Neurological Tests
Several types of specialist tests can be employed to help provide more information about the brain and nervous system in order to make an accurate diagnosis of the cause of the problem, and to help guide treatment and monitor progress.
Not all of these tests are available at London Medical but they may be booked locally via the consultant Neurologist.
(click on test for more information) |
MRI Scan |
MRI scans
Magnetic resonance imaging (MRI) is the state of the art method of scanning the brain and spine. This provides the neurologist with detailed images of the brain and/or spine and allows problems such as brain tumours, strokes, blocked or abnormal blood vessels (eg aneurysms) or trapped nerves in the spine to be accurately identified.
Magnetic Resonance Angiography
This test is designed to assess the blood vessels supplying blood to the brain (carotid and vertebral arteries) and the blood vessels within the brain itself. It is used to look for narrowing of the arteries taking blood to the brain (as a possible cause of stroke or TIA) and to identify aneurysm or malformations of the arteries as a cause of bleeding (haemorrhage) within the brain.
It employs the same technique as a conventional MRI scan but in a minority of cases an injection (intravenous) of contrast may also be required to give more accurate imaging of the blood vessels.
What does an MRI scan involve?
The scan uses a powerful magnetic field to create images of the brain. There is no exposure to ionising radiation or harmful X-rays. This type of scan is not appropriate for people with pacemakers or certain forms of metal implants. While there is no evidence that MRI scans are harmful in pregnancy, they are often avoided in the first months of pregnancy unless the problem is urgent.
Some people find MRI scanners claustrophobic, as it involves lying still in a confined space, and where this is a problem an ‘open' MRI scan may be appropriate in a scanner which is much less enclosed.
The scan is then reported by an experienced consultant neuro-radiologist and is subsequently available on a CD or printed out on hard copy films.
CT scan
Computerised tomographic scanning (CT) is on older technique than MRI which still has a role in brain imaging. The scan uses X-ray beams to provide pictures of the brain and skull. It is a very quick scan suitable for patients unable to have MRIs and is particularly effective at detecting bleeding in the brain.
CT Angiography
CT scanning may allow very detailed imaging of the blood vessels supplying blood to the brain and within the brain itself. This technique complements MR angiography (see above) and is recognised as being an increasingly accurate way of imaging the blood supply of the brain. This technique involves an iv injection.
Neurophysiology tests
This includes tests such as Nerve conduction studies and EMG (electromyogram) and EEG (electroencephalogram). These tests are performed by a medical specialist trained in this technique - a consultant Clinical Neurophysiologist.
EMG and Nerve conduction studies
This technique allows the integrity and functioning of nerves in the arms and legs to be tested. It is used to diagnose and identify nerve trapping or compression (eg carpal tunnel syndrome of ulnar nerve trapping at the elbow) as well as to identify damage to peripheral nerves (peripheral neuropathy eg in diabetes) or muscle disorders. The test may also provide information about nerve trapping within the spine, for example in the neck or lower spine due to ‘slipped (prolapsed) discs'.
Nerves function by conduction an electrical impulse along the length of the nerve fibre similar to a wire with insulation on the outside. This test involves using small electrical pulses to stimulate the nerves and record their activity and function. EMG involves inserting a very fine needle into muscles to record and analyse the electrical activity of the muscle. The test takes approximately 30-40 minutes.
EEG (Electroencephalogram)
EEG is used to record the electrical activity of the brain and analyse patterns of brain wave rhythms. It is particularly useful in the diagnosis and management of epilepsy as it allows different types of epilepsy to be distinguished and may identify the part of the brain from which the abnormal electrical activity is arising.
EEG involves placing several small electrical contacts on the scalp and in some cases use of deep breathing or viewing flashing light patterns may help to provide additional information. Occasionally patients are asked to stay up all night (or for as long as possible) the night before the EEG to allow subtle abnormalities to become more apparent on the EEG during sleep on the day of the test.
24 hour EEG and video EEG telemetry
Sometimes more extensive EEG techniques are required in the diagnosis of epilepsy and related disorders, for example to distinguish epilepsy from other types of non-epileptic black-out or to assess patients with established epilepsy for suitability for epilepsy surgery.
A 24 hour ambulatory EEG involves wearing EEG recoding electrodes attached to a recoding device at home for a day and night. This provides a powerful technique for prolonged recording of EEG to identify abnormalities that may be missed by routine EEG recordings.
Video EEG telemetry involves admission to a specialist hospital unit for 24-72 hours. During this time the EEG is constantly monitored and continuous video recording allows an seizures or attacks that occur to be analysed and correlated with the simultaneous EEG recording.
Dopamine Transporter (DAT) scan
This is a relatively new type of scan that may sometimes be useful in the diagnosis of Parkinson's disease and related disorders such as types of tremor, for example to distinguish benign forms of tremor from Parkinson's disease. A DAT scan is employed to help diagnose Parkinson's disease in only a minority of cases.
This test involves iv injection of a tracer compound which is radiolabelled and is taken up by dopamine producing cells in the brain. The scan following the injection allows assessment of the numbers of dopaminergic cells in the brain - a reduction in numbers of these cells being suggestive of Parkinson's disease or a related Parkinsonian condition.
Neuropsychometric (Memory) testing
Neuropsychometric testing involves detailed testing of memory and other aspects of intellectual functioning such as planning, speed of thinking, abstract thinking, calculation, language (including speech and reading), visio-spatial function and attention and concentration.
The test is performed by a clinical neuropsychologist (not to be confused with a psychiatrist) and usually takes an hour or longer. It is often used to assess if there is evidence of intellectual or memory decline, for example due to Alzheimer's disease or other disorders of memory, or following head injury. When performed serially (eg at annual intervals) it can be used to detect evidence of change in intellectual functioning with time.
©Dr Paul Jarman, 2008
