 Brain Stem Auditory Evoked Potential Test (BSAEP)
A Brain Stem Auditory Evoked Potential Test (B S AEP) is a recording of the electrical activity coming from the brain stem. Electrodes are attached to your head so that the electrical activity can be measured and recorded. The test is used to evaluate the health of certain brain pathways that cannot be readily accessed by an EEG test.
- It is a recording of the electrical activity coming from the brain stem
- used to evaluate the health of certain brain pathways not easily accessed by an EEG test.
- It is not a hearing test or a treatment of any kind.
- It takes a bout an hour to do BSAEP .
- It helps evaluate the cause of symptoms such as loss of balance, weakness, nausea, vomiting, hearing loss, unusual ringing of ears, headaches, vision problems, or numbness.
- No pain or discomfort is experienced .
How is it performed?
- You will sit in a comfortable chair while a Clinical Physiologist places four electrodes onto your head.
- A meter checks all electrode connections to ensure that they are working properly.
- Earphones are placed over your ears
- You may lean back in the chair, relax, and even sleep if you like. You are asked to remain as still as possible.
- A clicking sound is delivered to one ear at a time for several minutes. You may or may not hear the clicks.
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Cerebral Angiogram
Cerebral angiography or arteriography is a form of medical imaging that visualizes the arterial and venous supply of the brain . It is now the gold standard for detecting vascular problems of the brain.
Method
Any form of angiography involves the passing of a catheter into a large artery (e.g. the femoral artery ) and advancing this catheter through the carotid artery . When this has been achieved, a contrast agent that is relatively impervious to the passage of x-ray photons is injected, and a rapid series of radiographs is taken while this radiopaque fluid passes through the vasculature. Another series, taken when the contrast agent has passed through the tissues, visualizes the venous supply. Using modern equipment, this method offers better visual representation of cerebral blood vessels than less invasive methods such as computed tomography angiography and magnetic resonance angiography.
Uses
Most vascular abnormalities of the brain, e.g. arteriovenous malformations and aneurysms , can be detected on cerebral angiography.
Return to top Computerized Tomography (CT)
This computer-assisted imaging technique rapidly produces brain pictures which can identify blood clots, skulls fractures and certain types of tumour, ect.
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Electroencephalography (EEG)
An EEG is a non-invasive test used to detect abnormalities in the electrical activity of the brain. Brain cells communicate by producing tiny electrical impulses. In an EEG, electrodes are placed on the scalp over multiple areas of the brain to detect and record patterns of electrical activity and check for abnormalities. The technician will apply 23 small, flat, metal discs called electrodes in different positions on the patient scalp. The discs are held in place with a water-soluble paste. The electrodes are connected by wires to an amplifier and a recording machine. The electrical impulses are recorded onto a moving piece of graph paper.
What to expect during the EEG investigation?
An EEG causes no discomfort. The electrode applied to the patient's scalp will only record electrical activity and does not produce any sensation. It cannot "read minds," measure intelligence or diagnose mental illness. The test is usually performed while the patient is awake and also during sleep. The patient may be asked to do certain things during the test such as breathe deeply and quickly for several minutes or look at a bright flickering light. If the patient is given a mild sedative to induce sleep, he/she will be unable to drive for 24 hours.
Test time may take up to two hours. The results of the EEG will help the physician diagnose and evaluate the presence and type of seizure disorders and causes of convulsion.
Patient's with severe head injuries, receiving life support in an intensive care environment, may also require an EEG to investigate brain activities.
Prior to the EEG investigation
A physician must order an EEG. The patient should have no more than four hours of sleep the night before the exam and should have no alcohol, sedatives or caffeine 24 hours prior to the exam. The patient should arrive with clean hair (no mousse, gels, hairspray), and someone must come with the patient to drive him or her home.
What is an EMG/NCS test?
EMG/NCS testing is a measure of how well the nerves and muscles are working. It involves stimulating a nerve at different points and recording a response from a muscle or from another part of the same nerve. The number of nerves and/or muscles tested will depend upon the patient's presenting symptoms, the questions the consultant will ask, and the findings during the testing procedure.
What will happen during the test?
With NCS testing, the physician places small surface electrodes onto the patient's skin (of the leg/arm to be examined). The patient will receive a small impulse of stimulation (on the leg/arm to be tested), so that the physician can evaluate the nerve.
With EMG testing, the physician will use a small, disposable, sterile needle to examine various muscle groups. At first the patient will be asked to relax the muscle as the needle is inserted. The physician will then slowly move the needle around to examine the muscle. Later, the patient will be asked to move/contract the muscle to allow for further examination of the muscle.
