Otosclerosis – Causes, Symptoms, Diagnosis, Treatment and Ongoing care

Basics

Description

A primary bone dyscrasia involving the otic capsule; it is the leading cause of conductive hearing loss in adults.Histologic otosclerosis: Asymptomatic form in which abnormal bone spares vital structures of the earClinical otosclerosis: Abnormal spongy bone involves ossicular chain or other structures, leading to altered physiology.System(s) affected: Sensory; Hearing

Epidemiology

Incidence

Predominant age: Clinical onset usually in early 20sPeak incidence in 4th and 5th decadesPredominant gender: Female > Male (2:1)

Pregnancy Considerations

Progression may accelerate during pregnancy. Some women first notice hearing loss at this time.

Prevalence

4–8% among whites; 1% among African Americans (histologic form)Whites: 5,000/100,000; African Americans: 1,000/100,000 (histologic form)

Risk Factors

Unknown

Genetics

60% of those affected give positive family history.Appears to be transmitted by autosomal dominant gene with variable expressivity

Etiology

UnknownFluoride metabolism may play a role; flouride treatment under investigation, as early results demonstrate improved hearing outcomes.

Commonly Associated Conditions

Van der Hoeve syndrome (rare triad of osteogenesis imperfecta, blue sclera, and otospongiosis)Tinnitus, usually low frequency

Diagnosis

History

Progressive conductive hearing loss, usually with well-preserved speech discriminationPatients often soft spoken and aware they seem to hear better in noisy environments

Physical Exam

Schwartze sign: Reddish hue in front of oval window, on promontory at otoscopic exam

Diagnostic Tests & Interpretation

Imaging

Initial approach

Coaxial or computed tomography scan sometimes helpful

Diagnostic Procedures/Surgery

Tuning fork and audiometric testing for conductive and/or sensorineural hearing loss:

Will lateralize to more impaired ear with Weber testConductive hearing loss; may be as severe as the 60dB maximumMay have sensorineural hearing loss with cochlear involvementCarhart notch: A dip in bone conductive threshold at 2,000 Hz on audiometric testing

Pathological Findings

Gross: Off-white to reddish bone formation, most often located anterior to the oval window and extending to involve the stapedial footplate; sometimes covers entire oval window (obliterative); may be found anywhere in otic capsuleBilateral in 75% of patientsMicro: Spongy-appearing bone with increased vascular spacesOsteoblasts and osteoclasts are plentiful.

Differential Diagnosis

Chronic suppurative otitis mediaSerous otitis mediaExternal auditory canal occlusionOssicular chain disruptionCongenital fixation of stapesPresbycusisAdvanced otosclerosis mimics sensorineural deafness.

Alert

Important differential diagnosis for presbycusisSurgical results similar in older vs younger patient cohorts (1)[A]

Treatment

Medication

No specific drug therapy, but sodium fluoride, vitamin D, and calcium gluconate have been tried, especially in cases of predominantly sensorineural hearing loss.

Surgery/Other Procedures

Surgical correction (stapedectomy): Usually involves mobilization or removal of the stapedial footplate with placement of a stapes prosthesisRecent procedural innovations have involved use of lasers.Cochlear implantation may achieve better results in advanced cases (2)[B].Relative indications for surgery include negative Rinne test (air-bone audiometric gap at least 20 dB) and bilateral involvement.

Ongoing Care

Follow-Up Recommendations

No restrictions on activityHearing aids

Patient Monitoring

Interval audiometric testing

Patient Education

Because speech discrimination is usually preserved, patients should be advised of the possible benefit from hearing aids as an alternative or adjunct to surgery.Mayo Foundation for Medical Education and Research, Section of Patient and Health Education, Sieber Subway, Rochester, MN 55905; (507) 284-8140

Prognosis

Progressive hearing loss if not treatedSurgery improves hearing by at least 15 dB in 90% of patients.

Complications

Surgical risks include chorda tympani nerve injury, tympanic membrane laceration, ossicular chain disruption, otitis media and externa, labyrinthitis, granuloma formation, perilymph fistulas, and total deafness (“dead ear”).

References

1. Meyer TA, Lambert PR. Primary and revision stapedectomy in elderly patients. Curr Opin Otolaryngol Head Neck Surg. 2004;12:387–92.

2. Berrettini S, Burdo S, Forli F, et al. Far advanced otosclerosis: stapes surgery or cochlear implantation? J Otolaryngol. 2004;33:165–71.

Additional Reading

Lee KJ. Essential Otolaryngology: Head & Neck Surgery, 4th ed. New Hyde Park, NY: Medical Examination Publishing, 1987.

Weber PC, Klein AJ. Hearing loss. Med Clin North Am. 1999;83:125–37, ix.

See Also (Topic, Algorithm, Electronic Media Element)

Hearing Loss

Codes

ICD9

387.2 Cochlear otosclerosis387.9 Otosclerosis, unspecified

Snomed

11543004 otosclerosis (disorder)91108004 cochlear otosclerosis (disorder)

Clinical Pearls

The audiometric signature of otosclerosis is a dip in conductive hearing at 2,000 Hz.Hearing aids are helpful in patients with preserved speech discrimination.Bilateral involvement and an air-bone audiometric gap of 20 dB or more are indications for surgery.