Thursday, November 27, 2008


Alternative Names :
Evoked auditory potentials; BAEP - brainstem auditory evoked potentials; Evoked response audiometry

Definition :

The brainstem auditory evoked response (BAER) test measures brain wave activity that occurs in response to clicks or certain tones.

How the Test is Performed :

You lie on a reclining chair or bed and remain still. Electrodes are placed on your scalp and on each earlobe. The earphones give off a brief click or tone. The electrodes pick up the brain's responses to these sounds and record them.

How to Prepare for the Test :

You may be asked to wash your hair the night before the test.

How the Test Will Feel :

There is little discomfort.

Why the Test is Performed :

The test is performed to help diagnose nervous system abnormalities and hearing losses (especially in low birth weight newborns), and to assess neurological functions.

Normal Results :

The auditory brain stem values are in a normal range. This range varies among patients and instruments used.

What Abnormal Results Mean :

Abnormal findings may indicate a hearing loss, multiple sclerosis, or stroke.

Additional conditions under which the test may be performed:
Acoustic neuroma
Central pontine myelinolysis

Risks :

There are no risks.


A mammogram is a special type of X-ray of the breasts. Mammograms can show tumors long before they are big enough for you or your health care provider to feel. Mammograms are recommended every year or two for women older than 40. They are also recommended for younger women who have symptoms of breast cancer or who have a high risk of the disease.

Mammograms are quick and easy. You stand in front of an X-ray machine. The person who takes the X-rays places your breast between two plastic plates. The plates press your breast and make it flat. This may be uncomfortable, but it helps get a clear picture. You will have an X-ray of each breast. A mammogram takes only a few seconds and it can help save your life.

National Cancer Institute

MRI ( Magnetic Resonance Imaging )

What is an MRI scan?

An MRI (or magnetic resonance imaging) scan is a radiology technique that uses magnetism, radio waves, and a computer to produce images of body structures. The MRI scanner is a tube surrounded by a giant circular magnet. The patient is placed on a moveable bed that is inserted into the magnet. The magnet creates a strong magnetic field that aligns the protons of hydrogen atoms, which are then exposed to a beam of radio waves. This spins the various protons of the body, and they produce a faint signal that is detected by the receiver portion of the MRI scanner. The receiver information is processed by a computer, and an image is produced.

The image and resolution produced by MRI is quite detailed and can detect tiny changes of structures within the body. For some procedures, contrast agents, such as gadolinium, are used to increase the accuracy of the images.

When are MRI scans used?

An MRI scan can be used as an extremely accurate method of disease detection throughout the body. In the head, trauma to the brain can be seen as bleeding or swelling. Other abnormalities often found include brain aneurysms, stroke, tumors of the brain, as well as tumors or inflammation of the spine.

Neurosurgeons use an MRI scan not only in defining brain anatomy but in evaluating the integrity of the spinal cord after trauma. It is also used when considering problems associated with the vertebrae or intervertebral discs of the spine. An MRI scan can evaluate the structure of the heart and aorta, where it can detect aneurysms or tears.

It provides valuable information on glands and organs within the abdomen, and accurate information about the structure of the joints, soft tissues, and bones of the body. Often, surgery can be deferred or more accurately directed after knowing the results of an MRI scan.

What are the risks of an MRI scan?

An MRI scan is a painless radiology technique that has the advantage of avoiding x-ray radiation exposure. There are no known side effects of an MRI scan. The benefits of an MRI scan relate to its precise accuracy in detecting structural abnormalities of the body.

Patients who have any metallic materials within the body must notify their physician prior to the examination or inform the MRI staff. Metallic chips, materials, surgical clips, or foreign material (artificial joints, metallic bone plates, or prosthetic devices, etc.) can significantly distort the images obtained by the MRI scanner. Patients who have heart pacemakers, metal implants, or metal chips or clips in or around the eyeballs cannot be scanned with an MRI because of the risk that the magnet may move the metal in these areas. Similarly, patients with artificial heart valves, metallic ear implants, bullet fragments, and chemotherapy or insulin pumps should not have MRI scanning.

During the MRI scan, patient lies in a closed area inside the magnetic tube. Some patients can experience a claustrophobic sensation during the procedure. Therefore, patients with any history of claustrophobia should relate this to the practitioner who is requesting the test, as well as the radiology staff. A mild sedative can be given prior to the MRI scan to help alleviate this feeling. It is customary that the MRI staff will be nearby during MRI scan. Furthermore, there is usually a means of communication with the staff (such as a buzzer held by the patient) which can be used for contact if the patient cannot tolerate the scan.

How does a patient prepare for an MRI scan and how is it performed?

