Visiting ENT, diagnosis and testing
After visiting their GP most people with severe vertigo are referred to their hospital’s audiology, ear nose and throat (ENT) or neurology department for investigation, diagnosis and management of their condition. Many people often notice dizziness before tinnitus and hearing loss. Episodes of dizziness can have many causes. To diagnose Ménière’s disease it is necessary to exclude many other possible causes during the consultation and investigations at the hospital.
Why perform these tests?
The various tests are performed to:
- Confirm the diagnosis
- Exclude other conditions which require different treatment
- Find out how bad the condition is
- Monitor the progress of the disease so treatment can be given at the right time
- Monitor the response to treatment.
The health professional will want a detailed history of the patient’s condition.
Questions they may ask:
- How the dizziness started?
- How often the symptoms occur?
- What affect they have on the patient?
The doctor will also want to know about any hearing loss, distortion of sounds, tinnitus, the patient’s general balance and other symptoms along with the patient’s general health.
Information about any treatments taken and if they were beneficial will be discussed along with any fears or concerns about the illness, such as work, family or quality of life. The first consultation will involve a physical examination of the patient’s ears, nose and throat looking for local problems such as infection, and a full examination of the nervous system especially the balance system and eyes.
Here is a list of the tests which you may undergo as part of your diagnosis and ongoing management of your condition.
An audiogram tests a patient’s hearing. The test is carried out in a soundproof room. The patient wears headphones and a machine produces tones which are heard through the headphones. This test measures air conduction thresholds, i.e. how sounds are normally heard, coming through the air, down the ear canal and onto the eardrum. The patient also wears a hair band on their head with a bone vibrator which usually sits behind the ear which tests inner ear function. The hearing test does not explain how well everyday sounds are heard but tests response to the quietest sounds which may be heard in a totally artificial scenario. This test is well standardised and does give a reliable guide as to what level a patient’s hearing is at. The machines used are highly calibrated, and there are regulations stating what the sound environment needs to be like to get a reliable test.
The caloric test investigates the function of the horizontal semicircular canal in the inner ear. It gives useful information about balance function and may indicate which ear is affected. It involves stimulating the canal and recording the eye movements (nystagmus) produced and is the test used by most hospital departments. Although the test involves little sophisticated equipment it is complicated and requires the patient’s co-operation. It produces the sensation of vertigo, and the test needs to be repeated several times. The semicircular canal is stimulated by introducing warm or cold water or air into the outer ear canal. The patient lies on their back with their head on an angled rest and asked to fix their eyes on a point or light on the ceiling. The nystagmus will be recorded either visually or by small electrodes adhered to the temples. The sensation of vertigo will stop within a minute or two of the water or air flow stopping. It can be unpleasant for many people as it may resemble the start of an attack. For this reason it is important the patient is calm and fully understands the procedure. The caloric test produces vertigo and nystagmus in a normally functioning ear.
In Ménière’s disease the caloric test is used, together with other evidence, to make a diagnosis. The caloric test gives essential information when surgical procedures are considered, and can give useful information about progression of the disease. Many people have the test at some time, either prior to surgery or when being examined for bilateral disease.
This is an electrical test of the organ of hearing. Sound goes into the organ of hearing. The cells inside which register sound fire off little electrical impulses into the brain. With the patient lying down a long thin probe is pushed into the ear canal, either so it touches the ear drum, or alternatively, a needle is used to pass through the ear drum (under local anaesthetic). A speaker playing loud clicks is set up next to the patient while electrodes are places on their head to pick up the nerves firing. The computer is programmed to look at the first few thousandths of a second after each click and then averages out the electrical activity, taking out the background brain activity.
In Ménière’s disease there is a lot of pressure in the inner ear, ballooning out of endolymphatic space, pressing on the cells of the inner ear. When these little cells are pressed the electricity they produce changes, so the test is a measure of how much the cells are being pushed. The test is not always performed in the UK because it is quite invasive and fairly advanced skills are required to interpret the results. But it can be useful in making a diagnosis.
Electrodes are placed on the patient’s head and their eye movement tracked by glasses which are linked up to a computer. As the eyes move they create a little electric field and changes in this electric field are measured and traced onto a computer screen. Patients start off looking at a bar with a red dot. The system is calibrated so the computer knows how far their eyes move. The patient is then asked to follow the dot with their eyes as it rocks back and forth like a pendulum. They are then asked to look at dots jumping around the bar. These tests work out how well the eyes are wired into the brain and how well the nerve responds controlling the eyes.
Glasgow Benefit Inventory
The Glasgow Benefit Inventory is a patient-orientated questionnaire. There are other questionnaires to choose from but the Glasgow Benefit Inventory allows overall impact to be assessed. Validated questionnaires are useful as they show the impact the condition has on day-to-day living.
When attacks of BPPV are occurring, the Hallpike positional test is diagnostic. The patient sits on the examination couch and lies rapidly backwards, head over the end (30 degrees below the horizontal) and turned 45 degrees to the side. The position is maintained for a minimum of half a minute. If the test is positive, the patient will become briefly very dizzy and will develop a characteristic repetitive eye movement called nystagmus. From the exact pattern of the nystagmus, the doctor can determine which semi-circular canal and which ear is involved. The treatment depends critically on this information. At the same time the other (mainly neurological) causes of these symptoms can be positively ruled out. When the patient is sat up again, further vertigo will usually be experienced, with the nystagmus reversing direction. The test is then repeated with the head turned the other way. In the commonest form of BPPV, involving the posterior semi-circular canal (over 90% of all cases), the Hallpike test is positive (i.e. induces vertigo and nystagmus) when the affected ear is downmost. Up to ten percent of cases may involve both ears.
