Pure Tone Audiometry
Diagnostic tests assesses the hearing sensitivity of patients. It is performed in a sound booth/sound treated room. This test uses a highly specialized instrument called the audiometer and only a trained personnel, usually an audiologist or equivalent, can perform the testing. A patient will be introduced to a series of sound tones and is expected to react each time upon hearing the sound.
Average testing time is around 20-30 minutes and requires active participation of the patient (subjective test). A diagnostic PTA test assesses two sound conduction pathways; the air conduction and the bone conduction. The results are then plotted in an Audiogram.
Audiogram is a function of frequency and intensity. Audiogram enables accurate diagnosis of hearing loss for an individual.
This is an objective test which assesses the status of the middle ear. This test is performed by placing a probe into the ear canal. Air pressure is pumped into the ear canal via the probe which is connected to a tympanometer. The compliance of the tympanic membrane/ear drum is measured and compared to the norms. Tympanometry is a valuable component of the audiometric evaluation. In evaluating hearing loss, it helps in differential diagnosis of sensorineural and conductive hearing loss.
Otoacoustic Emissions (OAEs)
(OAEs) procedure is fairly quick and involves a small probe (or plug) being placed in the ear. The child then hears a series of “clicks” or tones through the probe. OAEs measure whether or not the outer hair cells in the cochlea are functioning normally in response to sound. OAEs test each ear individually but cannot give information about the degree of hearing loss. If a hearing loss greater than 40dB is present, no emissions will be measured. OAEs are used mainly as a way of finding out whether or not the hair cells in the inner ear are functioning properly. If a child has OAEs they are likely to have near normal hearing in that ear or at the frequencies where OAEs are measured. The exception to this is where a child has Auditory Neuropathy and the OAEs do not predict the hearing ability.
Acoustic Reflex Threshold Test (ART)
ARTs record the contraction of the stapedius muscle in response to higher intensity (70-100 dB) tones at various frequencies. Presence of ART’s at 70-80 dB are indicative of hearing within the normal hearing range; while elevated or absent ART’s are indicative of hearing loss. A complete ART testing involves the testing of ipsilateral and contralateral pathways.
Speech Discrimination Test
This test is usually done to assess the patient’s ability to detect speech sounds (Speech Reception Threshold) and the ability to recognise speech sounds (Discrimination). Scoring is done at phoneme level (individual speech component sounds).
Speech reception is typically the threshold where the patient scores approximately 50%. Discrimination scores are plotted on a speech audiogram and the objective is to verify its consistency to the pure tone audiogram and to plot the predictive value of amplification (pre-hearing aid fitting).
The test can also be used to assess the benefit of hearing aids used (post-hearing aid fitting). In such cases, the test is done in live-voice in the free-field.
Eustachian Tube Dysfunction Test
This test is done to verify the status of the Eustachian tube, which is the communication pathway between the middle ear and nasopharynx. This is usually done to confirm suspected Eustachian tube dysfunction secondary to otitis media, middle ear effusion and other nasopharyngeal abnormalities.
The presence or absence of dead regions can have important implication for fitting of hearing aids and for predicting the likely benefit of hearing aids for that individual. It is also a good test to assess potential usefulness of cochlear implants.
Tinnitus Diagnosis & Management
Once the medical causes of tinnitus are ruled out, tinnitus must be managed by a professional. There is no one-size-fits-all solution for tinnitus, and so, it must be managed by determining the best approach for each patient’s unique and individualised needs.
Tinnitus handicap Inventory (THI) is administered to measure the severity of the tinnitus as experienced by the patient. Tinnitus retraining therapy (TRT) uses various counselling techniques to help the patients overcome their perception on tinnitus. Sound generators are used in TRT to produce background noise. Such noise provides both distraction and relief in silent situations when tinnitus is most exposed.There is no one-size-fits-all solution for tinnitus, and so, it must be managed by determining the best approach for each patient’s unique and individualised needs.