In this article, we will discuss Auditory Function Tests (Tuning Fork Tests). So, let’s get started.
Auditory Function Tests (Tuning Fork Tests)
Differentiate hearing loss cause
A. Sensorineural hearing loss
B. Conductive hearing loss
Tuning fork should be 512 Hz (preferred) to 1024 Hz.
It is focused on determining whether the loss is sensorineural or conductive. In the Weber test, the stem of a tuning fork is placed gently against a midline structure of the skull (vertex) and the patient is asked where she/he hears the sound. Sound is transmitted to both ears through the air, but particularly through the vibrations of the bones of the skull. If sound is transmitted to both sides equally, the sound is heard in the midline and it can be presumed that the conduction and neural apparatus is intact. With neural deafness, the sound transmits best to the normal side and the patient lateralizes the sound to that side. With conduction deafness, sound transmits best to the side of the deafness. This is thought to occur because ambient sound is prevented from getting to the cochlea on the blocked side. This causes the nervous system to amplify sounds on that side by sensitizing cochlear transduction.
This tests both bone and air conduction. The examiner places the butt of a vibrating tuning fork on the mastoid region, and when the patient ceases to hear the vibration, the examiner places the tines close to the external auditory meatus to check air conduction. Vibrations perceived through air are heard twice as long as those perceived through bone, so the normal individual reports, e.g., hearing the bone vibration for 30 sec and then continues to hear the vibration through air for another 30-60 sec altogether. If there
is conductive deafness, bony conduction is either normal or slightly enhanced, whereas air conduction is decreased. If there is neural deafness, both bone conduction and air conduction are equally suppressed. As with the watch tick, the examiner should compare the ability of both sides to perceive the fork. A comparison of the patient’s ability to perceive the fork, as well as the watch tick, with the examiner’s ability is also useful (Schwabach test).