Various tuning fork tests are used to detect functional impairment of peripheral nerves and to identify and differentiate hearing problems according to conductive and sensorineural disorders. Medical offices usually use a specialized tuning fork that vibrates at 128 hertz for hearing tests and at half the frequency, 64 hertz, for vibration tests of the nerves with small weights attached.
What is the tuning fork test?
Tuning fork tests are used at specific points on the body to test the function of peripheral nerves and to determine if hearing is impaired. Tuning fork tests are used at specific points on the body to test the function of peripheral nerves and to detect hearing impairments. Different tuning fork tests can be used to distinguish between conductive and sensorineural problems. Sound conduction problems affect the mechanical part of the auditory organ, i.e. the outer ear (pinna and external auditory canal) with the eardrum and the middle ear with the mechanical-acoustic transmission of sound waves to the cochlea. In the cochlea in the inner ear, the incoming sound waves are converted by the hair cells into electrical nerve signals, which are transmitted by the auditory nerve (vestibulocochlear nerve) to the central nervous system (CNS). Reduced hearing due to conversion, transmission or processing problems of the sound stimuli, i.e. the electrical-nervous part of the auditory organ, are sound perception disorders. Three different, easy to perform, tuning fork hearing tests are available to distinguish sound conduction disorders from sound perception disorders. The hearing tests are performed with the so-called Rydel and Seiffer tuning fork at 128 Hz. Neurological tuning fork tests to check the functionality of peripheral nerves take advantage of the fact that a certain type of rapidly adapting and particularly vibration-responsive mechanoreceptors in the skin, the Vater-Pacini corpuscles, very sensitively reflect nerve conduction problems. Like the hearing tests, the neurological vibration tests are performed with the Reidel and Seiffer tuning fork, but with the vibration halved to 64 Hz compared to the hearing tests. On the stem of the tuning fork, a scale of 0 – 8 can be read to determine the strength at which the vibrations are perceived.
Function, effect and goals
Vibration tests with the Rydel and Seiffer tuning fork are used for early detection of any neuropathies that may be present due to pre-existing conditions such as diabetes or the autoimmune disease multiple sclerosis (MS). Functional damage to the nerves caused by chemotherapy, medication or chronic alcohol abuse can also be tested. Lesions of certain nerves due to entrapment (carpal tunnel syndrome), herniated discs and the like or due to an injury are also areas of application of the vibration tests. Vibration tests can also be used to draw conclusions about functional failures of certain regions in the brain, for example after a stroke or a craniocerebral trauma. For the easy-to-perform tuning fork or vibration tests, the Rydel and Seiffer tuning fork with a vibration rate of 64 Hz is used. The vibration rate is within the response spectrum of Vater-Pacini cells, which are commonly found in the skin and are particularly sensitive sensory cells belonging to the class of rapidly adapting mechanoreceptors. Typical points for testing vibration sensation are the outer and inner ankle of the foot, on the tibia below the kneecap at the attachment point of the thigh muscles, on the iliac crest and on the sternum. The specialized tuning fork allows determination of a (subjective) threshold for vibration sensation on a scale of 0 to 8, with 8 representing the lowest strength. Vibration tests that reveal pathological values at specific body regions must be further clarified with other diagnostic procedures for verification and a more differentiated statement. Three different methods, the Weber, Rinne and Gellé tests, are available for the relatively simple hearing tests. In the Weber test, the tuning fork is struck and the foot is held firmly on the center of the skull (crown). The sound is transmitted to the skull bone and is perceived equally strongly in both ears of a normal hearing person.If the sound is perceived louder in one ear, this indicates a one-sided sound conduction disturbance in the ear with which the bone sound is better perceived or there is a sound reception problem in the other ear. The subsequent gutter test then provides clarity as to what type of hearing loss is actually present. The vibrating tuning fork is held on the bony process behind the auricle. When the patient no longer perceives the fading sound, the still softly vibrating tuning fork is held in front of the auricle. If the patient now hears the sound again via the air conduction through the external auditory canal, but at the same time suffers from reduced hearing, the findings indicate a sound perception disorder. If the patient is suspected of having otosclerosis, a calcification of the ossicles in the middle ear, the suspicion can be confirmed or refuted by the Gellé test. As in the Rinne test, the tuning fork is held on the bony process behind the auricle and at the same time the external auditory canal is closed and a slight positive pressure is built up, which stiffens the ossicular chain a little and temporarily reduces hearing. If the sound of the tuning fork sounds softer after the pressure is built up, the sound conduction in the area of the ossicular chain is okay. If the volume does not change, this may be taken as confirmation of suspected otosclerosis.
Risks, side effects, and hazards
All tests and experiments performed with the Rydel and Seiffer Tuning Fork in neurology or hearing are non-invasive and are not associated with the administration of any medications or other chemicals. Therefore, the tests and experiments do not involve any hazards, risks or side effects and, moreover, are easy to perform. The risk of misinterpretation of the results is also very low. In case of doubt, further diagnostic procedures can be used to clarify the results. When investigating neuronal problems, measurements at the same body points should be repeated several times to ensure that there are no slips in one direction or the other.
