Prepare for Procedure

Prepare for a Procedure

Radiologic Testing
Magnetic Resonance Testing (MRI)
PET Positron Emissions Tomography
Intracarotid Sodium Amobarbital Test (Wada)
NeuroPsych Testing
Single Photon Emission Computed Tomography
Magnetic Resonance Spectroscopy

Radiologic Testing
Imaging studies are used to evaluate the structure of the brain or its function. There are five different radiologic tests which are most often ordered for preoperative/epilepsy evaluations in seizure patients. These are MRI, PET, Wada, Ictal SPECT and MRS.

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Magnetic Resonance Testing (MRI)
Magnetic Resonance Imaging (MRI) allows a physician to see a patient's internal body structures without using x-rays. With this technology, a physician can detect developing diseases or abnormalities earlier than ever before. MRI involves a powerful but harmless magnetic field and radiowaves like the kind that transmit FM music. The combination of radiowaves and magnetic field produces very clear images of body structures like the brain, the spine and other vital organs. By looking for abnormalities in structure, our team can determine if there may be seizure producing areas in or adjacent to the regions of structural change. At Johns Hopkins, we order an epilepsy protocol MRI that contains a 3-D portion and special coronal cuts so the epileptologist can evaluate the temporal lobes for signs of mesial temporal sclerosis or hippocampal malformation.

What Kinds of Machines Are Used to Perform MRI? The patient's scan will be performed in a room containing "the magnet." The MRI unit looks like a large box with an open-ended tunnel running through the middle. Many different kinds are in use, but they all work in the same way. The patient will be asked to lie on a comfortable, padded table that is gently moved into the opening of the magnet where the scanning is performed.

Sometimes a "coil," which is really just a special radio receiver, will be placed around the body part being scanned (the patient's head, knee or stomach, etc.). The data from the scan is fed into computers which compose very clear pictures that the physician will use to make a diagnosis.

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What Happens the Day of the Exam? The patient should allow about two hours for the MRI exam, although most scans take an hour or less.

Unless the patient's doctor indicates otherwise, the patient can eat normally the day of the exam. The patient should not wear any makeup, since some brands contain metallic components. On arrival at the MRI center, the patient will be asked to put on a gown and remove all personal possessions such as jewelry, wallet, car keys or metallic items such as dentures, pins, etc.

It's very important not to take anything that could be affected by a magnet into the examining room. For example, the information on credit cards could be erased if the patient has them in a pocket during the exam.

While the vast majority of people can undergo an MRI exam with no problems, some cannot. The radiologist or the staff at the MRI center will probably ask the patient questions like:

Does the patient weigh more than 300 pounds?
Can the patient lie flat for an extended period of time?
Does the patient suffer from claustrophobia?
Is the patient pregnant?

Since the MRI scan involves the use of a powerful magnet, the patient will also be asked the following:

Does the patient have any implanted devices such as a cardiac pacemaker, a cerebral aneurysm clip, a neurostimulator or a hearing aid?
Does the patient have any metal shrapnel in the body or any metal fragments in the eyes?

After providing all of the necessary information, the patient should feel free to air any concerns about the upcoming examination.

What Happens During the Actual Exam? The patient will be escorted into the room containing the "magnet" by a technologist and will be asked to lie down on the padded table. The technologist will position the patient inside the magnet so that the appropriate part of the patient's body is ready to be scanned. During the exam, the patient will be able to talk with the people conducting the exam by means of an intercom. The people conducting the exam will be able to watch the patient through a glass window.

The machine makes loud clanking and thumping sounds as the technologists adjust the radio frequencies and other controls. These sounds are completely normal. Some centers supply ear plugs for patients who may be bothered by the sound.

Sometimes a radiologist, nurse, or technologist may come into the scanning room to inject an enhancement agent to help the radiologist interpret the pictures taken during the exam.

Side Effects: Since MRI uses harmless radiowaves and magnetization instead of x-rays, it is considered to be safer than other radiologic techniques. There are no known side effects.

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PET Positron Emissions Tomography
With a PET scan, changes in brain metabolism and chemistry can be observed. Although a PET scan can help to evaluate many medical conditions, it can be of particular value in evaluating patients with epilepsy.

The PET scan Procedure: To begin the procedure, a plastic mask is fitted onto the patient's face. This aids in positioning the patient's head in the scanner. Baseline x-rays are often taken, either by CT scan or MRI at another location. The PET scan begins when a small amount of radioactive material is injected into a vein in the arm and, at the same time, a blood sample is taken from the other arm. For some types of PET scans, the patient's eyes will be covered and the patient's ears plugged for thirty minutes after the injection to minimize sensory stimulation.

