Hearing loss (deafness) can be classified into three main types: conductive, sensory-neural, and central hearing loss.
Conductive hearing loss may be caused by simple situations such as accumulation of wax in the ear. However, it may also be due to an inflammation and infection of the middle ear (otitis media), or to otosclerosis.
Otitis media is most commonly caused by infection with viral, bacterial, or fungal pathogens. Acute otitis media (AOM) is most often purely viral and self-limited, as it usually accompanies viral upper respiratory infection. 1st phase – exudative inflammation lasting 1–2 days, fever, rigours, meningism (occasionally in children), severe pain (worse at night), muffled noise in the ear, deafness, sensitive mastoid process, ringing in ears (tinnitus). 2nd phase – resistance and demarcation lasting 3–8 days. Pus and middle ear exudate discharge spontaneously and afterwards pain and fever begin to decrease. This phase can be shortened with topical therapy. 3rd phase – healing phase lasting 2–4 weeks. Aural discharge dries up and hearing becomes normal.
Otitis media with effusion (OME), also called serous or secretory otitis media (SOM), is simply a collection of fluid that occurs within the middle ear space as a result of the negative pressure produced by altered Eustachian tube function. This can occur purely from a viral upper respiratory infection, with no pain or bacterial infection, or it can precede and/or follow acute bacterial otitis media. Fluid in the middle ear sometimes causes conductive hearing impairment, but only when it interferes with the normal vibration of the eardrum by sound waves. Over weeks and months, middle ear fluid can become very thick and glue-like.
Chronic suppurative otitis media involves a perforation (hole) in the tympanic membrane and active bacterial infection within the middle ear space for several weeks or more. There may be enough pus that drains to the outside of the ear (otorrhoea), or the purulence may be minimal enough to only be seen on examination using a binocular microscope. This disease is much more common in persons with poor Eustachian tube function.
Otosclerosis is an abnormal growth of bone near the middle ear. The primary form of hearing loss in otosclerosis is conductive hearing loss, whereby, sounds reach the ear drum but are incompletely transferred via the ossicular chain in the middle ear, and thus partly fail to reach the inner ear (cochlea). This usually will begin in one ear but will eventually affect both ears with a variable course. Treatment of otosclerosis relies on two primary options: hearing aidsand a surgery called a stapedectomy. Hearing aids are usually very effective early in the course of the disease, but eventually a stapedectomy (or more frequently a variant called the stapedotomy) may be required for definitive treatment. A stapedectomy consists of removing a portion of the sclerotic stapes footplate and replacing it with an implant that is secured to the incus. This procedure restores continuity of ossicular movement and allows transmission of sound waves from the eardrum to the inner ear. A modern variant of this surgery called a stapedotomy, is performed by drilling a small hole in the stapes footplate with a micro-drill or a laser, and the insertion of a piston-like prosthesis.