Magnetic resonance imaging (MRI) scan
Scans are a routine part of the investigation of many diseases. Visualising the middle and inner ear is difficult and MRI scans are the most useful. The MRI scan will not confirm a diagnosis of Ménière’s disease, nor will it show which ear is affected or how severe the condition is. During initial investigation it is important to exclude many serious conditions which can cause vertigo or unilateral hearing loss and tinnitus. The scan looks for the presence of some of these illnesses. It can show the internal auditory canal and exclude the presence of tumours. It can also check that other areas of the brain are structurally normal and help to exclude brain tumours and multiple sclerosis. It is useful during the early stages of the disease especially if symptoms are severe and the other diagnoses need to be considered. The MRI scan uses a strong magnetic field, not x-rays. The scan of the head to include both inner ears takes about 30-40 minutes. During this time the patient has to keep their head perfectly still. The scan is painless and can be noisy, but there is a necessity for the head and upper body to be in a tunnel like space and this can make the MRI scan a difficult and unpleasant procedure for many people. Because of the strong magnetic field involved, patients with cardiac pacemakers and surgical brain clips cannot have an MRI scan. The MRI scan is a diagnosis of exclusion. As there is no definitive test for Ménière’s disease other causes of the symptoms need to be excluded and a normal test is sought. This is probably the most important and reassuring element of the MRI scan; that it is entirely normal.
Posturography is a computerised test of balance. This system looks at a patient’s balance function in its entirety. Normal balance is a coordination between the body’s balance system, eyes (how the body is moving in space relevant to its surroundings) and joints (where the body is in space). The posturography system looks at all these inputs and allows the health professional to confuse each patient’s input by moving the floor, surroundings and by wearing a blindfold. The patient stands up in the machine and is secured with a harness. During the test the patient is constantly moving; although not very much. The body constantly allows movement backwards and forwards. If it tilts too far one way, the body senses bring it back again, and vice versa. The test watches how far people sway; the less of a balance mechanism a person has, the more they sway. This system can give useful information on the relative weighting of the patient’s eyes, joints and balance system. It also helps to train the patient’s remaining systems to help compensate after a balance loss.
Speech audiometry is a measure of the patient’s ability to understand speech. The patient listens to a recording of ten words. Each word has three phonemes (blocks of sounds which make up words) e.g. mat is made up of the sounds ‘m’, ‘a’ and ‘t’. The patient listens to each word and the audiologist asks them to repeat the words they hear. If they hear ‘mat’ the patient gets three points, because they heard all three sounds. There are ten words in total so the test gives a total score of 30. If the patient hears ‘bat’ but the word was ‘mat’ then they get two points for hearing the ‘a’ and ‘t’ but not the ‘m’. The words are played at different volumes, starting quietly and getting louder. There are likely to be more mistakes on the quieter words, but patients are asked to produce their best guess.
A small rubber bung on a probe attached to the tympanometer is placed in the ear. The patient feels a pressure change and usually a varying noise. This machine measures how well the Eustachian tube is working by bouncing sound off the eardrum. The eardrum is floppy when the pressure on each side of it is the same. When the pressure increases on one side of the drum it becomes tight and the sound bounces off more easily. The machine produces a measure of middle ear pressure. If middle ear pressure is equalising well under normal circumstances, then it will be at atmospheric level, the same pressure as the pressure around us. If the Eustachian tube becomes blocked, then that pressure goes down; it becomes a vacuum because the blood supply of the middle ear resorbs the air. This makes the pressure lower in the middle ear which stiffens the eardrum up and the pressure then becomes negative.
Vestibular evoked myogenic potentials (VEMPs)
In recent years VEMPs have been receiving increasing attention. VEMPs are generated by the vestibular system, they have to be evoked in some way, they are myogenic, which means it is a muscle response, and they are an electrical potential, i.e. an electrical pulse that can be picked up. VEMPS tap into the fact that the balance organ responds to sound to see if it is actually functioning or not. This is one of the positive aspects of VEMPs and why they are likely to become more prominent. VEMPs are non-invasive and don’t really cause any discomfort. However the sound used to elicit a response can be loud and therefore care should be taken if the patient has tinnitus. Recording leads with sticky pads are put on the patient, along with the standard sort of headphones used in hearing tests.
The test itself takes less than five minutes; even quicker than a hearing test. An auditory stimulus is put into the ear which stimulates the otoliths. It goes through some neurological pathways and manifests itself as a muscle response that is measured either at the neck or around the eyes. VEMPs can be cervical or ocular. The established of the two is the cervical or C-VEMP. The C-VEMP tests the saccule (up and down movement). Electrodes are placed on the sternocleidomastoid (SCM) muscle on the side of the neck to measure this test. The ocular VEMP (O-VEMP) is a more recent adjunct to the vestibular test battery. It is thought to be a test of the utricle (forward and back movement). O-VEMPs are measured by electrodes placed just below the eye. The stimulation and setup is otherwise the same as the C-VEMP. Evidence supporting the use and interpretation of this test is increasing and it is hoped that it will become more routinely available over the next few years.