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Acoustic neuroma diagnosis

Unsatisfactory situation with diagnosis of acoustic neuroma

Diagnosis is still the weakest link in the chain of the acoustic neuroma disease: early and late symptoms – diagnosis – decisions on treatment – treatment – rehabilitation. This is very serious as if it is diagnosed late, the chances of curing it worsen drastically.
The fact is that an acoustic neuroma shows clear symptoms » (Link to acoustic neuroma symptoms). It is also a fact that these symptoms are not solely specific to this brain tumour. However, unfortunately it is also a fact that when it comes to explanations, interpretation and analysis of these symptoms a lot still goes very wrong, both with patients and doctors.

Those affected, particularly females and workaholics, tend to play down, belittle and negate complaints. Doctors (only some, but unfortunately still too many) tend to dismiss such symptoms like tinnitus, sudden deafness, hearing loss, headaches and dizziness as general complaints, as a consequence of overworking, stress or "normal aging". As such, treatment is equally outrageous and ranges from tranquilising drops to massages. Those affected feel like wimps or hypochondriacs and the acoustic neuroma grows and grows ......It still happens that the situation comes to a head and genuine emergency operations become necessary, such as was the case for forum members monula and Dirky Harry.

Luckily, there are also several doctors – general practioners, specialist ENT doctors, neurologists and even orthopaedists – who either immediately, or at the latest with the onset of two or more of these symptoms, arrange for the sole test that can prove the presence of an acoustic neuroma brain tumour: a Magnetic resonance Tomography (MRT).

Intra and extrameatal positioned acoustic neuroma in Stage B as per WIGAND and of Type 2 as per SAMII; schematic representation.

The Anamnesis

Prior to beginning the particular diagnostic procedure, the anamnesis (medical history) should always be compiled in a thorough discussion between the doctor and patient.

What can be done with tinnitus?

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.

Hearing tests for hearing loss

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./p>

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.

Determination of impulse transmission via the acoustic nerve

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.

BERA results: the healthy ear on the left, and on the right the ear where an acoustic neuroma has damaged the auditory nerve. It is clear to see the increase in the so-called Latency I to V in the right-hand picture (source: Homepage of the University Hospital Gießen and Marburg).

Review of the sense of balance with balance disorders

Similarly here, first of all obvious and frequent presumable causes, such as extreme blood pressure readings, physical exhaustion, and inflammations in the middle and inner ear need to be checked and ruled out. Of the countless possible balance tests, here only a few are mentioned.

Nystagmus test
... by means of a calorimetry:
By rinsing the outer ear canal with warm water, the balance organ is provoked, which triggers a reflex in the eye muscles – the eye jerks horizontally. If this reflex is absent or fails to be symmetrical, this indicates a disorder in the balance organ. The eye movements are observed via the so-called Frenzel glasses.

... by means of a swinging swivel chair:
The patient sits on a swivel chair that is rotating, and opens and closes alternate eyes whilst turning and after the chair is stopped. Similarly the eye reflexes are registered, this time via small sensors attached near the eyes.

Stepping tests and blind walk:
The patient stands on the spot with outstretched arms with open and closed eyes. At the same time, the deviation of the centre of the head from the starting position shall be recorded by a camera placed over the head. During this test the patient wears a cap with small lamps.

Standing test:
The patient stands (with secured straps) on a free-moving, small disk and has to keep their balance whilst upright. For this he/she exercises shifting pressure with parts of the foot on the disk. This "print" provides conclusions on the degree of damage to the balance organ.

Standing test (source: Homepage of the University Hospital Erlangen)

A compilation of the most important functional tests in the case of a suspected acoustic neuroma can be seen in a compilation by Erlangen University Hospital: » Functional tests for a suspected acoustic neuroma (german).

Proof of an acoustic neuroma through an MRT

Whilst hearing and balance tests prove functional disorders and thereby permit conclusions on the (possible) existence of an acoustic neuroma, the Magnetic Resonance Tomography (MRT) shows the anatomic relationships in a selected part of the body.

The Magnetic Resonance Tomography (MRT), previously also called a nuclear spin tomography, has an outstanding importance for tumour diagnoses as an imaging method. The possibility to generate very high contrast and overlap-free images of soft tissue is particularly valuable. Its specialty, in contrast to a CT, lies in the fact that sectional images cannot only be represented horizontally, but rather in every and any level of space. For example, this makes it possible to have a virtual view of the area being examined from an angle which an observer cannot normally view the area in question. Therefore, the MRT not only provides the best data for diagnoses, but also immediate information for later treatment, both for planning radiotherapy and operations.

