Deafness (Hearing Loss)
Subjective impairment of hearing.I. Conductive
A. Congenital: congenital meatal atresia.
B. Aquired
1. External ear: wax and foreign bodies.
2. Middle ear:
a. Trauma: TM perforation & ossicular disconnection.
b. Inflammatory: acute & chronic supp. otitis media.
c. Eustachian tube: secretory otitis media.
d. Tumours: glomusjugulari & sq. cell carcinoma.
3. Otic capsule: otosclerosis.
II. Sensorineural Hearing Loss
Sensory (cochlear) hearing loss = cochlear lesion.
Neural (retrocochlear) hearing loss = auditory nerve lesion, spiral ganglion and its connections.
A. Congenital:
a. Syndromes; Pendred's & trisomy 18.
b. Intrauterine infections; rubella, syphilis & toxoplasmosis.
c. Toxins; hypoxia and kernicterus.
B. Acquired:
1. Cochlear
a. Traumatic; head injury and blast injury.
b. infective; Labyrinthitis, measles, mumps and syphilis.
c. Metabolic; Meniere's disease.
d. Toxins; ototoxic drugs.
e. Degenerative; presbyacusis.
2. Retrocochlear
a. Neoplastic; acoustic neuroma.
b. Meningitis.
c. Multiple sclerosis.
Otosclerosis (Otospongiosis)
Is hereditary localized disease of the otic capsule in which new spongy bone causes ankylosis of the foot plate of stapes leading to conductive deafness. Cochlear involvement with sensorineural hearing loss may also occur.
Aetiology
1. Hereditary factors: there is family history in 50% of cases. It is inherited by autosomal dominant pattern with incomplete penetrance.
2. Racial distribution: white races (Caucasian) are more commonly affected than coloured.
3. Age: clinical manifestations usually begin between 15-45 years of age.
4. Sex: the disease appears more frequently in females 2:1.
5. Pregnancy: may accelerate the condition but never cause it.
Pathology
The condition is commonly bilateral (80%). The normal bone is absorbed and replaced by vascular spongy osteoid bone. The most common site of disease is on the promontory immediately anterior to the oval window (Fissula ante fenestram). In advanced cases the stapes become ankylosed in position causing conductive deafness. Cochlear involvement may also occur leading to sensorineural hearing loss.
Clinical Picture
(Deafness Tinnitus Vertigo)1. Hearing loss: the predominant symptom of otosclerossis is slowly progressive hearing loss, usually bilateral (80%) and conductive in type. Characteristically, the patient speaks in a quiet voice, very different from the loud and harsh speech of those with sensorineural hearing loss. Not infrequently, the patient can hear better in a noisy environment (Paracusis Willisii). Paracusis probably results from the simple fact that in these places people with normal hearing automatically raise their voice to overcome the background noise.
2. Tinnitus: is present in 75% of cases. It tends to be worse in patients with cochlear involvement and during periods of rapid progression.
3. Vertigo: is a rare symptom more likely to be provoked by sudden changes of posture.
Examination
1. Otoscopy: the tympanic membrane is normal. In 10% of cases a "flamingo pink blush" (Schwartze's sign) may be seen through the membrane due to hyperaemia of the promontory. This usually indicates rapid progression of the disease.
2. Tuning fork tests: negative Rinne's test and the Weber test are lateralized to the more affected ear.
3. P.T.A: conductive deafness. In advanced cases there may be sensorineural hearing loss which is associated with masses of otosclerotic bone involving the cochlea.
Differential Diagnosis
1. Secretory otitis media (glue ear).2. Adhesive otitis media.
3. Ossicular fixation or disconnection: congenital, traumatic or inflammatory.
4. Pagers disease: Elevated alkaline phosphatase and skeletal bone involvement
5. Osteogenesisimperfecta: autosomal dominant defect of osteoblast activity, stapes fixation, multiple bone fractures & unique blue sclera.
Treatment
1. Medical: Hearing Aids
2. Surgical: stapedectomy which is total or partial removal of the foot plate of the stapes and replacement by a prosthesis.
Complication: perilymph fistula which is characterized by sudden sensorineural hearing loss and vertigo. It is liable to occur after sudden changes of pressure, so the patient should avoid diving and only fly in pressurized aircrafts.
