Vestibular (Balance) Tests
If you have been experiencing any form of persistent dizziness, light-headedness or imbalance vestibular (balance) tests will be carried out to diagnose the underlying cause. None of the investigations are painful but may induce some degree of temporary dizziness or light-headedness. Patients attending on their own may need to rest in our waiting room for a few minutes after the tests. Some prefer to be accompanied by a friend or relative.
Certain drugs may affect the accuracy of the results. Therefore before undergoing these tests you will need to stop taking any balance medication, sleeping or sedative drugs and alcohol for at least 48 hours before testing begins. You should also not eat anything too heavy or rich beforehand. Ladies should not wear ANY eye makeup as this can interfere with placing the special camera goggles over the eyes.
The VNG test analyses the eyes in detail to study whether any anomalous movements are present. The control of eye movements are also studied whilst the patient undertakes several visual tasks. This helps to determine whether your balance problems are related to a central (brain) vestibular disorder or a peripheral balance organ (labyrinth) problem.
This test is conducted by the Vestibular Scientist in a room which can be completely darkened. Focusing on an object allows the brain to suppress and therefore reduce any abnormal eye movements. It is therefore not unusual to observe anomalous eye movements in the dark which disappear when the lights are switched on. You will be required to wear a set of goggles incorporating infrared-sensitive video cameras, which digitally record your eye movements onto a computer for subsequent analysis. You will be asked to focus your eyes on a red light on a bar ahead of you. You must co-operate and keep your head still while following various movements of the red light with your eyes as closely as possible. This test takes about 20 minutes.
This test can determine if you have a weakness in the balance organ (labyrinth) of your inner ear that may be contributing to your symptoms. Warm or cool water is gently irrigated into the external ear canal at a standard temperature which is different to that of the body tissues. Temperature transfer across the thin ear drum (tympanic membrane) heats up or cools the air in the middle ear space. The temperature change causes fluid movement inside the outermost balance canal (semi-circular canal) leading to stimulation of the delicate balance hair cells in the ampulla. This results in the generation of an electrical discharge in the balance (vestibular) nerves which stimulates the balance part of the brain causing temporary dizziness and nystagmus. The amount of nystagmus and dizziness correlates with the amount of function of the labyrinth. The normal response of the brain to the sensation of dizziness is to try to suppress it, which could therefore affect the result. Subjects are therefore asked to carry out a mental task such as counting backwards from 100 to distract the brain. Many conditions affecting the labyrinth cause damage and reduced function.
A water stimulus caloric test can only be carried out when the ear drum is intact. It is therefore best practice to confirm this by preliminary tympanometry. Warm or cool air can be used as a stimulus when there is a hole in the ear drum, but the results are much less accurate and the clinical reliability uncertain.
The caloric test is also conducted by the Vestibular Scientists in a room which can be completely darkened. You will be required to wear a set of goggles incorporating infrared-sensitive video cameras, which digitally record your eye movements onto a computer for subsequent analysis. You will be required to lie on your back with your head at a 30° angle, to keep your eyes wide open and look straight ahead after each ear is filled with warm and cool water in turn. This causes nystagmus which can be accurately measured exactly as in videonystagmography (VNG) testing. In between each irrigation you will be asked to close your eyes and rest for a few minutes. You may experience some dizziness and perhaps slight nausea, but this is a normal reaction and should not last for more than a few minutes. This test may take up to 45 minutes depending on the results.
Posturography (Sensory Organisation Test)
Maintaining balance depends on a number of different factors apart from the vestibular system. Visual cues and the information obtained from pressure receptors in our muscles, joints and soles of our feet provide important information for the balance “computer” in the brain. Posturography gives a measure of your overall balance, and helps to separate out and assess the functioning of these various additional input systems.
You will be required to wear a harness for safety and to stand on a platform without shoes and with your hands at your sides. The platform has pressure sensors which enable the centre of gravity of your body to be accurately measured and recorded on a computer. Different things will happen at different stages of the test, such as slight movement of the platform or the surrounding screen, which could affect your balance and cause you to sway. but the Vestibular Scientist will warn you in advance and tell you exactly what to do. Any sway movements from your normal centre of gravity are recorded for subsequent analysis. This test may take up to 30 minutes depending on the results.
Figure Information: Posturography is helpful in monitoring improvement with treatment and can assist balance re-education by giving the subject instant visual bio-feedback.
