It is important to detect hearing loss early because undetected hearing loss: Impairs intellectual development. Poor speech and language. Serious communication handicap.
Sensorineural deafness prior to the 3 years of age is about 1/1000. Conductive deafness is probably higher in incident but it is more difficult to ascertain(about 15% of preschool children) and it is remediable if detected. More common in low socioeconomic classes. More common in down syndrome, mental retardation, cleft palate and other craniofacial disorders.
Causes of hearing loss in children:3. hereditary(49%) Congenital: mondinis (abnormality in the inner ear that can be the cause of hearing loss.A person with Mondini dysplasia has a cochlea that is incomplete. A normal cochlea has two and a half turns, a cochlea with Mondini dysplasia has two, one and a half, one, or no turns (or increments). This results in gradual or even sudden hearing loss that may be profound. Delayed: familial progressive sensory neural hearing loss, otosclerosis ; an abnormal growth of bone near the middle ear(AD, teenages).
1. Non-hereditary (51%) Prenatal: ototoxic drugs, alcoholism, dm, irritation and infection such as rubella, CMV and syphilis. Perinatal: hypoxia, ototoxic drugs, traumatic delivery, premature labor, and maternal infections. Neonatal and postnatal: hypoxia, ototoxic drugs, noise induced and infections such as measles, mumps, meningitis and encephalitis.
Family history Defects of ENT (low set ears, cleft palate). Birth weight < 1500 g. High serum bilirubin concentration > 20 mg/dl (potentially neurotoxic). Meningitis Hypoxia Maternal infection.
The test of choice in a baby up to 24 months of age is orientation test using noise maker which is put outside the visual field of the child for at least 10 seconds then a sound is made. Response :-4. Up to 4 months: auropalpebral reflex (eye widening or blinking, beginning of primitive head turn or arousal from sleep or sudden tightening of the eyelids if he was asleep)
1) 4-7 months :- localized to side (horizontal only)2) 7-9 months :- localized to side and indirectly below3) 9-13 months :- localized to side and below4) 13-16 months :- localizing to side and below and indirectly above.5) 16-24 months :- localizing all signals at any angle.
No localizing doesn’t always mean hear loss, it may mean :- Lack of interest Delayed auditory maturation. Mental impairment. Physical impairment.as the child grows older >2 years his threshold response to noise maker decreases from 70 to 25 dB.
This is connected to the maturation of auditory function. 1st month: normal infants gurgles and crying 2nd month: infant starts to put out certain sounds more than the others 2-4th month: babblings begins. 6th month: glottal and labial sounds begin. 9-10th month: glottal sounds decreases and alveolar sounds are frequently used. 12th month: should have at least 1 word.
18th month: should have at least 6 words. 2 years: express himself in two words sentences. 2.5 years: point to body parts on command. 3 years: should know his first name, name of toys. Babbling ceases at the age of 6 months, and the next months comprise progress in vocalization, during this period the mothers feed back helps him to form his first words, so deaf infants have normal vocalization up to age of 5-6 month, after that lack of feed back cause vocalization to cease.
Impedance audiometry: used to evaluate middle ear, it is sensitive in differentiating between normal and pathological middle ear includes: tympanometry + measuring middle ear pressure + phyisical volume test to evaluate the tympanic membrane. Tympanometry measures sound reflection from the tympanic membrane, while the operator varies air pressure in the ear canal.
Heart rate audiometry: increase in heart rate following loud sounds, in neonates heart rate increases during 2-6 seconds following the stimulus.
Respiratory rate audiometry: in respiratory rate following loud sounds. Brainstem evoked response audiometry: recording of the electrical potential of the auditory pathway based on computer averaged electroencephalographic recordings following acoustic stimulus presentation, it cancels the brain activity. The brain stem evoked response consists of 5 +ve waves occurring within the initial 12.5 ms post stimulus, it is useful in evaluating hearing in infants.
For older children, pure-tone audiometry can be performed, as well as tuning fork tests.
A pure-tone audiogram is the standard test of hearing level. The readings are recorded on a chart with intensity and frequency. A normal tracing is between –0 dB and +10 dB at all frequencies.
Has frequency of 512 Hz 1- RINNE’S TEST 2- WEBER’S TEST
A comparison is made bw hearing elicited by placing the base of the tuning fork applied to mastoid bone, then after the sound no longer appreciated, the vibrating top is placed one inch from external canal
The tuning fork is placed on the patient’s vertex or forehead, if the sound laterizes the Patient may have ipsilateral conductive deafness or contralateral sensorineural deafness. If the sound heard centrally so : Normal hearing person OR Equal degree of loss in each ear