Multiple sclerosis diagnosis: Testing for MS

Last updated March 14, 2022, by Patricia Silva, PhD
Fact-checked by Ines Martins, PhD

Multiple sclerosis (MS) is a neurological disorder that can lead to impaired nerve function in the brain and spinal cord due to a malfunction in the immune system. An early and accurate MS diagnosis is important as it can allow for earlier treatment, which in turn tends to yield better clinical outcomes.

Who diagnoses multiple sclerosis?

Neurologists — medical doctors who specialize in the diagnosis, treatment, and management of disorders affecting the brain and nervous system — are typically the clinicians qualified to make a definitive MS diagnosis.

What are the criteria for diagnosing MS?

There is no single test that by itself can diagnose MS. The 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 the individual’s medical history.

A set of diagnostic parameters called the McDonald Criteria, which were revised in 2017, has established guidelines to speed the correct identification of MS. According to these criteria, an MS diagnosis requires:

• evidence of damage in at least two separate areas of the central nervous system — comprised of the brain and spinal cord — a feature referred to as dissemination in space.
• evidence that the damage occurred at different time points — dissemination in time.

Another important step in this process is ruling out other conditions that may cause symptoms similar to those of MS. These can range from viral infections to nutritional deficits to other neurological disorders.

What tests are used to diagnose MS?

Several tests can be used to help in the diagnosis of MS. Some of the most common clinical assessments are:

• MRI scans
• evoked potential tests
• spinal tap
• vision tests

Other tests, including blood analyses, also can be useful.

Magnetic resonance imaging

Known simply as an MRI, magnetic resonance imaging is the preferred imaging tool — the most sensitive — to diagnose and track the progression of MS. An MRI uses a strong magnetic field and radio waves to assess water content in tissues, which can then be used to create a detailed image. It is a non-invasive technique and does not expose the patient to radiation.

In MS, MRI is typically used to look for characteristic damage in the central nervous system in the form of lesions, given that damaged parts of the nervous system — which lack myelin, the fatty coating around nerve fibers — retain more water than healthy parts.

There are multiple types of MRI, but those most commonly used in MS are T1-weighted scans (to detect active inflammatory lesions) and T2-weighted scans, which detect the overall lesion load, including both old and active lesions.

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 assess the speed of the electrical impulse that passes through specific nerve pathways, 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 investigated. Visual evoked potentials (VEP), which measure the activity of the optic nerves connecting the eyes to the brain, are used most frequently in an MS diagnosis. In a VEP test, the patient is seated in front of a screen and focuses on its center, where a checkboard pattern is shifting; one eye is tested at a time and each eye is tested twice.

Spinal tap

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 (the lower back).

Laboratory measurements of CSF can detect signs of inflammation in the central nervous system that are characteristic of MS. Specifically, lumbar puncture is often used to test for oligoclonal bands — antibodies, also called immunoglobulins, indicative of inflammation. Other proteins resulting from the breakdown of myelin also may be present.

Vision tests

About 20% of 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.

Additional tests used to diagnose MS

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 — that is, they allow clinicians to make differential diagnoses. They may include:

• Blood tests, which are often used to exclude other potential causes of symptoms, including 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, used to rule out causes of bladder problems apart from MS, including, for example, infections or cancer. Many people with MS will experience bladder-related complications, such as frequent urination or nocturia (frequently waking up to urinate) 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, that may help in evaluating bowel impairments in MS patients.
• A variety of tests of movement, coordination, and sensation, which can detect problems that may result from damage to specific nerve pathways. Such assessments range from looking for impaired muscle strength or 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 (neurological exams), useful for detecting 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 tests for emotional problems, which can be used to diagnose mental health issues, such as depression, that are common among people with MS

Conditions to rule out in MS diagnosis

According to the National MS Society, before confirming an MS diagnosis, other conditions with similar manifestations must be ruled out. These include:

• infections affecting the central nervous system, including syphilis or Lyme disease
• other inflammatory and/or autoimmune diseases, such as lupus or vasculitis
• genetic disorders that can result in neurologic symptoms, including leukodystrophies (conditions also characterized by myelin damage)
• brain tumors
• particular deficiencies, including copper or vitamin B12 — which is important for neurologic function
• conditions that cause structural damage in the brain and/or spinal cord, such as a herniated disc
• other demyelinating diseases, including neuromyelitis optica spectrum disorder (NMOSD) and acute disseminated encephalomyelitis (ADEM)

Both NMOSD and ADEM are diseases characterized by myelin loss (demyelination) due to an inflammatory attack, similar to MS. NMOSD primarily leads to inflammation of the optic nerve and the spinal cord. ADEM usually consists of a single, intense attack that results in myelin damage in the brain or spinal cord; occasionally the optic nerve also can be affected.

How long can MS go undiagnosed?

MS is usually diagnosed between the ages of 20 and 50, but it can go undetected for years. In fact, a 2021 study suggested that many people with MS experience disease symptoms several years before being officially diagnosed with the disease.

The symptoms of MS can vary considerably between patients, as well as over time, making the diagnosis difficult. Another factor contributing to delays is that other medical conditions need to be ruled out for a definitive MS diagnosis, and this process takes time. No single test is yet available to rule out or confirm MS.

Given that a misdiagnosis of MS could put a person at risk of receiving unnecessary treatment, healthcare professionals usually are careful, and meticulous in their assessments, before making a final diagnosis of the disease.

The diagnosis of MS in people with unusual disease manifestations can be more challenging. Furthermore, it usually is harder to make a diagnosis in those with progressive disease than in those with relapsing-remitting MS — around 85% of MS patients are diagnosed with this form of the disease — because the disease progresses more slowly.

What should people expect after a diagnosis of MS?

After an MS diagnosis, a treatment plan should be discussed between the healthcare provider and the patient. This allows the best MS treatment strategy to be established, based on the patient’s health condition, disease type, symptoms, needs, and preferences.

MS is a lifelong disease and no two people are affected by it in exactly the same way. Moreover, even a specific patient’s clinical status can change from day to day, making the course of the disease unpredictable to some extent. For some patients, symptoms can significantly worsen over time, having a considerable negative impact on daily life and functioning. In other cases, conversely, patients are able to live an active and productive life despite their disease.

The National MS Society advises a comprehensive, coordinated care approach to manage the disease, involving the expertise of different healthcare providers besides neurologists — such as primary care physicians, urologists, rehabilitation professionals, and mental health providers. The main focus areas of such an approach are:

• modifying the disease course
• treating exacerbations (relapses)
• managing symptoms
• rehabilitation focused on function
• emotional support

Adjustments to a person’s lifestyle might be needed after an MS diagnosis — for example, quitting smoking or losing weight, as these can be factors in this disorder. Concerning prognosis, MS is usually not fatal, but it may increase the risk of developing life-threatening complications, including severe infections.

As a chronic disorder, MS requires continual monitoring. Patients are advised to see their neurologist regularly, usually every six months, and to make an appointment for a consultation if their symptoms change.

Across the Multiple Sclerosis News Today website, one can find information, support, and resources to get more familiar with the different aspects of the disease. People also can participate in forums to connect with others within the MS community, and learn from the experiences of other patients through our columns. Special content dedicated to those who have been newly diagnosed with MS also is available.

Multiple Sclerosis News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.