Hearing Disorders

1. Hearing Disorders The most common hearing disorders are those that affect hearing sensitivity. When a sound is presented to a listener with a hearing sensitivity disorder, one of 2 things may occur: • The listener with a HS disorder may be unable to detect the sound. • The sound will not be as loud to that listener as it would be to a listener with normal hearing.

2. Note: Vision is different. The most common vision disorders affect acuity, not sensitivity to light. Acuity is the ability toresolve differencesamplifying it – but do not improve acuity. Important: This sensitivityvs. acuity distinction is not quite so simple with hearing (or vision): hearing loss of any significance nearly always involves problems of both sensitivity and acuity – sounds are harder to hear (sensitivity) and they are nearly always distorted (acuity). More about this later.

3. The Audiogram Most common way to measure hearingsensitivityis to measure pure-tone (sinusoid) thresholds. Threshold: Sound level required to barely detect a sound.

4. Mild high-frequency loss

5. Moderate-to-severe bilateral loss Severe loss in left ear, moderate loss in right ear. Pure Tone Average (PTA) Average thresholds at 500, 1000, 2000 Hz– the frequencies most important for speech understanding.From the audiogram above: Pure-tone Average, Left Ear: 93 dB Pure-tone Average, Right Ear: 50 dB

6. Terminology Normal Hearing: PTAs < 25 dB Hearing Impairment: PTAs 25-92 dB Deaf: PTAs > 92 dB The term deafness is reserved for cases in which “ … the handicap for hearing everyday speech … [is] … total” (Davis & Silverman, 1979). Despite these conventions: (1) there is no sharp dividing line between hearing impairmentand deafness, and (2) degrees of deafness are meaningful; e.g., there is a difference between PTAs of 110 and 95.

7. Types of Hearing Disorders Many ways to classify hearing disorders 1. Nature of the loss: Sensitivity vs. Acuity • Dysacusia – Deficit in discrimination or interpretation of sound: “Don’t shout, I can hear you just fine. I just can’t understand what you’re saying.” Disacusia is a good term that isn’t in very common use. • Acuity deficits sometimes due to disorders of the central auditory system. • Disorders of sensitivity and acuity are not mutually exclusive.

8. 2. Functional Classification • Conductive – Disorders involving the conduction of sound to the cochlea. • Sensori-neural – Disorders involving the cochlea (usually the hair cells) or 8th N. • Central – Disorders affecting the CNS (brain stem or auditory cortex). Two related terms: Peripheral – Not central; i.e., conductive or sensorineural. Retrocochlear – Disorders involving anatomical structures beyond the cochlea; i.e., 8th N, brain stem, auditory cortex.

9. 3. Cause or Etiology of the Disorder Hearing disorders can be classified on the basis of the cause of the disorder. Some examples: • Ototoxic drugs • Noise exposure • Old age (presbycusis) • Otitis media • 8th N tumors • Meniere’s Disease In this review, we will proceed by functional subsystem (conductive, sensorineural, central), and by etiology within each subsystem.

10. Conductive Hearing Disorders • External Ear • Congenital malformations. There are many of these. Most serious is congenital atresia – collapse or closure of the EAM (ear canal). May occur in isolation, but typically associated congenital malformations of the middle ear as well. • Impacted wax (cerumen) – results in mild hearing loss ; easily treated by removal of the wax.

11. 2. Middle Ear a. Otitis Media • By far the most common cause of conductive hearing loss. • By far the mostcommon healthproblem in children. THANK YOU Contacts Us:- Toll Free- 1800-121-4408 Mail-info@hearingsol.com