Question

What are the effects of this disorder on perception of the stimulus and homeostasis?

Disorder - Otosclerosis

Answer 1

Otosclerosis

Summary

Otosclerosis refers to abnormal bone growth of the bony labyrinth, primarily at the oval window. It manifests at the stapes, which becomes increasingly fixated to the oval window. This process leads to progressive conductive hearing loss because the ossicle's ability to vibrate becomes increasingly limited. Frequently, the other ear is also affected. Left untreated, the disease can progress to deafness. Audiometry reveals decreased air conduction and a characteristic Carhart's notch in the bone conduction curve. Replacement of the upper part of the stapes with a prosthesis (stapedotomy) is the treatment of choice.

Epidemiology

Sex: ♀ > ♂

Age of onset: 20–40 years

Epidemiological data refers to the US, unless otherwise specified

Etiology

50% of cases show autosomal dominant inheritance with incomplete penetrance; the rest occur sporadically

Pathophysiology

Stapedial otosclerosis (most common site) → fixation of stapes to oval window → conductive hearing loss

Clinical features

Slowly progressive conductive hearing loss with the 2nd ear affected in ∼ 70% of patients as the disease progresses

Tinnitus

Mild vertigo (approx. 25%)

Paracusis willisii: patients hear better in noisy rather than quiet surroundings

Quiet speech

Schwartze sign: a red-blue hue seen through tympanic membrane

Symptoms may increase during pregnancy or following menopause because of hormonal changes!

Diagnostics

Pure tone audiometry

↓ Air conduction (especially for lower frequencies)

Carhart's notch: an increase in the bone conduction threshold at 2,000 Hz

Impedance audiometry: absent stapedius reflex

Treatment

Surgical procedures

stapedotomy; stapedectomy

Cochlear implant: in the case of bilateral deafness