Audiologist TREATMENT

Pure Tone Audiometry Pure tone audiometry is a test of hearing sensitivity involving threshold determination at varying frequencies. It mainly involves measurement of hearing levels across a wide frequency range with the help of an audiometer. Threshold is the lowest or softest audible tone and is measured in decibels(dB). Normal hearing range is 25dB or lower across 250Hz to 8kHz. Audiometry test is done in a quiet environment. During the test, patient is made to wear headphones and he hears a range of sounds differing in pitch and intensity. It is thus a noninvasive test. The results are plotted on a graph called audiogram. It is thus a basic test of hearing. The results of the test are used to diagnose degree of loss (varying from mild to profound) or the type of loss whether neural(damage to nerve/cochlea) or conductive (ear drum or ossicles). It is also used to diagnose diseases of the ear or to monitor ill effects of ototoxic drugs and noise. Thus after diagnosis of hearing impairement, PTA provides a guideline in whether hearing aids or surgery will improve one’s hearing.

The primary purpose of impedance audiometry is to determine the status of the middle ear and mobility of the tympanic membrane and conduction of sounds by ossicles. It also assesses the acoustic reflex pathways including the auditory brainstem & cranial nerves 7th & 8th. This test cannot be used to directly assess auditory sensitivity, although results are interpreted in conjunction with auditory threshold measures. Acoustic immittance is a measurement of energy or air pressure flow, which involves the ear canal, ear drum, ossicular chain, tensor tympani, stapedius muscle, cochlea, cranial nerves 7th and 8th and the brainstem. Mass, mobility, and resistance of outer and middle ear systems affects this test. The reciprocal of acoustic impedance is acoustic admittance. Particularly in earlier years, these measurements were perfomed in impedance rather than immitance measures, thus impedance audiometry is sometimes used. Impedance audiometry mainly includes tympanometry, thresholds of acoustic reflex, reflex decay & eustacian tube function. They help in determining the functioning of central auditory system & determine conditions like eustacian tube dysfunction, tympanic membrane hypermobility, tympanosclerosis, otosclerosis, M. E. effusion, ossicular discontinuity, facial nerve function, hearing loss as well as brainstem disorders.

A Hearing aid is an electroacoustic device which typically fits in or behind the wearer's ear and designed to amplify and modulate sound for the wearer. Hearing aids are thus basically battery powered electronic devices which make listening easy for the individuals with hearing loss. It consists of a microphone, amplifier & a receiver. The microphone picks up the sound & converts it into an electrical signal, which is then amplified by the amplifier. This signal is then converted back into acoustic signal by the receiver & delivered to the patient’s ear. Hearing aids are mainly used to correct the impaired hearing of the patient or to make one’s speech more intelligible. These devices are just to make sounds more accessible and are not capable of truly correcting the hearing loss. They are thus used to improve the speech perception. Hearing aids can be either analogue, digital or wireless. Hearing Aids mainly use standard button cell zinc air batteries. Hearing aids are coupled to the ear with an ear mould which is created from an impression taken of individual’s ear. This usually ensures a comfortable fit and reduced possibility of feedback. TYPES Behind the ear aids (BTE) Body worn aids Receiver in the canal aids (RIC) In the ear aids (ITE) In the canal aids (ITC) Completely in the canal aids (CIC) Bone conduction Hearing Aids. INDICATIONS Hearing Aids can be used by patients of any age group ranging from infants to geriatric. It can be used for: Hearing loss since birth Hearing loss with old age - Presbycusis Hearing loss with trauma However, not every patient with hearing loss can use hearing aids & needs a doctor’s correct examination for determination.

Brainstem Evoked Response Audiometry (BERA) It is an objective hearing test most popular due to its non invasiveness and standardized parameters. In this test, brain stem potentials are elicited in response to click or tone burst stimuli & the waveform is recorded by placing electrodes over the scalp. >>BERA is useful in following conditions - >It is an effective tool in screening new borns for Hearing impairment. Detection, quantification & identification of nature of deafness in infants, mentally retarded and malingering subjects. . Identification of site of lesion in retrocochlear pathologies. Study of central auditory disorders, Brainstem disorders & certain suspected demyelinated disorders. Study of maturity of central nervous system in newborn. PRINCIPLE OF BERA :- When the sound reaches cochlea, it is converted into an electrical impulse which passes from the cochlea to auditory cortex, where it undergoes some degree of processing at each stations and generates an electrical activity which can be monitored by placing electrode on vertex of scalp. This test evaluates structural integrity of the pathway. CLINICAL USES OF BERA :- ABR is thus used mainly for newborn hearing screening, auditory threshold estimation, intraoperative monitoring, determining the type & degree of hearing loss,& auditory nerve & brainstem lesion detection.