Another advantage is that no x-ray or other ionising rays are applied. Sophisticated: the hydrogen atoms of a human body are used themselves to produce the image: the core of the hydrogen atoms aligns itself in a magnetic field, like a compass needle. After the introduction of radio waves, they record the energy and are deflected. After switching off the radio waves, they rotate back to their original state and emit the energy in the form of resonance waves. These signals are caught by coil-shaped antenna and converted by high-performance computers into images.

The resulting images have outstanding spatial resolutions, they are high-contrast and display even the smallest changes in soft tissue. The documentation is especially successful with coronary examination films. Coronary section images are tomographies that are produced from the crown towards the feet and parallel to the face. Through prior administration of contrast agents (Gadolinium) this effect can be further emphasised. Nowadays, by using an MRT an acoustic neuroma with an average diameter of only a few millimetres can be detected and displayed. With the so-called CISS sequence, you can even display the individual cranial nerves in the ear canal and cerebellopontine angle, as well as clearly detecting the spread of the acoustic neuroma.

To take the pictures, the patient lies down on a bed, which is slid into a so-called "tube" about one meter in length. The periodic, extremely loud beating of the crashing magnetic fields is not altogether pleasant. However, wearing earplugs makes it more manageable.

Recently , so-called open nuclear spin tomographies (High Field Open) have been used increasingly. With these, the patient lies freely and not in a narrow tunnel. These machines are particularly suited to those patients who suffer from claustrophobia in closed spaces.

No genuine acoustic neuroma diagnosis: CT

A Computer Tomography uses x-rays. While with classic x-rays a virtual screening of the body in one direction is taken leading to a summary picture with overlays, a Computer Tomography produces layer images at right-angles to the direction of the radiography, free from overlays. Therefore, this also creates a three-dimensional impression of the body part being examined. The patient also lies on a bed, while the x-ray machine silently rotates around his/her body axis.

With CT images the body is x-rayed in layers as the x-ray machine rotates round the body axis. This ensures that it is able to take overlay-free, cross-sectional images, in contrast to conventional x-ray images. Iodine can be used as a contrast agent to increase the contrast of the images.

Although a Computer Tomography doesn't show an acoustic neuroma directly, it does, however, show whether the bony ear canal has been widened, which would indicate the existence of an acoustic neuroma. CTs have more importance for operation planning, because they display the bone structures - the posterior fossa and the bony ear canal - very well.

Special neurological diagnostics

If the dreaded later symptoms appear, due to a late diagnosis of an acoustic neuroma, occasionally additional neurological and also potential internal examinations are required. These serve more for operation planning than for actual diagnosis and will not be described here in more detail.

Classification and categorisation of acoustic neuroma brain tumours

WIGAND has defined a three-stage classification – see the schematic representations here:

Initial situation

Initial situation: The tumour sits on the nerve in such a way that its weight prevents the blood supply required for proper nerve function (vascular compression).

Tumour size stage A

Tumour size stage A: The tumour is limited to the inner ear canal and its size (average diameter) is between 1 and 8 mm.

Tumour size stage B

Tumour size stage B: The tumour spreads into the cerebellopontine angle and has a size of between 9 and 25 mm.

Tumour size stage C

Tumour size stage C: The tumour has contact with the brain stem and is larger than 25 mm.

SAMII defines six tumour classes:

T1: clear intrameatal tumour (in the bony ear canal)
T2: intra and extrameatal tumour part (within and outside of the bony ear canal)
T3a: Tumour fills the cerebellopontine cistern (between the cerebellum and brainstem)
T3b: Tumour reaches the brainstem
T4: Tumour compromises the brainstem
T4b: Tumour compromises the brainstem and displaces the four ventricles (cerebral ventricle)

Recommendations for diagnosis of a suspected acoustic neuroma

All diagnosis procedures are painless for the patient and not particularly time consuming. The procedures are diverse and interesting both technically and in terms of methodology, so perhaps you can even take a little pleasure from the diagnosis. If they show a clear result, in any case it's always better to find out the truth in a timely manner than to find out later on.

As a lesson from many diagnoses that have unfortunately been made too late, the following is recommended:
If one of the typical acoustic neuroma symptoms occurs, you must push to get a clear response as to the possible causes and to rule out other causes. Watery explanations or dismissive statements should not be accepted. A Computer Tomography should be rejected as a cheap, imaging diagnosis procedure. With no obvious, yet to be clarified causes when it comes to a tumour, you always have to consider an acoustic neuroma. At the latest with the appearance of two symptoms you should demand a Magnetic Resonance Tomography. Initially, only small complaints are no reason to postpone an intensive diagnosis work up, rather it is an opportunity to seize: the sooner an acoustic neuroma is diagnosed, the bigger the chances of a successful and complication-free treatment!

» Guidelines of the DGNC (German Society for Neurosurgery) medical association for an acoustic neuroma diagnosis

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