Conductive Hearing Loss

Table of Contents

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Conductive hearing loss

Is caused by a disorder of the external & middle ear

Usually does not excess 60 dB

Etiology

Occlusion of EAC
Perforated of the TM
Occlusion of eustachian tube
Fixation of the ossicular chain c or s fixation of ear drum
Discontinuty of the drum ossicle chain mechnism
Congenital malformation

Occlusion of EAC

Occlusion of EAC may be result from

Congenital atresia
Acquired atresia from External otitis or trauma,FB or Impactcerumen,Furuncle, Polyp,exostosis,Neoplasm

Restoration of normal hearing can be expected after removal of the obstruction

Perforated of the TM

Degree of HL depend on size,location & nature of perforation

Caused by trauma,after an acute necrotic OM

Usually low frequency loss

Occlusion of eustachian tube

Hypertrophy of nasopharyngeal adenoid tissue

Allergic tubutympanitis,scars of tube orifice

Acute viral or bacterial nasopharyngitis

Descent in plane,train,deep sea diving->barotrauma or aero-otitis

Cleft palate,both before and after surgical repair

Tumor of nasopharynx

Malocculsion of mandibular jt (Costen’s syndrome)

Fixation of the ossicular chain c or s fixation of ear drum

Decreased of mobility of ossicular chain from fixation

Otosclerosis, tympanosclerosis, scar after sergery or infection

Can evaluated by pneumotic otoscope

Reconstruction ex Stapesdectomy in otosclerosis

Discontinuty of the drum ossicle chain mechnism

Infection or trauma

Incudostapedial joint floating in middle ear à increased risk of devascularized of its

Evaluated by pneumatic otoscope or tympanogram

Occurs maximum CHL by normal TM

Diagnosis

History

Physical examination

Otoscope (Diagnosis,Pneumatic)
Tuning fork test (Rinne, Weber test)
Audiometry
Tympanometry

History and physical examination for hearing loss

Onset

Age at onset

Abrupt versus gradual

Progressive, intermittent, or continuous

Antecedent illness

Duration of symptoms

Associated symptoms

Tinnitus
Dizziness or vertigo
Aural fullness
Pain
Allergy symptomatology
Actions that change intensity of symptoms
Distorted auditory perception
Worsening with pregnancy or oral contraceptive use

Family history of hearing loss

Occupational noise exposure

Recreational noise exposure

Trauma

Surgical history

Previous or current draining from ear

Quality of drainage

Systemic infections and treatments

Meningitis
Syphilis

Previous use of a hearing aid

Ototoxic medications

Cancer chemotherapy
Antibiotics

Recent air travel

Recent underwater diving

Tuning fork test

False negative Rinne test

When there is total or severe SNHL in one ear
The vibrations of the tuning fork are transmitted across the bone of the skull and are sensed by the opposite and healthy cochlea

Table 147-2. Degree of hearing loss estimated by Rinne testing

Rinne test result	Estimated conductive loss
Negative, 256 Hz Positive, 512 and 1024 Hz	Mild conductive loss of 20-30 dB
Negative, 256 and 512 Hz Positive, 1024 Hz	Moderate conductive loss of 30-45 dB
Negative, 256, 512, 1024 Hz	Severe conductive loss of 45-60 dB

Summarized By Thirayost Nimmanon

โดย ธีรยสถ์ นิมมานนท์

ปรับปรุงครั้งล่าสุด 15/06/2010