Diagnosing multiple sclerosis is not a simple issue. There is no one symptom that indicates the disease and no single test that diagnoses it. A diagnosis will be based instead on a thorough medical history, a neurological exam, and various tests. In the medical exam, your doctor will ask about your symptoms, including when they started.
Some tests are used to look for evidence of lesions, or scar tissue, in the brain or spinal cord. Magnetic resonance imaging (MRI) can be used to look directly at the brain and spinal cord, while a spinal tap or lumbar puncture might be performed to look for evidence of myelin breakdown in the cerebrospinal fluid. Evoked potentials are tests of nerve pathways that test whether MS has slowed the transmission of electrical impulses.
Criteria for diagnosis of multiple sclerosis include:
- Evidence of lesions in at least two separate areas of the central nervous system
- A course of disease in one of two patterns: two or more neurological episodes lasting at least 24 hours and occurring at least one month apart; or a progressive course of signs and symptoms over at least six months
- No other reasonable explanation of symptoms
Blood tests may be done to rule out conditions that imitate MS, such as inflammation of the blood vessels, multiple strokes, vitamin deficiency, brain infection, and stress-related disorders.
This section includes more information on tests used in diagnosing MS:
Some neurological examination is a standard part of most physical exams, but if your doctor suspects you may have multiple sclerosis, the neurological exam will be much more detailed. Your doctor will test your reflexes, balance, coordination, and vision, and check for any areas of numbness or problems with speech. Your mental ability may also be assessed, along with your emotional state. Any unusual results, such as weakness or problems with vision or balance could suggest multiple sclerosis. However, since these could also be symptoms of many other diseases, a neurological exam by itself is not enough to diagnose multiple sclerosis.
Magnetic resonance imaging (MRI) is always used as part of the diagnosis of MS. An MRI will usually show lesions—scar tissue—in the brain or spinal cord. However, similar lesions can be seen in the elderly and also in people with migraine headaches or high blood pressure.
MRI is a test that produces very clear pictures of the human body without the use of X-rays. MRI uses a large magnet, radio waves, and a computer to produce these images. The MRI is a highly sensitive test that is very helpful for imaging "soft tissues," such as organs. In most cases, the procedure takes 40 to 80 minutes, during which several dozen images are obtained. Certain MRI exams require an intravenous injection of a contrast material called gadolinium. This helps identify certain anatomical structures on the scan images. Generally, you can resume your usual activities and normal diet immediately after the exam.
Open MRIs are available to those patients with claustrophobia. However, open MRIs produce a picture that is significantly poorer in quality than that produced by the standard closed MRI—and thus may lack important information that the radiologist could use to make an accurate diagnosis. Instead, people who have difficulty with claustrophobia should discuss with their doctor or the MRI facility the possibility of being sedated.
As the MRI scan begins, you will hear the equipment making a muffled thumping sound that will last for several minutes. Other than the sound, you should experience no unusual sensations during the scanning.
The MRI examination poses no risk to the average patient if appropriate safety guidelines are followed. Since the test involves a giant magnet, precautions must be taken with some metal objects.
Post-cardiac-surgery patients and patients with the following medical devices can be safely examined with MRI:
- Most surgical clips or sutures
- Artificial joints
- Cardiac valve replacements
- Vena cava filters (after six weeks for certain types)
- Brain shunt tubes for hydrocephalus
- Metal stents
Some conditions may make an MRI examination inadvisable. Tell your doctor if you have any of the following conditions:
- Heart pacemaker
- Cerebral aneurysm clip (metal clip on a blood vessel in the brain)
- Implanted insulin pump (for treatment of diabetes), narcotics pump (for pain medication), or implanted nerve stimulators (i.e., "TENS" for back pain, vagal nerve stimulator for seizures)
- Metal in the eye or eye socket
- Cochlear (ear) implant for hearing impairment
- Implanted spine stabilization rods
- Severe lung disease (such as tracheomalacia or bronchopulmonary dysplasia)
- Gastroesophageal reflux
- Weight of more than 300 pounds
- Inability to lie on back for 40 to 80 minutes
- Claustrophobia. If this applies to you, you can make arrangements to receive sedation during the exam.
In a lumbar puncture, a sample of the fluid surrounding the spinal cord (called the cerebrospinal fluid or CSF) is withdrawn through a needle and examined in a laboratory. A patient with MS might have elevated levels of antibodies, certain proteins, and breakdown products of myelin in the CSF. This test might be helpful in diagnosing MS in some people, but it is no longer considered necessary in all instances.