The PET scan generally takes less than two hours, during which time the patient must lie quietly with the plastic mask in place. If the patient has had a CT scan, the experience of being "inside" the PET scan is similar.

Risks and Discomforts: There are no serious complications or discomforts with PET scanning. The patient may experience minor discomfort with the placement of the intravenous needle. Some patients find it uncomfortable to lie still in the PET scanning bed for the length of time required for the study.

As with all radioactive materials, including x-rays, there is a slight risk associated with the radioactive material that is injected. The dose of radiation received in a PET scan is slightly more than that received in a chest x-ray, but less than that received from most digestive studies. Women who are pregnant, or suspect that they are pregnant, should not have a PET scan.

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Intracarotid Sodium Amobarbital Test (Wada)
When we consider surgery for seizures, it is important that we know where certain speech, thinking and memory functions are located in the brain so that surgery does not affect these functions.

The information we gather from testing helps us to decide what the best type of surgery might be, and how much brain tissue can be removed safely. The Wada test is used to help make these determinations. The test combines neuroimaging and neuropsychological testing methods.

During the test, one side of the brain is put to sleep (anesthetized) by injecting a barbiturate into the carotid artery. For example, when the drug is injected into the left carotid artery, the left side of the brain is anesthetized for several minutes. Because the left side of the brain controls movement on the right side of the body, the right side of the body will not be able to move for this period of time. Also, if the anesthetized side is the side that controls speech, the patient will not be able to speak until the effect of the drug clears.

The patient will be scheduled as an outpatient for the test, the patient must bring someone who can drive and accompany them home. The patient will not be able to drive themselves home after the procedure. Generally, the procedure will begin in the morning and the patient should be ready to return home by mid-to-late afternoon.

On the day prior to the test, the patient will be scheduled for a consultation with a neuropsychology specialist. The purpose of this visit is to review the procedure with the patient and get baseline speech, cognitive and memory information. There also will be a practice session so that the patient will know what to expect during the actual test. The patient will also usually be scheduled for neuro psych testing in the afternoon of the day before the procedure.

The patient must notify us prior to the test if they hves any known allergies to drugs, particularly local anesthetics or barbiturates such as phenobarbital or Mysoline (primidone), Amytal (amobarbital), Mebaral, Nembutal, Seconal, or Tuinal. It is also important that they tell us of any allergies to foods, x-ray dyes which contain iodine, or allergic conditions such as eczema, asthma or hay fever.

Part One: Angiography - After the patient has been positioned on the back on the x-ray table, the neuroradiologist will give an injection of a local anesthetic into the groin. With the injection, the patient will feel a slight pressure and burning. A small incision is then made to allow passage of a small, flexible tube called a catheter through the skin into the artery.

The catheter will be guided painlessly into the vessels to be examined. Passage of the catheter from one position to another within the blood vessels is performed with the aid of an x-ray system, called fluoroscopy, which provides a television-like viewing of the inside of the body.

After the catheter is positioned within a specific blood vessel, x-rays are taken while x-ray dye is injected through the catheter. At this time, the patient will notice a very warm feeling lasting approximately ten to twenty seconds. At the same time the patient experiences the warm feeling, the patient will also hear noise as the x-ray machine takes pictures of the dye's passage through the blood vessels. It is very important that the patient remain motionless while the dye is injected and the x-rays are taken.

Although the length of the picture-taking process can be as brief as fifteen minutes, the actual time it takes will depend on the number of blood vessels that need to be examined. Most patients can anticipate lying on the x-ray table for one to two hours.

Part Two: The Wada Test - Next, the neuroradiologist will inject sodium amobarbital into the catheter. When the drug reaches the side of the brain under study, the patient will lose all strength on the side of the body opposite to the injection. This weakness is temporary, typically lasting five to fifteen minutes. It is during these few moments that the critical assessments of the patient's speech and memory will be made.

To test the patient's speech, the patient will be asked to read words, identify objects, pictures, shapes and numbers and answer questions about what they are shown. The patient also will be asked to remember what is shown. Later in the test, the patient will be asked to recognize these items again. The patient's hand or arm strength will be checked periodically to determine the full return of motor function of the weak side of the patient's body. The patient's speech and movements will be recorded using a tape recorder and/or a video camera for further study. Sometimes only one side is tested, at other times, one side will be tested first and then, after a short interval, the other side will be tested.