All metallic objects on the body are removed prior to obtaining an MRI scan. Occasionally, patients will be given a sedative medication to decrease anxiety and relax the patient during the MRI scan. MRI scanning requires that the patient lie still for best accuracy. Patients lie within a closed environment inside the magnetic machine. Relaxation is important during the procedure and patients are asked to breathe normally. Interaction with the MRI technologist is maintained throughout the test. There are loud, repetitive clicking noises which occur during the test as the scanning proceeds. Occasionally, patients require injections of liquid intravenously to enhance the images which are obtained. The MRI scanning time depends on the exact area of the body studied, but ranges from half an hour to an hour and a half.

How does a patient obtain the results of the MRI scan?

After the MRI scanning is completed, the computer generates visual images of the area of the body that was scanned. These images can be transferred to film (hard copy). A radiologist is a physician who is specially trained to interpret images of the body. The interpretation is transmitted in the form of a report to the practitioner who requested the MRI scan. The practitioner can then discuss the results with the patient and/or family.

Tuesday, November 4, 2008


An electroencephalogram (EEG) is a test to detect problems in the electrical activity of the brain.

How the Test is Performed

Brain cells communicate with each other by producing tiny electrical impulses. In an EEG, this faint electrical activity is measured by putting electrodes on the scalp.

The test is performed by an EEG technician in your health care provider's office, at a hospital, or at an independent laboratory. You will be asked to lie on your back on a bed or in a reclining chair.

The technician will apply between 16 and 25 flat metal discs (electrodes) in different positions on your scalp. The discs are held in place with a sticky paste. The electrodes are connected by wires to an amplifier and a recording machine.

The recording machine converts the electrical impulses into patterns that can be seen on a computer screen, as well as stored on a computer disk. Before computers, the activity was printed on paper. In either case, the electical activity looks like a series of wavy lines. You will need to lie still with your eyes closed because any movement can alter the results.

You may be asked to do certain things during the recording, such as breathe deeply and rapidly for several minutes or look at a bright flashing light.

How to Prepare for the Test

You will need to wash your hair the night before the test. Do not use any oils, sprays, or conditioner on your hair before this test.

Your health care provider may want you to stop taking certain medications before the test. Do not change or stop medications without first talking to your health care provider.

You should avoid all foods containing caffeine for 8 hours before the test.

Sometimes it is necessary to sleep during the test, so you may be asked to reduce your sleep time the night before. If you're asked to sleep as little as possible before the test, don't consume any caffeine, energy drinks, or other products that help you stay awake.

How the Test Will Feel

This test causes no discomfort. Although having electrodes pasted onto your skin may feel strange, they only record activity and do not produce any sensation. No significant electricity passes from the electrode into your skin.

Why the Test is Performed

EEG is used to help diagnose if you're having seizures and if so, what type. An EEG is also used to find the causes of confusion, and to evaluate head injuries, tumors, infections, degenerative diseases such as Alzheimer's disease, and abnormal changes in body chemistry that affect the brain.

It is also used to evaluate problems with sleep (see: sleep disorders) and to investigate periods of unconsciousness. The EEG may be done to show that the brain has no activity, in the case of someone in a deep coma. It can be helpful when trying to decide if someone's brain is dead.

EEG canNOT be used to measure intelligence.

Normal Results :

Brain electical activity has certain frequencies (the number of waves per second) that are normal for different levels of consciousness. For example, brain waves are faster when you are awake, and slower when you're sleeping. There are also normal patterns to these waves. These frequencies and patterns are what the EEG reader looks for.

What Abnormal Results Mean :

Abnormal results on an EEG test may mean:
- An abnormal structure in the brain (such as a brain tumor)
- Attention problems
- Cerebral infarction (tissue that is dead because of a blockage of the blood supply)
- Drug or alcohol abuse
- Encephalitis (inflammation of the brain)
- Head injury
- Hemorrhage (abnormal bleeding caused by a ruptured blood vessel)
- Migraines (in some cases)
- Seizure disorder (such as epilepsy or convulsions)
- Sleep disorder (such as narcolepsy)

Note: a normal EEG does not mean that a seizure did not occur.


The procedure is very safe. If you have a seizure disorder, a seizure may be triggered by flashing lights or by fast breathing ( hyperventilation) that is done during the test. The health care provider performing the EEG is trained to take care of you if this happens. It may be difficult to get the paste out of your hair, but it should come out after a few washings with regular shampoo.