Prior to the test
No special preparation is required. The patient does not need to restrict his/her diet prior to their test and they will not have to restrict their activities after the test.
How long will the test take?
The test will take between 45-60 minutes. Provides valuable information about headaches, seizure, and other puzzling problems.
EEG is also used to evaluate: infections of the nervous system strokes tumors growth and development of the brain in babies and children.
EEGs are often done during surgery on the arteries of the neck to make sure there is enough blood flow to the brain.
During an EEG, small pads are placed on the head to record brain waves. EEG cannot record thought, and the test is totally painless.
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Electromyography (EMG)
The action of nerves and muscle is essentially electrical. Information is
transmitted along nerves as a series of electrical discharges carrying
information in pulse repetition frequency. This may be in the range of 1 to
100 pulses/s.
Contraction of muscle fibres is also associated with an electrical discharge
which can be detected by measuring electrodes or brought about by electrical
stimulation. EMG is most often used when people have symptoms of weakness,
and examination shows impaired muscle strength. It can help to differentiate
primary muscle conditions from muscle weakness caused by neurological
disorders. EMG can be used to differentiate between true weakness and
reduced use because of pain or lack of motivation.
EMG equipment consists of recording electrodes, preamplifiers (which are
normally placed very close to the patient to avoid pick-up of electrical
interference), amplifiers to provide the correct gain, calibration and
frequency characteristics, a display system (usually an LCD monitor), a range of
integrators and averagers - partly to achieve some data compression (chart
records may be very long and difficult to read), and a recording medium,
which is often a photographic (fibre-optic) system.
The most typical method for testing uses a needle electrode inserted through
the skin into the muscle. The electrical activity detected by this electrode
is displayed on an LCD monitor (and may be displayed audibly through a speaker).
Because skeletal muscles are isolated and often large units, each electrode
gives only an average picture of the activity of the selected muscle.
Several electrodes may need to be placed at various locations to obtain an
accurate study. After placement of the electrode(s), the patient may be
asked to contract the muscle (for example, by bending the arm). The
presence, size, and shape of the wave form produced on the oscilloscope (the
action potential) provide information about the ability of the muscle to
respond to nervous stimulation. Each muscle fibre that contracts will
produce an action potential, and the size of the muscle fibre affects the
rate (how frequently an action potential occurs) and size (amplitude) of the
action potential(s). A nerve conduction velocity test is often done at the
same time as an EMG.
There may be some discomfort with insertion of the electrodes (similar to an
intramuscular injection). Afterward, the examined muscle may feel tender or
bruised for a few days. Muscle tissue is normally electrically silent at
rest. Once the insertion activity (caused by the trauma of needle insertion)
quiets down, there should be no action potential on the oscilloscope. When
the muscle is voluntarily contracted, action potentials begin to appear. As
contraction is increased, more and more muscle fibres produce action
potentials until a disorderly group of action potentials of varying rates
and amplitudes (complete recruitment and interference pattern) appears with
full contraction.
Many EMG tests involve the use of stimulators to induce discharges in a
nerve trunk, and detect the response by surface electrodes over a muscle
served by that nerve. In this case the signals may be as large as 2 mV, and
may be presented audibly or for recording on a high-speed chart recorder.
Such evoked response tests might be for determining the nerve conduction
time, or for assessing the performance of the neuromuscular control system.
There are many different disorders of the nervous system and EMG examination
has to be tailored to the particular requirements of the individual patient.
Thus, these tests are normally carried out by a specialist in
electromyography within the neurology department.
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Electro Retinogram (ERG)
Electroretinography, is used to measure the electrical responses of various cell types in the retina, including the light-sensitive cells (rods and cones) and the ganglion cells. Electrodes are placed on the cornea and the skin near the eye. During a recording, the patient is watching a standardised stimulus and the resulting signal is interpreted in terms of its amplitude (voltage) and time course. Stimuli include flashes (flash ERG) and reversing checkerboard patterns (pattern ERG). Applications are predominantly in Optometry and ophthalmology, where the electroretinogram (ERG) is used for the diagnosis of various retinal diseases.
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Evoked Potential (EP)
Evaluate the conditions of nerve pathways. EPs are electrical signals of the nerves, spinal cord and brain in response to light (stimulation of the eyes), sound (stimulation of the ears) or mild electrical current (stimulation of the nerves) in the arms or legs.
EPs are used to diagnose disorders of the nervous system such as Multiple Sclerosis, hearing loss and spinal cord problems.
During surgery on the back and neck, EPs are used to check the patient's condition. Neurosurgeons may also use EPs during surgery to help locate important brain structures.
