To diagnose this often very early symptom there is no need for any diagnostic procedure. The patient feels it, describes it, and the listener, whether it is a doctor or not, must accept it as so.
Identifying and classifying tests, pitch, frequency, rhythms or types of noise, are irrelevant for the tinnitus results in connection with an acoustic neuroma brain tumour.
First of all, the outer accessible part of the ear should always be examined for visible pathological changes, foreign bodies or inflammations in the ear, etc. Independently of whether the hearing loss arises gradually or abruptly (sudden deafness), there are several (audiometric) procedures to diagnose and quantify it.
A tone audiometry tests the hearing ability, whereby tones of different levels (frequencies) and volumes are fed into one ear through headphones, whilst the other ear is neutralised by means of a general noise level. The result is a so-called tone audiogramme.
The speech audiometry tests hearing ability for speech, whereby words are introduced via headphones at different volumes into each ear. Above all, it relies on the understanding of one syllables and the clear recognition of similar sounding words. The result is a so-called speech audiogramme.
Both these procedures are subjectively moulded. The patient plays an active part, in that he/she signals when he/she hears a tone and what he/she has understood.
Objective procedures are notbased on statements made by those affected. They measure the functionability of the auditory nerves without direct active participation from patients and this is recorded. The terms for it sound complicated: (E)AEP – (early) Auditory Evoked Potential or BERA – Brainstem Electric Response Audiometry.
Clicks, that are very short sound stimuli, are generated on an amplifier and played via headphones at a distance of a few hundredths of a second (the short intervals all allow for transmission of a lot of signals), transmitted through the middle ear and triggering nerve impulses in the inner ear, which reach the brainstem via the auditory nerve. On the way there, the signals are processed several times in so-called switching stations, switched and triggering a typical electric potential change, which can be measured by measurement electrodes on the scalp. The stimuli are measured with electrodes, which are mostly attached to the skin in the upper half behind the ear, placed on the mastoid bones of the petrous bone, on the forehead and the crown.
These potential fluctuations appear in the BERA records as mountains and valleys (maxima and minima). The speed of the impulses relayed between the cochlea (where the impulse enters) and the brainstem (the impulse response) are measured. The time delay (latency) between the impulse entry and the impulse response is longer if the auditory nerve, or its nerve sheath, is damaged. Therefore, functional disorders in the auditory nerve, which would be caused by an acoustic neuroma, can be unequivocally detected and localised. It is possible with very small acoustic neuroma that no time difference between the ears will be detected.