Physiology of Hearing and Audiology - 2 - Free MCQ Practice Test with solutions,

The other options being conductive pathologies so show no change in hearing.

• In a patient of suppurative labyrinthitis, positive Rinne means SN hearing loss.
• Positive fistula test, see chapter on vestibular system, suggests that there is a fistula on the medial wall of middle ear probably this is the cause of labyrinthitis.
• The fistula test becoming negative after two weeks in the absence of treatment suggest that the ear has become dead and therefore nonresponsive (false negative fistula). So Rinne here will be false negative because of severe SN hearing loss.

In this patient there is 30 dB deafness in left ear, the right ear is normal (so right Rinne positive) and Weber’s is lateralised to the left ear indicating conductive pathology of the left ear (BC > AC on left side).
In left ear the Rinne will be negative.

Here the patient has right sided hearing loss. In the right ear Rinne is negative so there can be 2 possibilities: (a) Conductive hearing loss of right ear (b) Severe SN loss of right ear (false negative Rinne) Weber’s will help us to differentiate between the two.
Since it shows lateralisation to left side which is the better side it means that there is severe SN hearing loss on the right side.

With Rinne test positive in both ears means either the hearing is normal or there is SN hearing loss in other words there is no conductive hearing loss.
Since here the Weber lateralizes to the right means that the left ear has a SN hearing loss as it cannot be the conductive hearing loss of the right side, Rinne being positive here. So the diagnosis is left SN deafness and Schwabach can confirm this.

High frequency audiometry:

• Conventional audiometry tests frequencies between 250 Hz–8000 Hz, whereas high frequency audiometry tests frequencies in the region of 8000 Hz–20,000 Hz.
• It is used to detect early ototoxicity and early noise induced hearing loss as these lead to high frequency hearing loss initially and therefore if detected early these conditions can be prevented or minimised.

If WHO not given go with ASHA categories. Please note for moderately severe it is 56–70 dB. Easy to remember MMS–Moderate and Moderately Severe; 41–70 dB.

Decibels (dB) are measured using a logarithmic scale. The ratio of intensities for a difference in decibels is calculated using the formula: intensity ratio = 10 to the power of (difference in dB divided by 10).

For a 20 dB difference (40 dB compared to 20 dB), this becomes 10 to the power of (20 divided by 10), which is 10 to the power 2 or 100. Therefore, 40 dB is 100 times more intense than 20 dB.

• Ossicular disruption with perforated tympanic membrane will have rather less hearing loss (38 dB) because some sound is able to enter the windows directly through the perforated TM.
• In Otitis media with effusion the hearing loss is never more than 40 dB.
• In otosclerosis the hearing loss increases with increasing fixation of foot plate and reaches a maximum conductive hearing loss of 60 dB in complete fixation.

Trough shaped or U shaped or cookie bite curve is seen in congenital SN hearing loss and in cochlear otosclerosis.

In impedance audiometry we do tympanometry which is a measure of the condition of the middle ear at the level of TM.

• Pure tone audiometry tests the threshold of hearing at various frequencies. It tells about the type and degree of hearing.
• Caloric test is a test of vestibular function.
• BERA tests the peripheral and central auditory pathways.

• In Otosclerosis As type curve is seen.
• In ossicular discontinuity Ad type curve is seen.
• In TM perforation Tympanometry cannot be done as it is not possible to do pressure changes hence a flat curve is obtained.