Somatosensory Evoked Potentials (SEPs)
SEPs can provide a unique insight into nervous function since they result from direct stimulation of sensory nerves. Particular aspects of the response can be investigated by choice of stimulation and recording sites. Clinical applications of SEPs are the investigation of Multiple Sclerosis, Brachial Plexus and Spinal Cord injuries, Coma, Brain Death and other neuropathies.
Return to top F Wave
The F Response results from a centrifugal volley in an alpha motor neurone, following antidromic excitation of the nerve cell body in the ventral horn of the spinal cord. Clinical applications of F Response are conditions such as entrapment neuropathies and root compression syndrome and estimation of motor neurone excitation.
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Full body scanning
Full body scanning is a noninvasive, painless procedure that uses low-dose x-rays to screen the body from the brain to the pelvis for various diseases of the major organs. Full body scanning can detect heart, lung, musculoskeletal, endocrine, and prostate and ovarian disease as well as tumors, aneurysms, osteoporosis, hernias, and kidney and gall stones. Full body scanning is performed on a multislice computed tomography (CT) scanner in only 30 seconds. This study provides both two-dimensional (2D) and three-dimensional (3D) images of all types of tissue, allowing for more accurate detection of various cancers and diseases before symptoms occur.
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H Reflex
The H Reflex results from stimulation of sensory fibres with the resulting afferent discharge causing an excitatory potential in the motor neurone pool, following a synaptic delay. Exceeding the potential threshold for a particular motor neurone generates an action potential and the resulting afferent discharge will cause the muscle fibres innervated by that neurone to be activated.
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Intra-Operative Monitoring (IOM)
Intraoperative monitoring (IOM) is a technique that is directly aimed at reducing the risk of neurological deficits after operations that involve the nervous system. IOM is a technique that has evolved during the last two decades; it makes use of recordings of electrical potentials from the nervous system during surgical operations.
The use of IOM offers a possibility to detect injuries before they become so severe they cause deficits after the operation. Introduction of IOM has reduced the risk of debilitating deficits such as muscle weakness, paralysis, hearing loss, and other loss of normal body functions.
With Bespoke Healthcare, IOM is performed by a consultant neurophysiologist assisted by a clinical physiologist. Clinical physiologists are not permitted to make interpretations of recorded potentials and give information to the surgeon; the supervising consultant does that. It is necessary to have certification to do IOM. Similar techniques as used in IOM are now used in a few kinds of operations for guiding the surgeon in an operation to help obtain the best results.
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Long-Term Video EEG Monitoring
Long-term video EEG monitoring refers to the simultaneous recording of EEG and clinical behaviour over extended periods of time to evaluate patients with paroxysmal disturbances of cerebral function. Long-term video EEG monitoring is used when it is important to correlate clinical behaviour with EEG phenomena.
How long does it take?
This test requires an admission to the hospital with an average stay of 3 to 5 days.
Why is this test performed?
To diagnose episodic events (those which happen from time to time). These events may be, but are not limited to:
• epileptic seizures
• fainting or black-out spells
• spells of unknown origin
• confusion
• hallucinations or behaviour problems
• withdraw or change in medications
Return to top Motor Unit Action Potentials (MUAPs)
Measurements of various parameters of MUAPs can provide valuable data for differential diagnosis. MUAP measurements can be made manually or with an automated analysis package for recognising and averaging potentials from particular motor units. In general, myopathies lead to a decrease in duration and amplitude of MUAPs, whereas neuropathies cause an increase in duration and amplitude.
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Muscle Response Test
A test to measure muscle response to nervous stimulation (electrical activity within muscle fibres).
When a muscle fibre loses its nerve supply, it exhibits a characteristic irritability manifested as spontaneous discharges at rest. Single muscle discharges, called FIBRILLATIONS have a short duration (.5 to 1.5 msec), low amplitude (50-300 microvolts) and a REGULAR rhythm. They are usually positive (downward) in their initial deflection.
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Magnetic Resonance Imaging (MRI, MRA, MRV)
This equipment allows imaging of the brain and body organs by using radio frequencies generated by a revolving magnetic field around the subject. We can identify small tumours, tissue abnormalities, blood vessels and venous structures or even fluid by using various special techniques.
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Nerve Conduction Studies
A Nerve conduction Study (NCS) is a test used to measure the efficiency / integrity of the nerve being examined. It is used to diagnose nerve entrapment or dysfunction due to injuries or other medical disorder.
The extremity (arm or leg) that is to be studied must be warm prior to the test.
Our highly qualified Clinical Physiologist or a Consultant Neurophysiologist place surface electrodes on the skin over the muscles at various locations on the limbs. Then using a stimulating electrodes the nerve is stimulated using a mild electrical impulses. The resulting electrical activity is recorded. The machine calculates the nerve conduction speed using the distance between electrodes and the time it takes for electrical impulses to travel between these electrodes.