X-axis: Conditions 1-6 are increasingly difficult balance challenges
Y-axis: Coloured bars show percentage score for 3 attempts at each condition
Subjects must achieve the percentage height of the grey box to pass the assessment.
Green bars: Normal
Red bars: Abnormal
VEMP (Vestibular Evoked Myogenic Potentials)
This test determines whether the saccule and the inferior vestibular nerve are intact and working normally. Sound stimulation of the labyrinth excites the saccule and leads to a reflex contraction of certain muscles of the neck It can also specifically identify a bony dehiscence of the superior semi-circular canal (SSCD) as the VEMP responses become sensitive and are present at much lower levels of sound stimulation.
Headphones are placed over the ears and small electrodes are attached with an adhesive to the skin over the neck muscles. When sound is transmitted through the headphones, the electrodes record the response of the muscle to the vestibular stimuli.
Hallpike Positional Test
This manoeuvre may be performed if you are suspected of having benign paroxysmal positional vertigo (BPPV). In this condition debris particles form in the balance canal fluids. A rapid downward movement of the head shakes up the debris rather like the commonplace Christmas snow models. As the particles sediment downwards under gravity they can stimulate some of the sensitive balance cells in the ampulla of the posterior semi-circular canal causing temporary vertigo and nystagmus, which occurs after a short delay. Induced dizziness during a downwards and/or upwards movement without nystagmus is not typical BPPV, but most likely due to a malfunctioning sensitive balance organ (labyrinth) and is a feature of an uncompensated peripheral vestibular disorder.
You will be positioned sitting on a bed, keeping your eyes open and looking straight ahead. Your head will be held firmly by the examiner’s hands and turned 45° to one side.
You will then be rapidly laid backwards with your head over the bed keeping your eyes fixed on the examiner’s nose. YOU WILL NOT BE ALLOWED TO FALL. You will be asked if this provokes your symptoms. If nothing happens within 30-60 seconds you will be returned to the upright position and asked if this has now provoked your symptoms. This process may be repeated on the other side. Sometimes the test is carried out using VNG goggles to obtain a digital computer record of the induced nystagmus.
This test will be performed if you have a history of giddiness and where erosion of the bony labyrinth (inner ear) is clinically suspected perhaps due to infection, cholesteatoma or a tumour. Sometimes a fistula may be suspected when the patient reports dizziness during initial tympanometry.
The Vestibular Scientist will alter the pressure in the ear canal either by pushing on the tragus, which is the soft cartilage flap just in front of the external ear canal, creating a repetitive pumping action or by using a pneumatic otoscope. The test is positive if you develop vertigo or nystagmus. Sometimes the test is carried out using VNG goggles to obtain a digital computer record of the induced nystagmus.
The hearing part of the inner ear (cochlea) is closely associated with the balance organ (labyrinth). Numerous conditions of the inner ear can therefore cause both hearing loss and dizziness or imbalance. The hearing may be affected at specific frequencies which are not generally apparent to the patient for everyday purposes. Low pressures in the middle ear can also affect the labyrinth. It is therefore essential to undertake audiometry and tympanometry in the assessment of every patient with dizziness or imbalance.
Pure Tone Audiometry (PTA)
Pure tone audiometry is a basic subjective hearing test to determine your ability to hear various sounds at different tone frequencies.
You will be required to sit in a soundproof booth with headphones and press a button every time you hear a bleep sound, even if it is very faint. You should ignore any rushing sounds used to mask the opposite ear and only react to the bleeps. This test may take up to 20 minutes depending on the results.
This is an objective test of your middle ear function and is useful for determining whether:
- there is any fluid or congestion in your middle ear
- there is a perforation (hole) in your eardrum
- the eardrum is flaccid and weak
- there is loss of continuity of the ossicles (middle ear bones) by disease or trauma
- a grommet is blocked
- changing pressure in the ear canal causes dizziness indicating a fistula (defect) in the bone surrounding the labyrinth (balance organ)
You are not required to do anything for this test other than sit very still. The audiologist will hold a soft rubber probe at the entrance of your ear canal and you may feel a slight change of pressure in your ear.
Auditory Brainstem Response (ABR)
This objective test assesses the central hearing pathways from the cochlea along the auditory nerve all the way to the auditory cortex (the part of the brain where sounds are perceived). It is helpful in assessing possible obstruction to sound transmission due to tumours, demyelination or other problems. The central hearing pathways pass close to the central vestibular system (brain balance computer) and may be affected in neurological central balance disorders.
