December 16, 2013
Screenings vs diagnostic evaluations
Hearing centers may occasionally produce marketing materials enticing potential patients or clients with “free hearing screenings”. While the idea of getting some service for free may be appealing, and while quick screenings can be useful at informal occasions such as health fairs, they are of extremely limited benefit to people who have genuine concerns for their hearing or ear health.
The purpose of a screening is to identify a potential problem with hearing or the health of the ears. The subject is asked to respond to tones presented to one or both ears until the lowest levels of sound detected by the subject are recorded. This may be performed in a room that is not isolated from outside noise. The only information generated in this scenario is difficulty with certain tones in the specific environment used for the screening. Precise hearing levels in quiet, word recognition, and “site of lesion” (outer ear, middle ear, inner ear, auditory nerve pathway, etc.) cannot be evaluated in this manner. A “failed” screening identifying a potential problem should necessitate a full diagnostic battery.
Diagnostic audiometric evaluations are always the standard in identifying and quantifying disorders of hearing and their likely origins. Appropriate treatment depends on accurate, reliable and valid examinations of the elements of hearing in a sound-shielded environment. In our office we “work our way inward”. We begin with a fiber-optic high-resolution magnified video image of the outer ear structures, from the pinna (visible area) through the canal to the eardrum. Is cerumen (ear wax) interfering with hearing? Then, since we cannot see past the drum, we use tympanometry to determine the health of the middle ear space. This includes the three tiny bones (ossicles) behind the drum and the Eustachian tube. This structure drains the middle ear to the throat and allows air to infiltrate the space. Acoustic reflexes rely on the auditory nerve and facial nerve while protecting us from loud sounds. Otoacoustic emissions use a variation of SONAR technology to gauge the integrity of cells in the inner ear hearing organs.
Along with these “objective tests”, the subject must enter a sound-treated booth and don special headphones or earphones and respond to tones. Ear-specific threshold levels are obtained for many frequencies, revealing the absolute limits of hearing. Threshold levels for words are also measured, after which word recognition percentage is determined for each ear using approved word lists at a “comfortably loud” level. Bone conduction tone thresholds should be measured, in order to determine if a “conductive loss” in the outer or middle ear is preventing sound from reaching the inner ear.
All the diagnostic information can be integrated by an audiologist to determine if atypical results require referrals to other professionals, such as otolaryngologists. These physicians may order imaging studies and/or diagnose diseases of the ear that may be treated medically or surgically. More typical results are evaluated for level of impairment, in order to inform the audiologist and patient and guide the best options. Caring for ears and hearing often takes a team effort. A five minute screening is not sufficient for effective management of most patients.