On average, if one extremity is studied, the nerve conduction study takes anywhere between 15 and 30 minutes.
Typical reasons for a Nerve Conduction referral:
- Carpal tunnel syndrome
- Peripheral neuropathy due to diabetes mellitus
- Alcoholic, metabolic or endocrine neuropathies
- Neck pain or low back pain after injury or accident
- Sciatic nerve symptoms causing Sciatica
- Tarsal tunnel syndrome causing foot pain and numbness
- Ulnar nerve dysfunction causing hand weakness and numbness
- Industrial screening of workers in the industry for evaluation of nerve entrapment neuropathies, such as Carpal Tunnel Syndrome
- Peroneal nerve dysfunction with foot drop
- Radial nerve dysfunction with wrist drop
- Brachial Plexus injury
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Neuroimaging
Neuroimaging includes the use of various techniques to either directly or indirectly image the structure , function/ pharmacology of the brain . It is a relatively new discipline within medicine and neuroscience / psychology . Neuroimaging falls into two broad categories: structural imaging and functional imaging . Structural imaging deals with the structure of the brain and the diagnosis of gross (large scale) intracranial disease (such as tumor), and injury. Functional imaging is used to diagnose metabolic diseases and lesions on a finer scale (such as Alzheimer's disease) and also for neurological and cognitive psychology research and building brain-computer interfaces . Functional imaging enables, for example, the processing of information by centers in the brain to be visualized directly. Such processing causes the involved area of the brain to increase metabolism and "light up" on the scan.
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Neurophysiology
Neurophysiology is a diagnostic specialty concerned with recording and interpreting electrical signals from the nervous system. It is important in the evaluation of peripheral nerve and brain function, often a key element in the diagnosis and assessment of diseases of the nervous system, such as epilepsy, muscle and peripheral nerve disease, sleep disorders, or monitoring of nerve function.
There are three main areas:
- Electro-encephalography (EEG)
- Nerve conduction studies and electromyography (EMG)
- Responses evoked by sensory stimulation (EP)
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Single Fibre EMG (SFEMG)
Single Fibre EMG can be used to estimate the density of fibres belonging to a single motor unit. These fibre density measurements are valuable in identifying reorganisation of the motor unit in neurogenic conditions and in certain primary myopathies.
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Single Fibre Jitter (SFJ)
Single Fibre Jitter measurement is a technique used for assessing transmission at the motor end plate. Measurements can be made manually or with an automated analysis package providing a sensitive technique for detecting abnormalities of neuromuscular transmission at an early stage.
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Somatosensory Evoked Potential (SSEP)
Somatosensory Evoked Potential (SSEP) is a test showing the electrical signals of sensation going from the body to the brain. The signals show whether the nerves that connect to the spinal cord are able to send and receive sensory information like pain, temperature, and touch. When ordering electrical tests to diagnose spine problems, SSEP is combined with an electromyogram (EMG) , a test of how well the nerve roots leaving the spine are working.
Why is it done?
An SSEP indicates whether the spinal cord or nerves are being pinched. It is helpful in determining how much the nerve is being damaged and if there is a bone spur, herniated disc, or other source of pressure on the spinal cord or nerve roots. EMG is used to show if a nerve is being irritated or pinched as it leaves the spine on its way down the arm or leg. During spine surgery, the EMG is used to monitor nerve output to the muscles in procedures where screws are placed in the middle or lower part of the spine. SSEP is used to double check whether the sensory part of the nerve is working correctly.
How is it done?
Surface electrode s are placed over the skin over the nerve or sensory centre of the brain. Measurements of how long it takes an electrical signal to travel through the nerve pathway are recorded. The function of the nerve is determined by the speed of these electrical signals. When the nerve pathway is pinched, the signals are slower than expected.
What are the limitations?
An SSEP does not show why the problem occurred or what is causing it. The test looks primarily at whether sensation is affected by a problem in the spinal cord or nerves. There could be a problem in the nerve somewhere between the central nervous system and the area tested. The problem may not necessarily be in the spine itself.
Return to top Visual Evoked Potentials (VEP)
Visual evoked potential (VEP) tests evaluate how the visual system responds to light. VEP tests are used to evaluate optic neuritis, optic tumours, retinal disorders, and demyelinating diseases such as multiple sclerosis.
During a VEP test, three or more electrodes are attached to the patient's head with an adhesive. The patient is then asked to stare at a strobe light or checkerboard pattern on a television screen. Each eye is tested separately. The electrodes record hundreds, sometimes thousands, of electrical responses from the patient's visual nervous system, and these responses are recorded by a special computer for interpretation by a physician.
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