectomy for Otosclerosis. Otolaryngol Head Neck Surg, 2005; 133(1): 116-20.
Battista RA, Wiet RJ and Joy J. Revision Stapedectomy. Otolaryngol Clin N Am, 2006; 39:677-97.
Wiet RJ, Harvey SA, and Bauer GP. Complication in Stapes Surgery. Otolaryngol Clin N Am, 1993; 26(3):471-90.
Hanna HH and Collins FG. Effect of Barometric Pressure Change on the Ear Following Stapedectomy. Aerospace Med, 1974; 45:548-50.
Rayman RB. Stapedectomy: A Threat to Flying Safety? Aerospace Med, 1972; 43:545-50.
Schall DG. On Combat Pilots, Letter to the Editor. Am J Otology, 1997; 18:687-88.
Katzav J, Lippy WH, Shamiss A and Davidson BZ. Stapedectomy in Combat Pilots. Am J Otology, 1996; 17:847-49.
Thiringer JK and Arriage MA. Stapedectomy in military aircrew. Otolaryngol Head Neck Surg, 1998; 118:9-14.
Shea JJ. Forty Years of Stapes Surgery. Am J Otology, 1998; 19:52-55.
Prepared by Drs. David Schall and Dan Van Syoc
November 14, 2011