Spinal taps can also be performed for other reasons, such as to look for signs of infection, measure the pressure around the brain and spinal cord, or inject dye for an X-ray diagnostic test. People with multiple sclerosis may have medications such as Baclofen injected via lumbar puncture.
Before the test, you should maintain your regular eating schedule. There are no dietary or fluid restrictions before the test. But you should ask your doctor for specific guidelines about discontinuing alcohol use, aspirin products, or anticoagulant medications before the procedure. Tell your doctor if you are allergic to Betadine or Novocaine.
Be sure to make arrangements for transportation, as you should not drive immediately after the test.
During the test, you will either lie on your side with your knees drawn as close to your chest as possible and your chin toward your chest, or sit with your arms and head resting on a table. After your skin is cleaned with an antiseptic, sterile cloths (called drapes) will be placed around the area. A local anesthetic will be injected into the area on your back. You may feel a slight burning sensation. When the area is numb, a hollow needle is inserted in the lower back between two lumbar vertebrae. This sometimes causes pressure. The spinal canal is penetrated, and fluid is collected or medication is injected. The needle does not touch the spinal cord during the test. You may feel some discomfort or have a minor headache. The needle is removed after the medication has been injected or fluid has been removed. The area will be cleaned with an antiseptic and covered with a bandage. You will lie on your back or stomach for about an hour.
A blood sample will be taken from a vein in your arm and tested, along with the spinal fluid, in the laboratory. A blood sample will not necessarily be taken if the procedure was done to inject medication.
Approximately 10 percent to 20 percent of people develop a spinal headache (one that worsens when sitting or standing) as a result of a lumbar puncture. The risk of infection is extremely low. Occasionally, a small blood vessel is pierced, causing bloody discharge, but no treatment is needed. The procedure is usually not painful, but momentary twinges of pain may be felt if the needle brushes against nervous tissue.
Immediately after the test, you will be monitored for up to one hour. A nurse should discuss post-procedure instructions with you and should give you the instructions in written form.
After the test:
- Remain flat on your back as much as possible over the next 24 hours.
- Avoid strenuous or vigorous exercise for a day or so following the lumbar puncture.
- Drink 2-1/2 quarts of liquid the day of the spinal tap and the day after (regardless of headache).
- Notify the center that carried out the test if you have a headache that persists for more than one day or experience any drainage from the puncture site.
- If you have a headache, lie down as much as possible and drink plenty of caffeinated beverages.
Call your doctor immediately if:
- You notice any unusual drainage, including bloody discharge, at the puncture site.
- You develop a fever.
- Your pain symptoms worsen.
Evoked potentials are used to show abnormalities in the function of nerve pathways that can be caused by MS. These tests are conducted by examining the brain's response to stimulation such as watching a pattern on a video screen, hearing a series of clicks, or receiving electrical impulses in the arm or leg.
Evoked potentials test and record how quickly and completely nerve signals reach the brain. Evoked potentials can indicate problems along nerve pathways that are too subtle to show up during a neurological examination or to be noticed by the patient. The disruption may not even be visible in an MRI exam.
There are several main kinds of evoked potentials, which stimulate nerves in different ways:
- Visual evoked potentials: The patient sits before a screen on which alternating patterns are displayed. It is fairly common for optic nerve transmission to slow early in MS, even if the patient hasn't noticed any change in vision.
- Auditory evoked potentials: The patient listens to a series of clicks in each ear.
- Sensory evoked potentials: Short electrical impulses are administered on the arm or leg.
- Motor evoked potentials: These can detect disruption on a motor pathway of the brain or spinal cord (not commonly used to diagnose MS).
During an evoked potential test, wires are attached to the scalp, neck, and limbs. Wash your hair before coming to the test, and don't put any sprays, gels, etc., on your hair. It usually takes about one to two hours to do each test. The testing is generally harmless and painless. The only discomfort is a slight tingling of the arms and/or legs during stimulation. No needles or injections are involved, and there is no radiation. You may not have to go through all of the tests.
Tell your doctor about any medications you are taking, as some may affect the results of the test. You can eat as usual before the test. The test is not invasive, and you can go to work or home afterward.
While evoked potentials are used to assist with the diagnosis of MS, other conditions can also produce abnormal results. For that reason, a neurologist or a neurophysiologist who has special training in these tests should interpret the results. Information provided by these tests will be considered, along with other findings from a clinical history, neurological exam, MRI, and other clinical or laboratory information when diagnosing a medical condition.
Last reviewed on 03/19/2007
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