Deafness statistics & causes

Dr Sheelu Srinivas Consultant ENT Surgeon

Statistics about hearing lossHearing loss is the third leading chronic

disability following arthritis and hypertension.9 out of every 10 children who are born deaf

are born to parents who can hear.profound hearing disability in India is about

one million 1.2 million people with severe hearing disability0.9 million people with moderate hearing

disability and 7.1 million people with very mild hearing disability.

Taylor/Smiley/Richards, Exceptional Students

What is the History of Hearing Impairments?Denied legal and human rights as well as

education and social interaction1500-1600’s - Spanish began teaching deaf

individuals to communicate.1700s - First free public schools for deaf

individuals began in France.1864 - A. Lincoln authorizes the National Deaf-

Mutes College to grant degrees; the institution later becomes Gallaudet University.

Late 1800s - Oralist movement20th Century – Advocacy for protection of

individual rights and access to inclusion in schools and communities

Development Timing Week 3 - otic placode, otic vesicle Week 5 - cochlear part of otic vesicle elongates (humans

2.5 turns) Week 9 - Mesenchyme surrounding membranous labrynth

(otic capsule) chondrifies Week 12-16 - Capsule adjacent to membranous labrynth

undegoes vacuolization to form a cavity (perilymphatic space) around membranous labrynth and fills with perilymph

Week 16-24 - Centres of ossification appear in remaining cartilage of otic capsule form petrous portion of temporal bone. Continues to ossify to form mastoid process of temporal bone.

3rd Trimester - Vibration acoustically of maternal abdominal wall induces startle respone in fetus.

(These are Human embryonic timings, not clinical which is based on last menstral period +2 weeks)

3 Sources: Inner ear - epidermal otic placode at level of hindbrain. Middle ear - cavity: 1st pharyngeal pouch, ossicles:

mesenchyme 1st and 2nd pharyngeal arches. Outer ear - external auditory meatus: 1st pharyngeal cleft,

auricle: 6 hillocks 1st and 2nd pharyngeal arches

Proactive action in child’s hearing problemCommonest cause of Temporary hearing loss

in children: occurs at critical stage of speech at development

Leads to speech & attention difficulties

Delay in picking up

Hearing loss tricky to spot & give impression of a slow learner

Actually certain sounds do not reach the brain

Brain does not get complete picture

Difficult to comprehend speech at normal volume

Misunderstand or Confused about things in their environment

May appear hearing normally

Reacting to soundsMiss certain pitches or

frequency in sound spectrum

Precious time lost

Between birth & 2 1/2 years child is programming the basic systems

Common causes of conductive deafness-fluid/infection

Primary acquired cholesteatoma

Managing hearing lossConductive- Myringotomy, Tympanoplasty,

Stapedotomy, Mastoid surgery

Sensorineural - Hearing aids, BAHA, Cochlear Implants

Sensorineural hearing lossAbnormality of inner ear & auditory nerve

Majority of the cases inner ear hair cell damage-Cochlear Implant

Auditory nerve damage -Brain stem implant

The Deaf CommunitySupportive, strong

community Does not view hearing

loss as a disabilityRich history and

language (e.g., ASL)Children with

cochlear implants may have limited access to the Deaf community

Cochlear ImplantBionic earHearing is the only special sense which is

conquered Electronic device when implanted provides

sense of soundThe cochlear implant is the most significant

technical advance in the treatment of hearing impairment since the development of the hearing aid around the turn of the century.

Cochlear Implants

Designed to restore some sense of hearing for:• Children or adults who receive little or no benefit from hearing aids.

• Loss must be: (a) profound, (b) bilateral, and (c) sensorineural.

• Problem: Auditory nerve is intact, but hair cell transducers are not functioning.