Optimized Diagnostics - Hearing

Otogram™ Test Battery

The Otogram’s comprehensive test battery includes Pure-tone Air and Bone Conduction, Speech Reception Threshold, Speech Discrimination, Stenger and Patient Self Assessment Survey. Some models also include Most Comfortable Loudness Levels (MCLs), Uncomfortable Loudness Levels (UCLs), Tympanometry, Acoustic Reflexes and DP Otoacoustic Emissions. Masking is applied as appropriate for all subjective tests.

 

Pure-Tone Air and Bone Conduction with Masking

Pure-tone air conduction testing presents a series of tones through the ear inserts to the patient (ranging from 250 Hz to 8000 Hz) to measure the lowest level (in decibels) that the patient can hear the tones fifty percent of the time. Tones are presented using accepted conventional modified Hughson-Westlake method to vary the intensity of tones at randomized intervals.

Pure-tone bone conduction tests the same discrete frequencies as with air conduction but does so in a way that bypasses the outer and middle ear systems, thereby revealing the hearing thresholds of the inner ear alone. This test is used to isolate the location of the impaired part of the auditory system.

The Otogram automatically calculates and applies the amount of masking needed in real-time as thresholds are obtained. The algorithm calculates the worst-case scenario for crossover from the test ear to the contralateral or non-test ear using frequency-and transducer-dependant interaural attenuation values for insert earphones.  If the crossover exceeds the bone threshold on the contralateral ear, then masking is required.  The Otogram then sets the masking intensity at minimum effective maksing plus 5dB.  This level is required in the non-test ear in order to overcome the air-bone gap and deliver masking noise sufficient to mask the crossover tone. The algorithm is designed to prevent the non-test ear from hearing the test stimulus and is applied only as needed. The amount of masking above or below effective masking levels may be configured by the clinician for each stored protocol. Prior to implementing masking, the Otogram provides instructions to the patient through the insert earphones.

 

Speech Reception with Masking

While pure tone testing reveals how well a patient hears, speech testing examines how well a patient is able to understand what he hears. Because we communicate using speech instead of tones, understanding how well a patient is able to use his hearing to understand speech is important for gaining an overall appreciation for a patient’s loss and its effects on daily conversation.

The Speech Reception Threshold test measures the lowest level (in decibels) that a patient can understand speech. The Otogram uses recorded speech which is more consistent than “monitored live-voice”. The closed-set Picture Identification Task (PIT) is a validated protocol using commonly accepted spondee words. The Otogram scores closed-set tests by giving more weight to an incorrect response than a correct response.

 

Speech Discrimination with Masking

Speech discrimination testing presents rhyming words (e.g., mop, stop, top, shop) to the patient at a comfortable volume to determine whether or not the patient has difficulty discriminating between words that sound similar. The presentation level is set to the level that the Articulation Index predicts will yield the best speech discrimination for the patient’s measured pure-tone thresholds. It may also be configured based on the pure tone average or a fixed amount. Between 12 and 48 words are presented in each ear until an 85% confidence interval is achieved. The Otogram also calculates Unexplained Discrimination Loss and can be tested using open-set NU-6 or CID W-22 word lists.

 

Tympanometry

Tympanometry measures the mobility and the pressure within the middle-ear system by presenting a tone and varying air pressure in the ear canal and then measuring the ability of the tympanic membrane to reflect and absorb sound. As a measure of middle ear function, tympanometry can help identify issues with the eardrum or the middle ear such as a perforated tympanic membrane or otitis media.

 

Acoustic Reflexes

The acoustic reflex is a reflexive contraction of middle ear muscles in response to a loud sound. There is much debate about the purpose of the acoustic reflex. It could serve a protective function against overly-loud sounds or perhaps be designed to maintain proper positioning and tension on the ossicular chain. Although there are different theories regarding the purpose of the acoustic reflex, it is agreed that the response follows an arc from the cochlea, up the 8th cranial nerve to the lower brainstem and down the 7th cranial nerve to ultimately contract the stapedius muscle. Different pathologies or degrees of hearing loss can affect the acoustic reflex making it a useful diagnostic tool.

 

Distortion Product Otoacoustic Emissions

Otoacoustic emissions are sounds generated by healthy outer hair cells inside the cochlea. In measuring Distortion Product Otoacoustic Emissions or DPOAEs, two different tones are simultaneously presented to the ear at different intensity levels. When the outer hair cells are healthy (i.e., there is no peripheral hearing loss), they will respond to the stimulus tones by generating a third unique tone that is not identical to either of the two stimulus tones. Because only healthy cochleas produce emissions, when the otoacoustic emissions are absent, a diagnosis of hearing loss is definitive. The limitation of otoacoustic emissions is that when they are absent, the only thing that is certain is that the patient has a hearing loss but it does not reveal the type or degree of hearing loss that is present. Whether the loss is mild or profound, sensorineural or conductive, the emissions are simply absent so further testing must be done to define the hearing loss.

 

Stenger

The Stenger principle states that if a sound is played in each ear, the listener is only aware of the louder tone. Based on that principle, it is possible to evaluate a patient for a unilateral functional hearing loss. A functional hearing loss is a non-organic loss or one in which a patient is “functioning” as a person with hearing loss when hearing loss is not actually present or is less significant than that indicated by a patient’s volunteered thresholds. There are many different reasons why a patient may be motivated to malinger from monetary to psychological, but there is generally some perceived benefit from having a hearing loss. Since accurate diagnosis is paramount to patient management, the Otogram discreetly and automatically employs a frequency-specific Stenger Test any time a patient’s behavioral thresholds deviate by more than 35dB between ears. The results of the Stenger Test are displayed on the patient report.

 

Self-Assessment Survey

The Otogram offers a few patient-report surveys including the Hearing Handicap Index for the Elderly (HHIE), the Hearing Handicap Index for the Elderly-short version (HHIE-S), the Mayo Clinic Survey and the Hearing and Balance Survey. Each survey presents a variety of questions to assess the perceived impact of the patient’s hearing loss on his or her everyday communication. The questions target issues surrounding difficulty communicating in different environments (e.g., one-on-one, group, TV viewing, etc) as well as the emotional consequences of those communication breakdowns. Two patients with similar test results can have drastically different reports of how debilitating the hearing loss is making it important to consider personal perception.