Thursday, October 30, 2008

Electroencephalogram (EEG)

An electroencephalogram (EEG) is a test that measures and records the electrical activity of your brain. Special sensors (electrodes) are attached to your head and hooked by wires to a computer. The computer records your brain's electrical activity on the screen or on paper as wavy lines. Certain conditions, such as seizures, can be seen by the changes in the normal pattern of the brain's electrical activity.
Why It Is Done
An electroencephalogram (EEG) may be done to:
Diagnose epilepsy and see what type of seizures are occurring. EEG is the most useful and important test in confirming a diagnosis of epilepsy.
Check for problems with loss of consciousness or dementia.
Help find out a person's chance of recovery after a change in consciousness.
Find out if a person who is in a coma is brain-dead.
Study sleep disorders, such as narcolepsy.
Watch brain activity while a person is receiving general anesthesia during brain surgery.
Help find out if a person has a physical problem (problems in the brain, spinal cord, or nervous system) or a mental health problem.
How To Prepare
Before the day of the electroencephalogram (EEG) test, tell your doctor if you are taking any medicines. Your doctor may ask you to stop taking certain medicines (such as sedatives and tranquilizers, muscle relaxants, sleeping aids, or medicines used to treat seizures) before the test. These medicines can affect your brain's usual electrical activity and cause abnormal test results.
Do not eat or drink foods that have caffeine (such as coffee, tea, cola, and chocolate) for 8 hours before the test.
Since the electrodes are attached to your scalp, it is important that your hair be clean and free of sprays, oils, creams, and lotions. Shampoo your hair and rinse with clear water the evening before or the morning of the test. Do not put any hair conditioner or oil on after shampooing.
To find certain types of abnormal electrical activity in the brain, you may have to be asleep during the recording. You may be asked not to sleep at all the night before the test or to sleep less (about 4 or 5 hours) by going to bed later and getting up earlier than usual. If your child is going to be tested, try to keep him or her from taking naps just before the test. If you know that you are going to have a sleep-deprived EEG, plan to have someone drive you to and from the test.
How It Is Done
An electroencephalogram (EEG) may be done in a hospital or in a doctor's office by an EEG technologist. The EEG record is read by a doctor who is specially trained to diagnose and treat disorders affecting the nervous system (neurologist).

How It Is Done continued...
You will be asked to lie on your back on a bed or table or relax in a chair with your eyes closed. The EEG technologist will attach 16 to 25 flat metal discs (electrodes) to different places on your head, using a sticky paste to hold the electrodes in place. A cap with fixed electrodes may be placed on your head instead of individual electrodes. In rare cases, these electrodes may be attached to the scalp with tiny needles.
The electrodes are hooked by wires to a computer that records the electrical activity inside the brain. A machine can show the activity as a series of wavy lines drawn by a row of pens on a moving piece of paper or as an image on the computer screen.
Lie still with your eyes closed during the recording, and do not talk to the technologist unless you need to. The technologist will watch you directly or through a window during the test. The recording may be stopped from time to time to allow you to stretch and reposition yourself.
The technologist may ask you to do different things during the test to record what activity your brain does at that time.
You may be asked to breathe deeply and rapidly (hyperventilate). Usually you will take 20 breaths a minute for 3 minutes.
You may be asked to look at a bright, flashing light called a strobe. This is called photic or stroboscopic stimulation.
You may be asked to go to sleep. If you cannot fall asleep, you may be given a sedative to help you fall asleep. If an EEG is being done to check a sleep problem, an all-night recording of your brain's electrical activity may be done.
An EEG takes 1 to 2 hours. After the test, you may do your normal activities. However, if you were sleep-deprived or given a sleep medicine, have someone drive you home after the test.
How It Feels
There is no pain with an electroencephalogram (EEG).
If paste is used to hold the electrodes, some paste may stay in your hair after the test, so you will have to wash your hair to remove it. If needle electrodes are used (which is rare), you will feel a brief, sharp prick (about like having a hair pulled out) when each electrode is inserted. If electrodes are placed in your nose, they may cause a tickling feeling and, rarely, some soreness or a small amount of bleeding for 1 to 2 days after the test.
If you are asked to breathe rapidly, you may feel lightheaded or have some numbness in your fingers. This reaction is normal. It will go away a few minutes after you start breathing normally again.
An electroencephalogram (EEG) is a very safe test. The electrical activity of your brain is recorded, but at no time is any electrical current put into your body. An EEG should not be confused with electroshock (electroconvulsive) therapy.
If you have a seizure disorder such as epilepsy, a seizure may be triggered by the flashing lights or by hyperventilation. If this occurs, the technologist is trained to take care of you during the seizure.
An electroencephalogram (EEG) is a test that measures and records the electrical activity of your brain. Special sensors (electrodes) are attached to your head and hooked by wires to a computer. EEG test results are ready on the same or the next day.