Otosclerosis (otospongiosis)

Otosclerosis (otospongiosis)

OVERVIEW:

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 ear
• Clinical otosclerosis: Abnormal spongy bone involves ossicular chain or other structures leading to altered physiology

System(s) affected: Nervous
Genetics:
• 60% of those affected give positive family history
• Appears to be transmitted by autosomal dominant gene with variable penetrance
Incidence/Prevalence in USA:
• 4-8% among Caucasians; 1% among African-Americans (histologic form)
• Caucasians 5000/100,000; Blacks 1000/100,000 (histologic form)
Predominant age: Clinical onset usually in early 20's. Peak incidence fourth and fifth decades.
Predominant sex: Female > Male (2:1)

SIGNS AND SYMPTOMS:

• Progressive conductive hearing loss, usually with well preserved speech discrimination. May have sensorineural hearing loss with cochlear involvement.
• Carhart's notch: A dip in bone conductive threshold at 2000 Hz. on audiometric testing
• Schwartze's sign: Reddish hue on promontory upon otoscopic examination
• Patients often soft spoken and aware they seem to hear better in noisy environments

CAUSES:

Unknown; fluoride metabolism felt by some authorities to play a role in etiology

RISK FACTORS:

Unknown

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS:

• Chronic suppurative otitis media
• Serous otitis media
• External auditory canal occlusion
• Ossicular chain disruption
• Congenital fixation of stapes
• Presbycusis
• Advanced otosclerosis mimics sensorineural deafness

LABORATORY:

N/A

Drugs that may alter lab results: N/A
Disorders that may alter lab results: N/A

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 capsule. Bilateral in 75% of cases.
• Micro: Spongy appearing bone with increased vascular spaces. Osteoblasts and osteoclasts are plentiful.

SPECIAL TESTS:

Tuning fork and audiometric testing for conductive and/or sensorineural hearing loss. Will lateralize to more impaired ear with Weber's test.

IMAGING:

Coaxial or computerized tomography sometimes helpful

DIAGNOSTIC PROCEDURES:

N/A

TREATMENT

APPROPRIATE HEALTH CARE:

Inpatient for surgery. Outpatient if surgery not feasible.

GENERAL MEASURES:

Hearing aids

SURGICAL MEASURES:

• Surgical correction (stapedectomy): Usually involves mobilization or removal of the stapedial foot plate with placement of a stapes prosthesis. Recent procedural innovations have involved use of lasers.
• Relative indications for surgery include: Negative Rinne's test (air-bone audiometric gap at least 20 dB); bilateral involvement

ACTIVITY:

No restrictions

DIET:

No special diet

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

MEDICATIONS

DRUG(S) OF CHOICE:

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

Contraindications: Refer to manufacturer's literature
Precautions: Refer to manufacturer's literature
Significant possible interactions: Refer to manufacturer's literature

ALTERNATIVE DRUGS:

N/A

FOLLOW UP

PATIENT MONITORING:

Interval audiometric testing

PREVENTION/AVOIDANCE:

N/A

POSSIBLE COMPLICATIONS:

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

EXPECTED COURSE AND PROGNOSIS:

Progressive hearing loss if not treated. Surgery improves hearing by at least 15 dB in 90% of cases.

MISCELLANEOUS

ASSOCIATED CONDITIONS:

• Van der Hoeve's syndrome (rare triad of osteogenesis imperfecta, blue sclera, and otospongiosis)
• Tinnitus
• Vertigo

AGE-RELATED FACTORS:

Pediatric: N/A
Geriatric: Important differential diagnosis for presbycusis
Others: N/A

PREGNANCY:

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

SYNONYMS:

N/A

ICD-9-CM:

387.9 Otosclerosis, unspecified

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Medical Diagnosis » O » Otosclerosis (otospongiosis)