Multiple sclerosis (MS) is a neurological disorder in which the immune system erroneously launches an attack against the myelin sheath, the insulating cover around nerve fibers, leading to impaired nerve function in the brain and spinal cord.
An early and accurate diagnosis is very important, as it can allow for earlier treatment, which in turn tends to yield better clinical outcomes. However, there is no single test to diagnose MS.
A first step in diagnosing the disease is a thorough physical and neurologic examination that includes imaging and other tests, combined with a careful study of an individual’s medical history.
A set of diagnostic parameters called the McDonald Criteria, which was revised in 2017, has established guidelines to speed the diagnosis of MS. According to these criteria, such a diagnosis requires evidence of damage in at least two separate areas of the central nervous system, comprised of the brain and spinal cord, along with evidence that the damage occurred at different points. It also is necessary to rule out other conditions — ranging from viral infections to nutritional deficits, to other neurological conditions — that may cause symptoms similar to those of MS.
Several of the most common clinical assessments used to diagnose MS are discussed below.
Magnetic resonance imaging
Known simply as an MRI, magnetic resonance imaging is the preferred imaging tool used to diagnose and track the progression of MS. It uses a strong magnetic field and radio waves to measure water content in the body’s tissue, which then can be used to create an image of the inside of the body.
In an MS diagnosis, an MRI is typically used to look for characteristic damage in the central nervous system. Nearly all people with MS have such damage, which is visible on an MRI as lesions because damaged parts of the nervous system — which lack the fatty coating around nerve cells — retain more water than healthy parts.
There are multiple types of MRI, but those most commonly used in MS are T1-weighted scans and T2-weighted scans.
In a T1-weighted scan, a contrast material (gadolinium) is injected into the patient’s veins before the scan. The contrast material can only enter the brain in places where there is current inflammation; as such, this type of scan is used to detect areas of active inflammation.
By contrast, a T2-weighted scan is used to detect areas of nervous system damage, both old and new, regardless of whether or not there is active inflammation at the time of the scan.
Once a person is diagnosed with MS, MRI scans help in tracking the disease’s progression and in making treatment decisions such as whether to continue with a given therapy or change to a new one. Follow-up MRIs are recommended every six months to two years, and should be obtained on the same scanner to enable comparisons from one MRI to the next.
Evoked potential tests
Evoked potential (EP) tests are used to measure the electrical activity of the brain in response to a stimulus — such as sight or sound — by placing electrodes on specific parts of the body. These tests can detect the speed of the electrical impulse that passes through the nerves, and can detect abnormalities even before lesions show up on neurological exams or symptoms become obvious.
There are several types of EP tests, depending on the specific nerves that are being investigated. Visual evoked potentials (VEP), which measure the activity of the optic nerves connecting the eyes to the brain, are the most commonly used in MS diagnosis. In a VEP test, the patient is seated in front of a screen and focuses on the center, where a checkboard pattern is shifting. One eye is tested at a time and each eye is tested twice.
A lumbar puncture, also known as a spinal tap, is a procedure in which a small sample of the cerebrospinal fluid (CSF), the liquid surrounding the brain and spinal cord, is collected. This is done using a thin needle to draw the CSF from the lower lumbar region, which is the lower back.
Laboratory measurements of CSF can detect signs of inflammation in the central nervous system that are characteristic of MS.
Specifically, in MS, lumbar puncture is often used to test for oligoclonal bands. These bands contain antibodies (also called immunoglobulins), which are immunological proteins indicative of inflammation. Other proteins resulting from the breakdown of myelin also may be present.
About one in five people with MS will experience optic neuritis, or inflammation of the nerves that connect the eyes to the brain, as their first symptom. Vision tests can help to assess optic neuritis and other eye-related complications that may occur in MS, such as double vision (diplopia) and involuntary eye movements known as nystagmus.
A variety of other clinical and laboratory tests may be used to diagnose MS. These tests also can evaluate disease symptoms, and rule out other conditions. They may include:
- Blood tests, which are often used to exclude other potential causes of symptoms, such as infections. Measuring levels of certain proteins in the blood, such as neurofilament light chain (NfL), can provide information about the extent of nervous system damage.
- Urine tests, which can rule out causes of bladder problems apart from MS such as, for example, infections or cancer. Many people with MS will experience bladder-related complications, such as frequent urination or nocturia (frequently waking up to pee) as a result of nerve damage. But since many different conditions can cause these symptoms, it is important to rule out other causes.
- Colonoscopy and other lower digestive system examinations can help to evaluate bowel impairments in MS patients.
- A variety of tests can be used to assess movement, coordination, and sensation problems that can result from nerve damage. These can range from looking for impaired muscle strength, a loss of control over small movements, and/or the inability to feel certain sensations such as a prick on the feet.
- Assessments of cognition can detect cognitive impairments that result from brain damage. Typically, these are first reported by the patient or their caregivers, and a clinician can then conduct other assessments as appropriate. There are a variety of standardized questionnaires that can help to detect cognitive impairment in MS. These include the MS Neuropsychological Screening Questionnaire and the Symbol Digit Modalities Test.
- Standard test for emotional problems can be used to diagnose mental health issues like depression, which are common among people with MS.
Last updated: June 21, 2021
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