Whenever a child, up to the age of 5 years develops severe loss of hearing due to any cause, the speech is distorted, lost or is not acquired at all. This happens even though the speech center and the speech organs are normal. A person who has never heard the speech or hears a distorted speech, may not speak at all or has a distorted speech which is reproduction of the speech heard by him. If deafness occurs up to the age 5 years, whatever speech that has been acquired, may be lost. Hence this condition is called Deaf–Mutism or server deafness with defective speech. Only sensory–neural deafness can be so server that it may cause Mutism.
Causes of Deaf–Mutism
- Hereditary developmental defects.
- Consanguineous marriages.
- Rhesus incompatibility.
- Diseases affecting the mother during pregnancy:
- German measles.
- Hypertension, pre–eclampasia.
- Prolonged and difficult labor.
- Forceps delivery with injury to the head.
- Autotoxin drugs.
- Virus infections like mumps.
- Head injury.
- Deafness: The child dose not respond to a call from another room or from behind. Patients having very server deafness are unperturbed by a very loud sound produced by a flying airplane or by banging of door.
- Mutism: The child dose not develop speech. If he speaks, his vocabulary is limited to a few words, and his speech is distorted.
- Mental Retardation: If it is present, situation is worsened.
- Mentally Retarded child has a good hearing, but other milestones of development are delayed. His intelligence quotient is low.
- Delayed Development of speech may occur in some children because of being over pampered or neglected by the parents, but their hearing is normal.
- Aphasia of central origin is a rare condition.
- Glue Ear (Serous otitis media) should be kept in mind, but it produce only mild to moderate deafness without impending the development of speech.
- Free field eudiometry may reveal sensory–neural deafness which may very long degree from moderately severe deafness to severe hearing loss, but usually no child is totally deaf. Objective audiometry like tympanometry or evoked response audiometry may also be utilized.
- Intelligence quotient of the patient should be assessed to rule out mental retardation.
Care of such children should be started as early as possible. It should not be delayed beyond the school–going age.
Augmentation of hearing
Hearing aid should be started as early as possible. It can be given to the children even under the age of one year.
Development of speech
Speech therapy: These children do not have defective speech mechanism. Hence the speech should be developed by special training by a speech therapist or a teacher for the deaf, who encourages production of speech by imitation and palpation of spread to other frequencies. Tinnitus may also be present. The damage to the hair cells in the cochlea is irreversible and hence prevention of acoustic trauma is important. 40 hours per week of 90 dB noise is the upper limit of safety for factory workers.
Prevention of Deaf–Mutism
Use of efficient earplugs and periodic audiometric screening may prevent noise induced deafness. Exposure to noise should be minimized, and ideally the noise pollution should be controlled.