At the end of the test, the catheter will be removed. The blood vessel from which the catheter is removed must be compressed for ten to fifteen minutes until clotting at the entry site forms a firm seal to prevent leakage. The patient will feel the pressure as a member of the radiology team presses on this area. A small bandage will be placed on the site; no stitches are required.

The patient will stay in the Neuroradiology Department four to five hours after which the patient will be able to go home accompanied by a companion. As mentioned earlier, the patient will not be able to drive home alone. The patient may want to bring a book or a radio with earphones to help pass the time. Written instructions for home care will be given to the patient before leaving the hospital.

The patient and family should inform the nurse or physician of any discomfort or unusual developments without delay.

After the test, the injection site may be tender and bruised. Ice packs may be applied and the leg elevated with a pillow to ease discomfort.

Although the test has proven safe, the patient's physician will discuss possible complications prior to the procedure. Again, if the patient has allergies or is sensitive to drugs such as sleeping pills, barbiturates, local anesthesia, x-ray dye, etc., the patient must inform nurses and doctors beforehand, so that they can be prepared to avoid complications.

Test Results: It usually takes several days for the physicians to review test results and submit a report. The patient's physician will discuss the results with the patient.

Wada Preparation: For pre wada testing: Get a good night’s sleep, eat a good breakfast and wear comfortable clothing and shoes.

For day of the Wada: Do not eat or drink anything past midnight, wear comfortable clothing, wear no make up and take AM meds with a little water as possible. Please do not take aspirin or aspirin containing products for 2 weeks before this procedure.

Neuropsychological testing usually consists of a battery of psychological tests which are designed to quantitatively measure a patient's cognitive abilities as they relate to the normal or abnormal functioning of different brain structures. For example, impaired memory may indicate an abnormality in the function of a part of the brain called the temporal lobe. It also may entail a specialized testing of audiological processing to assess verbal processing and comprehension. This testing is done before most Epilepsy surgeries (usually the day of a pre wada for prospective temporal lobectomy patients) and about a year after surgery for a post surgical assessment.

Patients with epilepsy occasionally suffer from memory problems or other cognitive difficulties, such as with the ability to come up with the correct word to use in a conversation. These problems may result from repeated seizures or from a brain disease which is causing the patient's seizures. Under these circumstances patients may benefit from a quantitative assessment of their cognitive abilities in order to gain insight into the severity and perhaps the cause of their seizures.

In the special circumstance in which a patient is being evaluated for surgical treatment of their epilepsy, neuropsychological testing may provide information about the parts of the brain from which the patient's seizures are being generated. Since recurrent seizures over long periods of time may interfere with brain function, neuropsychological testing is used to detect which parts of the brain are not functioning normally, in order to locate the origin of the patient's seizures within the brain. This information is then used in conjunction with other tests to decide what parts of the brain should be removed to prevent further seizures.

Neuro Psych Preparation: Get a good night’s, sleep eat a good breakfast and wear comfortable clothing.

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Single Photon Emission Computed Tomography (Ictal SPECT)
Single Photon Emission Computed Tomography (SPECT) can be used to look for areas of the brain with altered metabolism, blood flow, or neurotransmitter function. The idea is that these areas of altered activity are more likely to be areas producing seizures in a given patient.

This test is done to evaluate localization of onset for patients whose EEG might not show an exact focus of onset. It can be used to guide the placement of grids. This specialized testing is done in two phases, Ictally (during a seizure) and Interictally (in-between seizures). Patients will be admitted to the EMU for the Ictal portion of the test, the Neurolite is injected at the bedside, during a seizure, by a specially trained nurse. The patient is then transported to Nuclear medicine for a specialized scan. This will used to assess cerebral blood flow at the seizure onset. The patient will have an interictal injection as an out patient and will be scanned afterwards as well.

The scans from the interictal and ictal injections are compared. The area of seizure focus is associated with an area of increased blood flow in an area which showed decreased blood flow after the interictal injection.

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Magnetic Resonance Spectroscopy
Along with the MRI, a MRS might be ordered. This is specialized imaging which is used to evaluate and compare the metabolic/chemical function of different parts of the brain. It can be used to compare temporal lobes size and metabolic function. It cannot be used evaluate the whole brain at once. It is used to assess areas of focused interest. This procedure is performed in the MRI Suite and the preparation would be the same as for an MRI.