After cleaning the skin thoroughly to remove surface oils, electrodes will be placed on your forehead and behind your ears and connected to a computer to measure your electrical brain activity (EEG). You will be required to sit in a dark room with your eyes closed and wearing headphones. You will hear some loud repetitive clicking noises but you are not required to respond to them as all measurements are taken automatically by the computer which records the electrical activity in the hearing pathways in the brain. This test may take up to 30 minutes depending on the results.
Various parts of the auditory system produce electrical signals in response to sound stimulation. This objective test measures those compound electrical signals produced by the cochlea (action potential/summating potential complex) and auditory nerve. It is in effect an “ECG” of the cochlea. It can give useful information about the function of the cochlear hair cells and in particular the pressure of endolymph fluid in the surrounding membrane compartment. Because the pressure of fluid in the cochlea closely mirrors the fluid pressure in the labyrinth an EcoG may therefore give objective diagnostic information in Ménière’s disease and other allied disorders affecting inner ear fluid balance at a very early stage, before all the typical clinical features are apparent and irreversible damage has occurred.
Local anaesthetic cream will be applied to the outer surface of the eardrum. You will have surface skin electrodes placed on your head and a tiny electrode and sponge foam speaker will subsequently be inserted into the external canal of the ear that is being tested. You will hear some repetitive clicking noises but you are not required to respond to them. It is very important that you try and be as relaxed as possible, since any tension can affect the skin resistance/electrode interface and slow down the recording process. This test takes about 30 minutes to complete.
Computed tomography (CT) is a medical imaging method using X-ray tomography created by computer processing. It provides important diagnostic information in various anatomical planes. The main advantage over MRI scanning is that it demonstrates bone as well as soft tissue features. A temporal bone CT scan may therefore show details of bone abnormalities of the inner ear, such as a labyrinthine fistula, or developmental problems affecting the labyrinth, such as a dilated vestibular aqueduct.
The scanning techniques involves lying still with the head in a medical “hair-dryer”-like capsule for approximately 20 minutes. It is a completely painless procedure.
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to study internal soft tissue structures in detail. It provides good contrast between the different types of tissue, which is a major advantage over CT. MRI does not use ionising radiation unlike CT or traditional X-rays. Instead it uses a powerful magnetic field to align tissue atoms, and then uses radiofrequency fields to change and record their alignment. This scanned information is then used to construct images of specific parts of the body. An MRI scan may be required to exclude the possibility of an underlying acoustic neuroma, particularly if there is an inner ear hearing loss in one ear or a worse hearing ear. It can also show other disorders that may affect the central balance pathways in the brain and cause imbalance.
The patient lies still on a couch with their head in a metal tube. Some patients find this enclosed experience unpleasant, which has resulted in the development of so-called “open scanners”. Patients at The Harley Street ENT Clinic requiring an MRI are therefore routinely referred to an open scanner.
Impairment of oxygen-carrying blood to the central balance part of the brain by the vertebro-basilar artery can cause dizziness and lightheadedness. High blood pressure (hypertension) may be associated with hardening and narrowing of the arteries (arteriosclerosis) whilst drug treatment may cause excessive reduction of the blood pressure. When a person stands up reflex contraction of muscles in blood vessel walls of the legs prevents pooling of blood due to gravity. The automatic (autonomic) nervous system controls this reflex. Patients with an autonomic neuropathy may suddenly drop their blood pressure (hypotension) and suffer lightheadedness, a faint or a drop attack.
Blood pressure is measured by the ENT practice nurse with a standard cuff applied to the upper arm. Postural hypotension is identified by measuring the blood pressure initially with the patient lying down. The patient is then asked to stand up quickly and the blood pressure reading recorded again.
A low red blood cell count (anaemia) can affect the amount of oxygen reaching the balance part of the brain even when the blood pressure is normal. A low blood sugar level (hypoglycaemia) may also cause dizziness. Patients complaining of lightheadedness, a faint sensation or imbalance should therefore have a blood test to exclude anaemia.
A blood sample is taken by the ENT Practice Nurse after the application of a rubber tourniquet to the upper arm. The samples are sent directly to the TDL laboratories for immediate analysis.